Promax 2D Seismic Processing & Analysis

ProMAX 2D Seismic Processing and Analysis copyright © 1998 by Landmark Graphics Corporation

626075 Rev. B

June 1998

Copyright © 1998 Landmark Graphics Corporation All Rights Reserved Worldwide This publication has been provided pursuant to an agreement containing restrictions on its use. The publication is also protected by Federal copyright law. No part of this publication may be copied or distributed, transmitted, transcribed, stored in a retrieval system, or translated into any human or computer language, in any form or by any means, electronic, magnetic, manual, or otherwise, or disclosed to third parties without the express written permission of: Landmark Graphics Corporation 15150 Memorial Drive, Houston, TX 77079, U.S.A. Phone: 713-560-1000 FAX: 713-560-1410

Trademark Notices Landmark, OpenWorks, SeisWorks, ZAP!, PetroWorks, and StratWorks are registered trademarks of Landmark Graphics Corporation. Pointing Dispatcher, Log Edit, Fast Track, SynTool, Contouring Assistant, TDQ, RAVE, 3DVI, SurfCube, SeisCube, VoxCube, Z-MAP Plus, ProMAX, ProMAX Prospector, ProMAX VSP, MicroMAX, DepthTeam and Landmark Geo-dataWorks are trademarks of Landmark Graphics Corporation. Technology for Teams is a service mark of Landmark Graphics Corporation. ORACLE is a registered trademark of Oracle Corporation. IBM is a registered trademark of International Business Machines, Inc. AIMS is a trademark of GX Technology. Motif, OSF, and OSF/Motif are trademarks of Open Software Corporation. UNIX is a registered trademark of UNIX System Laboratories, Inc. SPARC, SPARCstation, Sun, SunOs and NFS are trademarks of SUN Microsystems. X Window System is a trademark of the Massachusetts Institute of Technology. SGI is a trademark of Silicon Graphics Incorporated. All other brand or product names are trademarks or registered trademarks of their respective companies or organizations.

Note The information contained in this document is subject to change without notice and should not be construed as a commitment by Landmark Graphics Corporation. Landmark Graphics Corporation assumes no responsibility for any error that may appear in this manual. Some states or jurisdictions do not allow disclaimer of expressed or implied warranties in certain transactions; therefore, this statement may not apply to you.

ProMAX 2D Seismic Processing and Analysis Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Mouse Button Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Exercise Organization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Manual Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Agenda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Day 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introductions, Course Outline, and Miscellaneous Topics . . . . . . . . . . . . . . . . . . . . . . 1 ProMAX 2D Geometry - Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 ProMAX 2D Geometry - Full Extraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 ProMAX 2D Geometry - Extraction with Editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Trace Editing using Trace Statistics and DBTools . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Day 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Parameter Selection and Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Elevation Static Corrections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Brute Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Neural Network First Break Picking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Refraction Static Corrections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Stack Comparisons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Velocity Analysis and the Volume Viewer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Day 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Residual Statics Corrections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Dip Moveout (DMO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 PostStack Signal Enhancement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Velocity: QC, Editing, Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 PostStack Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Additional Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

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Manual Geometry Assignment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-1

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 ProMAX Geometry Assignment Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3 Geometry assignment path for this exercise. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

Land Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5 View Shot Gathers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6 First look at the data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

Load Geometry into the Spreadsheet and Database . . . . . . . . . . . . . . . . . . . . . 1-7 Description of Geometry for this line. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7 Load Survey information to the spreadsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9 Receivers spreadsheet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11 Sources spreadsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-17 Patterns spreadsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-19 TraceQC spreadsheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-24 Binning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-25

View Database Attributes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-29 Load Geometry to the Trace Headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-33 Graphical Geometry QC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-35 QC your Geometry Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-36

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-38

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Full Extraction Geometry Assignment . . . . . . . . . . . . . . . . . . . . . . . . 2-1 Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 ProMAX Geometry Assignment Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3 Geometry assignment path for this exercise . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Extract Database Files Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4 Database file extraction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Full Extraction Geometry Assignment with Editing . . . . . . 3-1 Chapter Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 ProMAX Geometry Assignment Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3 Geometry assignment path for this exercise . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Extract Database Files Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 Database file extraction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4 Spreadsheet completion and binning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6 Load Geometry to the trace headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

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Trace Editing using Trace Statistics and DBTools

. . . . . . . . . 4-1

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 Picking a Time Window for Statistical Analysis . . . . . . . . . . . . . . . . . . . . . . . . 4-3 Running the Trace Statistics Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4 Displaying the Statistics using DBTools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5 Selecting the Data of Interest Graphically. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9 Focusing on a Range of data on the Histogram . . . . . . . . . . . . . . . . . . . . . . . . 4-12 Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14

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System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1 Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2 Directory Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3 /ProMAX (or $PROMAX_HOME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . /ProMAX/sys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . /ProMAX/port . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . /ProMAX/etc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . /ProMAX/scratch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . /ProMAX/data (or $PROMAX_DATA_HOME). . . . . . . . . . . . . . . . . . . . . . . .

5-3 5-5 5-5 5-6 5-6 5-6

ProMAX Data Directories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7 Program Execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8 User Interface ($PROMAX_HOME/sys/bin/promax) . . . . . . . . . . . . . . . . . . . . 5-8 Super Executive Program (super_exec.exe) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9 Executive Program (exec.exe) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10 Processing Pipeline Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11 Types of Executive Processes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14 Stand-Alone Processes and Socket Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14

Ordered Parameter Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15 Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OPF Matrices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Database Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . File Naming Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-15 5-16 5-18 5-19

Parameter Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-20 Creating a Parameter Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-20 ASCII Import to a Parameter Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-21 ASCII File Export from the Parameter Table Editor . . . . . . . . . . . . . . . . . . . . 5-22

Disk Datasets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-23 Secondary Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-24

Tape Datasets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26 Tape Trace Datasets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26

Tape Catalog System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28 Tape Catalog Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28

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Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-28

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-30

Parameter Selection and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6-1

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2 Parameter Table Picking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3 Pick Parameter Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

Parameter Test. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5 Test True Amplitude Recovery with Parameter Test . . . . . . . . . . . . . . . . . . . . . 6-5

IF/ENDIF Conditional Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-11 Compare Data With and Without Deconvolution . . . . . . . . . . . . . . . . . . . . . . 6-12

F-K Analysis and Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16 F-K Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16 Compare F-K filtered shots using an IF loop . . . . . . . . . . . . . . . . . . . . . . . . . . 6-20

Interactive Spectral Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-22 Spectral Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-22

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-30

Elevation Static Corrections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-1

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2 Elevation Statics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3 Calculate Elevation Statics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6 Apply Elevation Statics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8

Apply User Statics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11 Apply External Statics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

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Brute Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1 Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2 RMS Velocity Field ASCII Import . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3 CDP/Ensemble Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8 Display Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-10 Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-12

Neural Network First Break Picking . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1 Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2 Interactive NN First Break Training/Picking . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3 Interactive Training. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3

Batch Neural Network First Break Picking . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-10 Pick First Breaks for entire survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-10

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-12

Refraction Static Corrections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1 Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2 Refraction Statics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3 Refraction Statics - 2D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3

Coordinate Based Refraction Statics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-8 Apply Refraction Statics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-13 Apply Refraction Statics to your data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-14

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-16

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Stack Comparisons

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2 Compare Stacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-3 Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-4

Velocity Analysis and the Volume Viewer. . . . . . . . . . . . . . . . . . .

12-1

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-2 Velocity Analysis Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-3 Velocity Analysis Precompute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-4 Precompute Velocity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-5 Velocity Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-9 Velocity Analysis Icons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-12 Using the Volume Viewer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-13 Velocity Analysis PD Tool. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-16

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-18

Residual Statics Corrections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13-1

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-2 Autostatics Flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-3 Data Preparation for Input to Residual Statics . . . . . . . . . . . . . . . . . . . . . . . . . 13-4 Data preparation and horizon picking for residual statics . . . . . . . . . . . . . . . . 13-4

Calculation of Residual Statics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-9 Autostatics calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-10

QC and Application of Residual Statics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-12 Compare Static Solutions in the Database . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-13 Compare Autostatics Stacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-15

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Compare two or more Autostatics Stacks. . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-16

External Model Autostatics Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-17 External Model Autostatics Flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-18 Create Eigen Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-19

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-30

Dip Moveout (DMO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-1 Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-2 Common Offset Binning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-3 Determine trace binning parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-4 Assign DMO offset bins to the data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-12

DMO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-17 Apply DMO to the data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-18 Final Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-20

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-21

Poststack Signal Enhancement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1 Chapter Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-2 F-X Decon, Dynamic S/N Filtering, and BLEND . . . . . . . . . . . . . . . . . . . . . . 15-3 Signal Enhancement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-3

Trace Math . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-7 Use Trace Math to view differences between stacks . . . . . . . . . . . . . . . . . . . . 15-7

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9

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Contents

Velocity: QC, Editing, Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16-1

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-2 Velocity Viewer/Point Editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-3 Smooth RMS velocities, and convert to interval velocity . . . . . . . . . . . . . . . . 16-3

Velocity Manipulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-8 Shift smoothed RMS velocities to final datum. . . . . . . . . . . . . . . . . . . . . . . . . 16-8 Shift interval velocities to final datum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-10 Output a single interval velocity function . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-11

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-12

PostStack Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17-1

Chapter Objectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-2 PostStack Migration Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-3 Tapering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-4 Poststack Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-5 Apply FK migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-5 Apply Phase Shift Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-8 Apply FD Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-10 Compare Migrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-11

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-12

Appendices Appendix 1: Additional Geometry Information . . . . . . . . . . . .

1-1

Geometry Core Path Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 How to Decide on the Primary Geometry Path . . . . . . . . . . . . . . . . . . . . . . . . . 1-2 Transferring the Database to Trace Headers . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3 x


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Details of the Geometry Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 Steps Performed by Inline Geom Header Load . . . . . . . . . . . . . . . . . . . . . . . . . Valid Trace Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Valid Trace Number Origin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steps Performed By Extraction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Between Extraction and Geom Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Geometry Load Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-4 1-5 1-6 1-6 1-7 1-8

Pre-Geometry Database Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9 Pre Geometry Initialization flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11 Complete the Spreadsheet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-12

Inline Geometry Header Load after Pre-Initialization . . . . . . . . . . . . . . . . . . 1-13 Load Geometry to Trace Headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-13

Appendix 2: Supergathers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 Create Supergather . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 Create Supergather and Horizontally Stack. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Appendix 3: Alternate Velocity Analysis Methods . . . . . . . . . 3-1 CVS Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 Interactive Velocity Analysis (IVA). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7

Appendix 4: Database/Header Manipulation

. . . . . . . . . . . . . . . 4-1

Header Manipulation Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 Apply a Linear Moveout Correction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

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Appendix 5: Training Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-1

Reference Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2 Organization of Ordered Parameter Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2 PostStack Migration Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3 Apply Statics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

Reference Graphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5 Datum Statics Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Geometry Assignment Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Promax Directory Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Promax Data Directories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-5 5-6 5-7 5-8

Flows and Data Summaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9 Flows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9 Datasets: Seismic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10 Datasets: OPF-TRC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11 Datasets: OPF-SRF. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12 Datasets: OPF-SIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-13 Datasets: OPF-CDP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14 Datasets: OPF-CHN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15 Datasets: OPF-OFB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15 Datasets: OPF-PAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-16

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Preface

Preface About The Manual This manual is intended to accompany the instruction given during the standard ProMAX 2D course. Because of the power and flexibility of ProMAX, it is unreasonable to attempt to cover all possible features and applications in this manual. Instead, we try to provide key examples and descriptions, using exercises which are directed toward common uses of the system. For more progressive training please take Advanced 2D. The manual is designed to be flexible for both you and the trainer. Trainers can choose which topics, and in what order to present material to best meet your needs. You will find it easy to use the manual as a reference document for identifying a topic of interest and moving directly into the associated exercise or reference. You are encouraged to copy the exercise workflows and optimize them to your personal situation. How To Use The Manual This manual is divided into chapters that discuss the key aspects of the ProMAX system. In general, chapters conform to the following outline: •

Introduction: A brief discussion of the important points of the topic and exercise(s) contained within the topic.

•

Topics Covered and Chapter Objectives: Brief list of skills or processes, in the order that they are covered in the exercise.

•

Topic Description: More detail about the individual skills or processes covered in the chapter.

•

Exercise: Details pertaining to each skill in an exercise, along with diagrams and explanations. Examples and diagrams will assist you during the course by minimizing note taking requirements, and providing guidance through specific exercises.

•

Chapter Summary: A brief list of skills the chapter was designed to train.

This format allows you to glance at the topic description to either quickly reference an implementation, or simply as a means of refreshing your memory on a previously covered topic. If you need more information, see the Exercise sections of each topic.

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1

Preface

Conventions Mouse Button Help This manual does not refer to using mouse buttons unless they are specific to an operation. MB1 is used for most selections. The mouse buttons are numbered from left to right so: MB1 refers to an operation using the left mouse button. MB2 is the middle mouse button. MB3 is the right mouse button. Actions that can be applied to any mouse button include: •

Click: Briefly depress the mouse button.

•

Double Click: Quickly depress the mouse button twice.

•

Shift-Click: Hold the shift key while depressing the mouse button.

•

Drag: Hold down the mouse button while moving the mouse.

Mouse buttons will not work properly if either Caps Lock or Nums Lock are on.

Exercise Organization Each exercise consists of a series of steps that will build a flow, help with parameter selection, execute the flow, and analyze the results. Many of the steps give a detailed explanation of how to correctly pick parameters or use the functionality of interactive processes. The flow examples list key parameters for each process of the exercise. As you progress through the exercises, familiar parameters will not always be listed in the flow example. The exercises are organized so that your dataset is used throughout the training session. Carefully follow the instructor’s direction when assigning geometry and checking the results of your flow. An improperly generated dataset or database may cause a subsequent exercise to fail.

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Preface

Manual Organization The manual will take you through a typical workflow of a geoscientist processing a land 2D seismic dataset. The processing functions of ProMAX will be introduced and discussed as they appear in the workflow.

Processing WorkFlow 1. Geometry Assignment

Field Data

2. Trace Editing 3. Parameter Selection 4a. Elevation Statics 4b. Refraction Statics

Pick First Breaks

5. Brute Stack 6. Velocity Analysis 7. Residual Statics 8. Dip Moveout (DMO) 9. PostStack Signal Enhancement 10. PostStack Migration

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Velocity Modeling


3

Preface

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Agenda

Agenda Day 1 Introductions, Course Outline, and Miscellaneous Topics ProMAX 2D Geometry - Manual • • • •

Input Data into the Spreadsheet CDP Binning Loading Geometry to Trace Headers QC Database Attributes

ProMAX 2D Geometry - Full Extraction •

Database File Extraction

ProMAX 2D Geometry - Extraction with Editing • • •

Database File Extraction Spreadsheet Completion and CDP Binning Loading Geometry to Trace Headers

Trace Editing using Trace Statistics and DBTools • • •

Running Trace Statistics Display Trace Statistics using DBTools Selecting Bad Traces with DBTools

• • • • • •

Directory Structure Program Execution Ordered Parameter Files Parameter Tables Disk Datasets Tape Datasets

System Overview

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1

Agenda

Day 2 Parameter Selection and Analysis • • • • • •

Parameter Table Picking Parameter Test IF/ENDIF Conditional Processing F-K Analysis and Filtering F-K Filtering Comparisons Interactive Spectral Analysis (ISA)

Elevation Static Corrections • • •

Elevation Statics Discussion Apply Elevation Statics Apply User Statics

• •

RMS Velocity Field ASCII Import Brute Stack with Elevation Statics

Brute Stack

Neural Network First Break Picking • •

Interactive NN First Break Training/Picking Batch Neural Network First Break Picking

Refraction Static Corrections • • • •

Refraction Statics Refraction Statics Calculation - coordinate based Apply Refraction Statics Stack with Refraction Statics

Stack Comparisons •

Compare Stacks

Velocity Analysis and the Volume Viewer • • •

2

Velocity Analysis Precompute Velocity Analysis Volume Viewer/Editor


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Agenda

Day 3 Residual Statics Corrections • • • •

Data Preparation for Input to Residual Statics Calculation of Residual Statics QC and Application of Residual Statics External Model Autostatics

Dip Moveout (DMO) • • •

Common Offset Binning DMO Final Stack

PostStack Signal Enhancement • •

F-X Decon, Dynamic S/N Filtering, and BLEND Trace Math

Velocity: QC, Editing, Modeling • •

Velocity Viewer/Point Editor Velocity Manipulation

PostStack Migration • • •

Poststack Migration Processes Tapering Poststack Migration

Additional Topics

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Agenda

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Chapter 1

Manual Geometry Assignment Geometry Assignment is designed to create the ProMAX Database Files and load header information into the trace headers of ProMAX data. The sequence of steps, or flows, depends upon available information. This chapter serves as an introduction to different approaches of geometry assignment. The Geometry Overview section in the Reference Manual and online helpfile provides further details of the geometry assignment process. Geometry is clearly one of the most important aspects of processing. These next three chapters are examples of a difficult, an easy, and a most common approach to geometry assignment.

Topics covered in this chapter: ❏ Chapter Goals ❏ Geometry Assignment Map ❏ Land Geometry ❏ View Shot Gathers ❏ Load Geometry in Spreadsheet and Database ❏ View Database Attributes ❏ Load Geometry to the Trace Headers ❏ Graphical Geometry QC ❏ Chapter Summary

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1-1

Chapter 1: Manual Geometry Assignment

Chapter Objectives

1. Geometry Assignment

Field Data

We are at step one, Geometry Assignment, of our processing workflow. Geometry is probably the longest and most difficult subject in the manual, as it is in a normal processing sequence. If we can get the geometry correct we are well on our way to having the best possible seismic data for the interpreter. Upon completion of this chapter you should:

1-2

•

Understand what the Ordered Parameter Files (OPF’s) represent

•

Edit the OPF’s via the Geometry Spreadsheet

•

View Trace Header values for Geometry Attributes

•

Import Observer Data into the Geometry Spreadsheet

•

QC and Edit Geometry via DBTools and XDB

•

Understand ProMAX Sign Conventions

•

Understand what a Pattern Represents

•

Understand the steps of Binning

•

Graphically QC Geometry with Farr Displays


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ProMAX Geometry Assignment Map All Possible Geometry Assignment Paths UKOOA O.B. Notes

Manual Input

ASCII

Field Data

UKOOA Import Spreadsheet Import

SEG-? Input

Database Import Seismic Data (ProMAX)

Geometry Spreadsheet

Extract Database Files Inline Geom Header Load

Ordered Parameter Files

Disk Data Output

Disk Data Output Inline Geom Header Load Valid Trace Numbers Overwrite Trace Headers Seismic Data

Seismic Data

(ProMAX)

(ProMAX)

Geometry assignment map for output to disk Landmark


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Geometry assignment path for this exercise ProMAX geometry assignment is designed to be both flexible and robust. The previous map, however, displays the complicated price we pay for that flexibility. The following map shows a simplified path that we will use for geometry assignment in this exercise.

Manual Geometry Assignment Path ASCII

O.B. Notes and Survey Information

Spreadsheet Import Manual Input

Field Data

SEG-Y Input


Inline Geom Header Load

Ordered Parameter Files Disk Data Output

Seismic Data (ProMAX)

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Land Geometry The 2D Land Geometry Spreadsheet is used to assign the geometry. The spreadsheet is an editor used to input/modify geometry information, residing in the ProMAX database. While you can manually key in data, the spreadsheet has options to import geometry information, such as source and receiver coordinates from ASCII files. If the input seismic data has pertinent geometry information in the trace headers, you can extract this information using the process Extract Database Files prior to working with the spreadsheet.

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View Shot Gathers First look at the data Before we get into the geometry assignment steps, let us look at the data that we will be using. First we will create a workspace by adding an Area and Line, then we will build a flow to display the raw shots. 1. From the Area menu add a new area. Give your area a descriptive name that has meaning to you. You might want to use your name in this case. 2. When the Line menu appears add a new line named “Watson Rise”. 3. Add the following flow.

Editing Flow: 1.1-View Shots Add

Delete

Execute

View

Exit

SEG-Y Input Type of storage to use: ------------------------------Disk Image Enter DISK file path name: ---------------------------------------------------/misc_files/2d/segy_0_value_headers ----Default the remaining parameters----

Automatic Gain Control ----Default all parameters for this process----

Trace Display Number of ENSEMBLES (line segments)/screen: -------2 ----Default the remaining parameters---4. Execute the flow. Use the Next Ensemble icon to move through all 20 shots for this line. Notice how the shot rolls onto the spread and that there is a discontinuity between channels 60 and 61.

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Load Geometry into the Spreadsheet and Database Description of Geometry for this line The following figure and table describe the acquisition geometry for the Watson Rise line. Pattern for Source 1 388.5

Channel 1 Station

Channel 1

120

449 450 451 452 453 . . . 505 506 507 508

387 388 389 390 391 392 393 394 . . . 446

392.5

Station

61

60

Pattern for Source 2 61

60

120

449 450 451 452 453 . . . 505 506 507 508

387 388 389 390 391 392 393 394 . . . 446

Pattern for Source 16 448.5

Channel 1 Station

60

388 389 390 391 392 393 394 395 . . . 447

61

120

450 451 452 453 454 . . . 506 507 508 509

20 Sources 120 Channels 55 ft. Receiver Interval 220 ft. Source Interval 2 Second Record Length 4 ms Sample Rate Dynamite Source

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1-7


Observer’s Report Group Int.=55

Shot Int.=220

Sample Int.=4 ms

Shot Loc.

Depth

Offset

Uphole Time

File no.

Chan 1

Chan 60

Chan. 61

Chan 120

388.5

2

93

0

22

387

446

449

508

392.5

3

93

0

20

387

446

449

508

396.5

4

93

50

20

387

446

449

508

400.5

5

93

0

23

387

446

449

508

404.5

6

93

15

18

387

446

449

508

408.5

7

93

0

24

387

446

449

508

412.5

8

93

0

20

387

446

449

508

416.5

9

93

0

19

387

446

449

508

420.5

10

93

0

17

387

446

449

508

424.5

11

93

0

20

387

446

449

508

428.5

12

93

0

22

387

446

449

508

431.5

13

93

0

19

387

446

449

508

436.5

14

93

0

19

387

446

449

508

440.5

15

93

0

20

387

446

449

508

444.5

16

93

0

21

387

446

449

508

448.5

17

93

0

23

388

447

450

509

452.5

18

93

0

22

392

451

454

513

456.5

19

93

0

20

396

455

458

517

458.5

22

93

0

20

398

457

460

519

464.5

23

93

0

20

404

463

466

525

Source. and Receiver Azimuth=90 degrees

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# of Chan=120

First Live Station=387


Last Live Station=525

Source Type = Shot, Units=ft

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Load Survey information to the spreadsheet In this exercise, you will assign geometry to the 2DTutorial dataset, Watson Rise, using the geometry spreadsheet. Two flows are required to accomplish this task. •

One flow will use the spreadsheet as an editor to automatically enter data to the database.

•

The second flow will load the geometry from the database to the trace headers.

The following spreadsheet guide is designed to help you assign geometry to the line you are processing in the class. It is by no means a complete description of all the capabilities. Please consult the Reference Manual for additional documentation. 1. Build the following flow :

Editing Flow: 1.2-Geometry Spreadsheet Add

Delete

Execute

View

Exit

2D Land Geometry Spreadsheet* 2. Execute the flow. The following 2D Land Geometry Assignment window appears:

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3. Select Setup, and fill out the menu with information from the observer’s log.

4. Select to assign midpoints by Matching pattern numbers using first live chan and station. 5. Enter source and receiver station interval, and leave the survey azimuth blank as it will be calculated later. 6. Enter the first and last live station numbers, select Yes to base source station numbers on receiver station numbers. Set source type to shot holes, and units are feet. You may also enlarge the font. 7. Select OK when you have entered all the information.

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Receivers spreadsheet 1. Select Receivers from the main spreadsheet window.

2. Mark all rows active by clicking MB3 on any of the numbered blocks under the Mark Block column. Marked blocks will turn a different color. Station, X, and Y are required in 2D geometry. 3. Insert enough rows to accommodate all receiver stations.

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•

Notice how many rows are present in your default spreadsheet (this number will vary depending on your font). There are 139 receiver stations in this survey, so you will need to insert rows into the default spreadsheet so that there are 139 rows.

•

Select Edit ➛ Insert, and insert the proper number of rows after the last marked block. Scroll to the bottom of the spreadsheet. If you created more than 139 blocks, mark the excess blocks by selecting block 140 with shift-MB2. This will select all blocks numbered 140 and greater. Select Edit ➛ Delete, and OK.

•

After you are certain that you have exactly 139 rows in the spreadsheet, mark all rows active with MB3 again, so that you can easily work with the entire spreadsheet.


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4. Fill in the appropriate values for the Station column. Mark the Station column by clicking MB1 on the Station column heading. From the menu bar select Edit ➛ Fill. This will bring up a popup menu. Enter 387 as a starting value and an increment of 1, then select OK. (An easier way to fill, is to click MB2 on the column header. This immediately causes the fill window to display.) 5. Follow the same procedure to fill the X coordinate, starting with 0 and incrementing by 55 and the Y coordinate with all 0s. This is an old land line, for which there were no XY values recorded. We will make up some fake XYs assuming that the line is straight, runs from West to East, and has a nominal receiver spacing of 55ft. 6. Import the Elevation values from an ASCII file. When working with ASCII file import there are three required steps:

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•

Open the ASCII file.

•

Define which numbers are in which columns.

•

Define which “cards” or rows to exclude from the import.


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7. Select File ➛ Import to import ASCII elevation values. Two windows will pop up allowing you to open an ASCII file.

1 3

4

2

In the Filter box of the File Import Selection window, enter the directory path (.../misc_files/2d/*) to your ASCII file, followed by /*, then select Filter. Select the ASCII filename and OK.

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8. Click Format and enter a name “recs” for a format description containing ASCII import column definition information. You will see a new window at this point.

Example ASCII Import Column Definition 9. In the “Column Import Definition” menu, click on a “parameter” attribute name, such as station, to define that column’s information Note that the selection turns white. NOTE: Look at the Mouse Button help descriptions at the bottom of the ASCII text window. Note that they reflect the MB1 “press and drag” operation for column definition

10. Highlight the columns that contain the numbers for the attribute you selected by holding down MB1 and dragging from left to right. 11. Repeat the previous two steps for elevations.

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Switch to “card” or row exclusion mode. 12. Now freeze the column definitions by clicking MB3 over the Parameter Column. 13. Click MB3 with the cursor positioned over the word “Station” or one of the other columnar attributes. NOTE: Look at the Mouse Button help descriptions at the bottom of the ASCII text window. Note that they now reflect block selection and deletion options.

14. Use MB1 to select the first row to exclude, and MB2 to select the last row to exclude, and press Ctrl-d. You will want to exclude title rows, blank rows, and rows with information that you do not want to import.

This writes a “Ignore Record for Import” message on all the defined rows. 15. There are also rows at the bottom of this file containing source information that need to be ignored. 16. From the main import menu, select Filter. This will check for any “cards” with inappropriate information, and allows you to interactively delete them.

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17. From the main import menu, select Apply. 18. Select Merge existing station values with matching station data and click OK.

This will add the elevations to your spreadsheet by matching the station numbers in the ASCII file with those already in the spreadsheet. The import windows will disappear. 19. Leave the Static column filled with zeros. 20. Make sure you have 139 stations defined in your receiver spreadsheet, and the information looks correct. 21. Select File ➛ Save. 22. Use the display capabilities in the spreadsheet to QC the imported elevations. • •

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Select View ➛ View All ➛ XYGraph from the menu bar. Click MB1 in the X column heading, and MB2 in the Elev column heading.


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•

After the XYGraph displays, select Color ➛ Bar from the menu.

•

Notice that the X Coordinate is displayed on the horizontal axis, the Elevations are on the vertical axis, and the Station numbers are represented by color. • Activate the Notebook icon. When this icon is activated, you can select a point in the XYGraph, and automatically jump to that line in the spreadsheet. • Select a point in the XYGraph with MB1. • This is a powerful QC tool. You can easily locate bad values in the XYGraph, and then edit the value in the spreadsheet. • Exit the XYGraph by selecting File ➛ Exit ➛ Confirm. 23. Use the File ➛ Exit pulldown menu to save the information and exit the receiver spreadsheet.

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Sources spreadsheet 1. Select Sources from the main spreadsheet window.

2. The Sources (SIN) spreadsheet appears. You must go through the same procedure as in the Receiver spreadsheet to make 20 rows in the spreadsheet to accommodate the 20 shots in this survey. 3. Fill the Station column. Start at 388, and increment by 4.

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•

Notice that you did not input 388.5 as the observers report states. This is because the spreadsheet will only accept integer numbers. You will specify this half station difference using the skid column later.

•

Also notice that the x, y, and z values updated. Because you told the spreadsheets that the source and receiver station numbers were linked, the Sources spreadsheet uses the x, y, and z values entered in the Receivers spreadsheet. Therefore, the source elevations are the elevations of the previous receiver location. In our case, you need to interpolate elevations between receiver locations. We will do this later from the Database tool.

•

Finally, you can see from the Observer’s Report that a few of the shot station numbers do not increment by four. Fix the station numbers for those shots in the spreadsheet now. Notice that the x, y, and z values change as you change the Station number.


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4. Fill the Source column to match the Station column. Source numbers are user defined and could be set to any value. Some people prefer to use this number as a counter, and will fill the column starting with 1, and incrementing by 1. 5. Fill the FFID column starting at 2, and incrementing by 1. Notice from the Observer’s Report that there is a gap in the FFID numbers between 19, and 22. Enter this gap in the spreadsheet. 6. Enter the offsets of 50 and 15 for the appropriate stations in the Offset column of the spreadsheet. Instead of North, South, East, and West, ProMAX uses the following sign convention:

Offset Sign Convention (-) Negative Offset

Direction of Increasing Station Numbers (Source Azimuth)

Shot (x,y)

(+) Positive Offset 7. Scroll the spreadsheet to the right, and fill the Skid column with 27.5. This is where you specify the inline offsets that move the shots from integer station numbers to half station numbers. ProMAX uses the following sign convention:

Skid Sign Convention Shot (x,y) (-) Negative Skid Toward lower stations

Source Azimuth (Direction of Increasing Station Numbers)

(+) Positive Skid Toward higher stations

8. Import the Uphole time and Hole Depth information from the ASCII file using the same procedure as described in the Receivers spreadsheet.

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Patterns spreadsheet At this point, leave the Sources spreadsheet, and fill in the patterns spreadsheet. After filling out the pattern, you will finish the remainder of the Sources spreadsheet. There are two methods of defining patterns. If the shot gap stays in a constant location, use the Static Gap Method. This method is only available if you chose to assign midpoints by matching pattern numbers using first live chan and station in the setup menu. If your shot gap changes locations, use the Dynamic Gap Method. This method is available if you chose either to assign midpoints by matching pattern numbers using first live chan and station, or matching pattern number using pattern station shift. Static Gap Method:

Static Gap Size and Gap Chan Definition Stn 387

Stn 446

Stn 449

Stn 508

Ch 1

Ch 60

Ch 61

Chn 120

Shot Sources Spreadsheet Gap Chan=0 and Gap Size=0 Patterns Spreadsheet Pat

Min Max/Gap Chan Rcvr Chan Chan Inc MinChan

Rcvr Rcvr MaxChan Inc

1

1

60

1

387

446

1

1

61

120

1

449

508

1

In this method gap size and location is specified in the Patterns spreadsheet. In the Sources and Receivers spreadsheets, each shot or receiver used one row of the spreadsheet. In the Pattern spreadsheets, one pattern can use as many rows of the spreadsheet as necessary.

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Dynamic Gap Method:

Dynamic Gap Size and Gap Chan Definition Stn 387

Stn 446

Stn 449

Stn 508

Ch 1

Ch 60

Ch 61

Chn 120

Shot Sources Spreadsheet Gap Chan=60 and Gap Size=2

Patterns Spreadsheet Pat 1

Min Max/Gap Chan Rcvr Rcvr Chan Chan Inc MinChan MaxChan 1

120

1

387

506

Rcvr Inc 1

In this method, you specify the first and last channels and stations in the Pattern spreadsheet. The shot gap size and location is specified in the Sources spreadsheet. 1. Select Patterns from the main spreadsheet window. You will now define your cable configuration, that is the relationship of channels to receiver locations. When you enter the Pattern spreadsheet for the first time, a window will appear that asks you to enter some information about the number of channels.

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2. Enter 120 for the maximum number of channels, select Constant number of channels/record, then OK. These values will be used for error checking when you exit the patterns spreadsheet. If you define your pattern for more or less than 120 channels, the error column in the spreadsheet fills with ***** and will force you to correct your error before exiting the Patterns spreadsheet. If you need to edit the number of channels later select Edit ➛ NChans. 3. Since our shot gap is in a constant location, fill in the Pattern spreadsheet using the Static Gap Method.

4. Select File ➛ Exit to save the information, and exit the Patterns spreadsheet. 5. Return to the Sources spreadsheet, and reorder the columns so that the pattern description columns will be displayed next to the Station column. • • •

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With the default column order, you cannot see the Station column after scrolling the spreadsheet to the right. To change the displayed order of the columns select Setup ➛ Order the menu bar. Follow the mouse button help, and click MB1 in the column heading for Station, Pattern, Num Chn, Shot Fold, 1st Live Sta, 1st Live Chn, Gap Chan Dlt, Gap Size Dlt, and Static.


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•

Finish the selection by clicking MB2 in the column heading for Static. The columns you selected will now move to the left of the spreadsheet as pictured below.

6. Fill in the Pattern column with ones. This tells the Sources spreadsheet to use pattern number 1 from the Patterns spreadsheet. Recall that you only defined one pattern for this survey. 7. Fill the Num Chn column with 120. This specifies that there are 120 channels for each shot on this survey. 8. You cannot edit the Shot Fold* column. This column will be calculated and filled when you assign midpoints later in the exercise. 9. Fill the 1st Live Sta column with information from the Observer’s Report. Notice that the first live station for this survey is 387 for all but the last five shots. 10. Fill the 1st Live Chn column with ones. This specifies that the first live channel for each shot is 1.

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11. Leave the Gap Chan Dlt column blank, and leave the Gap Size Dlt column filled with zeros. The information entered in these two columns depends on which method you chose for entering the pattern in the Patterns spreadsheet. Since you chose the Static Gap method, you have already specified the shot gap’s size and location in the pattern spreadsheet, and do not need to specify it here. If you had chosen the Dynamic Gap method, you would enter the shot gap’s location in Gap Chan Dlt, and the shot gap’s size in Gap Size Dlt. 12. Leave the Static column filled with zeros. If the information were available, you could enter any previously calculated datum static values in this column. 13. Select File ➛ Save.

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14. Display a basemap of both the shots and receivers, and measure the station azimuth. •

Select View ➛ View All ➛ Basemap

2

1

•

•

•

Notice that the receivers are displayed as a plus ‘+’ sign, and the shots are displayed as an asterisk ‘*’. Also notice the two offset shots. To get a better view of the shots select Display ➛ Sources Control Points ➛ White. Now select the Cross Domain icon to allow you to measure the station azimuth. Press MB3 (notice the mouse button help) near the first shot on the line, and drag the mouse to the end of the line. While still holding down MB3, make note of the azimuth (Azi) readout in the mouse button help. For this line, the azimuth should be 90 degrees. Select File ➛ Exit ➛ Confirm in the XYGraph display.

15. From the main Land Geometry window, select Setup, and enter 90 for the Nominal Survey Azimuth. Select OK to save the information an close the window. 16. Make sure that you only have 20 rows in the Sources spreadsheet. 17. Exit the Sources spreadsheet by selecting File ➛ Exit.

TraceQC spreadsheet 1. The information in the traces spreadsheet will be calculated by the binning process. You can not edit this information.

