2010_Mapping & Geological Workflows

Mapping and Geological Workflows

Petrel 2010

About Petrel* Development on Petrel seismic-to-simulation software began in 1996 in an attempt to combat the growing trend of increasingly specialized geoscientists working in increasing isolation. The result was an integrated workflow tool that allows E&P companies to think critically and creatively about their reservoir modeling procedures and enables specialized geoscientists to work together seamlessly. With the enhanced geophysical tools and the integration of ECLIPSE* reservoir simulation software and streamline simulation, Petrel is now a complete seismic-to-simulation application for •

• • • • • • • • • • • • •

3D visualization 3D mapping 3D and 2D seismic interpretation well correlation 3D grid design for geology and reservoir simulation depth conversion 3D reservoir modeling 3D well design upscaling volume calculation plotting post processing streamline simulation ECLIPSE

Copyright Notice © 2010 Schlumberger. All rights reserved. No part of this manual may be reproduced, stored in a retrieval system, or translated in any form or by any means, electronic or mechanical, including photocopying and recording, without the prior written permission of Schlumberger Information Solutions, 5599 San Felipe, Suite 1700, Houston, TX 77056-2722.

Disclaimer Use of this product is governed by the License Agreement. Schlumberger makes no warranties, express, implied, or statutory, with respect to the product described herein and disclaims without limitation any warranties of merchantability or fitness for a particular purpose. Schlumberger reserves the right to revise the information in this manual at any time without notice.

Trademark Information *Mark of Schlumberger. Certain other products and product names are trademarks or registered trademarks of their respective companies or organizations.

Table of Contents About Petrel* ...........................................................................2 Copyright Notice........................................................................3 Disclaimer..................................................................................3 Trademark Information..............................................................3 Module 1 - Introduction and Display Settings......................9 Prerequisites..............................................................................9 Learning Objectives...................................................................9 What You Will Need.................................................................9 What to Expect........................................................................10 Icons........................................................................................11 Workflow Diagram..................................................................12 Lesson 1 Display and Color Management..............................13 Exercise 1 – Display and Color management.........................25 Displaying a Surface in a 3D Window....................................25 Contouring...............................................................................25 Grid lines.................................................................................28 Solid.........................................................................................28 Using Light Sources.................................................................29 Modify Surface Properties – Show Contours in Solid............32 Displaying Multiple Surfaces in a 3D Window.......................33 Adding an Attribute to a Surface............................................35 Drape Bitmap on a Surface.....................................................36 Display Grid Nodes..................................................................38 Global and standalone color templates..................................39 Summary..................................................................................41 Module 2 – Surfaces and Grid Algorithms..........................43 Introduction.............................................................................43 Lesson 2 – Surfaces and grid algorithms................................44 Exercise 2 – Surfaces and grid algorithms.............................61 Make/Edit Surface..................................................................61 Gridding: 3D and 2D Seismic Interpretation...........................61 Gridding: Well Tops (or other point data)................................64 Gridding with Boundaries........................................................67 Boundary from Data................................................................69 Digitize a Boundary.................................................................69 Edit an existing Boundary (Optional).......................................71 Mapping and Geological Workflows

Table of Contents • 5

Gridding with Faults................................................................72 Gridding using fault polygons.................................................75 Gridding using additional inputs.............................................78 Summary..................................................................................81 Module 3 – Surface Editing and Operations.......................83 Introduction.............................................................................83 Lesson 3 – Surface editing and operations............................84 Exercise 3 – Surfaces editing and operations .....................103 Purpose..................................................................................103 Create fault polygons and map.............................................103 Prepare grid for exercises.....................................................106 Lightly smooth entire surface................................................107 Remove local features...........................................................108 Smooth local features...........................................................109 Edit surface ..........................................................................110 Tie to points...........................................................................111 Surface Operations................................................................113 Fluid Contact Polygons .........................................................113 Blank surface inside polygons...............................................114 Grid and Contour Editing.......................................................116 Surface resampling...............................................................117 Summary................................................................................118 Module 4 – Isochore Processing.........................................119 Introduction...........................................................................119 Lesson 4 - Isochore Processing.............................................120 Deviated Wells......................................................................126 Exercise 4 – Isochore Processing..........................................131 Purpose..................................................................................131 Build isochore data points.....................................................131 Vertical wells technique........................................................131 Deviated wells technique (or mixed deviated and vertical) and missing Dip/Azimuth data..............................................134 Post processing.....................................................................138 Well adjustment....................................................................141 Build structures by hanging or stacking isochores...............143 Summary................................................................................144

6 • Table of Contents


Module 5 – Surface Operations...........................................145 Introduction...........................................................................145 Lesson 5 – Surface operations..............................................146 Exercise 5 – Surface Operations...........................................155 Purpose..................................................................................155 Surface volumetrics with fault polygons..............................156 Combine fluid contacts and structures..................................158 Build gross thickness grid ....................................................158 Preparing petrophysical grids ..............................................161 Build net, pore and hydrocarbon thickness grids..................162 Calculate volumes for hydrocarbon thickness .....................164 Summary................................................................................166 Module 6 – Intersections......................................................167 Introduction...........................................................................167 Lesson 6 - Intersections........................................................168 Input Settings........................................................................174 3D-Grid Settings....................................................................175 Exercise 6 – Intersections.....................................................177 Intersections (Cross Sections)...............................................177 General Intersection..............................................................178 Intersection Window.............................................................186 Summary................................................................................189 Module 7 – Plotting and Model Maps................................191 Introduction...........................................................................191 Lesson 7 – Plotting and Model Maps...................................192 Exercise 7 – Plotting and Model Maps.................................199 Structure Maps – For Display...............................................199 Structure Maps - For Export..................................................203 Pillar Isochore Map – Automatic Method.............................205 Exercise Steps.......................................................................205 TVT Isochore Map.................................................................207 Optional: Faulted Isochore Map – Manual Method.............210 Layer Maps............................................................................213 Slice Maps (Elevation)...........................................................215 Average Property Maps.........................................................218 Property Thickness Maps......................................................220 Volume Thickness Maps (Pay)...............................................222 Mapping and Geological Workflows

Table of Contents • 7

Colorizing a depth surface with a Pay Map .........................224 Fluid Contact Maps...............................................................226 Summary................................................................................228 Appendix..................................................................................229

Index.........................................................................................251

8 • Table of Contents


Module 1 - Introduction and Display Settings This course will guide you through many of the common workflows performed in the life cycle of exploration and model interrogation. Among other things, you will learn to produce isochores, perform simple volume calculations between surfaces, subtracting information from a 3D grid and setting of plots.

Prerequisites • • • •

English Proficiency Basic Windows and practical computing skills Familiarity with Geological and Geophysical fundamentals Basic understanding on how to build 3D models in Petrel

Learning Objectives After the completion of this training, you should be able to: • Change the appearance of any object, for example, color templates, contours, k-layers and light sources • Be able to calculate isochores from vertical and deviated wells • Do surface-surface operations, including volume calculations • Setting up maps, including the user defined information boxes

What You Will Need In this course, you