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Binning 1. Select Bin from the main window. There are three steps to be completed in order: •

Assign Midpoints

•

One of the several Binning options

•

Finalize database

2. Select Assign midpoints by: Matching pattern numbers using first live chan and station, and then select OK. In this case the Assignment step is performing the following calculations:

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•

Computes the SIN and SRF for each trace and populates the TRC OPF.

•

Computes the Shot to Receiver Offset (Distance.)

•

Computes the Midpoint coordinate between the shot and receiver.

•

Computes the Shot to Receiver Azimuth.


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An Assignment Warning window will pop up warning that some or all of the data in the Trace spreadsheet will be overwritten. Click Proceed.

A number of progress windows will flash on the screen as this step runs. A final Status window appears notifying that you “Successfully completed geometry assignment.” Click Ok. If this step fails, you have an error in your spreadsheets somewhere. Not much help is given to you, but, the problems are usually related to the spread and/or pattern definitions. 3. Choose Binning with a method of “Add source and receiver stations, user defined OFB parameters”. Fill in the parameters in the bottom of the window, and select OK.

This step calculates CDP numbers for each trace by adding source and receiver numbers. The first CDP will be 775 (387 + 388), the last CDP will be 989 (464 + 525). This step also creates the OFB ordered parameter file. 4. Select OK in the final status window when successfully completed.

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•

Select Finalize Database, then click OK.

• •

Clcik OK in the final status window when successfully completed. Click Cancel in the Land 2D Binning window to exit the binning window.

5. Open the Receivers spreadsheet. 6. The binning step filled in the data in the Traces spreadsheet. You can QC this information from a basemap. From the Receivers spreadsheet, select View ➛ View All ➛ Basemap.

7. Highlight the Cross Domain icon. Click and hold MB1 near a source location to see which receivers contributed to that shot. Drag your mouse to the end of the line to see the receiver range change. Click and hold MB2 near a receiver location to see which shots contributed to that receiver.

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8. Select File ➛ Exit ➛ Confirm to exit the basemap display. 9. Select File ➛ Exit from the Receivers spreadsheet. 10. Select File ➛ Exit from the main spreadsheet window.

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View Database Attributes 1. Select Exit from the Flow Editing menu of the User Interface. In the Flows menu select Database. The DBTools window allows basic viewing and editing of the 8 orders (spreadsheets) of the database: LIN, TRC, SRF, SIN, CDP, CHN, OFB, PAT. The contents of the OPF files are summarized in Table 1: Table 1: Organization of Ordered Parameter Files

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LIN (Line)

Contains constant line information, such as final datum, type of units, source type, total number of shots.

TRC (Trace)

Contains information varying by trace, such as FB Picks, trim statics, source-receiver offsets.

SRF (Surface location)

Contains information varying by surface receiver location, such as surface location x,y coordinates, surface location elevations, surface location statics, number of traces received at each surface location, and receiver fold.

SIN (Source Index #)

Contains information varying by source point, such as source x,y coordinates, source elevations, source uphole times, nearest surface location to source, source statics.

CDP (Common Depth Point)

Contains information varying by CDP location, such as CDP x,y coordinates, CDP elevation, CDP fold, nearest surface location.

CHN (Channel)

Contains information varying by channel number, such as channel gain constants and channel statics.

OFB (Offset Bin)

Contains information varying by offset bin number, such as surface consistent amplitude analysis. OFB is created when certain processes are run, such as surface consistent amplitude analysis.

PAT (Pattern)

Contains information describing the recording patterns.


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To graphically QC and edit the database select Database ➛ XDB Database Display.

2. From the XDB window select Database ➛ Get. 3. Project SRF elevations into SIN. By projecting the SRF elevations into the SIN elevations you will correct for the “skid” of the elevation being on the half station. For example, compare the land geometry database for receiver and shot elevations at station number 428. You see that they both read an elevation of 842 feet. Looking at the elevation for station number 429, however, you see an elevation of 845.3. From the observer notes and geometry assignment you remember that the shot is actually at station location 428.5, and therefore at an elevation around 843.6. To fix the source elevations go to the attribute selection window, and click on the SIN order, then GEOMETRY ELEV. After this is displayed, click on the SRF order, then GEOMETRY ELEV.

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While SRF Geometry Elev is highlighted, select New ➛ Project ➛ Sin.

In the popup window, type in “ELEV” for the new attribute name, then click on OK. Your new attribute will be plotted. Notice how station 428 has been corrected.

4. To save this new attribute, select Database ➛ Save. In the popup list, click on the name of the new attribute, SIN:GEOMETRY:ELEV. Select OK from the overwrite warning and from the acknowledgment window, then Exit the Database tool. 5. You can verify the source elevation was corrected by going back into the source spreadsheet. 1-32


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6. There are several useful QC plots that can be made from the DBTools or from the XDB Database Display. Some examples are listed below.

XDB CDP: GEOMETRY: FOLD (DBTools: double click on FOLD from CDP tab)

• Used to check CDP fold for variations. XDB SIN: GEOMETRY: NCHANS (DBTools: double click on NCHANS from SIN tab)

• Used to check for variations in number of channels per source. XDB 3D XYGraph: TRC:SRF, SIN, OFFSET (DBTools: View ➛ Predefined ➛ SIN-SRF-offset)

• Used to check the live receivers for each shot. XDB 3D XYGraph: TRC: OFFSET, CDP, SIN (DBTools: View ➛ Predefined ➛ offset-CDP-SIN)

• Used to check offset distribution in CDPs for velocity analysis placement and DMO binning.

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Load Geometry to the Trace Headers 1. Build the following flow:

Editing Flow: 1.3-Inline Header Load Add

Delete

Execute

View

Exit

SEG-Y Input Type of storage to use: ------------------------------Disk Image Enter DISK file path name: ---------------------------------------------------/misc_files/2d/segy_0_value_headers ----Default the rest of the parameters----

Inline Geom Header Load Primary header to match database: ---------------------FFID Secondary header to match database: ----------------None Match by valid trace number?: -------------------------------No Drop traces with NULL CDP headers?: --------------------No Drop traces with NULL receiver headers: ----------------No Verbose diagnostics?: --------------------------------------------No

Disk Data Output Output Dataset Filename: -----------Shots-with geometry New, or Existing, File?: ----------------------------------------New Record length to output: ------------------------------------------0. Trace sample format: ----------------------------------------16 bit Skip primary disk storage?: -----------------------------------No 2. In SEG-Y Input, select Disk Image and enter the path given to you by your instructor for the raw shot dataset. 3. In Inline Geom Header Load, select FFID as the Primary and None as the Secondary headers to match the database. A trace is excluded from further processing if it is not described in the geometry. 4. In Disk Data Output, enter a name for a new output dataset. 5. Execute the flow.

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6. Edit your flow “1.1-View Shots” to check the trace headers of your dataset.

Editing Flow: 1.1-View Shots Add

Delete

Execute

View

Exit

Disk Data Input Select dataset: ----------------------------Shots-with geometry Trace read option: -----------------------------------------------Sort Select Primary trace header entry:--------------SIN Select secondary trace header entry:---OFFSET Select order list for dataset----------------------------------*:*


Trace Display Number of ENSEMBLES (line segments)/screen: -------2 Do you want to use variable trace spacing?------------Yes ----Default the remaining parameters---7. Change the sort order as shown in the flow. 8. In the trace display use variable trace spacing to highlight the source gap in the shots. 9. While viewing the data in Trace Display, use the dx/dt icon to measure the first break velocity of a few shots. Write down this value as it will be used later in the Graphical Geometry QC section.

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Graphical Geometry QC Graphical Geometry QC* is a macro designed to quickly find mistakes in your geometry assignment. The process applies linear moveout to shots and splices multiple shots together in a vertical fashion based on receiver surface station. This display is often referred to as a Farr display.

Shot

LMO Shot

Farr Display

t

Mistakes in geometry assignment show up as obvious anomalies, such as the last panel in the Farr display. In other cases, you may find that your first break data is far from being flat, with your onset of energy coming in much later with longer offsets. Another indicator is when all first breaks tend to line up at 100 ms, but for one shot they line up at 200 ms. Check the geometry in these areas.

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QC your Geometry Assignment 1. Build the following flow:

Editing Flow: 1.4-Graphical Geometry QC Add

Delete

Execute

View

Exit

Graphical Geometry QC* Select input trace data file: ----------Shots-with geometry SIN and SOU_SLOC range of dataset: ---------------------*:* dB/sec gain value to apply: ------------------------------------6. Specify LMO velocity function(s): -------------------1:0:8000 Additional bulk shift: -------------------------------------------100 Maximum time for each spliced trace: -------------------400 Maximum number of shots (traces) to vertically splice: --------------------------------------------------------------------4 Resulting maximum number of traces per screen: --139 Select display device: -------------------------------This Screen Scalar for sample value multiplication: ---------------------1. Trace scaling option: -----------------------------------Individual 2. Select your input dataset name. 3. Specify the LMO velocity function. An editor appears for specifying a velocity function; 1:0:8000 should work fine. In this example, we will enter one LMO velocity for the entire dataset. Therefore, we only need to specify one primary value (1) for the first shot, one absolute offset value (0 ft), and one velocity (8000 ft/sec). 4. Enter 4 for the Maximum number of shots to vertically splice. For a quick check of all the data, you could input all 20 shots instead of 4. 5. Set the maximum number of traces per screen to 139. This will cover the full spread 120 channels plus 5 extra shots 4 channels apart. 6. Select Individual for Trace scaling option, if you have any spikes in your data. Landmark


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The spikes will bias the entire screen scaling scalar and cause many of the traces to appear having zero amplitude. 7. Execute the flow using MB2. This process uses Screen Display for displaying your data, instead of Trace Display. When you execute with MB2, the data is automatically displayed. Use the Header tool icon to check vertically constant SRF_SLOC trace header values. Note what shot you are on. Look for anomalies, such as a back spread shifted 50-100 ms higher than a front spread, or severely undercorrected or overcorrected shots. Also, any reversed traces should remain at a constant surface location. NOTE: If you find any mistakes you must go back to the spreadsheets and correct them. Then you will need to rebin. Finally, to get the proper trace headers loaded you need to rerun the inline header load flow.

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Chapter Summary Upon completion of this chapter you should be able to answer the following questions:

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•

Do you understand what the Ordered Parameter Files represent

•

Can you edit the OPF’s via the Geometry Spreadsheet

•

Can you view Trace Header values for Geometry Attributes

•

Can you import Observer Data into the Geometry Spreadsheet

•

Can you QC and edit Geometry via DBTools and XDB

•

Do you understand ProMAX Sign Conventions

•

Do you understand what a Pattern Represents

•

Do you understand the steps of Binning

•

Can you graphically QC Geometry with Farr Displays


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Chapter 2

Full Extraction Geometry Assignment Geometry Assignment is designed to create the ProMAX Database Files and load header information into the trace headers of ProMAX data. The sequence of steps, or flows, depends upon available information. This chapter serves as a simplistic alternative approach to Chapter 1 for geometry assignment. The Geometry Overview section in the Reference Manual and online helpfile provides further details of the geometry assignment process. In this chapter we will cover the steps necessary to assign geometry to a line if all of the required information is present in the trace headers of the input dataset. This approach can be very quick and effective for reprocessing data.

Topics covered in this chapter: ❏ Database file extraction

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2-1

Chapter 2: Full Extraction Geometry Assignment

Chapter Objectives


Field Data

This is an alternative method of completing step one, Geometry Assignment, of our processing workflow. For reprocessing data this method can be very fast and efficient. Upon completion of this chapter you should:

2-2

•

Understand how to Remap SEG-Y headers

•

Create Database Files from Extraction


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ProMAX Geometry Assignment Map Geometry assignment path for this exercise The following map shows the path that we will use for geometry assignment in this exercise.

Full Extraction

Field Data

SEG-Y Input

Seismic Data (ProMAX) Extract Database Files

Disk Data Output

Ordered Parameter Parameter Ordered Files Files


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Extract Database Files Method Database file extraction In this exercise you will assign geometry to the 2D user tutorial dataset, Watson Rise. This only involves extracting geometry information from the input SEG-Y trace headers and outputting the trace data in ProMAX format. If the input SEG-Y headers are fully populated then you are done and the data should be ready to be processed without touching the spreadsheet or having to run an Inline Geometry Header Load. A fully populated trace header must have the following valid values: • • •

Shot X Y and Station Receiver X Y and Station CDP X Y and CDP number

1. Create a new Line. Make sure you are in your Area. Go to the Line level of the ProMAX User Interface and click on Add. Type in the line name, “Database Full Extraction”, and then press Enter.

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2. Build the following flow:

Editing Flow: 1.1-Extract Database Files Add

Delete

Execute

View

Exit

SEG-Y Input Type of storage to use: ----------------------------- Disk Image Enter DISK file path name: ---------------------------------------------------------------------------/misc_files/2d/segy2d_remap Remap SEGY header values?: -------------------------------Yes Input/override trace header entries: --------------------------sou_sloc,,4I,,181/srf_sloc,,4I,,185/ cdp_sloc,,4I,,189/cdp_x,,4I,,193/ cdp_y,,4I,,197/cdp_elev,,4I,,201/

Extract Database Files Is this a 3D survey: ------------------------------------------------No Data Type: --------------------------------------------------------LAND Source index method: -----------------------------------------FFID Receiver index method: ------------------------------STATIONS Mode of operation: ----------------------------------OVERWRITE Pre-geometry extraction?: ---------------------------------------No Extract CDP binning?: -------------------------------------------Yes Minimum cdp bin in survey: ----------------------775 Calculate trace midpoints coordinates?: -----------------Yes Extract OFB binning?: --------------------------------------------No

Disk Data Output Output Dataset Filename: --------”raw shots w/ extract” New, or Existing, File?: ----------------------------------------New Record length to output: ------------------------------------------0. Trace sample format: ----------------------------------------16 bit Skip primary disk Storage?: -----------------------------------No 3. In SEG-Y Input, select Yes for Remap SEGY header values. This input SEG-Y file already has most geometry information in its trace headers. The remap option allows information in non-standard or extended header locations to be accessed and assigned to a ProMAX header word. The ProMAX spreadsheets use the values for SOU_SLOC, SRF_SLOC, CDP_SLOC, CDP_X, CDP_Y, and Landmark


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CDP_ELEV. These are not standard SEG-Y headers, and therefore must be stored in the extended header section of the SEG-Y data. Choose the remap option to read in these values. 4. In Extract Database Files, select No for Pre-Geometry database initialization. Enter FFID to Source index method. Select Stations for Receiver Index Method. However, coordinates can be selected since the SEGY file contains both station numbers and x,y values. Select No for Pre-Geometry initialization because you have receiver information in the input SEG-Y headers and thus the SRF OPF directory will be properly built.

NOTE: If no receiver information exists in the input trace headers and you answer no to PreGeometry Initialization, the job will fail. If no receiver information exists in the input trace headers and you answer Yes to Pre-Geometry Initialization, the SRF OPF will be built anyway. You must then enter the missing information into the Receivers spreadsheet, as well as define pattern information in the Sources and Patterns spreadsheets.

5. Output a new ProMAX disk dataset. 6. Execute the flow. 7. Now confirm that the SEG-Y headers were complete by doing some QC plotting from the Database to check that the trace, receiver, shot, and CDP OPF files look proper. 8. Did you notice how the receivers (SRF GEOMETRY X_COORD) were out of order? 9. Do you believe the extracted geometry?

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Can you Remap SEG-Y headers

•

Can you Create Database Files from Extraction


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Chapter 3

Full Extraction Geometry Assignment with Editing Geometry Assignment is designed to create the ProMAX Database Files and load header information into the trace headers of ProMAX data. The sequence of steps, or flows, depends upon available information. This chapter serves as the most likely alternative approach to Chapters 1 and 2 for geometry assignment. The Geometry Overview section in the Reference Manual and online helpfile provides further details of the geometry assignment process. In this chapter we will cover the steps necessary to assign geometry to a line if some of the required information is present in the trace headers of the input dataset.

Topics covered in this chapter: ❏ ProMAX Geometry Assignment Map ❏ Database file extraction ❏ Spreadsheet completion and binning ❏ Inline Geometry Header Load

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Chapter 3: Full Extraction Geometry Assignment with Editing

Chapter Goals


Field Data

This is another alternative method of completing step one, Geometry Assignment, of our processing workflow. For reprocessing data this method can be fast and efficient. Upon completion of this chapter you should:

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•

Better Understand OPF/SpreadSheet operations

•

Learn How to Finalize the Database

•

Load Geometry to Trace Headers


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ProMAX Geometry Assignment Map Geometry assignment path for this exercise The following map shows the path that we will use for geometry assignment in this exercise.

Extraction + Editing

Field Data

SEG-Y Input


Geometry Geometry Spreadsheet Spreadsheet

Extract Database Files

Ordered Parameter Parameter Ordered Files Files

Disk Data Output

Inline Geom Header Load Valid Trace Numbers Overwrite Trace Headers Seismic Data (ProMAX)

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Extract Database Files Method Database file extraction In this exercise you will assign geometry to the 2D user tutorial dataset, Watson Rise. You will first extract geometry information from the input SEG-Y trace headers. You will then need to update and add information using the geometry spreadsheet. You will also have to do the CDP binning. Three flows are required to accomplish this task: •

Flow 1 reads a SEG-Y file, extracts information from the headers, writes it to the database/spreadsheets, and outputs a ProMAX disk dataset.

•

Flow 2 uses the spreadsheet as an editor to update/add values, and to automatically enter the information into the database.

•

Flow 3 loads the geometry information to the trace headers of the ProMAX dataset.

The following spreadsheet guide is designed to help you assign geometry to the line you are processing in the class. It is by no means a complete description of all the capabilities. Please consult the Reference Manual for additional documentation. 1. Create a new Line. Make sure you are in your Area. Go to the Line level of the ProMAX User Interface and click on Add. Type in the line name, “Database Partial Extraction”, and then press Enter.

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Editing Flow: 1.1-Extract Database Files Add

Delete

Execute

View

Exit

SEG-Y Input Type of storage to use: ----------------------------- Disk Image Enter DISK file path name: ---------------------------------------------------------------------------/misc_files/2d/segy2d_remap Remap SEGY header values?: -------------------------------Yes Input/override trace header entries: -------------------------------------------sou_sloc,,4I,,181/srf_sloc,,4I,,185/

Extract Database Files Is this a 3D survey: ------------------------------------------------No Data Type: --------------------------------------------------------LAND Source index method: -----------------------------------------FFID Receiver index method: ------------------------------STATIONS Mode of operation: ----------------------------------OVERWRITE Pre-geometry extraction?: ---------------------------------------No Extract CDP binning?: -------------------------------------------Yes Minimum cdp bin in survey: ----------------------775 Calculate trace midpoints coordinates?: -----------------Yes Extract OFB binning?: --------------------------------------------No

Disk Data Output Output Dataset Filename: --------”raw shots w/ extract” New, or Existing, File?: ----------------------------------------New Record length to output: ------------------------------------------0. Trace sample format: ----------------------------------------16 bit Skip primary disk Storage?: -----------------------------------No 3. In SEG-Y Input, select Yes for Remap SEGY header values. This input SEG-Y file already has most geometry information in its trace headers. The remap option allows information in non-standard or extended header locations to be accessed and assigned to a ProMAX header word. The ProMAX spreadsheets use the values for SOU_SLOC and SRF_SLOC These are not standard SEG-Y headers, and therefore must be stored in the extended header section of the SEG-Y data. Choose the remap option to read in these values. Landmark


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4. In Extract Database Files, select No for Pre-Geometry database initialization. Enter FFID to Source index method. Select Stations for Receiver Index Method. However, coordinates can be selected since the SEGY file contains both station numbers and x,y values. Select No for Pre-Geometry initialization because you have receiver information in the input SEG-Y headers and thus the SRF OPF directory will be properly built.

NOTE: If no receiver information exists in the input trace headers and you answer no to PreGeometry Initialization, the job will fail. If no receiver information exists in the input trace headers and you answer Yes to Pre-Geometry Initialization, the SRF OPF will be built anyway. You must then enter the missing information into the Receivers spreadsheet, as well as define pattern information in the Sources and Patterns spreadsheets.

5. Output a new ProMAX disk dataset. This disk dataset is used in Flow 03 as input to the Inline Geom Header Load. 6. Execute the flow.

Spreadsheet completion and binning 1. Since some of the OPF files were not complete in the Database, you will need to build the following flow:

Editing Flow: 1.2-Geometry Spreadsheet Add

Delete

Execute

View

Exit

2D Land Geometry Spreadsheet* 2. Execute the flow.

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3. Select Setup from the main window.

Since you used Extract Database Files, the default option in setup is to Assign midpoints by existing index number mappings in the TRC. Reset the units to feet, leave the rest of the Setup window blank and select OK. 4. Select Receivers from the main window. All of this information should be correct. You may notice that some of the receivers are not in sequential order. You can sort these by selecting Setup ➛ Sort ➛ Ascending. Choose OK in the warning window that appears, and then select the Station column with MB2. This will sort the spreadsheet by ascending station number. Check for incorrect information, and select File ➛ Exit. Choose Proceed and then OK to the following messages.

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5. Select Sources. All of this information should be correct. Check for incorrect information, and select File ➛ Exit. 6. The Patterns spreadsheet option should be grayed out and not functional. The Patterns spreadsheet and the pattern related columns in the Sources spreadsheet are deactivated when you select Assign midpoints by existing index number mappings in the setup menu. If Assign midpoints by pattern number in the source and pattern spreadsheets is selected, the pattern columns in the Sources spreadsheet and the Patterns spreadsheet would have to be completed. 7. Select Bin.

NOTE: You must execute all three options available in this window. Each of these options may be time consuming in the case of 3D data, so they are separated out in this menu.

Select Assign midpoints by existing index number mappings in the TRC. Click OK, then select Proceed in the warning window.

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Select only one of the three Bin midpoints options. In this case, select Using previously assigned CDP numbers, user defined OFB parameters, since our input SEGY trace headers included CDP numbers. Use a Binning bias of 0 and an offset bin center increment of 55. Click OK. Select OK when successfully completed. 8. Select Finalize Database, then OK. This step fills in the LIN order

of the database with the final survey information. Click OK in the Status window when successfully completed. Click Cancel in the Land 2D Binning window to exit Bin.

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9. Select File ➛ Exit from the main Geometry window. 10. Exit the current flow. From the Flows window, access the database with the Database global command option, and check various attributes for correctness.

Load Geometry to the trace headers 1. Build the following flow:

Editing Flow: 1.3-Header Load Add

Delete

Execute

View

Exit

Disk Data Input Read data from other lines/surveys: ----------------------No Select Dataset: -------------------------”raw shots w/extract” Trace read option: --------------------------------------------Get All Read the data multiple times?: -------------------------------No Process trace headers only?: ---------------------------------Yes Override input data’s sample interval: --------------------No

Inline Geom Header Load Match by valid trace number?: ------------------------------Yes Drop traces with NULL CDP headers?: --------------------No Drop traces with NULL receiver headers?: ---------------No Verbose Diagnostics?: --------------------------------------------No

Disk Data Output Output Dataset Filename: ---------”raw shots w/extract” New, or Existing, File?: --------------------------------Overwrite Record length to output: ------------------------------------------0. Skip primary disk Storage?: -----------------------------------No 2. In Disk Data Input, select Yes to Process trace headers only. We will write the geometry information to the trace headers without reading the input traces. This dataset was written by ProMAX after using Extract Database Files, the TRC (trace flag) is valid. (If the TRC flag is not set to valid, you cannot process trace headers only).

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All traces in the dataset are described in the geometry. If there are any missing traces in the input file, the job will fail. 3. In Inline Geom Header Load, select Yes to Match by valid trace number. (There will be no Primary or Secondary headers listed.) The Inline Geom Header Load uses the valid trace number found on each trace of each ensemble to assign geometry. 4. In Disk Data Output, select Overwrite the input dataset. Overwrite allows us to process and overwrite only the trace header files (HDRs.) If the existing HDR files are not large enough to accept the data to write out, you must: •

Change Process trace headers only in Disk Data Input to No.

•

Change Overwrite to New in Disk Data Output.

•

Name a new ProMAX disk dataset name in Disk Data Output.

5. Execute the flow. 6. Create a simple display flow to check the trace headers of your dataset.

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•

Are you confident in OPF/SpreadSheet operations

•

What does it mean to “Finalize the Database”

•

Can you Load Geometry to Trace Headers


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Chapter 4

Trace Editing using Trace Statistics and DBTools In this chapter you will see how DBTools can be used to select which traces are sent to Trace Display for visual trace editing. You will run the Trace Statistics process to generate some values computed from the trace data that can be used to isolate “bad” traces. You will then only send the shots that contain these “bad” traces to Trace Display to visually edit these “bad” traces. This chapter will serve as your introduction to the real power the DBTools program.

Topics covered in this chapter: ❏ Picking a time window to use for Statistical Analysis ❏ Running the Trace Statistics Process ❏ Displaying the Statistics using DBTools ❏ Selecting the data to be viewed in Trace Display graphically using the DBTools displays. ❏ Focusing on a range of data on the Histogram

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Chapter 4: Trace Editing using Trace Statistics and DBTools

Chapter Objectives

2. Trace Editing

In this chapter you learn some of the power of DBTools using it to isolate bad traces via Trace Statistics. Upon completion of this chapter you should:

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•

Understand how to run Trace Statistics

•

Be functional at using DBTools

•

Understand how the Pointing Dispatcher communicates between processes


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Picking a Time Window for Statistical Analysis 1. Build the following flow to display a shot record:

Editing Flow: 2.1-Edit by Trace Stats Add

Delete

Execute

View

Exit

Disk Data Input Select dataset: --------------------------Shots - with geometry ----Default all other parameters----

Trace Display ----Default all parameters---2. Execute the flow. 3. We first need to pick a time gate that will be used by the Trace Statistics process. On the first shot select Picking ➛ Pick Miscellaneous Time Gate... “Trace Stats Gate” by AOFFSET.

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Pick the top of the gate following the first break times. Use MB3 to add “NEW LAYER” for the bottom gate. Track the end of the reflection data in this case, near 2 seconds:

Time Gate Top

Time Gate Bottom

When you are done picking choose File Exit/Stop Flow. Select Yes to save edits before exiting.

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Running the Trace Statistics Process 1. Edit the existing flow.

Editing Flow: 2.1-edit by trace stats Add

Delete

Execute

View

Exit

Disk Data Input Select dataset: -----------------------------shots - w/ geometry ----Default all other parameters----

Trace Statistics Types of trace statistics to compute --------------- select all Use first breaks or time gates?-------------------TIME GATE Time gate reference----------------------------------------- Time 0 Get analysis gates from the DB?--------------------------- Yes Select time gate parameter file----------- Trace Stats Gate Form of statistical output------------ Database & Headers

>Trace Display< 2. Execute the flow. Trace statistics is run to write the statistical attribute values to the database.

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Displaying the Statistics using DBTools 1. Edit the existing flow.

Editing Flow: 2.1-edit by trace stats Add

Delete

Execute

View

Exit

>Disk Data Input< >Trace Statistics< Disk Data Input Select dataset: -----------------------------shots - w/ geometry Trace Read Option -----------------------------------------------Sort Interactive Data Access ----------------------------------------Yes Primary sort key ----------------------- Source index number Secondary sort key ---------------------------------------------none Sort order ---------------------------------------------------------------*/ ----Default all other parameters----

Database/Header Transfer Direction of Transfer: Load TO header FROM database Number of parameters -------------------------------------------- 4 First DB parameter ----------- TRC TRCSTATS PRE_FB_A First Header ----------------------------------------------PRE_FB_A Second DB parameter ------- TRC TRCSTATS TRC_AMPL Second Header ---------------------------------------- TRC_AMPL Third DB parameter ----------- TRC TRCSTATS T_SPIKES Third Header --------------------------------------------- T_SPIKES Fourth DB parameter ------ TRC TRCSTATS AMPDECAY Fourth Header ---------------------------------------- AMPDECAY

Trace Display ----Default all parameters---2. Use Database/Header Transfer to selectively move the values of interest to the headers. You will need to “User Define” the trace header words. 3. Execute this flow and wait for the display.

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You should get the IDA window and the trace display window. Make sure IDA is working by using the forward and reverse arrows. 4. Add a header plot of the TRC_AMPL in the Trace Display: View ➛ Header Plot ➛ Configure ➛ TRC_AMPL. 5. Leave the Trace Display running, but, exit from the flow menus and press Database on the User Interface. The main DBTools window will appear.

6. Generate a pre-defined Source Fold map. Use the View ➛ Predefined ➛ Source fold map pull down menu.

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Background and Color ➛ Monochrome and Color ➛ Edit pull downs respectively. 7. Because of the dynamic range of the data large amplitude spikes obscure the rest of the data. Lets attack this problem by taking the log of the trace amplitude Edit ➛ Attribute ➛ Apply a Function.

8. Lets call the new attribute “LOG_AMP” with an infotype of “TRCSTATS”. Select OK when done.

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9. Use the View ➛ Summary Statistics... pull down menu to generate a “Summary Statistics” plot of OFFSET, SIN, SRF, and the trace statistics: TRC_AMPL, LOG_AMP, T_SPIKES, and AMP_DECAY from the TRC database. (Click MB1 on OFFSET and then CNTL MB1 on the others and then click on OK to generate the histogram display.

It should look like this:

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10. Arrange the displays as shown below:

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Selecting the Data of Interest Graphically 1. Highlight a range of points on the TRC_AMPL or the LOG_AMP histogram that covers the range of anomalously high amplitudes.

drag the mouse (holding MB1) across this region Using MB1, drag the cursor across the anomalous range of the plot. The points will turn red and all the others will turn black. Notice that a few points will also turn red on the other displays. This is the power of the summary statistics plot. This demonstrates that the high amplitude traces are distributed amongst the shots and receivers. (i.e. there does not appear to be any single high amplitude shot or receiver, these are randomly placed traces) 2. “SELECT” these points using the Select ➛ All Highlighted pull down. The points that were highlighted red will turn pink indicating that they are now “selected” Notice the difference between HIGHLIGHTING points and actually SELECTING them. 3. “PROJECT” these points to the shot domain using the Project ➛ SIN pull down so that we know which shots contain these high amplitude traces.

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Notice that some of the shots on the shot location map turned black:

These are the shots that have the high amplitude traces. 4. PD these shots to the trace display using the “bow and arrow” PD icon so that the display will only show you the shots that contain the high amplitude traces. This way you are only presented with a few shots to examine instead of the entire data volume of shots. You should only have three shots available to page through in the display. 5. Open a Trace Kill table using the Picking ➛ Kill Traces... pull down. Assign this table a name such as “Kill list from DBTools interactive” and choose CHAN as the secondary sort key for the list.

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6. Add the bad traces to the kill list.

7. To check that you killed the proper traces select the Paintbrush icon which toggles on and off the kills. 8. Repeat the sequence choosing different ranges of different attributes until you are happy that you have found all of the bad traces and have added them to the list. 9. As you change the attribute of interest add a header plot of that attribute to the Trace Display to help identify the anomalous traces.

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Focusing on a Range of data on the Histogram A logical extension to this exercise would be to re-display the histogram excluding the anomalously high traces so that a more “focused” range of information can be analyzed.

1. Highlight the one line of the histogram that represents all of the traces except for the highest amplitude on the TRC-AMPL plot. Notice that almost the entire plot remains red except for a few traces that are marked in black. 2. “SELECT” these traces, thus excluding the extremely high amplitude traces using the Select ➛ All Highlighted pull down.

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3. Now we need to re-focus the display on only the selected data points using the Focus ➛ On Selection pull down.

new range of interest?

4. You can now highlight a new range of points of interest. 5. Select these new points using the Select ➛ All highlighted pull down. 6. Project these points to the shot map using the Project ➛ SIN pull down. 7. PD these shots to the Trace Display using the “bow and arrow” PD icon. You can always reset the range of points displayed on the histogram by using the Focus ➛ On All pull down. 8. After all traces of interest have been selected to the edit list, Exit from the Trace Display, saving the results. Exit from the main DBTools window with the Database ➛ Exit pull down, select Commit to save the LOG_AMP attribute you created to the database.

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Can you run Trace Statistics

•

Are you functional at using DBTools

•

Are you comfortable with how PD is communicating between processes


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Chapter 5

System Overview In this chapter we discuss some of the behind-the-scenes program operation, as well as the basic ProMAX framework. Understanding the ProMAX framework and its relationship to the UNIX directory structure can be useful. The ability to manipulate the various components of the line database, such as ordered parameter files, from the User Interface is critical to smooth operation of the software.

Topics covered in this chapter: ❏ Directory Structure ❏ Program Execution ❏ Ordered Parameter Files ❏ Parameter Tables ❏ Disk Datasets ❏ Tape Datasets

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Chapter 5: System Overview

Chapter Objectives This chapter gives the processor a basic understanding of how ProMAX interacts with the operating system. Upon completion of this chapter you should:

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Understand where and how data files are stored

•

Know where menus and program executables are stored

•

Know how data passes through a ProMAX flow


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Directory Structure /ProMAX (or $PROMAX_HOME) The directory structure begins at a subdirectory set by the $PROMAX_HOME environmental variable. This variable defaults to /ProMAX, and is used in all the following examples. Set the $PROMAX_HOME environment variable to /my_disk/my_world/ProMAX to have your ProMAX directory tree begin below the /my_disk/my_world subdirectory. All ProMAX development tools are included within the following subdirectories: /ProMAX/sys/lib, /ProMAX/sys/obj, /ProMAX/port/ src, /ProMAX/port/bin, /ProMAX/port/include and /ProMAX/port/ man.

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ProMAX Directory Structure $PROMAX_HOME (default=.../ProMAX)

/sys

/exe exec.exe super_exec.exe *.exe from program

/frame /sdi /3rd party software

/bin *.exe from command line

/lib lib*.a

/port

/etc

/plot /help

/promax

*.lok - Frame help /lib/X11/app-defaults *.help -ASCII help Application window /promax3d managers /promaxvsp /menu /promax *.menu Processes /promax3d /promaxvsp /misc *_stat_math *.rgb-colormaps ProMax_defaults /bin start-up executable

config_file product install.doc pvmhosts qconfig license.dat

/scratch /queues /data

/area

/line

(or $PROMAX_DATA_HOME)

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/ProMAX/sys Software that is Operating System Specific resides in /ProMAX/sys which is actually a symbolic link to subdirectories unique to a given hardware platform, such as: /ProMAX/rs6000 for IBM RS6000 workstations, /ProMAX/sparc for Sun Microsystems Sparcstations running SunOS, /ProMAX/solaris for Sun Microsystems Sparcstations and Cray 6400 workstations running Sun Solaris OS, /ProMAX/sgimips for Silicon Graphics Indigo workstations using the 32 bit operating system and /ProMAX/sgimips4 for Silicon Graphics Indigo and Power Challenge workstations using the 64 bit operating system. This link facilitates a single file server containing executable programs and libraries for all machine types owned by a client. Machine specific executables are invoked from the UNIX command line, located in /ProMAX/sys/bin. Operating System specific executables and libraries, called from ProMAX, are located under /ProMAX/sys/exe. These machinedependent directories are named after machine type, not manufacturer, to permit accommodation of different architectures from the same vendor. Accommodating future hardware architectures will simply involve addition of new subdirectories. Unlike menus, help and miscellaneous files, a single set of executables is capable of running all ProMAX products, provided the proper product specific license identification number is in place. Third party software distributed by ProMAX will now be distributed in a subdirectory of /ProMAX/sys/exe using the company’s name, thus avoiding conflicts where two vendors use identical file names. For example, SDI’s CGM Viewer software would be in /ProMAX/sys/exe/sdi and Frame Technology’s FrameViewer would be in /ProMAX/sys/exe/frame.

/ProMAX/port Software that is Portable across all Platforms is grouped under a single subdirectory /ProMAX/port. This includes menus and Processes (/ProMAX/port/menu), helpfiles(/ProMAX/port/help), miscellaneous

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files (/ProMAX/port/misc.) Under the menu and help subdirectories are additional subdirectories for each ProMAX software product. For instance, under /ProMAX/port/menu, you will find subdirectories for ProMAX 2D (promax), ProMAX 3D (ProMAX3D), and ProMAX VSP (ProMAXVSP.) Menus for additional products are added as new subdirectories under /ProMAX/port/menu. If your system administrator is not afraid of the LISP programming language you can have them customize the ProMAX menus and defaults. The .../ProMAX/port/bin contains a very special file “Promax” which is the ProMAX start-up script. You may want to edit this file and personalize it to your environment. The .../ProMAX/port/lib/X11/app-defaults contains the color attributes and window configurations for the individual applications.

/ProMAX/etc Files unique to a particular machine are located in the /ProMAX/etc subdirectory. Examples of such files are the config_file, which contains peripheral setup information for all products running on a particular machine, and the product file, which assigns unique pathnames for various products located on the machine.

/ProMAX/scratch The scratch area defaults to /ProMAX/scratch. This location can be overridden with the environmental variable, PROMAX_SCRATCH_HOME. We recommend you point this to the biggest file system you have write permission. The DMO, Migrations, and Spreadsheets are heavy users of this file system. We also recommend that you periodically clean this file system.

/ProMAX/data (or $PROMAX_DATA_HOME) The primary data partition defaults to /ProMAX/data, with new areas being added as subdirectories beneath this subdirectory. This default location is specified using the entry: — primary disk storage partition: /ProMAX/data 200 in the /ProMAX/etc/config_file. This location can also be set with the environmental variable $PROMAX_DATA_HOME. We also recommend that you point this to a large files system you can write to.

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ProMAX Data Directories PROMAX_DATA_HOME

or /Data /Area DescName Project

Area subdirectory and its files

/Line DescName 17968042TVEL 31790267TGAT 36247238TMUT 12345678CIND 12345678CMAP

1) Parameter Table files

Index and Map Dataset files

/12345678 HDR1 HDR2 TRC1 TRC2

2) Dataset subdirectory and Header and Trace Dataset files

/Flow1 DescName TypeName job.output packet.job

3) A Flow subdirectory and its files

/OPF.SIN OPF60_SIN.GEOMETRY.ELEV

4) /OPF.SIN Database subdirectory and a non-spanned file

/OPF.SRF #s0_OPF60_SRF.GEOMETRY.ELEV

/OPF.SRF Database subdirectory and a span file

Each region identifies a collection of files and directories which can be summarized as the Area and Line separated into four main file types: 1) Parameter Tables, 2) Trace/Trace Headers, 3) Flows, and 4) Ordered Parameter Files database.

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Program Execution User Interface ($PROMAX_HOME/sys/bin/promax) Interaction with ProMAX is handled through the User Interface. As you categorize your data into Areas and Lines, the User Interface automatically creates the necessary UNIX subdirectories and provides an easy means of traversing this data structure. However, the primary function of the User Interface is to create, modify, and execute processing flows. A flow is a sequence of processes that you perform on seismic data. Flows are built by selecting processes from a list, and then selecting parameters for each process. A typical flow contains an input process, one or more data manipulation processes, and a display and/or output process. All information, needed to execute a flow, is held within a Packet File (packet.job) within each Flow subdirectory. This Packet File provides the primary means of communication between the User Interface and the Super Executive program. See next section, Super Executive Program. In addition, the User Interface provides utility functions for: •

copying, deleting and archiving Areas, Lines, Flows, and seismic datasets

•

accessing and manipulating ordered database files and parameter tables

•

displaying processing histories for your flows

•

providing information about currently running jobs

The User Interface is primarily mouse-driven and provides point-andclick access to the functions

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*

Program Execution

Super Executive Program (super_exec.exe) Execution of a flow is handled by the Super Executive, which is launched as a separate task by the User Interface. The Super Executive is a high level driver program that examines processes in your flow by reading packet.job and determines which executables to use. The majority of the processes are subroutines linked together to form the Executive. Since this is the processing kernel for ProMAX, many of your processing flows, although they contain several processes, are handled by a single execution of the Executive. Several of the processes are stand-alone programs. These processes cannot operate under the

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control of the Executive, and handle their own data input and output by directly accessing external datasets. In these instances, the Super Executive is responsible for invoking the stand-alone programs and, if necessary, multiple calls to the Executive in the proper sequence. The Packet File, packet.job, defines the processes and their type for execution. The Super Executive concerns itself with only two types of processes: •

Executive processes

•

Stand-alone processes

Executive processes are actually subroutines operating in a pipeline, meaning they accept input data and write output data at the driver level. However, stand-alone processes cannot be executed within a pipeline, but rather must obtain input and/or produce output by directly accessing external datasets. The Super Executive sequentially gathers all Executive-type processes until a stand-alone is encountered. At that point, the Packet File information for the Executive processes is passed to the Executive routine (exec.exe) for processing. Once this is completed, the Super Executive invokes the stand-alone program for processing, and then another group of Executive processes, or another stand-alone process. This continues until all processes in the flow have been completed.

Executive Program (exec.exe) The Executive program is the primary processing executable for ProMAX. The majority of the processes available under ProMAX are contained in this one executable program. The Executive features a pipeline architecture that allows multiple seismic processes to operate on the data before it is displayed or written to a dataset. Special processes, known as input and output tools, handle the tasks of reading and writing the seismic data, removing this burdensome task from the individual processes. This results in processes that are easier to develop and maintain. The basic flow of data through the Executive pipeline is shown below:

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Processing Pipeline Diagram

Disk Data Input

AGC Trace Display F-K Filter

InterProcess Communication Tool

Disk Data Output

Processing Pipeline Each individual process will not operate until it has accumulated the necessary traces. Single trace processes will run on each trace as the traces come down the pipe. Multi channel processes will wait until an entire ensemble is available. For example, in the example flow the FK

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filter will not run until one ensemble of traces has passed through the DDI and AGC. If we specify for the Trace Display to display 2 ensembles, it will not make a display until two shots have been processed through the DDI, AGC and FK filter. No additional traces will be processed until Trace Display is instructed to release the traces that it has displayed and is holding in memory by clicking on the traffic light icon or terminating its execution (but continuing the flow). Note: All the processes shown are Executive processes and thus operate in the pipeline. An intermediate dataset and an additional input tool process is needed if a stand-alone process were included in this flow. A pipeline process must accept seismic traces from the Executive, process them, and return the processed data to the Executive.

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Disk Data Input, Tape Data Input and standalone tools always start new pipes within a single flow

Disk Data Input

AGC F-K Filter

Decon Disk Data Input

Disk Data Output

NMO

CDP Stack

Bandpass Filter

Disk Data Output One pipe must complete successfully before a new pipe will start processing

Multiple Pipes in One Flow

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Types of Executive Processes The table below describes the four types of processes defined for use in the Executive. Table 2: ProMAX Executive Process Types Process Type

Description

simple tools

Accepts and returns a single seismic trace.

ensemble tools

Accepts and returns a gather of seismic traces.

complex tools

Accepts and returns a variable number of seismic traces such as, stack. This type of process actually controls the flow of seismic data.

panel tools

Accepts and returns overlapping panels of traces to accommodate a group of traces too large to fit into memory. Overlapping panels are processed and then merged along their seams.

Stand-Alone Processes and InterProcess Communication Tools Some seismic processing tools are not well suited to a pipeline architecture. Typically, these are tools making multiple passes through the data or requiring self-directed input. These tools can be run inline in a ProMAX job flow and appear as ordinary tools, but in reality are launched as separate processes. The current version of ProMAX does not provide the ability to output datasets from a stand-alone process. InterProcess Communication tools start a new process and then communicates with the Executive via UNIX interprocess communications. InterProcess Communication tools have the singular advantage of being able to accept and output traces in an asynchronous manner.

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Ordered Parameter Files Click to jump to the section

This section discusses the following issues relating to the Ordered Parameter Files database: •

Organization

•

Database Structure

•

File Naming Conventions

The Ordered Parameter Files database serves as a central repository of information that you or the various tools can rapidly access. Collectively, the ordered database files store large classes of data, including acquisition parameters, geometry, statics and other surface consistent information, and pointers between the source, receiver and CDP domains. The design of the Orders is tailored for seismic data, and provides a compact format without duplication of information. The Ordered Parameter Files database is primarily used to obtain a list of traces to process, such as traces for a shot or CDP. This list of traces is then used to locate the index to actual trace data and headers in the MAP file of the dataset. Once determined, the index is used to extract the trace and trace header data from their files.

Organization The Ordered Parameter Files contain information applying to a line and its datasets. For this reason, there can be many datasets for a single set of Ordered Database Files. Ordered Parameter Files, unique to a line, reside in the Area/Line subdirectory. The Ordered Parameter Files database stores information in structured categories, known as Orders, representing unique sets of information. In each Order, there are N slots available for storage of information, where N is the number of elements in the order, such as the number of sources, number of surface locations, or number of CDPs. Each slot contains various attributes in various formats for one

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particular element of the Order. The Orders are organized as shown in the table below. Table 3: Organization of Ordered Parameter Files LIN (Line)


TRC (Trace)








CHN (Channel)


OFB (Offset Bin)


PAT (Pattern)


OPF Matrices The OPF database files can be considered to be matrices or flat files. The OPF database files are not a relational database. Each OPF is indexed against the OPF counter and there are various single numbers per index. Note the relative size of the TRC OPF to the other OPF files. The TRC is by far the largest contributor to the size of the database on disk.

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SIN (Sources) Database

SRF (Receivers) Database

OPF Matrices

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Database Structure The ProMAX database was restructured for the 6.0 release to handle large 3D land and marine surveys. The features of the new database structure are listed below: Each order is contained within a subdirectory under Area and Line. For example, the TRC is in the subdirectory OPF.TRC. There are two types of files contained in the OPF subdirectories: •

Parameter: Contain attribute values. There may be any number of attribute files associated with an OPF.

•

Index: Holds the list of parameters and their formats. There is only one index file in each OPF subdirectory. The exception to this is the LIN OPF. The LIN information is managed by just two files, one index and one parameter, named LIN.NDX and LIN.REC.

OPF files are of two types: •

Span: These files are denoted by the prefix, #s. Non-span files lack this prefix. The TRC, CDP, SIN, and SRF OPF parameters are span files. The first span of 10MB for each parameter file is always written to primary storage. Span files are created in the secondary storage partitions listed in the config_file as denoted with the OPF keyword. Span files may be moved to any disk partition within the secondary storage list for read purposes. Newly created spans are written in the OPF denoted secondary storage partitions. All subsequent spans are written to the secondary storage partitions denoted by the OPF keyword in a round robin fashion until the secondary storage is full. Then, subsequent spans are created in primary storage. Span file size is currently fixed at 10 megabytes, or approximately 2.5 million 4 byte values per span file.

•

Non-span: All other OPFs are non-span.

Given the fact that each parameter is managed by a file, it may be necessary to increase the “maximum number of files open” limit on some systems, specifically, SUN, Solaris and SGI. From the csh, the following command increases the file limit to 255 files open, “limit de 255”. The geometry spreadsheet is a ProMAX database editor. Modifying information within a spreadsheet editor and saving the changes will automatically update the database. There is no longer an import or

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export from the geometry database to the ProMAX database files as was required prior to the 6.0 release. Database append is allowed. Data can be added to the database via the OPF Extract tool or the geometry spreadsheet. This allows for the database to be constructed incrementally as the data arrives. There is improved network access to the database. Database I/O across the network is optimized to an NFS default packet size of 4K. All database reads and writes are in 4K pages. Existing and restored 5.X databases are automatically converted to the 6.0 (and later) database format.

File Naming Conventions Parameter file names consist of information type and parameter name, preceded by a prefix denoting the Order of the parameter. For example, the x coordinate for a shot in the SIN has the following name: #s0_OPF60_SIN.GEOMETRY.X_COORD. Where #s0_OPF60 indicates a first span file for the parameter, _SIN denotes the Order, GEOMETRY describes the information type of the parameter, and X_COORD is the parameter name. Index file names contain the three letter Order name. For example, the index file for the TRC is called OPF60_TRC. NOTE: The index file for each Order must remain in the primary storage partition. Span parameter files may be moved and distributed anywhere within primary and secondary storage.

Within each Order, there are often multiple attributes, with each attribute being given a unique name.

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Parameter Tables Parameter Tables are files used to store lists of information in a very generalized structure. Some examples may be mute functions or decon design time gates. To increase access speed and reduce storage requirements, parameter tables are stored in binary format. They are stored in the Area/Line subdirectory along with seismic datasets, the Ordered Parameter Files database files (those not in separate directories), and Flow subdirectories. Parameter Tables are often referred to as part of the database. Parameter tables differ from the OPF database in OPF files contain many attributes that are one number per something. Parameter tables contain more than one number per something. For example a velocity function contains multiple velocity-time pairs at one CDP.

Creating a Parameter Table Parameter tables are typically created in three ways: •

Processes store parameters to a table for later use by other processes.

•

Parameter tables can be imported from ASCII files that were created by other software packages or hand-edited by you.

•

Parameter tables can be created by hand using the Parameter Table Editor which is opened by the Create option on the parameter table list screen.

An example is the interactive picking of time gates within the Trace Display process. After seismic data is displayed on the screen, you pull down the Picking Menu and choose the type of table to create. The end result of your work is a parameter table. If you were to pick a top mute, you would generate a parameter table ending in TMUT. If you were picking a time horizon, you would generate a table ending in THOR. These picks are stored in tabular format, where they can be edited, used

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by other processes in later processing, or exported to ASCII files for use by other software packages WARNING: Remember, you name and store the parameter tables in their specific Area/Line subdirectory. Therefore, you can inadvertently overwrite an existing parameter table by editing a parameter table in a different processing flow.

ASCII Import to a Parameter Table File Import reads either ASCII or EBCDIC formatted files with fixed columnar data into the spreadsheet editor. When the application is initialized, two windows appear: the main ASCII/EBCDIC File Import window and the File Import Selection dialog. After a file has been selected, it is displayed, and you can select rows. Note: Filter and Apply appear grayed out and are insensitive to mouse button actions. After Format has been pressed and a columnar format selected, Filter and Apply appear normally and are available for use. The steps involved in performing a file import are as follows: 1. Select File: Select a file to import. If the text file does not contain valid line terminators, use Width to set the line width and then reread the file. 2. Select Format: Select a previous format or create a new format. 3. Review or Edit Column Definitions: Review the previously defined columns in an existing format by selecting all the columns. Review the highlighted regions in the file display for accuracy. Columns can either be edited by hand entering Start Col. and End Col. values, or by performing click and drag column definition. 4. Save the Column Definition: Save any changes to the current column definition to disk for later retrieval. 5. Filter the File for Invalid Text: Search the marked columns and rows for any invalid text. Text may be excluded or replaced within this interactive operation. 6. Perform the Import: Select the Apply button. The application windows will close and the focus will return to the calling spreadsheet.

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ASCII File Export from the Parameter Table Editor Export writes either ASCII or EBCDIC formatted files with fixed columnar data from a spreadsheet editor. When the application is initialized, the main ASCII File Export window will appear. After a file and format has been selected, then the ASCII text is displayed and the Apply button is activated. The steps involved in performing a file export are as follows: 1. Select File: Select a file for export within the File Export Selection dialog. 2. Select Format: Select a previous format or create a new format. 3. Review or Edit Column Definitions: Review the previously defined columns in an existing format by selecting all the columns. Review the highlighted regions in the file display for accuracy. Columns can either be edited by hand entering Start Col. and End Col. values, or by performing click and drag column definition. 4. Save the Column Definition: Save any changes to the current column definition to disk for later retrieval. 5. Perform the Export: Select the Apply button. 6. Cancel the Export Operation: Press the Cancel button to close the export windows and return to the calling spreadsheet.

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Disk Datasets ProMAX uses a proprietary disk dataset format that is tailored for interactive processing and random disk access. Disk dataset files can span multiple filesystems, allowing for unlimited filesize datasets. A typical set of files might look like this: — /ProMAX/data/usertutorials/landexample/12345678CIND /ProMAX/data/usertutorials/landexample/12345678CMAP /ProMAX/data/usertutorials/landexample/12345678/TRC1 /ProMAX/data/usertutorials/landexample/12345678/HDR1 These files are described in more detail in the table below. Table 4: Composition of a Seismic Dataset

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File Name

Contents

Trace (...TRCx)

File containing actual sample values for data trace.

Trace Header (....HDRx)

File containing trace header entries corresponding to data samples for traces in the trace file. This file may vary in length, growing as new header entries are added. Keep trace headers in a separate file so trace headers can be sorted without needing to skip past the seismic data samples.

Map (....CMAP)

File keeps track of trace locations, even if data flows over many disks. Given a particular trace number, it will find the sequential trace number within the dataset. This rapidly accesses traces during processing. The map file is a separate file, as it may grow during processing, it is always held in the line directory.

Index (....CIND)

File has free-form format information relating to the entire dataset, including sample interval, number of samples per trace, processing history, and names of trace header entries. This file may grow during processing, and it is also always held in the line directory.


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CIND

CMAP

HDRx

TRCx

Disk Dataset Components - Relative Sizes

Secondary Storage In a default ProMAX configuration, all seismic dataset files reside on a single disk partition. The location of this disk partition is set in the $PROMAX_HOME/etc/config_file with the entry: — primary disk storage partition: /ProMAX/promax/data 200 In addition to the actual trace data files, the primary storage partition will always contain your flow subdirectories, parameter tables, ordered parameter files, and various miscellaneous files. The ...CIND and ...CMAP files which comprise an integral part of any seismic dataset are always written to primary storage. Since the primary storage file system is of finite size, ProMAX provides the capability to have some of the disk datasets, such as the ...TRCx and ...HDRx files, and some of the ordered parameter files span multiple disk partitions. Disk partitions other than the primary disk storage partition are referred to as secondary storage. All secondary storage disk partitions must be declared in the appropriate $PROMAX_HOME/etc/config_file. Samples entries are:

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secondary disk storage partition: /ProMAX/promax/data2 20 TRC OPF secondary disk storage partition: /ProMAX/promax/data3 20 TRC secondary disk storage partition: /ProMAX/promax/data4 20 OPF secondary disk storage partition: /ProMAX/promax/data5 20 Primary Data

Secondary

Secondary

Secondary

Secondary

Data2

Data3

Data4

Data5

Refer to the ProMAX System Administration guide for a complete description of the config_file entries for primary and secondary disk storage. 20 is the default disk file size in Megabytes. This default is probably too small for modern surveys as it was based on the old Unix 2Gig file system limitation. A better value would be 4000, or as large as your dataset, or as large as a file as your system will allow. WARNING: If the Primary file system fills up ProMAX will crash and will not be able to launch until space on Primary has been cleaned up.

Under the default configuration, the initial TRC1 and HDR1 files are written to the primary storage partition. It is possible to override this behavior by setting the appropriate parameter in Disk Data Output. If the parameter Skip primary disk partition? is set to Yes, then no TRC or HDR files will be written to the primary disk partition. This can be useful as a means of maintaining space on the primary storage partition. (To make this the default situation for all users, have your ProMAX system administrator edit the diskwrite.menu file, setting the value for Alstore to ‘t’ instead of ‘nil’). Secondary storage is used in a “as listed and available” fashion. As an attempt to minimize data loss due to disk hardware failure, ProMAX tries to write a dataset to as few physical disks as possible. If the primary storage partition is skipped by setting the appropriate parameter in Disk Data Output, the CIND and CMAP files are still written to the primary storage partition, but the TRCx or HDRx files will not be found there.

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Tape Datasets Tape datasets are stored in a proprietary format, similar to the disk dataset format, but incorporating required structures for tape input and output. Tape input/output operates either in conjunction with a tape catalog system, or without reference to the tape catalog. The tape devices used for the Tape Data Input, Tape Data Insert, and Tape Data Output processes are declared in the ProMAX device configuration window. This allows access to tape drives anywhere on a network. The machines that the tape drives are attached to do not need to be licensed for ProMAX, but the fclient.exe program must be installed.

Tape Trace Datasets A ProMAX tape dataset is similar to a disk dataset in that the index file (...CIND) and map file (...CMAP) still reside on disk in the Line/survey database. Refer to the documentation in the Disk Datasets portion of this helpfile for a discussion of these files. Having the index and map files available on disk provides you with immediate access to information about the dataset, without needing to access any tapes. It also provides all the information necessary to access traces in a non-sequential manner. Although the index and map files still reside on disk, copies of them are also placed on tape(s), so that the tape(s) can serve as a self-contained unit(s). If the index and map files are removed from disk, or never existed, as in the case where a dataset is shipped to another site, the tapes can be read without them. However, access to datasets through the index and map files residing solely on tape must be purely sequential. Tape datasets are written by the Tape Data Output process, and can be read using the Tape Data Input or Tape Data Insert processes. These input processes include the capability to input tapes by reel, ensemble number, or trace number. Refer to the relevant helpfile for a complete description of the parameters used in these processes. The use or non-use of the tape catalog in conjunction with the tape I/O processes is determined by the tape catalog type entry in the appropriate $PROMAX_HOME/etc/config_file. Setting this variable to full activates catalog access, while an entry of none deactivates catalog access. An entry of external is used to indicate that an external tape catalog, such as the Cray Reel Librarian, will be used. You can override the setting provided in the config_file by setting the environment

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variable for BYPASS_CATALOG to ‘t’, in which case the catalog will not be used. The actual tape devices to use for tape I/O must also appear as entries in the config_file, under the tape device: stanza.

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Tape Catalog System Tape Catalog Overview The fundamental strategy of the tape catalog is that a group of tapes are introduced or logged into the tape catalog, which then works in conjunction with the Tape Input, Tape Insert, and Tape Output processes to provide access to those tapes from within the ProMAX system. Before being introduced to the catalog, an ANSI label is written to each tape using the catalog utilities outlined below. The catalog system knows the label and status (initially SCRATCH) of every tape, and can monitor and validate the tape catalog resources accordingly. For example, when a request for an output dataset is made, the catalog can decide which tape to use, and can verify that the correct tape is mounted. When a dataset overflows a tape, the catalog can decide which tape to use next, and can again verify that the correct tape is mounted. When a request for an input dataset is made, the catalog knows which tapes belong to the dataset, and can verify that the correct tapes are mounted in the correct order.

Getting Started The first step in using the ProMAX tape catalog is to create some labeled tapes. The program $PROMAX_HOME/sys/bin/tcat is used for tape labelling, catalog creation and maintenance, and for listing current catalog information. The program is run from the UNIX command line. The following steps are required to successfully access the tape catalog: 1. Label tapes. 2. Read and Display tape labels. 3. Add labeled tapes to a totally new catalog. Before adding the tapes to a new catalog, it is a good idea to visually inspect the contents of the label information file for duplicate or missing entries. The contents typically look like: 0 AAAAAA 0 1 4 1 AAAAAB 0 1 4

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2 AAAAAC 0 1 4 3 AAAAAD 0 1 4 4 AAAAAE 0 1 4 The fields are: volume serial number (digital form), volume serial number (character form), tape rack slot number, site number, and media type, respectively. You can manually edit these fields. 4. Write a label information file from the existing catalog. 5. Add labeled tapes (and datasets) to the existing catalog. 6. Merge an additional catalog into the existing catalog. 7. Delete a dataset from the catalog.

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5-30

•

Where is the Seismic Data stored

•

Are the Trace Headers stored separate from the Data

•

Where are the Ordered Parameter Files stored

•

Where are the Parameter Tables stored

•

Can you build a ProMAX start-up Script

•

Can you personalize/change a default Menu

•

Can you explain how data passes through: single trace tools, ensemble tools, interprocess communication and stand-alone tools


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Chapter 6

Parameter Selection and Analysis ProMAX 2D contains a suite of processes, providing you with convenient, yet flexible parameter testing and data analysis capabilities. The processes are found in the process list category called Flow Control. Parameter testing is broken down by type: manual and automatic. Manual parameter testing refers to the use of IF-ELSEIF-ENDIF conditional processing sequences to define a particular test scenario. Using this method you can test multiple parameters in multiple processes. With the automatic parameter testing, you can easily test one parameter in a single process. Data analysis tools and the resulting filtering processes, such as F-K analysis and filtering, are good examples for parameter testing. In this chapter, one of the exercises is to design filters in the F-K domain and compare the F-K filtered data to your input seismic data.

Topics covered in this chapter: ❏ Parameter Table Picking ❏ Parameter Test ❏ IF/ENDIF Conditional Processing ❏ F-K Analysis and Filtering ❏ F-K Filtering Comparisons ❏ Interactive Spectral Analysis (ISA)

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Chapter 6: Parameter Selection and Analysis

Chapter Objectives

3. Parameter Selection

This chapter gives the processor a framework of how to define and test parameters, gates, windows and processing flows. Upon completion of this chapter you should:

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Be proficient at Picking Gates and Windows in Trace Display

•

Know how to Pick Bad Traces

•

Understand Automatic Parameter Testing

•

Be able to design IF/ENDIF conditional processing

•

Be able to interactively test FK Filters and Spectral Analysis


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Parameter Table Picking Parameter tables are generated when you interactively define lists or tables of information within various display tools. These files are stored in binary format and are intended for use in subsequent flows. The interactivity of Trace Display allows you to generate these tables.

Pick Parameter Tables In this exercise you will pick a top mute, deconvolution design gate, trace kill list, and a trace reversal list. 1. Build the following flow in your “Watson Rise” Line.

Editing Flow: 3.1-Pick Parameter Tables Add

Delete

Execute

View

Exit

Disk Data Input Read data from other lines/surveys?: ---------------------No Select dataset: ----------------------------Shots-with geometry Trace read option: -----------------------------------------------Sort Interactive Data Access?: --------------------------------------Yes Select primary trace header entry: -----------------------FFID Select secondary trace header entry: --------------OFFSET Select tertiary trace header entry: ----------------------NONE Sort order for dataset: ------------------------------------------*:*/

Automatic Gain Control AGC operator length: -----------------------------------------1000

Trace Display Number of ENSEMBLES (line segments)/screen: -------2 Do you want to use variable trace spacing?: ----------Yes 2. In Disk Data Input, select “Shots-with geometry”. Sort the data by FFID and OFFSET. 3. Replace the AGC operator length default value with 1000.

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4. In Trace Display, use variable trace spacing. This will use the secondary sort key of OFFSET to variably space the traces. Also, set the number of ensembles per screen to 2. 5. Execute the flow. Trace to be killed

Mute

Traces to be reversed

Decon Gate

Parameter tables 6. If you did not save your trace kill table from chapter 4, go ahead and pick the bad traces here: Picking ➛ Kill traces... “Kill list from Trace Display”. 7. Pick a top mute to get rid of first break and refracted energy: Picking Pick Top Mute... “FB Mute” by AOFFSET. Use the Paintbrush icon to see the effects of your current picks. In this case you should see only hyperbolas after Paintbrush applies the top mute.

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8. Pick a deconvolution gate on the first shot: Picking ➛ Pick Miscellaneous Time Gates... “decon gate” by AOFFSET. Remember to use MB3 New Layer to pick the bottom of the decon gate. 9. After projecting your windows use Interactive Data Access to move through all the shots and QC the windows. 10. If you desire you can pick the reverse traces: Picking ➛ Reverse traces... “reverse traces” by AOFFSET. In general the reverse traces will be flagged in the field by the observers log. The statics routines will also detect the reverse traces for you. 11. Select File ➛ Save Picks, then select File ➛ Exit/Stop Flow.

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Parameter Test The Parameter Test process provides a mechanism for automatically testing simple numeric parameters by creating multiple copies of input traces and replacing a key parameter in the process to be tested with specified test values. The output consists of copies of the input data with a different test value applied to each copy. Parameter Test creates two header words. The first is called REPEAT data copy number and is used to distinguish each of the identical copies of input data. The second is called PARMTEST and is an ASCII string, uniquely interpreted by the Screen Display processes as a label for the traces.

Test True Amplitude Recovery with Parameter Test In this exercise, you will use Parameter Test to compare True Amplitude Recovery on shot gathers with different values for dB/sec.

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Editing Flow: 3.2-Parameter Test Add

Delete

Execute

View

Exit

Disk Data Input Select dataset: ---------------------------Shots- with geometry Trace read option: ---------------------------------------------SORT Interactive Data Access?: ---------------------------------------No Select primary trace header entry: -------------------------SIN Sort order list for dataset: -------------------------------------16/

Trace Kill/Reverse Trace editing MODE: ---------------------------------------------Kill Get edits from the DATABASE?: ----------------------------Yes SELECT trace Kill parameter file: -----------------------------------------------------Kill list from DBTools interactive

Trace Kill/Reverse Trace editing MODE: --------------------------------------Reverse Get edits from the DATABASE?: -----------------------------No Trace selection MODE: --------------------------------EXCLUDE PRIMARY edit list header word: ----------------------------SIN SECONDARY edit list header word: ------------SRF_SLOC TERTIARY edit list header word: -----------------------NONE SPECIFY trace to be edited: ------------------------1-17:469/

Trace Muting Re-apply previous mutes: ---------------------------------------No Mute time reference: ----------------------------------------Time 0 TYPE of mute: ------------------------------------------------------Top Starting ramp: ------------------------------------------------------30. EXTRAPOLATE mute times?: ---------------------------------Yes Get mute file from the DATABASE?: -----------------------Yes SELECT mute parameter file: -------------------------FB Mute

Parameter Test True Amplitude Recovery Trace Display

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Delete

Execute

View

Exit

Disk Data Input Trace Kill/Reverse Trace Kill/Reverse Trace Muting Parameter Test Enter Parameter VALUES: ------------------------------ 12|9|6 Trace grouping to reproduce: ----------------------Ensembles

True Amplitude Recovery Apply spherical divergence corrections?: ----------------Yes Basis for spherical spreading: ---------------1/dist Apply inelastic attenuation corrections?: -----------------No Get TAR velocity function from database?: ---No Should the velocity be treated as space variable: -----No Specify TAR velocity function: --------------------------- 0-7000,850-9000,1300-12000, 2000-15000 Apply dB/sec corrections?: ----------------------------------Yes dB/sec correction constant: ------------------99999 Apply time raised to a power corrections?: --------------No APPLY function to data or REMOVE effect of amplitude corrections?: -------------------------------------Apply Maximum application TIME: -------------------------------5000

Trace Display Number of ENSEMBLES(line segments)/screen: --------2 Trace scaling option: ------------------------------Entire Screen Number of display panels: ---------------------------------------2 2. In Disk Data Input, select “Shots-with geometry.” Choose to sort data by SIN, and read the shot number 16. Parameter Test will not work with Interactive Data Access, so set this to No. 3. In the first Trace Kill/Reverse, select you trace kill file. 4. In the second Trace Kill/Reverse, choose to reverse SRF_SLOC 469 for SIN’s 1-17. 5. In Trace Muting, select your top mute file.

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6. Specify values for Parameter Test. Enter a list of parameter values for dB/sec correction constant, each separated by a vertical bar (|). To determine the format (real, integer, sequence) and a realistic range of test values, look at the default value in the True Amplitude Recovery process. (Use values of 12, 9, and 6 dB/sec for this exercise.) 7. Specify True Amplitude Recovery parameters. Select Yes to apply spherical divergence, and enter the following velocity time pairs (0-7000, 850-9000, 1300-12000, 2000-15000). Select Yes for Apply dB/sec Correction, and enter five nines (99999) for the dB/sec correction constant. NOTE: Entering five nines (99999) is a flag that tells the process to use the values found in Parameter Test for this parameter.

8. In Trace Display, choose to display 2 ensembles/screen, 2 display panels, and change the trace scaling from individual to entire screen. This will display the original shot plus the three parameter tests on a single screen. 9. Execute the flow to compare displays.

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Viewing Parameter Tests After viewing the tests and deciding on the most appropriate value for the dB/sec correction, select File ➛ Exit/Stop Flow.

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10. Select View from the flow builder menu and look at the processes that were actually executed in your flow. Near the bottom of the “job.output” file is a listing of the executed processes. There are some additional processes listed here, that were not in your original flow. Also notice that Parameter Test is absent. This occurs because Parameter Test is a macro, built from other processes. If you have problems with a ProMAX flow that you cannot solve simply email the “job.output” file to “[email protected]” and they will help out in anyway they can. 11. Edit you flow again, and change the following Trace Display parameters:


Delete

Execute

View

Exit

Disk Data Input Trace Kill/Reverse Trace Kill/Reverse Trace Muting Parameter Test True Amplitude Recovery Trace Display Number of ENSEMBLES(line segments)/screen: --------1 Automatically SAVE screens: --------------------------------yes Trace scaling option: ------------------------------Entire Screen Number of display panels: ---------------------------------------1 12. Execute the flow. 13. Use the Next ensemble icon to display the four tests, then use the Animation tool to review the tests. Check to see if you would still use the same value for dB/sec as you chose before. 14. Select File ➛ Exit/Stop Flow when finished.

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IF/ENDIF Conditional Processing Automatic parameter testing is not always an option. It can only be used when the testing parameter is a simple numeric value, such as the automatic gain control operator length, or a sequence of numerics, as in the case of corner frequencies used to define a bandpass filter. When your testing requires evaluating multi-level tests, or comparing nonnumeric parameters, such as a fan filter option instead of a polygon filter option in FK Filter, then manual testing must be used. In order to manually test parameters you must: •

Generate multiple copies of the data.

•

Branch your processing stream so that each copy of the data may be processed with different parameters.

One method of generating multiple data copies is to use the Reproduce Traces process. This is actually the same process, designed into Parameter Test macro. Reproduce Traces generates a specified total number of copies and appends a header word to each trace, allowing you to distinguish between the multiple versions of data. This header word is known as Repeated Data Copy Number or REPEAT for short. It is a numeric value from 1-N, where N is the total number of generated copies. You should place Reproduce Traces after any processing which is common to all copies of the data, but prior to the processes you wish to compare. Branching the flow is a conceptual term for controlling the processes your dataset utilizes. In other words, you do not actually break up any single flow into separate flows, rather utilize the capability of the IF, ELSEIF, and ENDIF processes to select and direct traces for processing. This is handled automatically by the Parameter Test process, as you saw if you looked at the View information when you executed the previous flow. More specifically, each copy of the data is passed to a different process, or the same process with different parameter selection using a series of IF, ELSEIF and ELSE processes in the flow. For example, if the data copy number (REPEAT) is 1, then pass that copy of the data to the next process. If the data copy number is 2, pass that copy to a different process, and so on until all copies of the data have been passed to unique processes. The series of conditions is ended with ENDIF.

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Finally, you may use a process called Trace Display Label to generate a header word for posting a label on the display.

Compare Data With and Without Deconvolution Incorporate Reproduce Traces with IF and ENDIF to compare processed and unprocessed data. In this exercise you will compare unfiltered shot gathers with deconvolution, and filtered shot gathers with deconvolution. It is always a good idea to have a control copy, the original input, for further comparison. This flow illustrates how to compare these three copies.

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1. Copy your previous flow and edit it to look like the following:

Editing Flow: 3.3-IF/ELSEIF Loop Add

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Disk Data Input Trace Kill/Reverse Trace Kill/Reverse Trace Muting True Amplitude Recovery dB/sec correction constant: ------------------------------------- 9

Reproduce Traces Trace grouping to reproduce: ----------------------Ensembles Total Number of datasets: ----------------------------------------3

IF Trace selection MODE: ------------------------------------Include SELECT Primary trace header word: --------------REPEAT SELECT secondary trace header word: --------------NONE SPECIFY trace list: ---------------------------------------------------1

Trace Display Label Trace label: ------------------------------------------Original Input

ELSEIF Trace selection MODE: ------------------------------------Include SELECT Primary trace header word: --------------REPEAT SELECT secondary trace header word: --------------NONE SPECIFY trace list: ---------------------------------------------------2

Spiking/Predictive Decon Trace Display Label ELSE Spiking/Predictive Decon Trace Display Label ENDIF Trace Display

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Editing Flow: 3.3-IF/ELSEIF Loop Add

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Disk Data Input Trace Kill/Reverse Trace Kill/Reverse Trace Muting True Amplitude Recovery Reproduce Traces IF Trace Display Label ELSEIF Spiking/Predictive Decon TYPE of deconvolution: -----------Minimum phase spiking Decon operator length(s): --------------------------------------160 Operator ‘white noise’ level(s): -------------------------------0.1 Window rejection factor: ------------------------------------------2. Time gate reference: ----------------------------------------Time 0 Get decon gates from the DATABASE?: ------------------Yes SELECT decon gate parameter file: -------------decon gate Output traces or filters: ---------------Normal decon output Apply a bandpass filter after decon? ----------------------No Re-apply trace mute after decon?: -------------------------Yes

Trace Display Label Trace label: ------------------------------------------------------Decon

ELSE Spiking/Predictive Decon Apply a bandpass filter after decon?:---------------------Yes Bandpass filter frequency values: --------------6-12-60-70 ----For remaining parameters, use those listed above----

Trace Display Label Trace label: ---------------------------------------Decon with filter

ENDIF Trace Display Number of ENSEMBLES (line segments)/screen: -------3 Number of display panels: ---------------------------------------1 Trace Scaling Option: ----------------------------------Individual

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2. Use the same parameters as the previous flow for the first four processes. 3. In True Amplitude Recovery, set the db/sec to the value you chose in the previous flow. 4. In Reproduce Traces, enter 3 for the total number of datasets. You will generate two additional copies (3 total), one ensemble at a time. 5. Select Repeat for Select Primary trace header word in IF and ELSEIF. IF acts as the gate keeper, providing the mechanism for selecting or restricting traces which will be passed into a particular branch of the flow. Header words are used (just as in Disk Data Input) to uniquely identify the traces to include or exclude in a particular branch. In the first IF conditional, select REPEAT as the primary trace header and 1 (copy number) as the trace list entry. Data copy 1 is passed to Trace Display Label in this example.This will be the control copy. The ELSEIF condition passes the second data copy number (REPEAT=2) to Spiking /Predictive Decon. The ELSE process selects all traces, not previously selected with IF or ELSEIF. In our case, having selected two of the three copies of data for filtering, leaves only the third data copy (REPEAT=3) for the ELSE branch. In this example, you will apply deconvolution and filter. 6. Use Trace Display Label to create labels for each copy. Label the copies according to their unique processing. For example, label the first copy with “Original Input,” the second with “Decon,” and the final copy with “Decon with filter.” 7. In Trace Display, choose to display all 3 copies on one screen. 8. Execute the flow. After viewing the data in this mode, you may choose to display each copy on a different screen, and use the screen swap mode.

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F-K Analysis and Filtering Separating trace data into signal and noise is often possible in F-K space. This separation can be exploited by defining a filter to reject the noise or accept the good data. There are ProMAX tools to view data in F-K space, design filters and subsequently apply filters to enhance your data.

F-K Analysis In this exercise you will bring in one shot with some slow linear noise. After inspection in both the time domain and F-K space, design a filter to reject the noise. You will want to try a polygon filter as well as a fan filter to attenuate the noise. NOTE: This is not a real processing flow, since, you would normally do the FK filter before the deconvolution. For class purposes we are using the deconvolution to enhance the ground roll so that we can demonstrate how powerful FK filters are at attenuating ground roll.

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1. Copy your previous flow, and add/delete processes so that it looks like the following:

Editing Flow: 3.4-FK Analysis/Filter Add

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Disk Data Input Trace Kill/Reverse - optional Trace Kill/Reverse - optional Trace Muting True Amplitude Recovery - optional Spiking/Predictive Decon Automatic Gain Control >F-K Filter< F-K Analysis Panel width in traces: ------------------------------------------120 Starting time for analysis: ---------------------------------------0. Ending time for analysis: ----------------------------------------0. Distance between input traces: ------------------------------55. Starting display configuration: ----------------TX-TK-FX-FK Position of zero wavenumber in display: --------CENTER Position of zero frequency in display: --------------------TOP Plot FK,TK,TX panels in DB or Linear: ----------DBSCALE Initial TX gain setting (percentile): --------------------------98. Initial FK maximum gain setting (db): -----------------------0. Initial FK minimum gain setting (db): ------------------------0. Percent flat for trace ramping: ------------------------------100. Percent flat for time ramping: -------------------------------100. Select mute polygon table: ------------------------------fk mute Mode of F-K filter operation: ---------------------------REJECT Percent flat for F-K filter windowing: ----------------------90. Time length of F-K filter (ms): -------------------------------500. Spatial extent of F-K filter (traces): --------------------------50 2. For all processes prior to F-K Analysis, use the same parameters as the previous flow.

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3. In F-K Analysis, enter 122 for the panel width to account for the shot gap in the transform. 4. Set 55 ft. for the distance between traces (do not let this default to 0). 5. Add an output mute polygon table “fk mute”. 6. Execute the flow. 7. With the default display you will see four panels. View only the TX, and FK panels by selecting Configuration ➛ TX-and-FK. 8. Use the dx/dt icon. You should identify the ground roll energy in the F-K domain by the velocity you measure in T-X space. 9. You may find it helpful to rotate the color scale using Controls ➛ Edit Colormap.

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10. With the F-K data displayed, select the Picking tool icon to build a table for interactively picking a reject zone.

3) Desired Polygon 2) Move points

1) Rectangle control points

Picking Mute for FK Filter 11. Pick a polygon to include all the noise to filter. It is best to start with a square or rectangle and then use MB1 to add new control points and MB3 to move the control points to customize the shape of the polygon as illustrated on the previous page.

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12. After building the desired polygon, examine the response of the data to the filter by selecting FilterResponse ➛ FilteredOutput.

FK Filtered Output 13. You may also want to view the impulse response of the filter by selecting FilterResponse ➛ ImpulseResponse. To better view the operator now select Controls ➛ TX Display... ➛ Clip by amplitude ➛ .008 and then select OK. 14. After using Interactive Data Access option to view other shots, select File ➛ Exit/Stop Flow, and then select Yes to save your polygon.

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Compare F-K filtered shots using an IF loop 1. Edit your flow to include an IF loop:

Editing Flow: 3.4-FK Analysis/Filter Add

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Disk Data Input Interactive Data Access?: ---------------------------------------No

Trace Kill/Reverse - optional Trace Kill/Reverse - optional Trace Muting True Amplitude Recovery - optional Spiking/Predictive Decon Automatic Gain Control Reproduce Traces IF F-K Filter Type of F-K filter: -----------------------------Arbitrary Polygon Distance between input traces: -------------------------------55 Panel width in traces: ------------------------------------------122 Test the filter impulse response?: ---------------------------No Percent flat for time ramping: -------------------------------100. Percent flat for offset ramping: -----------------------------100. Get polygon mute file from the database: ---------------Yes Select mute parameter file: ------------------fk mute Mode of F-K filter operation: ---------------------------REJECT Percent flat for F-K filter windowing: ----------------------90. Time length of F-K filter (ms): -------------------------------500. Spatial extent of F-K filter (traces): --------------------------50 Re-apply T-X trace mute after filter?: ---------------------Yes Percentage of K-space to keep around K=0: --------------0.

Trace Display Label Trace label: --------------------------------------------------FK Filter

ELSE Trace Display Label ENDIF Trace Display Number of ENSEMBLES (line segments)/screen: -------2

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2. Use the same parameters as before for the first seven processes, except turn off the Interactive Data Access. 3. Create two copies of the shot with Reproduce Traces. 4. Use the Repeat option in IF to send one copy of the shot to the F-K Filter process. 5. Execute the flow, and review the results. 6. Modify the FK filter to use a fan filter instead of the arbitrary polygon. 7. Execute the flow, and review the results. 8. You may try changing the mode of operation from REJECT to ACCEPT and re-running. If you see any signal/hyperbolas you have removed some signal.

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Interactive Spectral Analysis Interactive Spectral Analysis computes and displays power, phase and F-X spectra estimates for interactively selected subsets of traces. These displays can be configured both interactively and from the ProMAX menu. There are three modes of data selection: •

Simple Selection: Analyzes only the displayed traces. During the interactive session you may analyze new traces by choosing Next Data from the Data menu.

•

Single Subset Selection: Enables you to interactively select a rectangular subset of the data for spectral displays. The spectral displays are automatically updated for each new rectangle selection.

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Multiple Subset Selection: Displays at least two windows: a Data Selection Window and one or more Spectral Analysis windows. Subsets for Spectral Analysis are chosen from the Data Selection Window, using the selection tool from the toolbox. A Spectral Analysis window for the current selection is made by selecting Spectral Analysis from the Data Analysis menu. By default, the Spectral Analysis window updates itself for each new selection. You can freeze the subset in the Spectral Analysis window so that it does not update with new selections. This allows spectra from different subsets to be compared.

Spectral Analysis In this exercise you will run Interactive Spectral Analysis in all three modes, and then compare the results of running deconvolution on the data. Deconvolution testing may become very involved in certain situations. One criterion that you may use to help decide on decon parameters is to look at amplitude (or power) spectra of the trace data before and after decon. If the decon has worked properly, you should see some “flattening”, or “whitening” of the spectrum after decon relative to before. In this exercise we will look at such a comparison on a single shot record.

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1. Build the following flow to run the ISA in its simplest configuration:

Editing Flow: 3.5-Decon Test and ISA Add

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Disk Data Input Select dataset: -------------------------”Shots-with geometry” Trace Read Option: ----------------------------------------------Sort Interactive Data Access?: ---------------------------------------No Select primary trace header entry: -------------------------SIN Select secondary trace header entry: ---------------- NONE Sort order for dataset: ------------------------------------------16/

Automatic Gain Control Interactive Spectral Analysis Data select method: ---------------------------------------- Simple Display data by traces or ensembles: -------- Ensembles ----Default the remaining parameters---2. Execute the flow.

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Interactive Spectral Analysis - Simple Mode 3. Change the contents of the display by using the View ➛ Visibility pull down menu, and selecting the individual tiles of interest. 4. Exit from the display using the File ➛ Exit and Stop Flow pull down menu. 5. Edit the parameters of the Interactive Spectral Analysis to execute the Single Subset mode instead of the Simple mode.

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6. Execute the flow again.

Interactive Spectral Analysis - Single Subset Mode In this mode you can select a Single Subset of the available data for the purposes of computing the average power and phase specta.

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7. Click on the Select Rectangular Region icon and then draw a box around an area of interest. The data window and spectral windows will change configuration to match your data selection.

You can move or redraw this window as many times as you wish. 8. Exit from the display using the File ➛ Exit and Stop Flow pull down menu. 9. Edit the parameters of the Interactive Spectral Analysis to execute the Multiple Subset mode instead of the Single Subset mode. Also choose to Freeze the selected subsets.

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10. Execute the flow again.

11. Click on the Select Rectangular Region icon and draw a box around an area of interest and then select the Options ➛ Spectral Analysis pull down menu.

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12. If you select a new area and repeat the Options ➛ Spectral Analysis pull down selection, a new window will appear. In this way you can compare the spectral results for different areas. 13. Select File ➛ Exit and Stop Flow. 14. Copy your flow to compare a shot before and after deconvolution with an IF-ELSEIF loop.

Editing Flow: 3.6-Decon QC with ISA Add

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Disk Data Input Automatic Gain Control Reproduce Traces Trace grouping to reproduce: --------------------- Ensembles Total number of datasets: ----------------------------------------2

IF SELECT Primary trace header word: ------------- REPEAT SPECIFY trace list: ---------------------------------------------------1

ELSEIF SELECT Primary trace header word: ------------- REPEAT SPECIFY trace list: ---------------------------------------------------2

Trace Muting Select mute parameter file: --------------------------”FB Mute”

Spiking/Predictive Decon Decon operator length(s):---------------------------------------160 Select decon gate parameter file: -------------”decon gate”

ENDIF Interactive Spectral Analysis Data select method: --------------------------Multiple Subsets Freeze the selected subset?: ---------------------------------Yes Display data by traces or ensembles: -------- Ensembles 15. After the display comes up you can select the Options ➛ Spectral Analysis pull down menu to show the spectral estimate for the data before decon.

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16. You can use the Slope icon to calculate the dB roll on/off of the amplitude spectrum. 17. Click on the Next ensemble icon to display the data after decon. 18. Select the Options ➛ Spectral Analysis pull down menu again to show the spectral estimate for the data after decon. Observe the flattened amplitude spectrum and the change in the dB scale. Do you believe the amplitudes above 80 Hz? 19. When done File ➛ Exit and Stop Flow from each of the display windows.

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6-32

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Can you Pick Gates and Windows in Trace Display

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How do you Pick Bad Traces

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Do you understand Automatic Parameter Testing

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Can you design an IF/ENDIF conditional processing tree

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Can you interactively test FK Filters and Spectral Analysis


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Chapter 7

Elevation Static Corrections Datum static corrections are generally required for land data to compensate for adverse traveltime effects of topography and variations in weathering thickness and velocity. ProMAX offers three methods of applying datum-static corrections, depending on whether or not the sources are on the surface. All of these options are within the Datum Statics Calculation and the Datum Statics Apply processes, which actually calculate and apply the static corrections. This process utilizes a database_math file to create and manipulate related database entries. (This file can be found in the $PROMAX_HOME/port/misc directory.) These database values are then used to create trace header entries and apply appropriate static shifts to traces. You can also use refraction statics to calculate and apply datum statics. Refraction statics will be covered in a later chapter.

Topics covered in this chapter: ❏ Elevation Statics Discussion ❏ Calculate Elevation Statics ❏ Apply Elevation Statics ❏ Apply User Statics

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Chapter 7: Elevation Static Corrections

Chapter Objectives

4a. Elevation Statics

This chapter explains how to calculate and apply elevation statics. Upon completion of this chapter you should:

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Understand the concept of Elevation Statics

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Know how to choose a proper Processing Datum

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Be able to Calculate and Apply Elevation Statics

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Be able to Import and Apply User Statics


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Elevation Statics All statics computations are performed in the database. Datum Statics Calculation* calculates the elevation (datum) static corrections. Datum Statics Apply applies the static corrections to input data. Datum Statics Calculation* performs the following functions: •

Compute static time shifts to take the seismic data from their original recorded times, to a time reference as if the data were recorded on a final datum F_DATUM (usually flat) using a replacement velocity (usually constant).

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Compute N_DATUM (a smooth surface used as the processing datum).

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Partition the total statics into two parts, the Pre (before) NMO term and Post (after) NMO terms relative to N_DATUM.

Datum Statics Apply performs the following function: •

Apply the Pre (before) NMO portion of the statics and write the remainder to the trace header.

In Datum Statics Calculation* you have the option to shift prestack data to a floating datum or a final datum. You supply a final datum elevation and a replacement velocity. The elev_stat_math file then establishes values in the database for F_DATUM, N_DATUM, S_STATIC, R_STATIC, and C_STATIC. Details of this process can best be understood by examining the contents of the elev_stat_math file. This file typically resides in $PROMAX_HOME/port/misc. Datum Statics Calculation* then creates four new header entries for statics: NMO_STAT, FNL_STAT, TOT_STAT and NA_STAT. The integer multiple of the sample period (usually a multiple of 2 or 4 ms) portion of NMO_STAT is automatically applied by Datum Statics Apply, shifting traces to the floating datum. The fractional sample period portion is written to the NA_STAT header entry and applied later. Normally the NA_STAT is applied during NMO, which will interpolate the data to the fractional static properly. If you select to process to a final datum, C_STATIC is set to zero. Recall that NMO_STAT = S_STATIC + R_STATIC + C_STATIC and that C_STATIC = -1.0*FNL_STAT. NMO_STAT is the static that shifts Landmark


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traces to the final processing datum, and FNL_STAT is zero because your data are at the final datum.

Datum Statics Terminology S.P.

CDP

Receiver N_DATUM

NMO_STAT

Vweathering

Surface Elevation

NMO_STAT Shot Vreplacement

Base Weathering

S_STATIC

FNL_STAT

C_STATIC

R_STATIC

F_DATUM

Database Attributes: N_DATUM = floating datum F_DATUM = final datum S_STATIC = (F_DATUM - ELEV + DEPTH) / DATUMVEL R_STATIC = [(F_DATUM - ELEV + DEPTH) / DATUMVEL] - UPHOLE C_STATIC = 2 * [(N_DATUM - F_DATUM) / DATUMVEL]

Trace Header Values: N_DATUM = floating datum NMO_STAT = S_STATIC + R_STATIC + C_STATIC FNL_STAT = - C_STATIC TOT_STAT = cumulative applied statics NA_STAT = statics less than one sample period which are not-yet-applied (If TOT_STAT = 21.2 ms, and the sample period is 4 ms, NA_STAT = 1.2 ms)

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Calculate Elevation Statics 1. Create the following flow to calculate elevation statics for your data.

Editing Flow: 4a.1-Calculate Datum Statics Add

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Datum Statics Calculation* Elevation or Refraction: --------------------------------Elevation Final datum elevation: -----------------------------------------800 Replacement velocity: -----------------------------------------8000 Database math method:--Shot Holes Using Uphole Info NMO static method: ------------------------------------Elevations Length of smoother: -----------------------------------------------51 Processing DATUM: --------------------------------NMO DATUM Run ID:------------------------------------------------------------------01 2. Enter the final datum, replacement velocity, and length of smoother. For this dataset, use a final datum elevation of 800 ft. and a replacement velocity of 8000 ft/sec. 3. Select the Database Math Method - Shot Hole Using Uphole Info. The Database Math Method determines which *_stat_math file to utilize. There are 4 choices: •

Shot Hole Using Uphole Info: If you want to honor the shot depth and uphole information, use the elev_stat_math file.

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Shot Holes Ignoring Uphole Times: If you do not trust the uphole information, then you can override the weathering velocities calculated with uphole times and shot depths and supply your own weathering velocity. This option will use the noup_stat_math file.

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Surface Source: If you have a surface source.

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Other: If you have built a new *_stat_math file by modifying one of the existing *_stat_math files, you can input the path name to the modified *_stat_math file.

4. Select the NMO static method - Elevations. Use a smoother of 51.

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The smoother is defined as number of CDPs to smooth over. This parameter may require some testing to generate the desired N_DATUM. 5. Select NMO Datum (floating) for Processing datum. 6. Choose a Run ID of 01. This will generate S_STATIC, R_STATIC, and C_STATIC and copy them to S_STAT01, R_STAT01, and C_STAT01. 7. Execute the flow. 8. When the job completes exit the flow, and select the Database menu. 9. From the DBTools window select the SRF tab (order), and then by double clicking view the following attributes: R_STAT01, F_DATUM, DATUMVEL, and ELEV (receiver elevation). Notice the inverted relationship between the static and the elevation. Select the SIN tab, and view the following attributes: S_STAT01, and ELEV (elevation of surface at the shot locations). From the CDP order, view the C_STAT01 attribute. 10. Why are the source and receiver statics opposite signs? Perhaps the shots are buried beneath the final datum?

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11. Now from the DBTools window select Database ➛ XDB Database Display. 12. From the XDB display select Database ➛ Get. From the CDP order, view ELEV, and N_DATUM (floating datum). Notice the effect of the 51 point CDP smoother you applied.

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Apply Elevation Statics 1. Copy the flow “3.4-FK Analysis/Filter” to apply pre-processing, and elevation statics to your data.

Editing Flow: 4a.2-Apply Datum Statics Add

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Disk Data Input Select dataset: ----------------------------Shots-with geometry Trace read option: --------------------------------------------Get All ----Default all other parameters----

Trace Kill/Reverse Trace Kill/Reverse Trace Muting True Amplitude Recovery F-K Filter Spiking/Predictive Decon Datum Statics Apply Source datum statics database parameter: ----------------------------------------------SIN GEOMETRY S_STAT01 Receiver datum statics database parameter: ------------------------------------------SRF GEOMETRY R_STAT01 CDP datum statics database parameter: ------------------------------------------------CDP GEOMETRY C_STAT01

Disk Data Output Output Dataset Filename: ------Shots-decon/elev statics ----Default all other parameters---Data output from this flow will later be input to velocity analysis. 2. Execute the flow. 3. Once the job finishes view the shots with flow “1.1-View Shots”. Examine the trace headers for NMO_STAT, FNL_STAT, TOT_STAT, and NA_STAT using the Header icon.

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Apply User Statics If shot and receiver statics to a final datum have been calculated outside of ProMAX, the statics can be incorporated into a processing flow. Use the ASCII file import option in XDB Database Display to create entries which may be accessed by Datum Statics Apply. Datum Statics Apply creates the necessary database entries, and partitions these imported statics into NMO_STAT and FNL_STAT. The sample period multiple portion of NMO_STAT is applied to the traces by Datum Statics Apply, and the remainder is stored in NA_STAT to be applied later. Recall: NMO_STAT = S_STATIC + R_STATIC + C_STATIC. Therefore Datum Statics Apply will recalculate NMO_STAT using the N_DATUM and C_STATIC previously calculated by Datum Statics Calculation* When these statics are imported to the SIN and SRF Ordered Database Files, they must both be of type Geometry and the Attribute names must be USERSTAT.

Apply External Statics In this exercise, you will import static data calculated elsewhere, and then apply it to your trace data. For this class, no ASCII format statics file is available, therefore, you will use the XDB Database ASCII Save functionality to output an ASCII file of shot and receiver statics created in the previous exercise. You will then import these statics back to the database. This will allow you to see both the ASCII import and export portions of the database. Caution: Apply User Statics is an alternate method for applying datuming type statics. Only one of the datuming processes should be run on a dataset. Use either Datum Statics Apply, Apply User Statics, or Apply Refraction Statics, but only one. Refer to the helpfiles for additional statics related information.

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1. Place a copy of the statics file in a directory, accessible by ProMAX. •

Since no ASCII statics file is available, create one with the database ASCII save function. To initiate the save procedure, bring up DBTools with the Database global command in the flows window, and then select Database ➛ XDB Database Display.

•

Bring up the attribute selection by Database ➛ Get. Display SRF: R_STATIC. This attribute can now be saved to an ASCII file. Select ASCII ➛ Save from the global commands to get the following window.

•

Step 1 - Select User-defined File in the popup window and enter a full directory path and filename without an extension. (The extension, .a_db is created by the program.) Select OK.The defined path, filename, and attribute name appear.

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Step 2 - Click on the attribute name, in this case R_STATIC. Enter your own description or accept the default description and click on OK to create the ASCII file. Repeat this entire procedure to save S_STATIC to an ASCII file. You now have ASCII files that are ready to import in the next part of the exercise. When finished, select Cancel from the ASCII save window.

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2. Select ASCII ➛ Client from the menu bar.

3. Click on File and enter the full path and filename (including extension) of the ASCII file. Click OK and the contents of the ASCII file are displayed. The ASCII/CLIENT path is a generic ASCII file import functionality. 4. Once the ASCII file is displayed, select the Order (SRF or SIN), Infotype (GEOMETRY), and Attribute (USERSTAT). 5. Click on Location Index and then define the rows and columns to import. The rows and columns containing the values to be imported are identified one of two ways: •

Rows can be painted by holding down MB1 and moving the mouse over all rows. The included rows will highlighted black. Columns for Location Index numbers (station numbers) are painted using MB2 and highlight in red. Columns for Attributes (statics values in this example) are painted using MB3 and highlight in blue).

•

Click on any of the Rows or Columns buttons and you will be prompted to manually enter starting and ending values.

6. Click on Display.

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You will be prompted for an attribute description. Enter your description of the USERSTAT attribute “R_STATIC USER” and select OK. This displays the data you defined on import. 7. Save the new attribute in the database. Click Cancel in the Client ASCII Import window, then select Database ➛ Save from the main menu bar. Click on USERSTAT in the On-Screen Attributes to save window. Wait a moment and click OK in the acknowledgment window. Your USERSTAT values are now saved in the Database. Be sure you complete the ASCII Import steps for both shot and receiver ASCII files. 8. Copy flow “4a.2-Apply Datum Statics.” Replace the static values in Datum Statics Apply with the user statics.

Editing Flow: 4a.3-Apply User Statics Add

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Disk Data Input Trace Kill/Reverse Trace Kill/Reverse Trace Muting True Amplitude Recovery F-K Filter Spiking/Predictive Decon Datum Statics Apply Source datum statics database parameter: --------------------------------------------SIN GEOMETRY USERSTAT Receiver datum statics database parameter: ------------------------------------------SRF GEOMETRY USERSTAT CDP datum statics database parameter: -------------------------------------------------CDP GEOMETRY C_STATIC

Disk Data Output Output Dataset Filename: -----Shots-decon/user statics

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9. Datum Statics Apply will know to use the user_stat_math file for the Database Math Method. The user_stat_math file generates S_STATIC and R_STATIC by copying the SRF and SIN USERSTAT values that were imported to the database. These are partitioned into the database parameter C_STATIC and into the trace header value FNL_STAT. 10. Execute the flow. The trace headers are updated and the are traces shifted to the floating datum. 11. Once the job finishes view the shots with flow “1.1-View Shots”. Examine the trace headers for NMO_STAT, FNL_STAT, TOT_STAT, and NA_STAT using the Header icon.

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What are Elevation Statics

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What is a good smoother for the Processing Datum

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How do you Calculate and Apply Elevation Statics

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Can you Import and Apply User Statics


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Chapter 8

Brute Stack In this chapter you will import a velocity field. You will then use this field to apply NMO and create a stack.

Topics covered in this chapter: ❏ RMS Velocity Field ASCII Import ❏ Brute Stack with Elevation Statics ❏ Display Stack

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Chapter 8: Brute Stack

Chapter Objectives

5. Brute Stack

This chapter creates you first QC stack of the data. Upon completion of this chapter you should:

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Understand how to Import Velocities

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Understand the NMO and Stack Parameters


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RMS Velocity Field ASCII Import One critical part of the pre-stack sequence is to apply normal moveout. You may want to build a stacking (RMS) velocity parameter table from a pre-existing field. The following exercise allows you to import an ASCII RMS velocity field to build the parameter table. 1. From the Flows menu select Tables.

2. A list of possible parameter tables will appear. Use the scrollbar located on the right-hand side of the window to scroll to the bottom of the list. 3. Select the VEL (RMS (stacking) Velocity) table This will take you to the RMS velocity table menu. 4. Click on Create. Do not click on Add.

5. Enter the description name for your imported velocity. Use a name similar to “imported from ascii file”. This opens a parameter table editing window in the form of a spreadsheet.

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6. Click on the File ➛ Import pull down menu. This opens two new windows, an empty viewing window and a File selection window.

7. Input the absolute path name to the directory where the velocity file is stored and append a /* to the end of the pathname. Click on Filter. (/misc_files/2d/*.) 8. Select the file as indicated by your instructor and click on OK. The ASCII file is opened, and the contents displayed in the Import viewing window.

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9. Click on Format. 10. Enter a new format definition name “Vels Import Format” or select a previously defined format (you probably do not have any yet). 11. Click on OK. A format window will open.

12. Click on CDP and then drag the mouse over the appropriate columns on the import file window to define the correct columns for the CDP value.

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13. Continue to define column numbers for Time and Vel_rms.

14. Click on Apply. This will open an ‘Apply Import’ window. NOTE: You do not have to select the rows to import since the database will search for valid CDP numbers with associated velocities.

15. Select “Overwrite ALL existing values with new import values” and OK.

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This will load the values into the table:

16. The XCOOR and YCOOR columns are ignored for 2D. 17. Click on File ➛ Exit to save the parameter table and exit from the editor. 18. Check the table for correctness by going back to the list of tables from the User Interface and select to Edit the table. 19. Click on Edit and then select the table name.

20. Verify that the file has been saved properly. 21. Click on File ➛ Abort to exit from the editor.

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CDP/Ensemble Stack You will now use the CDP/Ensemble Stack process to create a stacked section of the data with elevation statics. 1. Build the following flow.

Editing Flow: 5.1-Stack Add

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Disk Data Input Select dataset: ----------------------Shots-decon/elev statics Trace read option: -----------------------------------------------Sort Interactive Data Access: -----------------------------------------No Select primary trace header entry: -----------------------CDP Sort order for dataset: ---------------------------------------------*/

Trace Display Label Trace label: ---------------------------------------elevation statics

Normal Moveout Correction Direction for NMO application: --------------------FORWARD Stretch mute percentage: --------------------------30. Apply any remaining static during NMO?: --Yes Long offset correction?:--------------------------------------NONE Anisotropy correction parameter eta:------------------------0. Apply partial NMO?: ----------------------------------------------No Get velocities from the database?: -------------------------Yes SELECT Velocity parameter file: --------------------------------------------------------------------imported from ascii file

CDP/Ensemble Stack Sort order of input ensembles: ------------------------------CDP METHOD for trace summing: ------------------------------Mean Root power scalar for stack normalization: -------------0.5 Apply final datum statics after stack? -------------------Yes Has NMO been applied?: --------------------------------------Yes

Disk Data Output Output Dataset Filename: -------------------STK-elev statics

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2. In Disk Data Input, select your shots with elevation statics applied, and sort by CDP. 3. Add a trace display label. 4. Apply Normal Moveout Correction. Select the imported velocity file. 5. Stack the data with CDP/Ensemble Stack. 6. Write a new stacked dataset to disk. 7. Execute the flow.

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Display Stack 1. Build the following flow to display your stack.

Editing Flow: 5.2-Display Stack Add

Delete

Execute

View

Exit

Disk Data Input Select dataset: -----------------------------------STK-elev statics

Automatic Gain Control ----Default all parameters----

Bandpass Filter Ormsby filter frequency values: ------------------ 3-6-50-60 ----Default all other parameters----

Trace Display Primary trace LABELING header entry: --------------NONE Secondary trace LABELING header entry: ------------CDP 2. Execute the flow.

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3. View the stacked dataset.

4. Exit the flow. 5. You may also stack and display the user statics dataset “STK-user statics” as a QC.

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Can you import Velocities

•

Do you understand the NMO and Stack Parameters


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Chapter 9

Neural Network First Break Picking Artificial neural networks have had excellent results solving pattern recognition problems. First break picking, trace editing, and reversed trace selection, typically tedious processing steps, are all pattern recognition problems and lend themselves to the application of neural networks. For First-break picking and trace editing, ProMAX uses a Cascade-Correlation Learning Architecture. Advantages of this algorithm include decreased network learning time and the ability to incrementally add to an existing network. The neural network compares various attributes of the correct pick to other possible picks within a window. The network recognizes the ability of an attribute to predict the correct pick and accordingly weights the network connection to that attribute.

Topics covered in this chapter: ❏ Interactive Neural Network (NN) First Break Training/Picking ❏ Batch Neural Network (NN) First Break Picking

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Chapter 9: Neural Network First Break Picking

Chapter Objectives

4b. Refraction Statics

Pick First Breaks

This chapter serves as set-up for Chapter 10 “Refraction Static Corrections.” Refraction statics are necessary in areas of severe topography or areas of complex weathering zones. First break picks are a required input to the refraction statics algorithms. Upon completion of this chapter you should:

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Understand how to Pick First Breaks

•

Be able to Train the Neural Network


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Interactive NN First Break Training/Picking The first break picker in Trace Display gives you the opportunity to interactively create and train a neural network to pick first breaks. You will manually pick some first breaks and use these picks to train a neural network. The neural network will then try to pick first breaks on selected shots, and you can QC these picks using Trace Display. NOTE: The NN First Break Picker menu in Trace Display only appears if geometry is defined, and your dataset matches the database. You can check if geometry matches the database vie MB2 under the Dataset listing from the Flows menu.

Interactive Training 1. Copy your flow “4a.2-Apply Datum Statics” and add/delete/edit processes so that it looks like the following:

Editing Flow: 4b.1-NN First Break Picking Add

Delete

Execute

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Exit

Disk Data Input Select dataset: ----------------------------Shots-with geometry Trace read option:------------------------------------------------Sort Interactive Data Access?: --------------------------------------Yes Select primary trace header entry: -------------------------SIN Sort order for dataset: ----------------------------------1,10,20/

Trace Kill/Reverse ----Use the same parameters as before----

Trace Kill/Reverse ----Use the same parameters as before----

True Amplitude Recovery ----Use the same parameters as before----

Trace Display ----Default all parameters for this process---2. Kill and reverse appropriate traces and apply true amplitude recovery before picking first breaks. Do not apply Trace Muting. Landmark


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3. Execute the flow to begin the NN sequence. Run Trace Display

“Train” the Neural Network Trace Display -> FirstBreakPicker -> Set Neural Network Parameters Create Training Dataset Create a new time gate parameter file Pick or edit a set of good picks to store in “FB Training Data” Pick or edit the time gate centered on the “FB Training Data” Neural Net Training Create a new NN weight table (e.g., “fb_weight”) or, if continuing “Training”, Use the existing NN weight table

Use Neural Network to make FB picks Trace Display -> FirstBreakPicker -> Neural Net Recall -> One time Recall Create a new OPF parameter file (e.g., “test nn picks”) Trace Display -> FirstBreakPicker -> NO Purge Neural Net Delete (MB2) “test nn picks”

Are the NN picks good? YES

Do you want to continue to “Train” the Neural Network?

YES

Go to next gather

NO Use Neural Network to pick every shot

Interactive NN FB picking Trace Display -> FirstBreakPicker -> Neural Net Recall -> Continuous Recall

Batch NN FB picking Exit Trace Display Run NN First Break Picker Run Trace Display

QC and Edit the NN FB picks on every shot

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4. From the main Trace Display menu bar, select FirstBreakPicker ➛ Set Neural Network Parameters. The following menu will appear.

Select the pick polarity and the signal/noise gate length. The neural network works well with peaks and a gate length of 100 ms. Select OK to accept these parameters. The neural network itself, however, may key off of instantaneous phase/frequency, amplitude before or after the first break, or any other pattern it can recognize. 5. From the main menu bar, select FirstBreakPicker ➛ Create Training Data set. A First Break NN Dataset window appears. Type in a name “nn first break gate” for your first break time gate, and select OK. A second window will appear for selecting a secondary key. Choose AOFFSET, and then OK. The Picking tool icon appears on the left side of the display. There will be two entries in the Pick Layers box: “FB Training Data” and the “nn first break gate.” 6. Select the “nn first break gate” table from the Pick Layers window, and pick the top of the gate. It is not necessary to make a pick on every trace, as the gate is interpolated between picks. The network tries to follow the slope of the top gate when picking first breaks, so it is necessary that the top gate closely follows the trend of the first breaks. Usually picking about 25ms above the first break, at timing line intersection works quite well. To pick the bottom of the gate click MB3 in the data window and select New Layer. The gate should contain at least three peaks, but not be so large as to lengthen execution time. It will be helpful to Zoom in on the first breaks before picking.

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7. Click on “FB Training Data” in the Pick Layer window and manually pick the first breaks.

First Break Picks

Top of time gate

Bottom of time gate

Manually pick first breaks using MB1. Pick first breaks on 20-30 traces. Because training is interactive you can incrementally train the network. This means you do not need many picks to begin training, as more picks can be added in future training runs. More picks means longer training time. Use MB3 to select the Snap to peak option.

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8. After picking, select FirstBreakPicker ➛ Neural Net Training...

A First Break NN Training window appears, including a list of First Break Weight Tables. Create a new table “weight1” and select OK. The network will be trained using your picks. While the network is training, the cursor will change from an arrow to a wristwatch. When the cursor changes back to an arrow, training is complete. 9. From the menu bar, select FirstBreakPicker ➛ Neural Net Recall ➛ One Time Recall.

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The One time Recall option applies the neural network to the currently displayed gather. A First Break NN Recall window appears.

You will be prompted to either choose an Ordered Parameter File(OPF) from the list, or create a new OPF for storing picks. Create a new OPF called “NN training test picks” for the name, enter 1000 for the offset to start picking, and default all other parameters. Select OK. The Neural Network is applied to the current gather display. The results of the picking are displayed. 10. If the picks are bad, modify your FB Training Data and retrain the network. To modify training picks, click on the Picking tool icon. Your new table of picks appears in the Pick Layers window. Remove the table from the list and activate the FB Training Data. Modify or add to these training picks, select First Break NN Training, and use the same weight table. Iterate through steps 6, 7, and 8 until you are satisfied with the results. If you still cannot get satisfactory results, try purging the Neural Network (FirstBreakPicker ➛ Purge Neural Net) and starting over. 11. Set Neural Net Recall to Continuous and click the Next ensemble icon to go to the next shot.

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You can retrain if necessary, or if you think the picks are close enough, select File ➛ Exit/Stop Flow, and choose to save edits before exiting. The weight table, and time gates are saved and can be used in the batch NN First Break Picker process to pick the entire dataset.

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Batch Neural Network First Break Picking This step uses the neural network weight matrix to pick first breaks on all shots. In the case of first-break picking, neural network picks are stored in the ordered database and can be accessed for various uses including refraction static analysis.

Pick First Breaks for entire survey In the previous exercise, we interactively created and saved a fb_weight matrix file, and a time gate. Now we will use these as input to the NN First Break Picker to pick all shots in batch mode. 1. Alter the existing flow as follows:

Editing Flow: 4b.1-NN First Break Picking Add

Delete

Execute

View

Exit

Disk Data Input Select dataset: ----------------------------Shots-with geometry Trace read option: --------------------------------------------Get All ----Default all other parameters----

Trace Kill/Reverse Trace Kill/Reverse True Amplitude Recovery >Trace Display< NN First Break Picker Select weight matrix parameter file: ----------------weight1 Number or traces in median line fit: --------------------------5 Maximum trace to trace static:---------------------------------20 Starting offset to determine first break pick slope: 1000 Select time gate parameter file: -------nn first break gate First break storage: ------------------Header and Database 4 digit ID to store pick time in TRC database: ------ 0001

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2. In Disk Data Input, input your entire dataset. Some preprocessing may be necessary, such as trace edits, filtering, scaling. Preprocessing is the same as input to the interactive NN First Break Pick Training. 3. Select NN First Break Picker parameters. Data dependent parameter selections are based on testing or experience. Parameters are consistent with those for the interactive NN FB Pick Training. Input the fb_weight matrix “weight1” file. You must specify a starting offset for the picker. Specify an offset with good S/N and no shingling of refractors. For this data, an offset value of about 1000 ft. is adequate. 4. Execute the flow. 5. Once the picker is completed, QC your picks. Edit the same flow, and toggle “NN First Break Picker” inactive, and “Trace Display” active, and execute the flow. From the menu bar in the Trace Display window, select Picking ➛ Edit Database Values (first breaks)... Select NN_PICK as the Infotype, and PICK0001 (the 12345678 picks are from the interactive picker) from the OPF File Selector, and use the same name to save edits. Don’t spend too much time editing picks here. The easiest way to view and edit your picks is to use the first break editing capabilities of the Refraction Statics process in the next chapter. Also do not worry about zero picks on the dead traces.

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9-12

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Can you Pick First Breaks

•

Do you know how to train the Neural Network


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Chapter 10

Refraction Static Corrections This section covers the steps for calculating and applying refraction statics. First break picks are required as input into this process. The refraction statics processes expects R_STATIC and S_STATIC to be present in the database. Once these attributes are in the database the refraction statics processes can fill them in with more accurate static values than simple elevation static calculations. The recommended method to create R_STATIC and S_STATIC database entries is to run the process Datum Statics Calculation*, before running the refraction statics processes.

Topics covered in this chapter: ❏ Refraction Statics ❏ Refraction Statics Calculation - coordinate based ❏ Apply Refraction Statics ❏ Stack with Refraction Statics

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Chapter 10: Refraction Static Corrections

Chapter Objectives

4b. Refraction Statics

Pick First Breaks

This chapter serves as an alternative to Chapter 7 “Elevation Statics Corrections.” Refraction statics are necessary in areas of severe topography or areas of complex weathering zones. Upon completion of this chapter you should:

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Understand the difference between Refraction and Elevation Statics

•

Be able to Calculate Refraction Statics

•

Be able to Apply Refraction Statics


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Refraction Statics ProMAX provides an interactive interface for final editing of first-break picks, layer assignment, velocity and delay time editing. The final results of this process are a near-surface depth/velocity model and travel-time corrections to the final datum written to the database. Solutions are calculated by three methods: Generalized Reciprocal Method (GRM), Standard Delay Time (DLT), and Diminishing Residual Matrices (DRM). Each solution is written to the database, giving you the option of selecting the most appropriate solution. NOTE: First breaks must be picked and written to the database prior to this exercise. Please refer to the Neural Network First Break Picking exercise earlier in this manual.

Refraction Statics - 2D In this exercise you will use the Refraction Statics* process and firstbreak pick times to calculate a near-surface model and travel-time corrections. NOTE: This process does not use XY values, therefore it is not applicable to crooked lines. Crooked may be defined as any line with a greater than 15 degree bend. If you are calculating refraction statics on a crooked line, refer to the Refraction Statics Calculation* process described later in this chapter.

This process calculates shot and receiver refraction statics to shift to the final datum and updates the database. Results of this exercise will be used by Datum Statics Apply in a later exercise.

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Editing Flow: 4b.2-Refraction Statics Add

Delete

Execute

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Exit

Refraction Statics* Select display DEVICE: -----------------------------This Screen Select First Break Times file: -TRC:NN_PICK:PICK0001 Get LAYER Picks from DATABASE: -------------------------No Get Refractor Velocities from DATABASE: ----------------No Select TRACE data file: ---------------Shots-with geometry Compute V0 from UPHOLE data?: -------------------------Yes Number of layers: ----------------------------------------------------1 Use Delay Times in velocity/depth model?: ------------Yes Use Deep Hole delay time algorithm?: ---------No Use GRM in velocity/depth model?: -----------------------Yes Specify GRM minimum XY distance: -------------0. Specify GRM maximum XY distance: ------------0. Specify GRM XY distance increment: ----------55. Final datum Elevation: -----------------------------------------800 Replacement Velocity: ----------------------------------------8000 Use Uphole Time in source statics algorithm?: ---------No 2. Select Refraction Statics parameters. Select your first break pick file. Picks are typically in the database in the TRC order and NN_PICK Infotype. Select the batch PICK0001 file for this exercise. Input trace data will be the raw shots. Enter a final datum of 800 ft. and a replacement velocity of 8000 ft/sec.

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3. Execute the flow.

A menu appears with a list of options. Follow the normal sequence from top to bottom using mouse button helps.

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4. Click on Edit Picks.

Use the Edit Picks option for final editing of first-break picks prior to inversion. Use the mouse button helps to guide your editing; use the options on the right side of the screen to edit your data. To guide your editing you may want to turn on the seismic by toggling on Add Traces. Click MB2 below the data to move to the next set of shots, or MB3 to move backwards. Select Done to go back to the main menu. Select Yes to Output Updated Picks to the Database, and provide a name “RefrEdit” for the pick file. Warning: The editing in this function currently snaps to a sample and not necessarily the true peak. This could lead to up to a 4ms pick error. Residual statics, however, should correct for these slight errors.

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5. Click on Define Layers.

This option displays pick times for both sides of the spread, as in the case of split spread shooting. Define the offset range for each layer by holding down and dragging MB1 over the corresponding range, then releasing MB1. This is an interpretive process. Note: The displayed velocity is only a guide; you are not assigning a velocity for the layer. Avoid inflection points where refractors are shingling. Also avoid low S/N areas. The velocity you get should be on the order of 7500 f/s. Select Done and then Yes to Output Refractor Picks to Database.

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6. Click on Refractor Velocity.

This option provides for interactive editing of the weathering velocity and the calculated velocity model for each refractor. The top display is a graph of velocity vs. station. Editing or smoothing of the velocity values is done only in the bottom display which is a zoomed version of the top display. Select a velocity to edit by selecting the appropriate box in the upper right, such as Edit V1. Refer to mouse button helps for editing functionality. The plotted points represent the layer number and are color coded by the calculation method used. Perhaps there is a problem in V0 resulting from questionable uphole times? You may want to smooth through V0 or replace it with a constant 5000 f/s. Select Done when editing is complete, and Yes to Output Refractor Velocities and V0 to Database.

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7. Click on View Static Solutions.

This option allows interactive editing of the calculated intercept times for each layer. You will first view/edit Receiver Delay Time Solutions, then Source Delay Time Solutions. The top display is a graph of intercept time vs. station. Editing of the intercept values is done in the bottom display. Refer to mouse button helps for editing functionality. Select Done when editing is complete. Select Yes to view either Receiver Delay Time corrected Shot Records or Source Delay Time corrected Receiver Records, depending on what you edited. Select Done when finished viewing.

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8. Click on Refractor Depth Model.

This option allows viewing the calculated near-surface depth model, calculated from the velocity and intercept data. Although there is editing functionality in this option, if the depth model is not geologically possible you may want to re-edit first break picks, velocities or intercept times, and then rerun this step. Notice how the GRM method falls short where there are no sources for the reciprocal method to calculate the receiver static. Select Done and Yes to Output Refractor DEPTHS to Database.

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9. Click on Output Statics.

This option allows viewing the shot and receiver statics calculated from the model data. Source statics from the elevation of the shot through the model to final datum are displayed with the character “s”. Receiver statics from the elevation of the receiver through the model to final datum are displayed with the character “r”. Select Yes to Output STATICS to the DATABASE. NOTE: In the main menu, click MB2 on any previous box to view its current values or MB1 to re-edit those values. If you choose to re-edit, be sure to step through all subsequent options to correctly recalculate your final statics.

10. Select Exit.

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11. Exit the current flow. From the Flows window, access the database with the Database global command option. To view the calculated refractor depths and statics solutions simply double click on the appropriate attribute. You can also go the XDB Database Display to overlay the static values. The Order is SRF or SIN, and the Infotype for the total static is Geometry. This is the value that will be used by the process Datum Statics Apply. In the Statics Infotype, there are incremental statics that represent the difference between the total refraction statics, and the original elevation statics. To the right of the attributes are detailed descriptions of each.

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Coordinate Based Refraction Statics ProMAX provides a coordinate based refraction statics algorithm that computes refractor velocities and delay times, a near-surface depth/ velocity model and travel-time corrections to the final datum from offset and first break information. There is also an option to edit first break pick files automatically. All of the preceding attributes are written to the database. Multiple layer models can be created, and refractor velocities and depths and velocities will be computed for each layer. There are many advantages to using this technique:

• • •

Very robust for noisy first break picks. Works independent of shooting geometry. First break picks are not required for every shot.

The main disadvantages are that there is not a graphical interface for editing. The source and receiver static solutions are applied to the data in a future step, Apply Refraction Statics. NOTE: First break times must be picked and written to the database prior to this exercise. Please refer to the Neural Network First Break Picking exercise earlier in this manual.

As a part of this exercise you will see that there are two ways to enter the refractor offset ranges. These are: •

Manually.

•

By picking a Pick Top Mute in Trace Display.

In this exercise you will use first-break pick times to calculate a nearsurface model and travel-time corrections. This process calculates shot and receiver refraction statics to shift to the final datum and updates the database. Results of this exercise will be used by Apply Refraction Statics in the next exercise.

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1. Edit the current flow as follows:

Editing Flow: 4b.2-Refraction Statics Add

Delete

Execute

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Exit

>Refraction Statics*< Refraction Statics Calculation* Select first break time file: -----TRC:NN_PICK:PICK0001 Number of layers: ----------------------------------------------------1 Identification number: ----------------------------------------------1 Minimum fold: ---------------------------------------------------------1 Shooting Geometry: -----------------------------2D split spread V0 options: -------------------Compute V0 from uphole data INPUT REFRACTOR OFFSET?: ----------------------------- Yes Refractor Offset specification: --------User typein Enter SIN and refractor offsets: -----------------------------------------------------10:-1800--500,500-1800/ COOMPUTE REFRACTOR VELOCITIES?: -------------- Yes Type of INITIAL velocity computation: ---- MEAN Smooth INITIAL velocities before output?: ---Yes Length of INITIAL velocity smoother: ----------201 Edit first break times (median velocity?: ------No COMPUTE DELAY TIMES?: ----------------------------------- Yes TYPE of delaytime ALGORITHM: -Gauss-Seidel Number of iterations: ------------------------------------5 TYPE of delay time computation: ----------- MEAN Iterate refractor velocity?: -------------------------- No COMPUTE REFRACTOR DEPTH MODEL?: ------------- Yes First refractor smoothing: -----------No smoothing COMPUTE SOURCE and RECEIVER STATICS?: ----- Yes Final datum Elevation: -----------------------------800 Replacement method: -----------Refractor Velocity COMPUTE RESIDUAL STATICS:? ----------------------------No

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2. Select Refraction Statics Calculation* parameters. Select the first break time to use for the statics decomposition. These time picks will be in the TRC OPF and will normally be of the type NNPICK. Select the PICK0001 file. If you have output an edited pick file, it will be stored with an infotype of FBPICK. Enter the number of layers to model, in this case use one layer. The identification number will be 1 for the first run through the process. The shooting geometry is 2D split spread. There are 5 steps to Refraction Statics Calculation* described in the menu. They may all be turned on for refraction statics computation or you may select to run one option at a time and view the output in the database. 3. INPUT V0 and REFRACTOR OFFSET. In this exercise we’ll compute V0 from uphole times and manually type in the refractor OFFSET range. Three database entries are created in the SIN OPF: SIN REFR_OFF OFFPSS11 ---Near positive offset of refractor. SIN REFR_OFF OFFPSE11 ---Far positive offset of refractor. SIN REFR_OFF OFFNGS11 ---Near negative offset of refractor. SIN REFR_OFF OFFNGE11 ---Far negative offset of refractor. SIN VELOCITY V0INIT11 ----Weathering Velocity. These database attributes may be edited. The V0INIT11 is written over each time you rerun the module. If you want to make a permanent change, edit the uphole times. 4. COMPUTE REFRACTOR VELOCITIES. With this subheading turned on a refractor velocity is calculated based on the first break times and the offset range from the previous step. Although you can smooth the velocity model in the menu, you may wish to look at your model in the database before smoothing. You could then either smooth in the database (Good to see immediate results of smoothing), or define a smoother in the menu.

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There is also an option to edit the first break picks automatically by setting a deviation from the median velocity described by the offsets. If any picks deviate more than the selected amount they will be killed, and set to NULL in a new first break picks database file TRC F_B_PICK FBPEDITX, where X is the run identification number. Only the good picks will be included in this file. Remember to examine this edited file. Three database entries are created. CDP VELOCITY VCINIT11 -- CDP velocity for 1st refractor. SIN VELOCITY VSINIT11 ----Source velocity for 1st refractor. TRC F_B_PICK FBPEDIT1 ----Edited first break pick file. These database attributes may be edited. 5. COMPUTE DELAY TIMES. Once CDP velocity is available, delay times for shots and receivers may be computed. This is done by iteration, starting with source delay time estimates, followed by receiver delay time estimates, and (optionally) finalized by CDP velocity updating. Values are not computed for any SIN, SRF or CDP that does not meet the minimum fold (menu parameter) criterion. Once the decomposition is complete for each refractor, these missing values are interpolated based on X and Y. Three database entries are created. SIN DELAYTIM SDELAY11----Source Delay times. SRF DELAYTIM RDELAY11--- Receiver delay times. CDP VELOCITY VCFIN011---- Final CDP velocities.

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6. COMPUTE REFRACTOR DEPTH MODEL. The depth model stage inputs delay times and refractor velocities in CDP, interpolates refractor velocity into SIN and SRF, computes a depth model for sources and another for receivers. Optionally, the first refractor depth in SRF may be projected into CDP, smoothed, projected back into SRF, V0 recomputed in SRF based on the smoothed depths, new V0 projected from SRF to SIN, and finally SIN and SRF depth models computed. Six database entries are created. SIN REFDEPTH SDEP_011---Source Refractor Depth. SIN VELOCITY VSFIN011 -- Final Source velocity for 1st refractor. SIN VELOCITY V0FIN011 ---Final Weathering Velocity. SRF REFDEPTH RDEP_011--Receiver Refractor Depth. SRF VELOCITY VRFIN011- - Final Receiver velocity for 1st refractor. SRF VELOCITY V0FIN011 ---Final Weathering Velocity. 7. COMPUTE SOURCE AND RECEIVER STATICS. The statics computation stage inputs refractor velocities and refractor depths, computes source and receiver depths to the FINAL datum of 800 feet and outputs static values. We have the choice of inputting a constant velocity or the bottom refractor velocity. For this exercise choose a user specified value of 8000 ft/sec. Two database entries are created. SRF GEOMETRY RSTAT00X --- Receiver statics. SIN GEOMETRY SSTAT00X ----Source statics.

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Apply Refraction Statics The Datum Statics Apply program uses refraction statics computed by the Refraction Statics* or Refraction Statics Calculation* processes, along with elevations from the database to compute NMO_STAT and FNL_STAT. As with the previous methods, these header entries are updated and the integer multiple of a sample period portion of NMO_STAT is applied to the trace and the remainder is written to NA_STAT to be applied later. If the option to process to a final datum is selected, C_STATIC is set to zero. Recall: NMO_STAT = S_STATIC + R_STATIC + C_STATIC. Therefore, C_STATIC is zero, NMO_STAT becomes the static shifting traces to the final datum, and FNL_STAT is zero because your data will already be at the final datum. It is important to note that the Datum Statics Apply process first checks to see if other statics have been applied to the traces by an earlier processing step. If statics are applied, Datum Statics Apply first removes these statics returning the traces to their original recorded time reference. Also, if previous statics contained any hand statics or shot delay corrections, these statics are also removed and should be reapplied. The refraction statics to be applied must be calculated prior to running Datum Statics Apply. Datum Statics Apply is generally executed in a processing flow prior to velocity analysis. This process updates the statics trace headers and applies the shifts to each trace.

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Apply Refraction Statics to your data. 1. Build the following flow:

Editing Flow: 4b.3-Apply Refraction Statics Add

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Disk Data Input Select dataset:-----------------------Shots-decon/elev statics Trace Read option:-------------------------------------------Get All ----Default all other parameters----

Datum Statics Apply Source datum statics database parameter: ---------------------------------------------SIN GEOMETRY SSTAT001 Receiver datum statics database parameter: ------------------------------------------SRF GEOMETRY RSTAT001 CDP datum statics database parameter: -------------------------------------------------CDP GEOMETRY C_STATIC

Disk Data Output Output Dataset Filename: ------Shots-decon/refr statics ----Default all other parameters---NOTE: We do not have to recalculate the datum statics (...C_STATIC...) unless you want to change the smoother of N_DATUM, the datum elevation, or the replacement velocity. Datum Statics Apply will back out the elevation statics before it applies the refraction statics.

2. In Datum Statics Apply, select your Source and Receiver statics. You have the option of choosing the statics from any of the refraction statics calculation methods.

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•

For Source statics, the order is SIN and the Infotype is Geometry. You will have an available list of parameters files, saved in Refraction Statics*. Select one of the following statics files:

•

GRM Refraction Statics for Sources to Final datum. The GRM method is not valid for this line since it is not split spread.

•

DRM Refraction Statics for Sources to Final datum.


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•

DLT Refraction Statics to Final datum.

•

Coordinate based- Source statics to Final datum from coordinate based method.

For Receiver statics, the order is SRF and the Infotype is Geometry. Select one of the following statics files: •

GRM Refection Statics for Receivers to Final datum. The GRM method is not valid for this line since it is not split spread.

•

DRM Refraction Statics for Receivers to Final datum.

•

DLT Delay Time Refr. Statics-Receivers to Final datum.

•

Coordinate based- Receiver statics to Final datum from coordinate based method.

3. Add a new output dataset “Shots-decon/refr statics” 4. Execute the flow. Traces are shifted to the floating or final datum, depending on your selection. 5. Build a flow to display gathers with refraction statics applied and use the Header icon to check updated statics header entries. Display gathers with elevation statics applied instead of refraction statics and check these trace header values on the same trace. Note the differences due to Datum Statics Apply. 6. Use your previous flow “5.1-Stack” to stack the refraction corrected shots to a dataset “STK-refr statics”.

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What is the difference between Refraction and Elevation Statics

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How do you Calculate Refraction Statics

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Chapter 11

Stack Comparisons In this chapter you will use Trace Display to compare two stacks. This flow is used throughout the rest of the class to compare stack sections.

Topics covered in this chapter: ❏ Compare Stacks

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Chapter 11: Stack Comparisons

Chapter Objectives

5. Brute Stack

In this chapter you learn a slick way to compare stack datasets. This technique is quite valuable in testing processing flows and parameters. Upon completion of this chapter you should: •

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Be able to graphically compare any two stacks


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Compare Stacks 1. Build the following flow to compare stacks:

Editing Flow: 5.3-Compare Stacks Add

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Disk Data Input Select dataset: -----------------------------------STK-elev statics ----Default all other parameters----

Disk Data Insert Select dataset: ------------------------------------STK-refr statics ----Default all other parameters----


Bandpass Filter Ormsby filter frequency values: ------------------ 3-6-50-60 ----Default all other parameters----

Trace Display Primary trace LABELING header entry: --------------NONE Secondary trace LABELING header entry: ------------CDP ----Default all other parameters---2. Execute the flow. The stack with elevation statics will appear first. Use the Next ensemble icon to display the stack with refraction statics. After both stacks have been displayed, use the animation tool to compare the stacks. You may want to execute this flow again, and display both stacks on a single screen.

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Chapter Summary Upon completion of this chapter you should be able to answer the following question: •

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How do you graphically compare two stacks


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Chapter 12

Velocity Analysis and the Volume Viewer Velocity Analysis provides comprehensive interactive velocity analysis, velocity quality control, and velocity field modification capabilities. Precomputing data at predefined locations is also supported to speed the interactive session. When used in the precomputed mode, the process reads in precomputed analysis data, as opposed to standard CDP-ordered data. This precomputed data is generated using Velocity Analysis Precompute. Preprocessing of data must be performed at the precomputing step.

Topics covered in this chapter: ❏ Velocity Analysis Precompute ❏ Velocity Analysis ❏ Volume Viewer/Editor

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Chapter 12: Velocity Analysis and the Volume Viewer

Chapter Objectives

6. Velocity Analysis

Velocity analysis is a critical aspect of any processing workflow. This chapter explores one of ProMAX’s techniques of picking and quality controling velocities. Upon completion of this chapter you should:

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Comprehend the parameters input to Velocity Analysis

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Understand how to use the Velocity Analysis Viewer in conjunction with the Volume Viewer/Editor

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Be confident in picking reasonable stacking velocity functions

ProMAX 2D Seismic Processing and Anlaysis

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Velocity Analysis Introduction Velocity Analysis is a InterProcess Communication tool (IPC tool); therefore, preprocessing of data can be performed in the same flow before passing the data on to the analysis. Velocity Analysis also allows random access to the dataset. With this feature, you can go back to the previously processed ensemble, rewind the data to the first CDP specified in the sort order for dataset, or go to any CDP in the dataset by specifying a new sort order. Velocity Analysis is used to quickly pick velocities with the semblance option. More detailed velocity information can be obtained by turning on the constant velocity strip option and the interval velocity display. Choice of the analysis locations is initially determined by selecting analysis locations using the Supergather Formation. Picks can be made on either the semblance plots or the constant velocity strips, and picks made on one display will appear on the other display. Velocity Analysis only processes single ensembles of data, such as CDPs or groups of CDPs. Creating supergathers prior to Velocity Analysis is often helpful to boost the fold in the ensembles and create more robust semblance calculations. Supergathers must be defined in a processing flow before input to Velocity Analysis or Velocity Analysis Pre-Compute. The Supergather Formation* Macro may be used to combine many CDPs. This will permit Velocity Analysis to read the combined CDPs for one analysis as one ensemble of data.

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Velocity Analysis Precompute Precomputing data at selected locations is also supported to speed the interactive session. Velocity Analysis Precompute provides a means to prepare the data to be input to the Velocity Analysis module by calculating the semblance values, stacking the CDP traces to create the supergather, and creating CVS traces at predefined locations CDP. When used in the precomputed mode, Velocity Analysis reads in only the precomputed data, as opposed to standard CDP ordered data. Preprocessing of data must be performed at the precomputing step. Precomputing velocity analysis data can significantly speed up the interactive Velocity Analysis session, especially when a large number of CDPs are used to create the supergathers.

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Precompute Velocity Analysis 1. Build the following flow to start Velocity Analysis Precompute:

Editing Flow: 6.1-Velocity Precompute Add

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Supergather Formation* Read data from other lines/surveys?: ---------------------No Select dataset: -----------------------Shots-decon/refr statics Presort in memory or on disk?: -----------------------Memory Maximum CDP fold: ---------------------------------------------180 Minimum center cdp number---------------------------------825 Maximum center cdp number--------------------------------950 Cdp increment--------------------------------------------------------25 Cdps to combine-------------------------------------------------------9

Bandpass Filter Ormsby frequency filter values: -------------------3-6-50-60 ----Default all remaining parameters----


Velocity Analysis Precompute Disk Data Output This flow is continued on the next page

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Editing Flow: 6.1-Velocity Precompute Add

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Supergather Formation* Bandpass Filter Automatic Gain Control Velocity Analysis Precompute Number of CDPs to sum into gather: --------------------------9 Apply partial NMO-to-binning:--------------------------------Yes Apply differential CDP mean statics?:---------------------Yes Absolute offset of first bin center: -------------------------27.5 Bin size for vertically summing offsets: -------------------55 Maximum offset: ---------------------------------------------6572.5 Use absolute value of offset for stacking?: --------------Yes Minimum semblance analysis value: -------------------7000 Maximum semblance analysis value: ----------------20000 Number of semblance calculations:--------------------------50 Semblance sample rate (in ms): ------------------------------20 Semblance calculation window (in ms): -------------------40 Number of stack velocity functions: -------------------------17 Number of CDPS per stack strip---------------------------------5 Scale stacks by number of live samples summed:---Yes Method of computing stack velocity functions:-----------------------------------------------------------Top/base range Velocity variation at time 0: ---------------------1000 Velocity variation at maximum time:---------3000 Velocity guide function table name:-----------------------------------------------------------------imported from ascii file Maximum stretch percentage for NMO: --------------------30 Long offset moveout correction?:-------------------------NONE

Disk Data Output Output Dataset Filename: -----------------------------------------------------------------Precomputed Velocity Analysis

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2. Select your best prestack dataset for Supergather Formation. Supergather Formation is a macro that reads the data as CDP’s, and combines them into supergathers. Data should be preprocessed gathers without NMO. Set the Maximum CDP fold to 180 (9 CDPs times 20 fold per CDP). Set the Min and Max CDP centers to 825 and 950 respectively. Set the CDP increment to 25. This will give you six analysis locations with supergathers starting at CDPs 825, 850, 875, 900, 925, 950. 3. Apply a bandpass filter. For velocity analysis, it is usually desirable to limit the frequency range of the input data. Select Ormsby filter values of 3-6-50-60. 4. Apply Automatic Gain Control. For velocity analysis, a relatively short AGC window is usually desirable. The default value of 500 ms will work fine for this exercise. 5. Set parameters for Velocity Analysis Precompute. Set the number of CDPs to sum into gathers as 9, and set the bin sizes.

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6. Select Yes to Apply partial NMO-to-binning. Supergather input to Velocity Analysis has reduced spatial separation between traces compared to the original CDP gather

Arrows indicate the direction of the Partial NMO

One Group Interval

Partial NMO and SUM Move the Traces to the NMO of the Bin Centers

Full NMO and SUM Flatten the Traces to the Zero Offset Time of the Gather

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7. Select minimum and maximum semblance values to 7000 and 20000, and set the number of stack velocity functions to 17. 8. Select Top/base range as the method of computing stack velocity functions. 9. Create a new Disk Data Output file called “Precomputed Velocity Analysis”. 10. Execute the flow.

Velocity Analysis In this flow we will set the prameters for velocity analysis to use the precomputed data from the previous flow.

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1. Build the following Velocity Analysis flow:

Editing Flow: 6.2-Velocity Analysis Add

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Disk Data Input Select dataset: ------------Precomputed Velocity Analysis Trace read option:-----------------------------------------------Sort Interactive Data Access?:---------------------------------------Yes Select primary trace header entry:-------SG_CDP

Velocity Analysis

Submenu Controls

Select display DEVICE: -----------------------------This Screen Is the incoming data Precomputed?: ----------------------Yes Set which items are visible?---------------------------------No Set semblance scaling and autosnap parameters?:--No --------------------------------------------------------------------------Semblance normalization mode: ---Scale Time Slice Contrast power factor: ------------------------------------- 1. Contrast noise factor: ------------------------------------- 0.1 Automatically snap------------------------------------------No Maximum velocity % change for snapping: ----------5 --------------------------------------------------------------------------Maximum vertical change for snapping: ------------------40 Display horizon(s)?: -----------------------------------------------No Use neural network velocity picker?: -----------------------No Interact with other processes using PD?:-----------------Yes Get guide function from existing parameter table?---Yes Velocity guide function table name: ----------------------------------------------------imported from ascii file --------------------------------------------------------------------------------Maximum stretch percentage for NMO: --------------------30 Long offset moveout correction?:-------------------------NONE Interval velocity below last knee: ------------------------------0 Table to store velocity picks: -------vels from precompute Copy picks to next location------------------------------------No

>Volume Viewer/Editor*<

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2. Set the Disk Data Input parameters as shown. Make sure to sort the input data by the user-defined header word SG_CDP. 3. Set the Velocity Analysis parameters. When you first parameterize the Velocity Analysis process, a subset of the parameters will be visible so begin by setting the “global parameters” highlighted in the flow. Be sure to create a table to store velocity picks such as “vels from precompute”. Next, select Yes for Set semblance scaling and autosnap parameters to display the semblance submenu. The default settings will work fine so turn off the semblance submenu by clicking No for Set semblance scaling and autosnap parameters. The submenu parameter settings will be retained and used even though they are not visible. The parameter Set which items are visible works the same way. Both the visiblity and semblance parameters can also be changed interactively from within the velocity analysis tool. NOTE: The Velocity Analysis parameters are only our initial guesses. Once inside the Velocity Analysis Viewer we can change any of the parameters interactively.

4. Execute the flow. The display shows a velocity semblance plot, a corresponding CDP gather or CDP supergather sorted by absolute offset, the dynamic stack positive and negative polarity, and the varying velocity stack strip panels. 5. The panel menus allows you to control several other items including the semblance scale, interval velocities derived from the RMS picks, and guide functions from previous velocity picks. From this menu you can also change the trace scaling.

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Velocity analysis window

Velocity Analysis Icons

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Next ensemble: Proceed to and process the next ensemble in the dataset. If you are currently processing the last ensemble in the dataset, this button is inactive.

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Previous ensemble: Step backward one ensemble and process. If you are currently processing the first ensemble of the dataset, this button is inactive.

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Rewind: Rewind the dataset and go back to the first ensemble as specified in the sort order. If you are currently processing the first ensemble in the dataset, this button is inactive.


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Point Dispatcher(PD): save and send the velocity picks in the current ensemble to the Velocity Viewer/Editor. This icon works only when Velocity Viewer/Editor is running, and you have told it to interact with Velocity Analysis.

6. Pick a stacking velocity function for the first ensemble. Activate the picking icon, and begin picking a function with MB1. You can pick in either the semblance display, or the velocity stack strips display. As you pick velocities on the semblance plot, the picks are also displayed on the velocity strips, and vice versa. Use the Next ensemble icon to move to the next analysis location After you pick the first location and move to the second you may want to overlay the function that you just picked as a second guide. You can do this by clicking on View ➛ Object visibility... ➛ Average of all CDPs (blue). This will display the average of all of the functions that have been picked in the output table to date. 7. Experiment with some of the other display attributes such as View ➛ Object visibility... ➛ Velocity Color Key, and View ➛ Object visibility... ➛ Interval Velocity. If your workstation performance suffers such as slow redraws, turn off the more resource intensive attributes. Once you have determined your favorite settings, you can set the flow parameters so your Velocity Analysis display is automatically configured that way.. NOTE: Your velocity picks are automatically saved to an RMS velocity ordered parameter file when you move from one location to the next or Exit the program. You also have the option to save picks using the Table/Save Picks option.

Using the Volume Viewer As you pick velocities along a line using the Velocity Analysis tool, you may want to QC the picked velocity field. This can be accomplished by simultaneously viewing a color isovelocity display of the entire velocity volume. The tool used for this is a standalone process called the Volume Viewer/Editor, and should be executed while you are running Velocity Analysis, as outlined below.

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1. After picking and saving at least one velocity analysis location, iconify the Velocity Analysis Window. 2. Return to the ProMAX User Interface. Toggle off all processes and add Volume Viewer/Editor to the flow. 3. Parameterize Volume Viewer/Editor as follows.

Editing Flow: 6.2-Velocity Analysis Add

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>Disk Data Input< >Velocity Analysis< Volume Viewer/Editor* Display DEVICE for cross-section: -------------This Screen Work in Time or Depth: -------------------------------------- Time Unit System: -----------------------------------------------DataBase Source of surface coordinate limits: ---------Seismic Data Source of depth coordinate limits: ------------Seismic Data Input Volume Type------------------ Stacking (RMS) Velocity Select input volume: -------vels from precompute To which datum is the velocity volume referenced?:----------------------------------------------------Floating Datum Display seismic data?: ------------------------------------------Yes Select poststack data file: --------STK-refr statics To which datum are the stack data referenced?:------------------------------------------------------------Final Datum To which datum are the horizons referenced?:---------------------------------------------------------------Final Datum Interact with other processes using PD?: --------------- Yes Display gather locations?:--------------------------------------Yes

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Make sure you use the same velocity table that you are currently using in Velocity Analysis.

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Also, make sure you select Yes to Interact with other processes using PD? This will allow the PD (point dispatcher) to communicate with Velocity Analysis.


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4. Execute the flow containing the Volume Viewer/Editor, and return to the Velocity Analysis display. The Volume Viewer/Editor window will eventually appear. Unless you have two screens, you will want to try different ways of arranging the windows on the screen until you have made an arrangement that is workable for you. The following diagram illustrates one way to arrange the windows on the screen:

Possible Window Arrangement If you have not picked any velocities, the display will contain zero values and the screen will be all blue and the velocity scale will be very large. If you have picked at least one velocity function, you will only see a vertical color variation in the Cross Section window.

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5. From the Velocity Viewer/Editor window, click on View ➛ Volume Display. A “Volume Controls” window will appear. Click on the Cross-section Nodes button, then Ok. This will display vertical lines in the Cross Section window indicating the positions of the Velocity Analysis centers already saved to the velocity table. The locations of these lines are referred to as nodes. 6. In the Velocity Analysis window, pick or modify the velocity function for the current location. 7. In the Velocity Analysis display, click on the “bow-and-arrow” PD icon to send the new information to the Volume Viewer/Editor. The velocity displayed in Volume Viewer/Editor updates in response to picks made in Velocity Analysis. You should now see a vertical line in the Cross Section window at the CDP location of the velocity function just picked. 8. In the Velocity Analysis window, click on the Next ensemble icon, and pick the next analysis location. When you are finished picking this new analysis location, click on the Next ensemble icon again. This will not only move you to the next analysis location, but will automatically send the velocity picks just made to the Volume Viewer/Editor displays. 9. In the Volume Viewer/Editor window, click on the PD icon. Any Velocity Analysis CDP location can be easily retrieved or deleted from Volume Viewer/Editor through the use of the mouse. This allows random access to any of the precomputed and picked locations.

Velocity Analysis Pointing Dispather By activating this icon, you can select a CDP and send it to Velocity Analysis. This icon does not appear if No was selected for Interact with Velocity Analysis? in the Velocity Viewer/Editor menu. With the PD icon activated, position the mouse cursor over a node. The cursor should change from an “x” to an “o”. Click MB1 to retrieve that velocity function into the Velocity Analysis display. Clicking MB2 deletes that analysis location.

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10. Try moving to a previous location by selecting it in the Volume Viewer window. 11. Continue picking velocities in Velocity Analysis until you finish all of the locations on this project. Remember, you may either use the “bow-and-arrow” PD icon to send the picks from Velocity Analysis to the Volume Viewer/Editor displays for QC before moving to the next analysis location, or you may move directly to the next ensemble and your previous picks will be automatically sent to the Volume Viewer/Editor displays. 12. To finish picking, first make sure that the “Point Dispatcher” PD icon in Volume Viewer is deactivated. Then in Velocity Analysis, click on the File ➛ Exit/stop flow pull down menu in the velocity analysis and the File ➛ Exit pull down in the Volume Viewer/ Editor.

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Do you understand the parameters input to Velocity Analysis?

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Can you operate the Velocity Analysis Viewer in conjunction with the Volume Viewer/Editor?

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Are you confident in picking a reasonable stacking velocity function?


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Chapter 13

Residual Statics Corrections Although datum static corrections have been applied to remove travel-time effects of elevation changes along the seismic line, it may still be necessary to remove residual near-surface traveltime delays that are the result of varying velocity and/or varying depth of the weathering layer. ProMAX offers several residual statics processes. All are surface consistent solutions except for the Trim Statics routines.

Topics covered in this chapter: ❏ Autostatics Flowchart ❏ Data Preparation for Input to Residual Statics ❏ Calculation of Residual Statics ❏ QC and Application of Residual Statics ❏ External Model Autostatics Overview ❏ External Model Autostatics Flowchart

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Chapter 13: Residual Statics Corrections

Chapter Objectives

7. Residual Statics

To correct for high frequency variations in the near surface weathering not solved by elevation/refraction statics or velocities, some type of residual statics is almost always applied for land data. High frequency can be thought of as shorter than one cable length. This chapter explores some of ProMAX’s techniques of calculating residual statics. Upon completion of this chapter you should:

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Know how to prepare data for input to Residual Statics

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Understand how Surface Consistent Statics are calculated

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Understand how Trim Statics are calculated

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Be able to build a Model Stack to pilot some of the statics routines


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Autostatics Flowchart

Autostatics Flowchart 1. Pre-Process (geometry, gain recovery, noise reduction, deconvolution, refraction or elevation statics, NMO, BPF, AGC)

RMS Velocities

2. Apply NMO and Sort to CDPs CDP Stack Pick Autostatics Horizon

3. Calculate Residual Statics

Correlation Autostatics SIN:STATICS:SCORxxxx SRF:STATICS:RCORxxxx

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Max. Power Autostatics SIN:STATICS:SPWRxxxx SRF:STATICS:RPWRxxxx


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Data Preparation for Input to Residual Statics All of the residual statics process are standalone and require that all preprocessing be applied to the data and output to a disk dataset prior to executing the residual statics processes. At this point in the processing sequence, the input to autostatics should have geometry information, gain recovery, noise reduction, deconvolution, refraction or elevation statics, and NMO applied. In addition to normal preprocessing, you may want to filter unwanted high and low frequency noise by band limiting the input data, and scale the data with an AGC. To execute an external model autostatics method, you will need to create an enhanced stack as the model using any of the signal enhancement techniques available in ProMAX. This will be covered in the section on External Model Autostatics.

Data preparation and horizon picking for residual statics In this exercise you are simply preparing a prestack dataset for input to autostatics, as well as picking your autostatic horizons on poststack data.

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Editing Flow: 7.1-Data Prep for Res. Statics Add

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Disk Data Input Select dataset: -----------------------Shots-decon/refr statics Trace read option: -----------------------------------------------Sort Interactive Data Access?: ---------------------------------------No Select primary trace header entry: -----------------------CDP Select secondary trace header entry: -----------------NONE Sort order for dataset: -------------------------------------------- */

Normal Moveout Correction SELECT Velocity parameter file: --vels from precompute


Bandpass Filter Ormsby filter frequency values: ---------------- 5-10-40-50

Disk Data Output Output Dataset Filename: ------CDP-input to res. statics

>Disk Data Input< >Trace Display< 2. In Disk Data Input, select your best pre-stack data. 3. In NMO, select your best RMS velocity parameter table. 4. Apply an AGC and bandpass filter to clean the data going into residual statics calculation. A 500 ms AGC gate width is sufficient. Apply Bandpass Filter to remove the lowest and highest frequencies, such as 5-10-40-50 Hz. 5. Output your NMO corrected CDPs to a new file “CDP-input to res. statics”. This data is input into the residual statics process in a later flow. 6. Execute the flow.

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7. Residual statics processes require that reference horizons (autostatics horizons) are picked from a preliminary stack and saved in a parameter table. Edit the following flow:

Editing Flow: 7.1-Data Prep for Res. Statics Add

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>Disk Data Input< >Normal Moveout Correction< >Automatic Gain Control< >Bandpass Filter< >Disk Data Output< Disk Data Input Select Dataset: -----------------------------------STK-refr statics Trace read option: --------------------------------------------Get All

Trace Display Primary trace LABELING header entry: --------------NONE Secondary trace LABELING header entry: ------------CDP 8. Input your refraction statics stack. 9. Execute the flow.

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10. From the menu bar in Trace Display, select Picking ➛ Pick Autostatics Horizons...

Picking Autostatics Horizon 11. A Table Selector window appears. Enter a new table name “horizon1” and select OK. Enter smash=11 (CDP traces). Smash is the number of CDPs to sum along the horizon to form the model trace for correlation. Gate width is symmetric about the picks. For steeply dipping areas a smash of 3 to 5 should be used. For flatter areas smash values of 11 to 21 are valid. Enter a gate width=100 (ms). The gate width should be bigger than twice the maximum residual static expected. In swampy/marshy areas this may be a large value. Click on OK when finished.

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12. Pick a horizon using MB1. This identifies the center of the time gate. Horizons may extend across the entire dataset or cover only a portion of the data. CDPs not included in a horizon will not be included in residual statics calculations for that horizon.

NOTE: Autostatics horizons are picked from stacked data that has been shifted to the final datum. The residual statics processes automatically shifts these time horizons to the processing datum, the same datum input CDP gathers are referenced to. This process of applying C_STATIC to the horizons is automatic and transparent to the user.

13. Additional horizons (up to 500) may be picked by clicking in the trace display area with MB3 and choosing a new layer. You will be prompted to enter a new smash value and time gate for each horizon. Notice also the new horizon is represented in the Pick Layers window with a number in parentheses. The residual statics process will average the static solutions in areas of overlapping windows. About a 10 trace overlap should provide a smooth transition between static solutions. Too much overlap can lead abrupt edges to the static solution. 14. To quit and save the autostatics horizon parameter table select File ➛ Exit/Stop Flow. Select Yes when asked to save your work.

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Calculation of Residual Statics ProMAX offers nine internal model surface consistent residual statics methods and three CDP consistent (trim) statics methods: •

Correlation Autostatics

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Cross Correlation Sum External Model Autostatics

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Cycle Skip Analysis Autostatics

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Differential Autostatics

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Gauss-Seidel External Model Autostatics

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Hybrid Genetic Algorithm /Steepest Ascent Autostatics

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Maximum Power Autostatics

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Steepest Ascent Autostatics

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Summed Differential Autostatics

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CDP Trim Statics: non surface consistent

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Horizon Trim Statics: non surface consistent

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Time Varying Trim Statics: non surface consistent

The most commonly used surface consistent methods are “Correlation Autostatics” and “Maximum Power Autostatics.” The max power method has proven very robust for good and bad data areas. The only downside to max power is that it is a little more expensive in terms of CPU usage. The max power simply maximize the power of the stack by shifting each trace and stacking for the maximum power. The “CDP Trim Statics” works similar, except the shifts are applied in the CDP domain, and thus the shifts are blind to surface consistency. Most of the methods have some problems at the edges and low fold areas. These edge problems are often corrected by editing the erroneous values in the database. Choose a method based on data quality, magnitude of statics problem, and merits of the residual statics method. Parameter selection for each method is also based on data quality and magnitude of statics problem. If nothing seems to work use Gauss-Seidel External Model Autostatics. Landmark


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Autostatics calculation In this exercise, you will calculate residual statics using Maximum Power and Correlation Autostatics. An additional exercise at the end of this section describes the external model routines, Gauss-Seidel External Model Autostatics and Cross Correlation Sum External Model Autostatics. 1. Build the following flow:

Editing Flow: 7.2-Calculate Residual Statics Add

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Correlation Autostatics* Select Trace data file: -------------CDP-input to res. statics Select Autostatics HORIZON file: --------------------horizon1 Select Autostatics VELOCITY file: vels from precompute Maximum velocity error (percent): ----------------------------5. Number of CDP’s for velocity smoothing: -----------------51 Minimum # of traces for vel. estimate: ---------------------36 Minimum % of offset range for vel. estimate: ------------25 Maximum statics allowed (milliseconds): -----------------20 Statics partitioning iterations: -----------------------------------4 Minimum live samples in a gate (percent): ---------------60 Seek/report reversed sources/receivers/channels: Yes Create a NEW database entry for each run?: -----------No

>2D/3D Max. Power Autostatics*< 2. Select your NMO corrected CDP gathers as the input trace data to Correlation Autostatics. Select your autostatic horizon and RMS velocity tables. Correlation Autostatics* uses a Gauss-Seidel method to partition statics into velocities, as well as source, receiver, channel and structure statics. 3. Execute the flow. Upon completion, click on View from the Flow menu and look at the contents of the job.output file. Check the range of source and receiver statics values. Do you have any reversed traces?

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4. Edit the previous flow.

Editing Flow: 7.2-Calculate Residual Statics Add

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>Correlation Autostatics*< 2D/3D Max. Power Autostatics* Select Trace data file: -------------CDP-input to res. statics Select Autostatics horizon file: -----------------------horizon1 RMS statics change convergence criteria: -------------0.05 Maximum number of iterations: ------------------------------10 Minimum live samples in a gate (percent): ---------------60 Maximum static allowed (ms): -------------5,7,10,15,20(6) Correlation accept percent: -------------------------------------10 Compute Statics for whole line?: ----------------------------Yes Use envelope of correlations?: --------------------------------No Apply previously computed residuals?: -------------------No Restrict offsets?: ----------------------------------------------------No Final minimum static: ------------------------------------------- -20 Final maximum static: --------------------------------------------20 Run ID: --------------------------------------------------------------0000 Report static values after each iteration?: ----------------No 5. In 2D/3D Max. Power Autostatics*, input your NMO corrected CDP gathers. Select your autostatic horizon tables. The Maximum static allowed is per iteration. We start these values out low in order to keep the solution from immediately diverging. Set the remaining parameters as indicated above. 2D/3D Max. Power Autostatics* estimates source, receiver and channel statics by maximizing the CDP stack power. 6. Execute the flow. Upon completion, click on View from the Flow menu and look at the contents of the job.output file. Check to see if your solution has converged. Also check the range of source and receiver statics values.

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QC and Application of Residual Statics Quality control of residual static results can be achieved by several methods: • • •

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Utilizing the Database display tool. Comparison of stacks with and without residual statics applied. Comparison of stacks with different residual statics methods applied.


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Compare Static Solutions in the Database A quick QC tool is to examine the computed static values with the Database display tool. 1. From the Flows menu select the Database option, and then select Database ➛ XDB Database Display from the main DBTools menu. Select Database ➛ Get from the XDB display. 2. Select SRF order, Statics infotype, and the two statics files RCOR000 & RPWR000.

Database plot of Receiver statics

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The source (SIN) and receiver (SRF) statics for Correlation Autostatics are SCOR0000 and RCOR0000. The source (SIN) and receiver (SRF) statics for Maximum Power Autostatics are SPWR0000 and RPWR0000. Computed static values from several methods can be plotted simultaneously for comparison. Values can then be zeroed or edited from this database display. See mouse button helps for instruction. 3. Quality Factors computed by each method are also output to the database. Quality Factors can be used as a criteria for zeroing statics values or editing shots and receivers. The quality factor file naming convention is S_CQ0000, and R_CQ0000. Quality factors from several methods can be displayed simultaneously to compare reliability of the computed statics. Statics with low quality factor values relative to neighboring values can be zeroed or the receivers could be edited. Quality factors can be used to weight traces before CDP stack. For more information see the Residual Statics helpfile.

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Compare Autostatics Stacks 1. Build the following flow:

Editing Flow: 7.3-Compare Autostatics Stacks Add

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Compare Autostatics Stack SELECT input trace data file: --CDP-input to res. statics SPECIFY the input CDP range(s): ----1-100000/ Temporary SCRATCH data file: -----------------------Scratch Automatically delete this file upon completion?: ----------------------------------------------------------------Yes Normal database entry naming mode?: -----------------Yes Type of residual statics to apply: -------------------------------------------------------Correlation Autostatics Select display DEVICE: -----------------------------This Screen Number of traces per display screen: --------------------215 This is a stand-alone macro that enables you to compare a preliminary stack without residual statics to a stack with residual statics. It uses the Screen Display process. 2. Execute (with MB2) and use the screen swap feature to compare stacks. 3. Execute this flow again (with MB2) using the Max. Power Autostatics.

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Compare two or more Autostatics Stacks 1. Build a flow for comparing stacked results from two or more statics methods. Use the following flow to get started:

Editing Flow: 7.3-Compare Autostatics Stacks Add

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>Compare Autostatics Stack< Disk Data Input Select dataset: -----------------------CDP-input to res. statics Trace read option: --------------------------------------------Get All

Reproduce Traces Trace grouping to reproduce: --------------------------All Data Total number of datasets: ----------------------------------------2

IF Apply Residual Statics Type of residual statics: -----------Correlation Autostatics

Trace Display Label Trace label:------------------------------Correlation Autostatics

ELSE Apply Residual Statics Type of residual statics: ----------Max. Power Autostatics

Trace Display Label Trace label:-----------------------------Max. Power Autostatics

ENDIF Apply Fractional Static Automatic Gain Control Bandpass Filter Ormsby filter frequency values: -------------------3-6-50-60

CDP/Ensemble Stack Trace Display Primary trace LABELING header entry: ---------------None Secondary trace LABELING header entry: ------------CDP

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External Model Autostatics Overview ProMAX currently offers two surface consistent autostatics routines for use with an external model (pilot). Both require using the External Model Correlation tool which correlates prestack traces with the model. Since correlation pick times can be written to the TRC database, these may also be applied directly to the data as external model trim statics. A typical External Model Autostatics job flow consists of four phases: external model building, correlation computation, statics computation, and statics application. The input to the external model building can be any stack of the dataset. This allows you to use the data enhancement techniques available in ProMAX to improve the model stack. For example, you can apply trace mixing, 2D filtering, or F-X decon to a brute stack to generate the model stack. Another method would be to use the Eigen Stack process to produce the model stack.

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External Model Autostatics Flowchart External Model Autostatics Flowchart 1. Pre-Process (geometry, gain recovery, noise reduction, deconvolution, refraction or elevation statics, NMO, BPF, AGC)

RMS Vels

2. Apply NMO and Sort to CDPs

SIN:STATICS:SGEMxxxx SRF:STATICS:SGEMxxxx

5a. EMC Gauss Seidel Eigen Matrix Time Gate

3. Eigen Stack

4. External Model Correlation

Autostatics Horizon

TRC STATICS TRM0001 Correlations (trace data)

5b. EMC Xcor Sum

SIN:STATICS:SPEMxxxx SRF:STATICS:SPEMxxxx

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Create Eigen Stack Eigen Stack process uses the Eigen vector decomposition techniques to isolate the principle component of the trace matrix from a supergather of pre-stack traces. Conceptually, the wavelet on the stack trace after eigen stack is more similar to the wavelets on the prestack data than a conventional stack. Theory says that all of the wavelets recorded from a reflection point are the same. These wavelets are time shifted due to near surface velocity variations. Typically we measure these time variations by cross correlating the pre-stack traces with a stacked trace. The Eigen Stack process attempts to make the stacked trace wavelet that is as similar as possible to the wavelet of the pre-stack traces. This should improve the cross correlation process by creating a higher resolution pilot trace. The cost of this process, however, is that some of the structural information may be lost. Some writings may refer to an Eigen stack as a K-L transform. Note that this is the same technology as the government uses for pattern recognition in scanning retinas or for enhancing faces on photographs. Input Traces on CDP with NMO applied

Conventional Stack Model Trace

Eigen Stack Model Trace

Principal Component input traces

Cartoon of Eigen Stack Decomposition Landmark


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You first need to pick a time gate that will be used in the Eigen Stack process: 1. Build the following flow to pick an eigen matrix time gate on NMO corrected CDP gathers.

Editing Flow: 7.4-Eigen Stack Add

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Disk Data Input Select dataset: -----------------------CDP-input to res. statics Trace read option: -----------------------------------------------Sort Interactive Data Access?: --------------------------------------Yes Select primary trace header entry: -----------------------CDP Sort order for dataset: ----------------------------800-950(25)/

>Eigen Stack< >Disk Data Output< Trace Display Number of ENSEMBLES (line segments)/screen: -----10 Primary trace LABELING header entry: ----------------CDP Secondary trace LABELING header entry: -----------None 2. Input a range of CDP gathers and execute the flow.

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3. From the Trace Display menu bar, select Picking ➛ Pick Miscellaneous Time Gates...

Pick Time Gate 4. Input a gate name like “eigen gate”. 5. Select a secondary key of CDP, and pick a window from a data area that has a high Signal/Noise ratio. Make sure that your window includes the area of interest. Use MB3 inside of the Trace Display area to select a new layer for the bottom of the window. This display is also a good QC to check your velocities. If the CDP gathers are not flat you may have a problem with your velocities. 6. Save picks and exit the Trace Display.

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7. Edit the flow to generate an Eigen Stack.


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>Disk Data Input< Disk Data Input Select dataset: -----------------------CDP-input to res. statics Trace read option: --------------------------------------------Get All

Eigen Stack Mode: --------------------------------------------Output Eigenstack Get matrix design gates from DATABASE?: ------------Yes SELECT design gate parameter file: ------------eigen gate Type of Computations?: ---------------------------------------Real Horizontal window width: ----------------------------------------5 Number of iterations: -----------------------------------------------0 Apply final datum statics after stack?: ------------------Yes

Disk Data Output Output Dataset Filename: ---------------------------STK-eigen

>Trace Display< The Eigen Stack process stacks flat events in a CDP gather. Events with large trace to trace moveout will not be included in the output Eigen Stack. 8. In Disk Data Output, output a new dataset “STK-eigen”. This is used for subsequent input to the external model correlation builder. 9. Execute the flow.

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10. Edit the flow to pick autostatics horizons on your Eigen Stack.


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>Disk Data Input< >Disk Data Input< >Eigen Stack< >Disk Data Output< Disk Data Input Select dataset: -------------------------------------------STK-eigen Trace read option: --------------------------------------------Get All

Trace Display Primary trace LABELING header entry: ---------------None Secondary trace LABELING header entry: ------------CDP 11. Execute the flow.

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12. From the menu bar in Trace Display, select Picking ➛ Pick Autostatics Horizons...

Pick horizon for Autostatics •

Enter a new table name and click on OK.

•

Enter smash=1 (in traces) and the gate width=300 ms and click on OK. For an external model, the smash is not used. Therefore, give it a value of 1. The pilot traces have already been somewhat “smashed” together by creating the Eigen Stack.

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Pick a horizon using MB1. This identifies the center of the time gate. Horizons may extend across the entire dataset or cover only a portion of the data. CDPs not included in a horizon are not included in residual statics calculations for that horizon. NOTE: Autostatics horizons are picked from stacked data that has been shifted to the final datum. The residual statics processes automatically shift these time horizons to the processing datum, the same datum input CDP gathers are referenced to. This process is automatic and transparent to the user.

13. Additional horizons (up to 500) may be picked by clicking MB3 in the trace display area and choosing a new layer. You will be prompted to enter a new smash value and time gate for each horizon. Notice also the new horizon is represented in the Pick Layers window with a number in parentheses. 14. To automatically move picks to the nearest peak or trough, click with MB3 in the data area and choose the appropriate snap. 15. Save your autostatics horizon picks and exit Trace Display.

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16. Build this flow to generate correlations:

Editing Flow: 7.5-External Model Correlations Add

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Disk Data Input Select dataset: -----------------------CDP-input to res. statics Trace read option: --------------------------------------------Get All

External Model Correlation Select model trace dataset: -------------------------STK-eigen Use autostatics horizon or gate file: --------------HORIZON Select autostatics horizon file: ------EMC horizon Minimum live samples in a gate(percent): ----------------60 Maximum static shift: ---------------------------------------------20 Write correlation pick TIMES to the database?: -------Yes Write correlation pick AMPLITUDES to the database?: ----------------------------------------------------------------Yes Write quality control estimates to the database?: ----Yes Database mode: ---------------------------------Overwrite/ New Enter 4 Digit ID number:------------------0001

Disk Data Output Output Dataset Filename: -------------------------correlations 17. In Disk Data Input, input the NMO corrected CDP gathers. 18. Select External Model Correlation parameters. Select Eigen Stack for the model trace dataset and select your autostatics horizons for the Horizon file. 19. In Disk Data Output, output the correlation trace data. The correlation trace data is used in EMC Autostat: Xcor Sum*. 20. Execute the flow.

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21. Build the following flow to calculate your residual statics using EMC Autostat: Gauss-Seidel*:

Editing Flow: 7.6-EMC Autostatics Add

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EMC Autostat: Gauss-Seidel* Select TRC database correlation pick entry:----------------------------------------------- TRC:STATICS: TRM_0000 Statics partitioning iterations: -----------------------------------7 Maximum source or receiver static: -------------------------20 Min trace offset MAGNITUDE for inclusion: ---------------0. Max trace offset MAGNITUDE for inclusion: ----999999. Weight solutions by pick quality factors: ----------------Yes Alpha trimmed mean percentage for pick exclusion:--40 Length of the CDP structure smoothing: ---------------------3 Dampen the structure term at low fold?: ----------------Yes Create a NEW database entry for each run?: -----------No

>EMC Autostat: Xcor Sum*< 22. For Gauss-Seidel, select TRC - STATICS - TRM_0000 from the Ordered Parameter Files. These time shifts will be decomposed into the source (SIN), receiver (SRF), and structure (CDP) statics. 23. Execute the flow. Upon completion, click on View from the Flow menu and look at the contents of the job.output file. You can graphically check the range of source and receiver statics values in the database with DBTools or XDB Database Display.

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24. Edit the previous flow to use EMC Autostat: Xcor Sum*.

Editing Flow: 7.6-EMC Autostatics Add

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>EMC Autostat: Gauss-Seidel*< EMC Autostat: Xcor Sum* Input correlations from Tape or Disk?: ------------------Disk Select input correlation file:-------------Statics-correlations First statics computation domain: ------------------------CDP Second statics computation domain: -----------------Source Third statics computation domain: -----------------Receiver Fourth statics computation domain: -------------------NONE Adjust correlations by a previous SOURCE static: ----No Adjust correlations by a previous RECEIVER static: -No Adjust correlations by a previous CDP RESIDUAL STRUCTURE?: -------------------------------------------No Method for correlation summing: ------Min/Max Exclude Maximum source or receiver statics: ------------------------20 Create a NEW database entry for each run?: -----------No 25. In Xcor Sum, input the correlation trace data that was output from the External Model Correlations flow. These correlations are summed and then the maximum is picked within the various domains in order to derive the statics. 26. Execute the flow. Upon completion, click on View from the Flow building menu and look at the contents of the job.output file. Check the range of source and receiver statics values. 27. QC your results as you did earlier in this chapter. Use the XDB Database Display and flow “7.3-Compare Autostatics Stacks” to do your comparisons. In the database you will see SPEM0000 for both source and receiver statics calculated using the Xcor Sum and SGEM0000 for the source and receiver statics from Gauss-Seidel.

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28. After comparing the various autostatics solutions, build the following flow to apply the best solution.

Editing Flow: 7.7-Apply Residual Statics Add

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Disk Data Input Select dataset: ------------------------Shot-decon/refr statics Trace read option: -----------------------------------------------Sort Select primary trace header entry: -----------------------CDP Sort order for dataset: -------------------------------------------- */

Apply Residual Statics Type of residual statics to apply: ----EMC Gauss-Seidel

Normal Moveout Correction SELECT Velocity parameter file: --vels from precompute

Disk Data Output Output Dataset Filename: ---------CDP-decon/refr/resid

CDP/Ensemble Stack Trace Display Label Trace label: ----------------------------------------EMC GS Statics

Disk Data Output Output Dataset Filename: ---------STK-decon/refr/resid

Trace Display Primary trace LABELING header entry: ---------------None Secondary trace LABELING header entry: ------------CDP 29. Fill in the parameters as listed above, and then execute the flow. 30. When you are finished viewing the stack in Trace Display, select File ➛ Exit/Continue Flow.

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Can you prepare data for input to Residual Statics

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What does it mean to be Surface Consistent

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How are Surface Consistent Statics calculated

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How are Trim Statics calculated

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Can you build a Model Stack to pilot some of the statics routines


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Chapter 14

Dip Moveout (DMO) Dip Moveout is also known as prestack partial migration where each data sample is migrated to its zero offset position. This collapses the CMP smear induced by dipping reflectors. Not only is the imaging of these dipping reflectors enhanced, but the stacking velocities picked after applying DMO are dip independent. This improves velocities for stacking and migration. Also, lateral resolution is increased and coherent noise is attenuated. Before DMO is applied to the data, the trace data are typically grouped into offset bins using the Trace Binning process. Once the data is binned, processes using Kirchhoff and F-K implementations of DMO are available to perform the prestack partial migration.

Topics covered in this chapter: ❏ Common Offset Binning ❏ DMO ❏ Final Stack

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Chapter 14: Dip Moveout (DMO)

Chapter Objectives

8. Dip Moveout (DMO)

The advent of DMO in the 80’s has greatly improved velocity calculation, migration of dipping reflectors and noise reduction. DMO improves the data because it migrates each sample to its zero offset position. This collapses the CMP smear induced by dipping reflectors. The DMO processes itself is quite simple, however, the prep of the input data can be a little tricky to the new user. Upon completion of this chapter you should:

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Be able to Common Offset Bin data for input to DMO

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Be familiar with some of the input parameters to DMO

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Understand the basic theory of what DMO does to the data


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Common Offset Binning Common offset binning is a critical part of the DMO process. In this step, we select traces belonging to common offset planes before applying DMO. A rule of thumb is to build common offset binning to create a maximum number of bins, yet still have 100% CDP coverage in both the common offset section and each bin. Common offset planes can be created with the Trace Binning process. Trace Binning requires a list of bin centers and bin increments. For offend shooting, the minimum offset bin increment is typically specified as either twice the shot interval or the nominal change in offset from trace to trace within a CDP. For symmetric split spread geometries, the shot interval should work. For asymmetric split spreads, the data will determine which interval is appropriate. In general the rules of thumb for DMO offset bin spacing are: • • •

Marine: OFB = 2 X Shot Interval Land Split Spread: OFB = 1 X Shot Interval Land End On: OFB = 2 X Shot Interval

It is relatively simple to determine the center of the first common offset bin. For example, assume that we have a survey with off-end shooting where the shot interval is 200 m, the group interval is 100 m, and 300 m is the distance to the first group. The shot-receiver offsets within this survey would be: 300, 400, 500, 600, 700, 800, 900,....... Since the shot interval of 200 m yields a bin increment of 400 m, the center of your first offset bin would lie midway between 400 and 500, or 450 m. Your DMO offset bins would now be 450 +/- 200, 850 +/200, 1250 +/- 200, etc. See diagram below: 300 400 500 600 700 800 900 1000 1100 1200 1300 1400........

450

850

1250

Skidded shots, or other irregular shooting geometry, may place two or more traces per CDP within a given DMO bin. Within the DMO process, traces within the same DMO bin having identical CDP numbers are stacked together prior to DMO.

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For regular shooting geometry, the recommended approach is to use Trace Binning as a function of absolute offset followed by F-K DMO on common offset ensemble. For datasets where the geometry is irregular and it is difficult to get good population of offset planes, Ensemble DMO in the T-X Domain should be run on common shot ensembles.

Determine trace binning parameters In this exercise, you will compute common offset bin centers using the off-end shooting assumptions. Recall that the first few shots on the line resembled off-end shooting, and the last few shots were the normal split spread geometry. We will then look at several database and trace displays to check the binning parameters. Bin centers may be based on either the signed offset or the absolute value of the offset. If absolute value of offset is used, traces with the same magnitude offset are combined in the same ensemble. You also have the opportunity to vary the width of the offset bins (the bin increment) as a function of trace offset. This may become important for lines that were collected with a regular, but asymmetric split spread geometry.

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1. Build the following flow to view the first offset bin in your survey:

Editing Flow: 8.1-DMO Binning Add

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Disk Data Input Select dataset: --------------------------CDP-decon/refr/resid Trace read option: -----------------------------------------------Sort Interactive Data Access?: ---------------------------------------No Select primary trace header entry: -----------------OFB_NO Select secondary trace header entry: --------------------CDP Sort order for dataset: ------------------------------------------*:*/

Ensemble Stack/Combine Type of operation: -------------------------Combine and Stack Input ensembles per output ensemble: ----------------------1 How are trace headers determined: ----------------Average Secondary key bin size: ------------------------------------------1. Maximum traces per output ensemble: ------------------215 Warnings if max traces/ensemble exceeded?: --------Yes Select PRIMARY Trace Order Header Word: ----OFB_NO Average the X and Y coordinates of primary key?: ---No Select SECONDARY Trace Order Header Word: -----CDP Output trace secondary key order: --------------Ascending Print results?:---------------------------------------------------------No

Pad Traces Header word to use for padding: --------------------------CDP Spacing of header value: ------------------------------------------1 Remove traces?: ----------------------------------------------------No Explicitly define the bounds of header values?: ------Yes First trace header value: --------------------------------------775 Last trace header value: ---------------------------------------989

Trace Display Primary trace LABELING header entry: ----------OFB_NO Secondary trace LABELING header entry: ------------CDP 2. Use Disk Data Input to sort the data first by offset bin number (from the Alternate List of header words) and then sort by CDP. Landmark


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3. Use Ensemble Stack/Combine to combine offset bins, and stack any CDPs which are the same. For this first exercise, we will only display the first offset bin, so set the number of input ensembles/output ensemble to 1. We will use this process later to combine more than one offset bin for display. 4. Pad missing CDPs with Pad Traces. This process will insert a dead trace anytime the spacing between CDPs is greater than 1. 5. Set the primary and secondary labeling headers in Trace Display to OFB_NO, and CDP. 6. Execute the flow.

Notice that there are very few live CDPs for this single offset bin. Since DMO operates in the offset domain, it would be desirable to 14-6


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have offset bins that contain live traces for nearly all CDPs. This is the reason that we merge several offset bins prior to performing DMO. 7. Compute first guess at bin width and center of first bin. For this geometry, the average shot interval is 220 ft. so the first guess at a DMO offset bin width (using the off-end assumption) would be 220 * 2 = 440 ft. The near offset of this data is 27.5 ft. and the traces are 55 ft. apart, so the source-receiver offsets would be: 27.5 82.5 137.5 192.5 247.5 302.5 357.5 412.5 467.5.....

220

660

For an offset bin width of 440 ft., the center of the first bin would lie halfway between 192.5 and 247.5 or at 220 ft. 8. Modify the flow to display the data with a bin width of 440 ft.

Editing Flow: 8.1-DMO Binning Add

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Disk Data Input Ensemble Stack/Combine Input ensembles per output ensemble: ----------------------8 Average the primary key values?: -------------------------Yes

Pad Traces Trace Display 9. The offset bin spacing for this line is 55 ft, so 8 offset bins would equal 440 ft. 10. Execute the flow.

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Notice that most of the CDP locations are filled by live traces. This is what we want for DMO binning. If you were to display the data with a bin width of 220 ft. (4 offset bins) you would see that a width of 220 ft. is adequate for the near offsets, but too small at the farther offsets. Remember that we have two conflicting goals in our DMO binning process: • •

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Create continuous CDP coverage in the offset bins to eliminate DMO artifacts. Create the greatest number of offset bins to enhance DMO velocity analysis.


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11. Next we will view the DMO binning parameters in the database. First we need to transfer the AOFFSET header to the database: Database ➛ Edit ➛ Attribute ➛ Apply a Function...

12. Choose the abs function, and the OFFSET attribute. Type in “AOFFSET GEOMETRY” for the result attribute and then select OK. Remember, if OFFSET is used, for every positive offset bin that is defined, a negative offset bin is also created. For example, in split spread shooting, the above example would contain DMO bins +220, -220, +660, -660. In marine shooting where the first channel is farthest from the boat, all of the offsets are negative, and only the negative DMO bins would be populated. 13. For a QC that the function worked choose View Tabular... AOFFSET and then OK. You can now use MB2 to drag OFFSET from the DBTools window to the Tabular View Window. Close the Tabular View when satisfied. 14. Permanently write AOFFSET to the database by selecting Database Commit. 15. Now lets go into Database ➛ XDB Database Display. Be patient the more data you put into the database, the longer the initial delay when you first execute the database.

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16. Plot two 3D XYGraphs. The first will be TRC: OFFSET, CDP, SRF and the second will be TRC: AOFFSET, CDP, SRF. The XYGraph using AOFFSET will look similar to the following:

Check the offset bin centers by looking at the graphs and verifying that each offset bin is evenly populated with CDPs. Also determine if it is appropriate to combine the traces by absolute offset or if the negative offsets should be processed separately from the positive offsets. A general rule is to simultaneously process like offsets. Use the Grid tool to analyze your bins on the display. Select Grid ➛ Display. This will generate new icons to rotate and move the grid, modify the cell size, and generate spider or histogram plots

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of the cells. Now select Grid ➛ Parameterise, and fill in the values as displayed.

The “dy” should be the length of the line in CDP’s. The “dx” should be the offset bin spacing. Click on the Green Light icon.You should have 15 offset bins displayed. Click MB3 on the top left icon in XYGraph, and see how your CDPs increment within each bin. For this data, if OFFSET is used, with a bin increment of 440, the near offset bin centers are -220 and +220, the far offset bin centers are -3300 and +6380, and we have 23 bins. If AOFFSET is used, the near offset bin center is 220, the far offset bin center is 6380, and we have 15 offset bins. Notice that the near offsets would only need a bin width of 220 ft. for continuous CDP coverage, but the far offsets need a bin width of

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440 ft. If you change “dy” to 1, “ny” to 215, and “Y origin” to 775 you will see a tight grid with a cell size of one CDP.

From this display you can zoom in and QC that each offset bin has cells populated with continuous CDPs.

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Assign DMO offset bins to the data In this exercise you will offset bin the data using the Trace Binning process, apply NMO in preparation for DMO, and QC the output common offset ensembles. 1. Build the following flow:

Editing Flow: 8.2-Assign DMO Offset Bins Add

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Disk Data Input Select dataset: --------------------------CDP-decon/refr/resid Trace Read Option: ----------------------------------------------Sort Interactive Data Access?: ---------------------------------------No Select primary trace header entry: ------------CDP Select secondary trace header entry: AOFFSET Sort order for dataset: -------------------------------*:*/

Trace Binning Header entry to bin: ------------------------------------AOFFSET Binned header entry: -----------------------------------DMOOFF Binned entry format: -------------------------------------------Real Header entry bin centers: ---------------------------------------------------- 110-1430(220),1760-6160(440) Binned header entry values: ----------------------------------------------- 110-1430(220),1760-6160(440) Set OFFSET and AOFFSET headers to bin center: --Yes

Database/Header Transfer Direction of transfer: ------------------------------------------------------------Load FROM Trace header TO database Number of parameters: --------------------------------------------1 First database parameter: -------------------------------------------------------TRC:Geometry:New - Enter DMOOFF First Header Entry: -------------------------------------DMOOFF

Disk Data Output Output Dataset Filename: ---CDP-dmooff/input to DMO 2. In Disk Data Input, input the NMO corrected gathers with a primary header entry of CDP and a secondary header entry of AOFFSET.

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3. Enter the bin centers from 110 to 1430 with an increment of 220,and bin centers from 1760 to 6160 with an increment of 440 based on the absolute offset. The discussion at the beginning of this section describes how to calculate these numbers. Remember our primary goals are to have the maximum number of bins, yet still have 100% CDP coverage. If you wish you can vary the bin spacing more along the line. Output the same values to a new header entry called DMOOFF. If you plan to further process the DMO gathers, you may want to set the OFFSET header word equal to DMOOFF values. 4. Transfer the DMOOFF header to the database by setting a new database value DMOOFF (floating point). 5. Output the gathers to a new dataset “CDP-dmooff/input to DMO”. 6. Execute the flow.

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7. Now lets QC the DMO offset bin centers in the database. Select Database ➛ XDB Database Display ➛ 3D ➛ XYGraph ➛ TRC:AOFFSET,CDP,DMOOFF. You may have to use the mouse button help on the bottom left of the window to help you locate which database entry is DMOOFF, since its label will be an 8 digit unix parsed name. When selected click Display. 8. From the XYGraph menu, select Color ➛ Edit. From the color editor menu select File ➛ Open, and select the contrast.rgb color file. Each DMO offset bin will now be displayed in a different color.

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9. Edit the 8.1 flow to display the results of your DMO binning:

Editing Flow: 8.1- DMO Binning Add

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Disk Data Input Select dataset: --------------------CDP-dmooff/input to DMO Trace Read Option: -------------------------------------------SORT Interactive Data Access?: ---------------------------------------No Select primary trace header entry: ----DMOOFF Select secondary trace header entry: --------CDP Sort order for dataset: ------------------------------ *:*/

Ensemble Stack/Combine Type of operation: --------------------------------------Stack only How are trace headers determined?: --Average Secondary key bin size: -------------------------------1 Maximum traces per output ensemble: ------------------215 Warnings if max traces/ensemble exceeded?: --------Yes Select PRIMARY Trace Order Header Word: ---DMOOFF Average the X and Y coordinates of primary key?: ---No Select SECONDARY Trace Order Header Word: -----CDP Output trace secondary key order: --------------Ascending

Pad Traces Header word to use for padding: --------------------------CDP Spacing of header value: ------------------------------------------1 Remove traces?: ----------------------------------------------------No Explicitly define the bounds of header values?: ------Yes First trace header value: --------------------------------------775 Last trace header value: ---------------------------------------989

Trace Display Primary trace LABELING header entry: ---------DMOOFF Secondary trace LABELING header entry: ------------CDP 10. In Disk Data Input, input the gathers sorting on DMOOFF:CDP. In Trace Display annotate DMOOFF and CDP. The Ensemble Stack/Combine step should be used when DMOOFF has been built from AOFFSET. It is used here to stack all like numbered CDPs within the same offset panel.

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Use pad traces to insert a dead trace whenever the spacing between CDPs is greater that 1. This display will show how many CDP traces exist per bin and will also show any gaps or unpopulated CDPs in the offset plane. 11. Execute the flow. 12. Are the trace gaps in the DMO offset panels reasonable? If not you will need to adjust you offset binning parameters and re-run flow 8.2.

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DMO Both F-K and integral DMO methods are available in ProMAX. Common Offset F-K DMO works in F-K space using the Stolt stretch technique to account for vertical velocity variations. The data should be binned into common offsets in preparation for this process. Ensemble DMO in the T-X Domain is a Kirchhoff implementation, which can be applied to arbitrary ensembles of input traces, such as common shot gathers, common receiver gathers, or common offset data. This process may be run in the shot mode for datasets with irregular shooting geometries instead of the F-K DMO. In a typical processing sequence, DMO follows statics and NMO. Since DMO may enhance stacking velocity picks, try the following sequence.

NMO

DMO

Inverse NMO

Velocity Analysis

Re-iterate this process until the difference between input and output velocities in velocity analysis is small.

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Apply DMO to the data. 1. Build the following flow:

Editing Flow: 8.3-DMO Add

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Disk Data Input Select dataset: --------------------CDP-dmooff/input to DMO Trace Read Option: ------------------------------------------SORT Select primary trace header entry: ----DMOOFF Select secondary trace header entry: --------CDP Sort order for dataset: ------------------------------ *:*/

Common Offset F-K DMO CDP interval: ------------------------------------------------------27.5 Typical common-offset trace spacing: -------------------27.5 Maximum number of CDPs in dataset: ------------------215 Maximum offset in data: ------------------------------------6600. Header entry to use for offsets: ---------------------DMOOFF Maximum frequency (in HZ): -----------------------------------80 Perform dip filtering?: -------------------------------------------Yes Get RMS velocities from database?: -----------------------Yes Select RMS velocity file: --vels from precompute DMO stretch factor: -----------------------------------------------0.6 Maximum memory to use (in Mbytes): -----------------------4 Re-apply trace mutes?: -----------------------------------------Yes Re-kill dead traces?: ---------------------------------------------Yes

Disk Data Output Output Dataset Filename: -----------------------DMO-gathers

Disk Data Input Select dataset: ---------------------------------------DMO-gathers Trace Read Option: ------------------------------------------Get All

Trace Display 2. In Disk Data Input, input the gathers using DMOOFF as the primary sort key and CDP as the secondary key. 3. Select Common Offset F-K DMO parameters.

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Input the same velocity field used to NMO correct the input gathers. 4. In Disk Data Output, output the DMO applied data. 5. In Trace Display, label DMOOFF and CDP. 6. Execute the flow, and view the common offset planes after DMO. 7. After viewing a few of the offset planes after DMO, select File ➛ Exit/Continue Flow. Remember to select the continue flow option, otherwise the job will stop without outputting the entire dataset. 8. Optional: After the DMO job finishes, build a flow that sorts the data to CDP and views the gathers. Toggle off the first three processes in the above flow. Change the sort to CDP in Disk Data Input, change the Trace Display ensembles per screen to 215 and execute. In a typical processing sequence you would apply inverse NMO and repick velocities.

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Final Stack 1. Build the next flow to stack results.

Editing Flow: 8.4-DMO Stack Add

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Disk Data Input Select dataset: ---------------------------------------DMO-gathers Trace Read Option: -------------------------------------------SORT Interactive Data Access?: ---------------------------------------No Select primary trace header entry: ------------CDP Sort order for dataset: ---------------------------------*/

CDP/Ensemble Stack ----Default all parameters----

Trace Display Label Trace label: ----------------------------------------------DMO Stack

Disk Data Output Output Dataset Filename: ----------------------------STK-dmo

Trace Display Primary trace LABELING header entry: ---------------None Secondary trace LABELING header entry: ------------CDP 2. In Disk Data Input, input your DMO data in CDP sort order. 3. Select an output dataset name. 4. Execute the flow, and examine the stack. If you notice any large artifacts from the DMO process, it probably resulted from a bad trace. You could either go back and kill the bad trace, or apply an AGC prior to DMO. 5. Use your flow “11-Compare Stacks” to examine the differences between the DMO stack, and the regular stack. 6. Optional: Replace Common Offset F-K DMO with Ensemble DMO in the T-X Domain. Build and execute a flow to compare the output gathers and stacks. Ensemble DMO in T-X Domain process will output as many traces per CDP per bin as were input by producing copies of the output traces.

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Can you Common Offset Bin data for input to DMO

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Do you understand the basic theory of DMO


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Chapter 15

Poststack Signal Enhancement ProMAX offers a variety of poststack signal enhancement tools including eigenvector filtering, trace mixing, F-K and bandpass filtering. You can use these processes in conjunction with windowed processing to limit the signal enhancement processing over a specific time window. In this chapter we will cover F-X Decon and Dynamic S/N Filtering as well as techniques to subtract adjacent traces (Trace Math) and to add back (BLEND) a proportion of the original data to the processed data.

Topics covered in this chapter: ❏ F-X Decon, Dynamic S/N Filtering, and BLEND ❏ Trace Math

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Chapter 15: Poststack Signal Enhancement

Chapter Objectives

9. PostStack Signal Enhancement

To further clean up and optimize the stack, some type of poststack signal enhancement is almost always applied. This chapter explores some of ProMAX’s techniques of reducing noise and enhancing signal in poststack data. Upon completion of this chapter you should:

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Be familiar with F-X Decon and Dynamic S/N Filtering techniques

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Understand how to use Trace Math to enhance stacks


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F-X Decon, Dynamic S/N Filtering, and BLEND F-X Decon is a tool designed to attenuate random noise on your stack. This process transforms data from time and distance to frequency and distance. Each sample in the transformed data has both real and imaginary components. Events with similar dip appear as complex sinusoids along a given frequency slice. Therefore, the signal is predictable. F-X deconvolution uses a complex prediction filter to predict the signal one trace ahead, across the frequency slice. Any difference between the predicted waveform and the actual waveform is considered noise and removed. Similar to F-X Decon, Dynamic S/N (Signal to Noise) Filtering transforms the data into frequency and distance and calculates noise in the same manner as described above. However, Dynamic S/N Filtering applies an amplitude only convolutional filter to each trace based on the signal to noise ratio. Therefore, unlike F-X Decon, there is little mixing or lateral smearing of data. BLEND is a tool which is useful for attenuating the effects of a given process by adding or subtracting a chosen ratio of input data to the processed data.

Signal Enhancement In this exercise, you will compare the results of your residual statics stack, with stacks that are processed with signal enhancement techniques.

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Editing Flow: 9.1-Poststack Enhancement Add

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Execute

View

Exit

Disk Data Input Select dataset: ---------------------------------------------STK-dmo

Reproduce Traces Trace grouping to reproduce: --------------------------All Data Total Number of datasets: ----------------------------------------4

IF Trace Display Label Trace label: ------------------------------------------Original Input

ELSEIF SPECIFY trace list: ---------------------------------------------------2

Trace Display Label Trace label: -------------------------------------------------FX Decon

F-X Decon TYPE of filter: ------------------------------------Wiener Levinson Percentage of white noise: ---------------------------------------0. Horizontal window length: -------------------------------------50 Number of filter samples: -----------------------------------------5 Time window length: -----------------------------------------1000 Time window overlap: ------------------------------------------100 F-X filter start frequency: -----------------------------------------3 F-X filter end frequency: -----------------------------------------90 Re-apply trace mute after filter?: ---------------------------Yes

ELSEIF Trace Display Label BLEND F-X Decon ELSEIF Trace Display Label Dynamic S/N Filtering ENDIF Disk Data Output Automatic Gain Control Trace Display 15-4


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Editing Flow: 9.1-Poststack Enhancement Add

Delete

Execute

View

Exit

Disk Data Input Reproduce Traces IF Trace Display Label ELSEIF Trace Display Label F-X Decon ELSEIF SPECIFY trace list: ---------------------------------------------------3

Trace Display Label Trace label: --------------------------------------FX Decon/Blend

BLEND Ratio of processed/original: ----------------------------------1:2

F-X Decon ----Use same parameters as the previous F-X Decon----

ELSEIF SPECIFY trace list: ---------------------------------------------------4

Trace Display Label Trace label: ------------------------------Dynamic S/N Filtering

Dynamic S/N Filtering Horizontal window length: -------------------------------------20 Time window length: -----------------------------------------1000 Time window overlap: ------------------------------------------100 F-X filter start frequency: -----------------------------------------3 F-X filter end frequency: -----------------------------------------90 Re-apply trace mute after filter?: ---------------------------Yes

ENDIF Disk Data Output Output Dataset Filename: -----STK-signal enhancement


Trace Display Primary trace LABELING header entry: ---------------None Secondary trace LABELING header entry: ------------CDP

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2. In Disk Data Input, input your residual statics stack. 3. Make four copies of your stack with Reproduce traces and choose a trace grouping of All Data. 4. Set up an IF-ELSEIF-ENDIF conditional with Trace Display Labels to easily compare the results of the different signal enhancement tools with your original stack. Enter the Repeat number to pass through this portion of the flow. Please refer to the chapter on parameter analysis if you are not familiar with the IF-ENDIF conditional logic. 5. Select F-X Decon and Dynamic S/N Filtering parameters. Refer to the online helpfiles for parameter selection of these processes. Note that the BLEND function applies to the process immediately following. 6. Output the four copies of the dataset with Disk Data Output. This dataset will be used in the next flow. 7. Execute the flow. View the 2D filtered data, and compare the stacks using the animation tool. Which dataset looks the most mixed?

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Trace Math Trace Math will allow you to add, subtract, multiply or divide adjacent traces, or apply a scalar to the traces. We will use this process to subtract stacks created using different processing techniques.

Use Trace Math to view differences between stacks 1. Create the following flow:

Editing Flow: 9.2-Trace Math Add

Delete

Execute

View

Exit

Disk Data Input Select dataset: ---------------------STK-signal enhancement Trace Read Option: ----------------------------------------------Sort Select primary trace header entry: ------------CDP Select secondary trace header entry: --REPEAT Sort order for dataset: ---------------------------*:2,1/

Trace Math MODE of operation: ---------------------------------Trace/Trace TYPE of trace/trace operation: ------------Subtract Traces Honor ensemble boundaries: ----------------------------------No

Trace Display Label Trace label: --------------------------------------FX Decon - Input

Trace Display Primary trace LABELING header entry: ---------------None Secondary trace LABELING header entry: ------------CDP 2. In Disk Data Input, input the file you just created, and select the FX Decon copy, and the Original Input copy. 3. In Trace Math, select Trace/Trace for the mode of operation, and Subtract Traces. 4. In Trace Display Label, indicate which stacks have been subtracted. 5. Execute the flow.

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A display representing the difference between the two stacks appears on your screen. Ideally all of the energy in this difference display would be noise that was removed by the FX Decon. The presence of actual signal in this display might indicate a need to try different parameters in the FX Decon. 6. Experiment with the different trace scaling methods from within Trace Display.

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Are you comfortable with F-X Decon and Dynamic S/N Filtering

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Are you comfortable with Trace Math


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Chapter 16

Velocity: QC, Editing, Modeling Preparation of your velocity field for migration is a crucial step in the imaging process. You may need to smooth the field in space and/or time and change the field type from a stacking (RMS) field to an interval velocity field. You will also need to convert your velocities from the floating processing datum to the final flat datum. Manipulation of velocity fields is necessary for other purposes such as seismic trace inversion, finite difference modeling and time to depth conversion. In this chapter, we will discuss how to edit and modify velocity fields, using two different velocity tools.

Topics covered in this chapter: ❏ Velocity Viewer/Point Editor ❏ Velocity Manipulation

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Chapter 16: Velocity: QC, Editing, Modeling

Chapter Objectives

10. PostStack Migration

Velocity Modeling

Preparation of your velocity field for migration is a crucial step in the imaging process. You may need to smooth the field in space and/or time and change the field type from a stacking (RMS) field to an interval velocity field. You will also need to convert your velocities from the floating processing datum to the final flat datum. In this chapter, we will discuss how to edit and modify velocity fields, using two different velocity tools. Upon completion of this chapter you should:

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Be able to use the Velocity Viewer/Point Editor

•

Be able to Manipulate the Velocities to various formats


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Velocity Viewer/Point Editor Velocity Viewer/Point Editor is a stand-alone module, enabling you to scan through a velocity field, identify and edit velocity control points, and analyze the interpolation between the control points. This tool also lets you smooth the velocity field and convert stacking velocities to interval velocities. A typical use of this tool is to analyze velocities for anomalous points that need editing. In particular, unrealistic velocities are frequently computed when converting stacking velocities to interval velocities. This tool ensures that a reasonable velocity field is passed to the migration.

Smooth RMS velocities, and convert to interval velocity In this exercise, you will edit and smooth a velocity field that was created with the Velocity Analysis tool. You will then convert the RMS velocities to interval velocities in time. These edited velocity fields will be used in the chapter on migrations later in the manual. Remember that FK Migrations need Vrms(t,x), Phase Shift Migrations need Vint(t), and Finite Difference Migrations need Vint(t,x).

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Editing Flow: 10.1-Velocity Editing Add

Delete

Execute

View

Exit

Velocity Viewer/Point Editor* Select the type of field you wish to edit: --------------------------------------------------------Stacking (RMS) Velocity Do you wish to edit an existing table?: -------------------Yes Select input velocity database entry: ----------------------------------------------------vels from precompute Do you wish to specify the bounds of the field?: ------No Select output velocity database entry: ---------------------------------------------------------------Smoothed for FK Mig Specify an alternative name for the output interval velocity?: -------------------------------------------------Yes Select output Interval velocity database entry: ----------------------------------Converted Stacking Vels Minimum depth (or time) of velocity field to edit: --------0. Maximum depth (or time) of velocity field to edit: --------0 2. Select Velocity Viewer/Point Editor parameters. Select Stacking (RMS) Velocity field as the type of field to edit. Select an output name of “Smoothed for FK Mig” for the RMS velocities and “Converted Stacking Vels” for the interval velocities. 3. Execute the flow.

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Edit Edit Vel Function

Function to Edit(Pink)

Function to Compare(Blue)

Interval Velocity

4. Edit velocity control points. To edit the velocity field, you must edit the control points that define the velocity. A velocity control point generally consists of a vertical group (or function) of velocity-time pairs at a certain CDP location. To view these control points, click on the Edit Vel Function icon and move your mouse into the velocity field. Move the mouse pointer from location to location and watch as the blue function changes in the edit window. You will also notice that the function nearest the mouse pointer changes from a solid line to a dashed line. Click MB2 near one of the locations to freeze the function in the edit window; the function does not change as the mouse moves across the velocity locations.

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Click MB1 near a different velocity location. You should now have a blue line and a pink line in the edit window. Click the Edit icon on the right of the edit window, and follow the mouse button help to edit the pink function. After editing, the velocity field can be updated by clicking on the Update button on the top of the edit window. 5. Once your velocity field has been edited to your satisfaction, apply a general smoothing. From the menu bar select Modify ➛ Smooth Velocity field. This brings up the Smoothing Parameters window.

Smoothing Parameter window 6. Enter the smoothing parameters as indicated above, and select OK. Examine the results of the smoothing process. If you want to undo the smoothing and try again with different parameters, select Modify ➛ Undo last change, then re-smooth the velocities. 7. Once your velocity field is sufficiently smooth, select File ➛ Save table to disk. This saves the “Smoothed for FK MIg” file to disk for use in the FK Migration.

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8. After you have saved your smoothed velocity field, you may compute and display Interval Velocities by selecting Modify ➛ Convert RMS to Interval Velocity ➛ Smoothed gradients Dix equation. If there are large anomalies in the interval velocity field, you may need to select Modify ➛ Undo last change, perform more editing on the RMS field, and then convert to interval velocities again. You can also directly edit and smooth this interval velocity field in the same manner as described above for the RMS velocities. 9. Once you are satisfied with your interval velocity field, select File ➛ Save table to disk and exit. This will save the “Converted Stacking Vels” file to disk for use in the FD Migration.

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Velocity Manipulation Velocity Manipulation is used to convert one type of velocity to another, datumize velocities, apply a percentage, and/or smooth velocities. In this section, you will output three new velocity functions. The new functions will be a RMS field shifted to final datum, an interval velocity field shifted to final datum, and a single average interval velocity function shifted to final datum.

Shift smoothed RMS velocities to final datum In this exercise, you will shift your smoothed RMS velocity field to final datum for later use in F-K migration.

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1. Edit your flow:


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View

Exit

>Velocity Viewer/Point Editor*< Velocity Manipulation* Type of velocity table to input:--Stacking (RMS) Velocity Get velocity table from database?: -------------------------Yes Select input velocity database entry: -----------------------------------------------------Smoothed for FK Mig Combine a second velocity table with the first?: -------No Resample the input velocity table(s): -----------------------No Shift or stretch the input velocity table?: ------------------No Adjust velocities to the final datum?: ---------------------Yes Maximum percentage to change velocities during datuming: --------------------------------------------------30 Type of parameter table to output:----------------------------------------------------------------Stacking (RMS) Velocity Select output velocity database entry: ------------------------------------Smoothed at datum for FK Mig Spatially resample the velocity table?:---------------------No Output a single average velocity table?: ------------------No Smooth velocity field?: -------------------------------------------No Vertically resample the output velocity table?: ---------No Adjust output velocities by percentages?: ----------------No 2. Select Stacking (RMS) velocity for both the input and output types. Select your smoothed velocity field as input, and assign a output name. 3. Select Yes to “Adjust velocities to the final datum?” 4. Execute the flow. Once you have created the new velocity table, you could QC the file by inputting the field into the Velocity Viewer/Point Editor.

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Shift interval velocities to final datum In this exercise, you will shift your interval velocities to final datum for later input to FD migration. 1. Edit your flow to output interval velocities at final datum:


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Exit

>Velocity Viewer/Point Editor*< Velocity Manipulation* Type of velocity table to input:--Interval Velocity in time Get velocity table from database?: -------------------------Yes Select input velocity database entry: ------------------------------------------------Converted Stacking Vels Combine a second velocity table with the first?: -------No Resample the input velocity table(s): -----------------------No Shift or stretch the input velocity table?: ------------------No Adjust velocities to the final datum?: ---------------------Yes Type of parameter table to output:-----------------------------------------------------------------Interval Velocity in time Select output velocity database entry: ---------------------------------Converted vels at datum/FD Mig Spatially resample the velocity table?:---------------------No Output a single average velocity table?: ------------------No Smooth velocity field?: -------------------------------------------No Vertically resample the output velocity table?: ---------No Adjust output velocities by percentages?: ----------------No 2. Select Interval Velocity in time as the input and output table types. Read in your interval velocity file, and assign an output file name. 3. Select Yes to “Adjust velocities to final datum?” 4. Execute the flow. Once you have created the new velocity table, you could QC the file by inputting the field into the Velocity Viewer/Point Editor.

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Output a single interval velocity function In this exercise you will output a single interval velocity function in time to be used in Phase Shift migration. 1. Edit your flow to output a single average function:


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Exit

>Velocity Viewer/Point Editor*< Velocity Manipulation* Type of velocity table to input:--Interval Velocity in time Get velocity table from database?: -------------------------Yes Select input velocity database entry: -----------------------------------Converted vels at datum/FD Mig Combine a second velocity table with the first?: -------No Resample the input velocity table(s): -----------------------No Shift or stretch the input velocity table?: ------------------No Adjust velocities to the final datum?: ----------------------No Type of parameter table to output:-----------------------------------------------------------------Interval Velocity in time Select output velocity database entry: ------------------------------------One Function at datum/PS Mig Spatially resample the velocity table?:---------------------No Output a single average velocity table?: -----------------Yes Smooth velocity field?: -------------------------------------------No Time step sizes for the output velocity table: ------------30 Adjust output velocities by percentages?: ----------------No 2. Select Interval Velocity in time as the input and output table types. Read in your interval velocities at final datum, and assign an output filename. 3. Select No to “Adjust velocities to final datum?”, and select Yes to “Output a single average velocity table?” 4. Execute the flow.

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Are you comfortable with the Velocity Viewer/Point Editor

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Can you Manipulate the Velocities to various formats


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Chapter 17

PostStack Migration The ProMAX suite of 2D migration tools includes pre and poststack time and depth migration and migration velocity analysis. The available poststack migrations are of the F-K, Finite Difference, Reverse Time, Phase Shift, and Kirchhoff types. The goal is to migrate the stack section with the most appropriate poststack migration process. To aid in this selection, this chapter includes a brief description of the processes. The Reference Manual and cited references give further detail.

Topics covered in this chapter: ❏ Poststack Migration Processes ❏ Tapering ❏ Poststack migration using: • • •

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FK migration Phase Shift migration FD migration


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Chapter 17: PostStack Migration

Chapter Objectives

10. PostStack Migration

Velocity Modeling

The ProMAX suite of 2D migration tools includes pre and poststack time and depth migration and migration velocity analysis. The goal here is to migrate the stack section with the most appropriate poststack migration process. To aid in this selection, this chapter includes a brief description of the processes. Upon completion of this chapter you should:

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Understand Tapering and other Migration Parameters

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Be familiar with running FK, Phase Shift, and FD Migrations


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PostStack Migration Processes Choosing a poststack migration process can be difficult. You must weigh CPU time, accuracy of velocity structure, steepness of imaging dip, and other factors, in order to choose the most appropriate process. Often, a number of different migrations must be run in order to compare results. To help you decide on the optimal migration for a given situation, the following is a summary of the poststack migrations and how they handle changes in velocity and dip: PostStack Migrations Migration Name

Category

Type

Velocity

V(x)

V(t/z)

Steep Dip

Rel Times

Memory Stolt F-K

F-K

Time

VRMS(x,t)

Poor

Poor

Fair

0.2

Phase Shift

Phase Shift

Time

VINT(t)

None

Good

Good

1.0

Fast Explicit FD Time

FD

Time

VINT(x,t)

Fair

Good

Fair

9.6

Steep Dip Explicit FD

FD (70 deg)

Time

VINT(x,t)

Fair

Good

Good

21.0

Time

FD (50 deg)

Time

VINT(x,t)

Fair

Good

Fair

10.0

Kirchhoff Time

Kirchhoff

Time

VRMS(x,t)

Fair

Good

Good

14.6

Reverse Time T-K

Reverse Time

Time

VINT(t)

None

Good

Good

2.5

Explicit FD Depth

FD

Depth

VINT(x,z)

Good

Good

Good

21.7

Kirchhoff Depth

Imp.Eikonal

Depth

VINT(x,z)

Fair

Good

Good

7.3

Max.Amp.

Depth

VINT(x,z)

Good

Good

Good

12.0

Mult. Arr.

Depth

VINT(x,z)

Excel.

Excel.

Excel.

64.0

NOTE: These tests were run on an IBM 370 RS6000 system. Your times will depend on your specific environment, workload, dataset, and processing parameters.

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Tapering Tapering is automatically applied to samples at the bottom and edges of the seismic section prior to migration. This prevents migration artifacts due to the abrupt truncation at the bottom of the input section (see diagram below). The magnitude of the edge taper should normally increase with depth, as migration artifacts originating deeper in the section tend to move a longer distance.

Upper edge taper default is 2 traces

Bottom Lower edge taper default is 20 traces

taper default is 200ms

A Hamming taper is used, which consists of a cosine weighting that varies from 100% to 8% over the length of the horizontal taper. The bottom taper goes from 100% to 0%. In the migration processes, there is a parameter that asks if you want to change the default tapering. This does not turn off the taper, instead, it allows you the change the tapering values. If you have steeply dipping events near the edge of your data you may want to pad traces rather than the taper the edges.

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Poststack Migration At this point, you should have your best stacked dataset with statics and velocities applied, a pre-processed input velocity parameter table (edited, smoothed, shifted to datum), and an idea of the types of migrations you would like to run.

Apply FK migration In this exercise, you will run a FK migration on your data.

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Editing Flow: 10.2-FK Migration Add

Delete

Execute

View

Exit

Disk Data Input Select dataset: -------------------------------------------------STK-dmo

Memory Stolt F-K Migration Minimum CDP to migrate: ------------------------------------------775 Maximum CDP to migrate: -----------------------------------------989 CDP interval (ft or meters): ---------------------------------------27.5 Maximum frequency to migrate (in Hz): ------------------------80 Get RMS velocities from database?: ----------------------------Yes Select velocity file: -Smoothed at datum for FK Mig Number of traces to smooth velocity field over: ---------------0 Percent velocity scale factor: ---------------------------------------95 Stolt stretch factor: ----------------------------------------------------0.6 Apply Stolt obliquity correction?: --------------------------------Yes Change maximum memory usage?: -----------------------------No Change the default tapering?: -------------------------------------No Re-apply trace mutes?: ----------------------------------------------Yes Re-kill dead traces?: --------------------------------------------------Yes

Trace Display Label Trace label: -------------------------------------------------FK Migration

Disk Data Output Output Dataset Filename: -------------------------------MIG-fk mig

Bandpass Filter Ormsby filter frequency values: --------------------- 5-10-60-70


Trace Display Primary trace LABELING header entry: ------------------NONE Secondary trace LABELING header entry: -----------------CDP 2. In Disk Data Input, input your best (DMO) stack dataset.

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3. Set FK migration parameters. Select your smoothed velocity field at final datum. Set the velocity scaling factor. Normal ranges are 85-100 percent. 4. Execute the flow. 5. After examining your migration in Trace Display, select File ➛ Exit/Continue flow.

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Apply Phase Shift Migration 1. Copy your previous flow, and add Phase Shift Migration:

Editing Flow: 10.3-Phase Shift Migration Add

Delete

Execute

View

Disk Data Input Select dataset: ----------------------------------------------------STK-dmo

Phase Shift Migration Minimum CDP to migrate: --------------------------------------------775 Maximum CDP to migrate: --------------------------------------------989 CDP interval (ft or meters): ------------------------------------------27.5 Minimum frequency to migrate (in Hz): ------------------------------0 Maximum frequency to migrate (in Hz): ---------------------------80 Get INTERVAL-velocity-versus-time function from database?: -----------------------------------------------------Yes Select velocity file: ---One Function at datum/PS Mig Percent velocity scale factor: ------------------------------------------95 Migrate dips: -------------------------up to and beyond 90 degrees Maximum amount of memory (in Mbytes): -----------------------16 Change the default tapering?: ----------------------------------------No Re-apply trace mutes?: -------------------------------------------------Yes Re-kill dead traces?: ----------------------------------------------------Yes

Trace Display Label Trace label: ----------------------------------------------------PS Migration

Disk Data Output Output Dataset Filename: ---------------------------------MIG-ps mig

Bandpass Filter Ormsby filter frequency values: ------------------------ 5-10-60-70


Trace Display Primary trace LABELING header entry: ---------------------NONE Secondary trace LABELING header entry: --------------------CDP 2. In Disk Data Input, input your best (DMO) stack dataset. 3. Select Phase Shift migration parameters. 17-8


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Select your smoothed velocity field at final datum. Set the velocity scaling factor. Normal ranges are 85-100 percent. 4. Execute the flow. 5. After examining your migration in Trace Display, select File ➛ Exit/Continue flow.

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Apply FD Migration 1. Copy your previous flow, and add FD Migration:

Editing Flow: 10.4-FD Migration Add

Delete

Execute

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Disk Data Input Select dataset: ----------------------------------------------------STK-dmo

Fast Explicit FD Time Mig. CDP interval (ft or meters): ------------------------------------------27.5 Maximum frequency (in Hz): -------------------------------------------80 Time step for migration diffraction term: ---------------------------0 Percent to pad trace length: --------------------------------------------30 Get interval velocities from database?: --------------------------Yes Select interval vs. time velocity file: ---------------------------------------------------Converted vels at datum/FD Mig Change paneling parameters?: --------------------------------------No Change the default tapering?: ----------------------------------------No Retain input sample rate?: --------------------------------------------Yes Re-apply trace mutes?: -------------------------------------------------Yes Re-kill dead traces?: ----------------------------------------------------Yes

Trace Display Label Trace label: ---------------------------------------------------FD Migration

Disk Data Output Output Dataset Filename: ---------------------------------MIG-fd mig

Bandpass Filter Ormsby filter frequency values: ------------------------ 5-10-60-70


Trace Display Primary trace LABELING header entry: ---------------------NONE Secondary trace LABELING header entry: --------------------CDP 2. In Disk Data Input, input your best (DMO) stack dataset.

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3. Select FD migration parameters. Select your interval velocity field at final datum. Choose to retain input sample rate. 4. Execute the flow. 5. After examining your migration in Trace Display, select File ➛ Exit/Continue flow.

Compare Migrations 1. Use your previous flow “5.3-Compare Stacks”, to compare the various migration datasets to the input stack.

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Do you understand Tapering and other Migration Parameters

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Are you comfortable running FK, Phase Shift, and FD Migrations


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Appendix 1

Additional Geometry Information This chapter contains appendix additional information on the geometry assignment processes.

Topics covered in this chapter: ❏ Geometry Core Path Overview ❏ Details of the Geometry Programs ❏ Pre-Geometry Database Initialization ❏ Inline Geometry Header Load after Pre-Initialization

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Appendix 1: Additional Geometry Information

Geometry Core Path Overview How to Decide on the Primary Geometry Path Vector Diagram

QUESTIONS

OPTIONS * Pre-Initialization no

* Does Shot and Receiver X, Y, and station information exist in the headers and do you want to use it?

yes * Full Extraction

no no yes

* Do you want to minimize the number of times that you have to read the data?

* From Field Notes and Survey no * Do I have “Valid Trace Numbers”?

yes

Table Diagram

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Question

Answer

Option

Is shot and receiver station, and x,y information in the headers; do you want to use it?

Yes

Full Extraction

No

Ask the next question

Do you want to minimize the number of times to read the data?

Yes

From Field Notes and Survey

No

Partial Extraction


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Transferring the Database to Trace Headers When the database is completed, the information contained in it is transferred to trace headers. The following question determines how to match a trace in the data file to a trace in the database: Question

Answer

Option

Was a Full or Partial Extraction used to create the database and a new output file written?

No

Inline Geom Header Load by Chan and other trace header words.

Yes

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Inline Geom Header Load by valid trace number.


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Details of the Geometry Programs In this section we will look in detail at the functions performed by the main programs used in the geometry assignment process. The specific processes that will be addressed are: •


•


•

Geometry Header Preparation

Inline Geom Header Load is the main program used to assign geometry values to individual trace headers from the OPF database files. One of the main issues related to this geometry assignment procedure is to define how a trace in a data file will be identified in the Trace Ordered Parameter file. One of the options is to use a specific trace header word called the "valid trace number". In order to utilize the "valid trace number" we will have to spend some time discussing it’s origin and how it can be used. Another program that may be used in the geometry assignment procedure is called Extract Database Files. We will see that this program is one of the ways that the "valid trace number" can be generated by running it in either the Partial or Full extraction modes. Geometry Header Preparation is another program that may be selected in the geometry assignment procedures. This program can be used for a variety of different purposes. We will look specifically at how it can be used when dealing with the problem of duplicate Field File Identification Numbers.

Steps Performed by Inline Geom Header Load

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Inline Geom Header Load is the program that populates the trace headers of an input data file with the geometry information stored in the database.

•

The outcome from running this program is to have a database and a data file that "match".


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This means that every trace in the output data file exists in the database and there is a one to one correspondence in all values in the trace header to those in the database.

•

After a successful run each trace will also be assigned the "valid trace number" if it was not pre-assigned using Extract Database Files.

There are two major options in this program pertaining to how to identify a trace in the input data file with a trace in the database. These options are: 1. to read the "valid trace number" from the input trace header, or 2. to read the recording channel number (automatic) and 1 or 2 trace header words that can uniquely identify this trace as having originated from a unique shot (SIN) that exists in the shot database. Once a trace in a data file has been identified in the Trace OPF, the information in all of the OPF’s for that trace is copied to the trace header.

Valid Trace Numbers Before we proceed, let’s make sure that we understand the idea of the "valid trace number".

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•

Understanding this will help us decide on the "best" course of action for our data.

•

The "valid trace number" is simply a ProMAX trace header word. Every trace in the database is numbered from 1 to N, where N is the total number of individual traces in the database.

•

This is a unique number for each trace in the line or 3D project.

•

A "valid trace number" combined with matching geometry is a flag that will allow fast random access sorting of disk datasets.

•

Every trace in the TRC database is assigned to a single SIN (shot), SRF (receiver) and CDP. Every trace has an individual Shot to Receiver Offset distance, an individual midpoint X and Y location and many other values that are single numbers, that may, or may not be different for every trace.


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•

Inline Geom Header Load matches the current trace being processed to the database and then copies all of the trace dependent values as well as the other order values to the trace header. The last thing that happens is that the traces are "stamped" as matching the database.

Valid Trace Number Origin Where does the "valid trace number" trace header word come from? Luckily, the answer to this is very simple. •

The Extract Database Files program writes this trace header word after it reads and counts a trace that it is entering into the TRC database. In this case the "valid trace number" is pre-assigned.

•

If it is not pre-assigned, the Inline Geom Header Load process will create it after it determines which trace in the database corresponds to a trace in a data file.

The "valid trace number" is a unique number for every trace and is stored in the trace header as TRACE_NO. This trace header word continues to exist ONLY if you write a new trace file after the extraction procedure. A common question that arises concerns the decision to pre-assign the "valid trace number" using Extract Database Files or to rely on the alternate header identification on the first read of the input data. You may consider using Extract Database Files if there is sufficient information in the trace headers that can be transferred to the database which will save time and increase accuracy of the geometry definition process. The extraction may be run in either the partial extraction or full extraction modes depending on what information is available in the trace headers of the input data.

Steps Performed By Extraction The steps performed by the extraction options are: Pre-Geometry Initialization (or partial extraction) which is sometimes used when no receiver information exists in the incoming headers. Partial Extraction counts each of the following: •

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the number of traces encountered


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• the number of shots encountered • the number of traces per shot and then •

writes the trace count number and SIN to the trace header

Full Extraction is used when you want to extract the shot and receiver location and coordinate information from the incoming headers. Full Extraction counts each of the following: • the number of traces encountered • the number of shots encountered • the number of traces per shot • the number of receivers encountered • the number of traces per receiver and then •

writes the trace count number and SIN to the trace header

IF you have run the extraction in either mode, AND written a new trace data file, AND have not altered the number of traces in the database, you now have “valid trace numbers” in the headers of the output data set which you can use to map a trace in a data file to a trace in the database. This mapping will be performed by Inline Geom Header Load after the database is completed.

Between Extraction and Geom Load After running Extract Database Files in either mode there are many steps that need to be completed prior to running the Inline Geom Header Load. The extraction only partially populates the database. More work will generally need to be done in the Spreadsheets to input the remaining information. After the Spreadsheets are complete, the next step would be to complete the CDP binning procedures and then finalize the database. With the database complete, you can continue with the next step of loading the geometry information from the databases to the trace headers. You may elect to address a trace by it’s "valid trace number"

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assigned during the extraction or you may read a combination of trace headers to identify the trace.

Geometry Load Procedures For the first option, Inline Geom Header Load operates as follows: 1) it identifies the TRACE_NO of the incoming trace and finds that trace in the TRC database. 2) it copies the appropriate TRC order values to the trace header and then 3) finds the shot, receiver, cdp, inline, crossline, and offset bin for that trace. The appropriate values from those orders are then copied to the trace headers as well. In the second option, Inline Geom Header Load does not know exactly which TRACE_NO it is looking for. It does know which channel and shot to look for based on the header word(s) that you selected. Given that this mapping is unique, the program now knows which SIN and CHAN to look for in the TRC database. Once the entry is found, the TRACE_NO is copied to the headers and the steps outlined in the first option are performed. Again, the key to the second option is that you need to identify which shot a trace came from by a "unique" combination of header words for that shot.

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Pre Geometry Database Initialization Note: In general, this process is not recommended for medium to large volume 3D projects. To create a minimum set of entries in the SIN and TRC Ordered Parameter files, based upon the information found in the trace headers of the data passed through the flow, selecting Yes to the option for PreGeometry Extraction. Basically this process counts how many traces, different FFIDs, and recording channels were present for each input FFID. Therefore, it can build the TRC and SIN ordered database files. An SRF OPF could be created, and may or may not have any information in it. Partial Extraction Flow Chart

Disk Output - Pre-Init Path O.B. Notes

UKOOA

Manual Input

Field Data

ASCII

SEG-? Input

UKOOA Import Spreadsheet Import Database Import

Geometry Spreadsheet Ordered Parameter Files Marine Data SSD correction Seismic Data (ProMAX)

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Builds TRC and SIN OPF’s only Pre Geom Init = yes

Valid Trace Numbers Overwrite Trace Headers

Disk Data Output



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This option may be appropriate for relatively small datasets which only have FFID and CHAN in the input trace headers. This option should be used when reading the field data and writing the data to disk for the first time. In so doing, information, such as FFID, number of shots, number of channels are written to the database, and are then available when the geometry is completed. Selecting this option will also stamp the output dataset with “valid trace numbers”, which allows you to process with trace headers only and overwrite the dataset with updated geometry from the database files. This is an important concept for the Inline Geom Header Load process. In the following example, you will assume that only the FFID and recording channel number exist in the incoming trace headers. This information will be extracted, using the perform pre-geometry database initialization option in Extract Database Files.

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Pre Geometry Initialization flow 1. Make a new line called “from pre-initialization”. 2. Build the following flow:

Editing Flow: A1.1-Pre-Geom Initialization Add

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SEGY Input Type of storage: --------------------------------------- Disk Image Enter DISK file path name: ---------------------------------------------------------------/misc_files/2d/segy_0_value_headers MAXIMUM traces per ensemble: ---------------------------120 Remap SEGY header values: -------------------------------- NO

Extract Database Files Is this a 3D survey: ------------------------------------------------No Data Type: --------------------------------------------------------LAND Source index method: -----------------------------------------FFID Receiver index method: ------------------------------STATIONS Mode of operation: ----------------------------------OVERWRITE Pre-geometry extraction?: --------------------------------------Yes

Disk Data Output Output Dataset Filename: ----------------”Shots-raw data” New, or Existing, File?: ----------------------------------------New Record length to output: ------------------------------------------0. Trace sample format: ----------------------------------------16 bit Skip primary disk Storage?: -----------------------------------No 3. Enter the parameters for the SEGY-Input process: Enter the full path name to the SEGY input dataset as described by the instructor. There are 120 traces per ensemble. 4. In Extract Database Files, select to identify which traces belong to which shots and receivers as follows: Sources: identify by FFID.

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Receivers: identify by STATIONS. 5. In Extract Database Files, select Yes for the option Pre-geometry extraction. This initializes the SIN and TRC domains of the Ordered Parameter Files, stamps the dataset with valid trace numbers, and allows for the use of overwrite mode when performing the Inline Geom Header Load step later. 6. In Disk Data Output, enter the name for a new output file, such as “Shots-raw data”. 7. Execute the flow. After the Flow Completes 8. Exit the flow building level and select Database from the global command line. 9. Check the OPFs, verifying the number of records in the dataset, the number of channels/record, and the FFID range. The only OPF files that should exist are LIN, SIN, and TRC. If SRF exists, this means that you identified traces for receivers by coordinates. You will also find that the SRF OPF has 1 value in it.

Complete the Spreadsheet In this sequence, the next steps would be to complete the Sources, Receivers and Patterns Spreadsheets and perform the CDP binning similarly to the sequence used in Chapter 1: Geometry Assignment.

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Inline Geometry Header Load after Pre Initialization In this sequence, we ran the Extract Database Files process in the preinitialization mode. Here, we will read the output data from the preinitialization step and identify a trace relative to its “valid trace number” with respect to the database.

Load Geometry to Trace Headers 1. If the geometry in the database looks good, build the following flow:

Editing Flow: A1.2-Load Geom to Headers and QC Add

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Disk Data Input Read data from other lines/surveys: ----------------------No Select Dataset: --------------------------------”Shots-raw data” Trace read option: --------------------------------------------Get All Read the data multiple times?: -------------------------------No Process trace headers only?: ---------------------------------Yes Override input data’s sample interval: --------------------No

Inline Geom Header Load Match by valid trace number?: ------------------------------Yes Drop traces with NULL CDP headers?: --------------------No Drop traces with NULL receiver headers?: ---------------No Verbose Diagnostics?: --------------------------------------------No

Disk Data Output Output Dataset Filename: ----------------”Shots-raw data” New, or Existing, File?: --------------------------------Overwrite Record length to output: ------------------------------------------0. Trace sample format: ----------------------------------------16 bit Skip primary disk Storage?: -----------------------------------No 2. In Disk Data Input, enter your input shot dataset. In this sequence, we only process the trace headers.

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3. In Inline Geom Header Load, match the traces by their “valid trace numbers”. Since the traces were read and counted with Extract Database Files, you have a “valid trace number” to identify a trace. You have binned all traces; therefore, do not drop any traces. Unless you have a problem, there is no need for verbose diagnostics. 4. In Disk Data Output, output to the same dataset as specified in Disk Data Input. We will use the overwrite option in conjunction with trace header only processing in the Disk Data Input. 5. Execute this flow. In the Extract Database Files path, the Inline Geom Header Load process operates on a sequential trace basis, and includes a check to verify that the current FFID and channel information described in the OPFs matches the FFID and channel information found on each trace of each ensemble. The Inline Geom Header Load process will fail if these numbers do not correspond. You must then correct the situation by changing the geometry found in the OPFs, or possibly by changing the input dataset attributes.

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Appendix 2

Supergathers Supergathers are ensembles which were created by combining two or more regular CDPs to form a single ensemble. Supergathers are commonly used for velocity analysis and quality control, post-NMO mute definition, and any other processes which might benefit from reduced spatial separation between traces in a CDP gather. ProMAX incorporates the functionality to create supergathers in a number of analysis and quality control processes. Examples include: Velocity Analysis, Interactive Velocity Analysis, and Velocity Quality Control. This exercise is useful to help understand the mechanism employed in creating supergathers in these various processes.

Topics covered in this chapter: ❏ Create Supergather ❏ Create Supergather and Horizontally Stack

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Appendix 2: Supergathers

Create Supergather Creating supergathers is really a matter of redefining a trace flag which establishes the “end-of-ensemble.” In other words, how the traces are grouped. The header word is called the End-of-ensemble flag (END_ENS) and its value is either 1 or 0 (one or zero). When END_ENS = 1, this alerts any process that the last trace in an ensemble has been reached, such as shot record, CDP, or offset gather. This way, if a process redefines the value for the END_ENS header word, then it is able to regroup the traces. The following exercise will illustrate how you may control trace grouping with a process called Ensemble Stack/ Combine. 1. Build a simple flow to input and display three CDPs.

Editing Flow: A2.1-Create Supergather Add

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Disk Data Input Select dataset: ----------------------------------Shot-decon/elev Trace read option: -----------------------------------------------Sort Interactive Data Access?: ---------------------------------------No Select primary trace header entry: -----------------------CDP Sort order for dataset: -------------------------------- 850-852/


>Ensemble Stack/Combine< Trace Display Number of ENSEMBLES (line segments)/screen: -------3 Primary trace LABELING header entry: ----------------CDP Secondary trace LABELING header entry: ------OFFSET 2. In Disk Data Input, select a dataset with some initial processing applied, such as edits, mutes, and gain. Sort by CDPs 850-852.

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3. In Trace Display, set the Number of ensembles/screen large enough to allow all three CDPs on the screen at one time. Also, label primary and secondary header entries as CDP and OFFSET in the Trace Display menu. 4. Execute the flow. Your screen should look similar to the following:

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5. Use the Header icon to display several trace headers. The value of the End-of-ensemble flag (END_ENS) header word can change from trace to trace. Be sure to check the last trace in any one of the ensembles. What is different?

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6. Activate Ensemble Stack/Combine in your flow to create one superCDP. Select Combine only for the Type of Operation, inputting three ensembles per output ensemble. This option will only reset the END_ENS flag for the first three CDPs so that the result is one single CDP. Also in this menu, select primary and secondary header words as OFFSET.

Editing Flow: A2.1-Create Supergather Add

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Disk Data Input Automatic Gain Control Ensemble Stack/Combine Type of operation: ---------------------------------Combine Only Input ensembles per output ensemble: ----------------------3 Maximum traces per output ensemble: --------------------60 Warnings if max traces/ensemble exceeded?: --------Yes Select PRIMARY Trace Order Header Word: ----------CDP Average the primary key values?: ---------------------------No Average the X and Y coordinates of primary key?: --No Select SECONDARY Trace Order Header Word: -------------------------------------------------------------------OFFSET Output trace secondary key order: --------------Ascending

Trace Display

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7. Execute the flow and compare your results to the original. It should look similar to the following:

You might use this type of operation to create a super-CDP with better offset coverage prior to Velocity Analysis.

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Create Supergather and Horizontally Stack 1. Insert NMO into the Create Supergather flow. The velocity function you use is not too critical. The reason for NMO will be clear in the next step.

Editing Flow: A2.2-Create & Stack Supergather Add

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Disk Data Input Normal Moveout Correction SELECT Velocity parameter file: --------------------------------------------------------------------imported from ascii file

Automatic Gain Control Ensemble Stack/Combine Type of operation: -------------------------Combine and Stack Input ensembles per output ensemble: ----------------------3 How are trace headers determined?: --------------Average Secondary key bin size: ---------------------------------------350 Maximum traces per output ensemble: --------------------60 Warnings if max traces/ensemble exceeded?: --------Yes Select PRIMARY Trace Order Header Word: ----------CDP Average the primary key values?: ---------------------------No Average the X and Y coordinates of primary key?: ---No Select SECONDARY Trace Order Header Word: -------------------------------------------------------------------OFFSET Output trace secondary key order: --------------Ascending

Trace Display 2. Modify Ensemble Stack/Combine to use the Combine and Stack option for the type of operation. After making this selection you will see a new parameter called Secondary Key Bin Size which was previously hidden. Set this value to 350.

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3. Execute the flow. Notice the difference between this display and your last. Why are they different this time?

One observation that should jump out is that there are fewer traces on the screen. This is due to the summation of adjacent traces performed by the Stack portion of the Combine and Stack option. The summation is dependent on which header word you select as a secondary key, and by the secondary key bin size. You might use this type of operation to reduce the amount of data going into a Prestack Migration.

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Appendix 3

Alternate Velocity Analysis Methods Besides the ‘Velocity Analysis’ tool covered earlier in this book, ProMAX has several other velocity analysis options available. Two of these methods will be covered in this chapter.

Topics covered in this chapter: ❏ CVS (Constant Velocity Stack) Analysis ❏ IVA (Interactive Velocity Analysis)

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Appendix 3: Alternate Velocity Analysis Methods

CVS Analysis CVS Analysis is a macro process. CVS can be helpful in areas of complex structure where velocity trends can change along the seismic section. Constant velocity stacks of the entire line or a subset are produced for a specified range of velocities. Horizons may be easier to track if the whole section is seen. Random picks can be made on any constant velocity stack panel and a final gridded velocity table is output. Creating constant velocity stacks can be a time consuming event especially if you have a large dataset with many panels to create. In this case you may want to use the process Constant Velocity Stacks to create and output the CVS panels ahead of time. Then Stack Display can be used to display and pick the velocities the same way as done with the macro.

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Editing Flow: A3.1-CVS Add

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Disk Data Input Select dataset: -----------------------Shots-decon/refr statics Trace read option: -----------------------------------------------Sort Interactive Data Access?: ---------------------------------------No Select primary trace header entry: -----------------------CDP Sort order for dataset: ---------------------------------------------*/

CVS Analysis Apply AGC to the data?: ---------------------------------------Yes AGC operator length: --------------------------------------------500 Maximum wavelet stretch: --------------------------------------30 Velocity input option: ----------------------------------Calculated Minimum velocity: ----------------------------------------------7000 Maximum velocity: -------------------------------------------17000 Number of velocity panels: -------------------------------------16 Select display DEVICE: -----------------------------This Screen Number of trace per display screen: ----------------------215 Do you wish to SCROLL your data?: -----------------------No Trace scaling option: -----------------------------------Individual SCALAR for sample value multiplication: ------------------1. 2. Select Disk Data Input parameters. A Disk Data Input step is required since it is not included within the macro. Data should be preprocessed gathers without NMO and should have a bandpass filter and scaling function applied. Sort to CDP and include the range of CDPs to be stacked. For this exercise, use all the CDPs in the line. 3. In CVS Analysis, apply an AGC prior to stacking with constant velocities. Specify the minimum, maximum velocity and number of velocity panels. Enter 7000 - 15000 ft/sec for an velocity range and create 16 panels.

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4. Select the number of traces to display per screen and an appropriate trace scaling option, such as Individual. Selecting Individual as the trace scaling option will make sure that spikes do not dominate the display. 5. Execute the flow with MB2. The display will appear in the old Stack Display tool. The last constant velocity panel will appear along with 16 screen swap boxes in the upper right of the display.

6. Click on the Pick icon to create a pick table. Click on Pick ➛ CVS/CVM panels ➛ Create new file and name it “cvs vels”. 7. Activate the CVS/CVM picking mode.

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Move the cursor to the screen swap boxes in the upper right hand corner of the display and use MB2 to enable picking of the CVS panels. NOTE: You should see all the icons disappear except for the scroll icon and you should be able to move your cursor into the data area. If you don’t see the scroll icon and your cursor remains in the screen swap boxes, you are not in CVS/CVM picking mode. To correct this error, click MB1 in the screen swap boxes and then click MB2 in the screen swap boxes. You should see the scroll icon remaining and you should be able to move your cursor into the data area.

8. Pick velocities on the display by using MB1. Move your cursor into the displayed stacked section. While holding down MB2, move the cursor back and forth within the stacked section. This will enable the screen swapping.

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Once you have found a velocity panel that stacks an event best, use MB1 to make a pick and to display it on-screen. You can manually enter a velocity value at your cursor location by double clicking MB1. A pop-up box will appear in the upper left hand corner of the display. You may now type in a velocity value. Hit enter to accept. This can be useful if the desired velocity falls between the displayed panel velocities. 9. To finish picking, click MB1 on any of the screen swap boxes in the upper right hand corner of the display. 10. Click the red Stop icon to exit the display. Choose “Save all work to the database before quitting”.

NOTE: Upon exiting the CVS Analysis display, two velocity tables are written to disk. One file contains just the picks you made in the CVS Analysis display. The second file is a fully interpolated velocity table based on the sparse picks you made on-screen.

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Interactive Velocity Analysis (IVA) Interactive Velocity Analysis is a standalone process that allows comprehensive velocity analysis and quality control of a new or existing velocity field. IVA combines displays of semblances, velocity fans, stacks, gathers and an isovel plot for interactive picking of a velocity field. With the use of active image, you see the appearance of real time moveout and stacking as the cursor is moved within the velocity fans. Since IVA has many options and interactive capabilities, this exercise is designed to teach you the basic functionality of the program. Consult the Reference Manual for more specific details about a particular operation.

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Editing Flow: A3.2-IVA Add

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Interactive Vel Analysis* Operation Mode: --------------------------------Fully Interactive Input trace data file: --------------Shots-decon/refr statics Minimum CDP on line: ------------------------------------------775 Maximum CDP on line: -----------------------------------------989 Increment CDP on line: ---------------------------------------------1 Dataset CDP Restriction: ------------------All available data Super Gathers Options: -----------------------Common Offset Minimum Offset bin center: ----------------------------------27.5 Maximum Offset bin center: --------------------------------6500 Common Offset bin center Inc: --------------------------------55 Common Offset bin Width: --------------------------------------55 Adjacent CDPs in Super Gather: -------------------------------9 Input (Initial) Velocity Table: -----imported from ascii file Output Velocity Table: ------------------------------------IVA vels Provide CDP mute Table?: --------------------------------------No Provide Horizon DATA Table?: --------------------------------No Minimum velocity: ----------------------------------------------7000 Maximum velocity: -------------------------------------------17000 Velocity Uncertainty at Tzero: -------------------------------900 Velocity Uncertainty at Tmax: -----------------------------3600 Interval Vel. below last knee: ----------------------------17500 Maximum Frequency: ---------------------------------------------70 Number of functions: ----------------------------------------------17 Span in CDPs for flip stack panels: --------------------------7 NMO Stretch Percent to allow: ---------------------------------30 Horizontal Enlargement Factor: ---------------------------0.75 Vertical Enlargement Factor: --------------------------------0.75

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2. Select Fully Interactive for the Operation Mode. Fully Interactive allows you to choose random locations once IVA is displayed and does not involve any precomputation. Precompute then Interactive allows you to specify CDPs at which to precompute analyses. Once IVA is displayed, you can move between locations more quickly. However, other random locations can still be selected. 3. Select your range of data to process. IVA allows the selection of a specific range of CDPs to process or All Available Data. Supergathers can also be created for analysis. 4. Select or create the Input (Initial) and Output velocity Table. The input velocity table and the output velocity table can be the same file or a new output table can be added. The output table is continuously updated as each new velocity function is picked. 5. Provide a CDP Mute Table and/or a Horizon Data Table. A post NMO mute table can be supplied provided it was created as a function of CDP:AOFFSET, or one can be created and interactively picked once IVA is running. The same can be done for a horizon data table. 6. Enter velocity information and maximum frequency of data. The menu asks for a minimum and a maximum velocity of interest plus an interval velocity below the last picked time or knee. For this data use a velocity range of 7000-17000 ft/sec and an interval velocity of 17500 ft/sec. Velocity Uncertainty at Tzero and Tmax basically defines the bounds of your velocity fan. For example the default uses 900 ft/sec for Tzero meaning the fan will be no wider than 1800 ft/sec (900 on each side of the reference function) at Tzero. The maximum frequency of the data is requested simply to internally resample the data to optimize screen resolution and execution time. It is not a filter. 70 Hz is reasonable for this data.

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7. Enter the number of velocity functions and number of CDPs for the stack panels. As the number of velocity functions increases, the resolution improves, but the run time and resource requirements also increase. For this data, you can get adequate resolution using 15-17 velocity functions and 7 consecutive CDPs in the stack panels. 8. Execute the flow with MB2.

The initial display includes a semblance plot, an isovel plot and a portion of the data stacked with the input velocity table. 9. Scan your data. The portion of the stacked data displayed is defined by the rectangle box in the isovel plot. Use MB3 with the cursor located in either the stack or the isovel to scroll through the data. Clicking on MB3 will

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quickly jump to a new location on the isovel plot. The size of the box in the isovel plot is controlled by the Horizontal and Vertical Enlargement Factor. NOTE: The mouse button helps are very important in this process because they change according to where the cursor is located on the screen.

10. Select your CDP analysis location by clicking MB2 for a previously picked location or MB1 for a new location. CDP numbers are displayed below the stack section along with time and velocity. Use MB1 to pop up a menu with analysis mode options. Select Semblance, Stacks and Gathers. In the lower right corner of the screen the Notification Window shows that the stack, semblance and gather images are being computed. 11. Click on Config and select Expand/UnExpand Top. This option appears below the semblance plot and allows the reconfiguration of the display. Eliminate the isovel plot to allow more room for the semblance, stack and gather.

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12. Begin picking the velocity function by clicking on Pick. Select Velocity Function from the Pick Operation menu. A message appears in the notification window that reads “Picking Function Auto_scroll enabled.” You can freely scroll the mouse up and down the display. MB1 adds a control point (knee) to your function and MB3 deletes a control point. As you move the cursor within the calculated functions, the active screen images change within the flip stack and gather. Once you have finished picking your velocity function, while keeping the cursor within the semblance plot, use MB2 to save and write the function to the velocity table. Go back to the Config option and UnExpand your window. Your function is displayed as a downline in the isovels plot. Start again and select a new CDP location for analysis. 13. Changing the velocity bounds of your fan is possible by using the Vbound option located to the right of Pick. Click here and the notification window reads “Picking Vbound 1. Auto_scroll enabled.” Use MB1 to add control points to the lower vbound (left side). When you are finished, click MB2 and the notification window reads “Picking Vbound 2. Auto_scroll enabled.” Use MB1 to select your control points for the upper vbound. When finished, MB2 recomputes a new velocity fan with new gather and stack panels. 14. Mute Analysis can be run at any CDP location. Click on your analysis location. When the Analysis Mode menu pops up, select Mute Analysis. Wait for the computations to complete. Follow the same instructions as picking a function, click on the Pick option and select Top Mute from the menu. You will notice in the gather display that mute points have already been selected. To choose your own mute, use MB1 to select time/aoffset points. When finished, use MB2 to save the output. Gathers and stacks are recalculated and you are prompted to Update the Semblance. A mark is displayed on the isovel where the analysis was done. Your mute is saved in the Parameter File menu for Mute Gates and is automatically labeled as IVA with a time/date stamp. 15. Restack Line. To restack your line with the new velocities, click on Action and select Restack Line from the popup menu. The notification window informs you that your CDPs are being restacked.

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16. Exit. When you are ready to exit IVA, use the Exit located at the bottom of the screen. Select from the menu to either save to the database or to abort the IVA session. Your velocity table can be found in the Parameter Files for RMS (stacking) Velocity menu.

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Appendix 4

Database/Header Manipulation The database is critical to ProMAX. Many processing attributes, such as statics and first break picks are kept in the database. In this chapter we examine the links between the database and the trace headers by determining first break linear moveout corrections. We will also create and alter trace headers and database attributes.

Topics covered in this chapter: ❏ Header Manipulation Processes

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Header Manipulation Processes This exercise uses the following ProMAX Header Manipulation processes: •

Trace Header Math: Trace header math has four modes of operation. The first three allow you to modify and/or create trace headers and the last changes global runtime attributes of the data, such as forcing the time to be depth. We will use the application called Fixed Equation Mode which allows us to create or modify headers using a mathematical function on existing header entries and constants.

•

Database/Header Transfer: This process transfers up to 8 values at a time between the database and the trace headers. The transferred value can be loaded into an existing database attribute or trace header name, or you can create your own names. However, if you create your own database attribute, a random number represents the database name and the description is what you typed in. This random number can be changed to a meaningful name using the new/copy option in the database.

•

Header Statics: This process applies statics to traces from header words or applies bulk shift statics.

Apply a Linear Moveout Correction In this exercise, you will compute and apply a linear moveout (LMO) correction to the data. This will create a new trace header that you can transfer to the database. Finally you will view your new attribute in the database.

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Editing Flow: A4.1-Trace Header/Database Manip Add

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Disk Data Input Select dataset: ----------------------------Shots-with geometry

Trace Header Math Select mode: ----------------------------------------Fixed equation DEFINE trace header equation: ----------------------------------------------------LMO=100-(AOFFSET/8000)*1000

Database/Header Transfer Direction of transfer: ---From Trace header to database Number of parameters: --------------------------------------------1 First database parameter: -------------------------------------------------------------TRC:Geometry:New - Enter LMO First Header Entry: ---------------------------------------------LMO

Header Statics Bulk shift static: ------------------------------------------------------0 What about previous statics?: ---Add to previous statics Apply how many static header entries?: -------------------1 First Header word to apply: ---------------------------------LMO HOW to apply header statics?: -----------------------------Add

Apply Fractional Static Trace Display Specify display END time: ------------------------------------500 Number of display panels: ---------------------------------------4 2. In Disk Data Input, input your raw shots with applied geometry.

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3. In Trace Header Math, create a static for applying a linear moveout correction to your data. The following equation creates the LMO static time: LMO = 100 - (AOFFSET/8000) * 1000 where: 100 is a bulk shift to move the trace samples away from time zero by 100 ms. 8000 is the refractor velocity. 1000 converts seconds to ms. Except for the near offsets, the final LMO corrections are fairly large negative numbers. 4. Select Database/Header Transfer parameters. Select to Load FROM trace header TO database. For “First database parameter” select TRC: Geometry: New to enter a name for your LMO static header and make it Floating Point. For “First Header entry” select User Defined and enter LMO. 5. Select Header Statics parameters. Add the LMO header entry, created in the Trace Header Math, to the previous statics. 6. Set the Trace Display parameters. You may find that setting this display to four panels, and limiting the time range from 0 to 500 ms is useful. 7. Execute the flow, and observe the effects of the LMO. 8. View your new LMO attribute in the database.

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Appendix 5

Training Summary This summary may be used as a quick reference for some of the most useful charts of information you have worked with during the week.

Topics covered in this chapter: ❏ Reference Tables ❏ Reference Graphs ❏ Flows and Data Summaries

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Appendix 5: Training Summary

Reference Tables Organization of Ordered Parameter Files LIN (Line)


TRC (Trace)








CHN (Channel)


OFB (Offset Bin)


PAT (Pattern)


The Ordered Parameter Files database stores information in structured categories, known as Orders, representing unique sets of information applying to an individual line.

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PostStack Migration Summary Migration Name

Category

Type

Velocity

V(x)

V(t/z)

Steep Dip

Rel Times

Memory Stolt F-K

F-K

Time

VRMS(x,t)

Poor

Poor

Fair

0.2

Phase Shift

Phase Shift

Time

VINT(t)

None

Good

Good

1.0

Fast Explicit FD Time

FD

Time

VINT(x,t)

Fair

Good

Fair

9.6

Steep Dip Explicit FD

FD (70 deg)

Time

VINT(x,t)

Fair

Good

Good

21.0

Time

FD (50 deg)

Time

VINT(x,t)

Fair

Good

Fair

10.0

Kirchhoff Time

Kirchhoff

Time

VRMS(x,t)

Fair

Good

Good

14.6

Reverse Time T-K

Reverse Time

Time

VINT(t)

None

Good

Good

2.5

Explicit FD Depth

FD

Depth

VINT(x,z)

Good

Good

Good

21.7

Kirchhoff Depth

Imp.Eikonal

Depth

VINT(x,z)

Fair

Good

Good

7.3

Max.Amp.

Depth

VINT(x,z)

Good

Good

Good

12.0

Mult. Arr.

Depth

VINT(x,z)

Excel.

Excel.

Excel.

64.0

To help you decide on the optimal migration for a given situation, the above table is a summary of the poststack migrations and how they handle changes in velocity and dip.

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Datum Statics Apply

For Elevation Statics

For Refraction Statics

1) Remove previously applied statics if TOT_STAT not equal 0

1) Remove previously applied statics if TOT_STAT not equal 0

2) Compute S_STATIC and R R_STATIC to Final Datum

2) COPY refraction statics to S_STATIC and R_STATIC

3) Compute N_DATUM (smooth surface / processing datum)

3) Compute N_DATUM (smooth surface / processing datum)

4) Partition the statics into PRE and POST NMO terms ----- NMO_STAT (pre) ----- FNL_STAT (post)

4) Partition the statics into PRE and POST NMO terms ----- NMO_STAT (pre) ----- FNL_STAT (post)

5) Apply the PRE NMO term NMO_STAT

5) Apply the PRE NMO term NMO_STAT

6) Update NA_STAT and TOT_STAT in the Trace Headers

6) Update NA_STAT and TOT_STAT in the Trace Headers

ProMAX uses the above logic when applying datum statics. Refer to the following “Datum Statics Terminology” graph for a further description of the statics variables.

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Reference Graphs Datum Statics Terminology S.P.

CDP

Receiver N_DATUM

NMO_STAT

Vweathering

Surface Elevation

NMO_STAT Shot Vreplacement

Base Weathering

S_STATIC

FNL_STAT

C_STATIC

R_STATIC

F_DATUM

Database Attributes: N_DATUM = floating datum F_DATUM = final datum S_STATIC = (F_DATUM - ELEV + DEPTH) / DATUMVEL R_STATIC = [(F_DATUM - ELEV + DEPTH) / DATUMVEL] - UPHOLE C_STATIC = 2 * [(N_DATUM - F_DATUM) / DATUMVEL]

Trace Header Values: N_DATUM = floating datum NMO_STAT = S_STATIC + R_STATIC + C_STATIC FNL_STAT = - C_STATIC TOT_STAT = cumulative applied statics NA_STAT = statics less than one sample period which are not-yet-applied (If TOT_STAT = 21.2 ms, and the sample period is 4 ms, NA_STAT = 1.2 ms)

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Geometry Assignment Map

All Possible Geometry Assignment Paths UKOOA O.B. Notes

Manual Input

ASCII

Field Data

UKOOA Import Spreadsheet Import

SEG-? Input

Database Import Seismic Data (ProMAX)


Extract Database Files Inline Geom Header Load

Ordered Parameter Files

Disk Data Output

Disk Data Output Inline Geom Header Load Valid Trace Numbers Overwrite Trace Headers

5-6

Seismic Data

Seismic Data

(ProMAX)

(ProMAX)


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Promax Directory Structure $PROMAX_HOME (default=.../ProMAX)

/sys

/exe exec.exe super_exec.exe *.exe from program

/frame /sdi /3rd party software

/bin *.exe from command line

/lib lib*.a

/port

/plot /help

/promax *.lok - Frame help

/etc

/lib/X11/app-defaults *.help -ASCII help Application window /promax3d managers /promaxvsp /menu /promax *.menu Processes /promax3d /promaxvsp /misc *_stat_math *.rgb-colormaps ProMax_defaults /bin start-up executable

config_file product install.doc pvmhosts qconfig license.dat

/scratch /queues /data

/area

/line

(or $PROMAX_DATA_HOME)

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Promax Data Directories PROMAX_DATA_HOME

or /Data /Area DescName Project

Area subdirectory and its files

/Line DescName 17968042TVEL 31790267TGAT 36247238TMUT 12345678CIND 12345678CMAP

1) Parameter Table files

Index and Map Dataset files

/12345678 HDR1 HDR2 TRC1 TRC2

2) Dataset subdirectory and Header and Trace Dataset files

/Flow1 DescName TypeName job.output packet.job

3) A Flow subdirectory and its files

/OPF.SIN OPF60_SIN.GEOMETRY.ELEV

4) /OPF.SIN Database subdirectory and a non-spanned file

/OPF.SRF #s0_OPF60_SRF.GEOMETRY.ELEV

/OPF.SRF Database subdirectory and a span file

Understanding the ProMAX directory structure and file naming conventions will be crucial for debugging flows and managing disk space.

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Flows and Data Summaries Flows

Upon completion of the course your flows menu should look similar to the above.

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Datasets: Seismic

Upon completion of the course your processing should have created the above datasets. Note: how the naming convention allows for clues as to the datasets contents.

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Datasets: OPF-TRC

The TRC “trace” database is the largest of the Ordered Parameter Files since it contains information varying by trace, such as FB Picks, trim statics, source-receiver offsets. Note: the format in the database table is variable name, variable/info type, and variable description.

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Datasets: OPF-SRF

The SRF “receivers” OPF contains information varying by surface receiver location, such as surface location x, y coordinates, surface location elevations, surface location statics, number of traces received at each surface location and receiver fold.

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Datasets: OPF-SIN

The SIN “source” OPF contains information varying by source point, such as source x, y coordinates, source elevations, source uphole times, nearest surface location to source, and source statics.

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Datasets: OPF-CDP

The CDP OPF contains information varying by CDP location, such as CDP x, y coordinates, CDP elevation, and CDP fold nearest surface location.

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Datasets: OPF-CHN

The CHN “channel” OPF contains information varying by channel number, such as channel gain constants and channel statics.

Datasets: OPF-OFB

The OPF “offset bin” OPF contains information varying by offset bin number, such as surface consistent amplitude analysis. OFB is created when certain processes are run, such as surface consistent amplitude analysis.

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Datasets: OPF-PAT

The PAT “pattern” OPF contains information describing the recording patterns.

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The End

ProMAX 2D Seismic Processing and Analysis I hope the class was beneficial, wlf.

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5-18


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Promax 2D Seismic Processing & Analysis

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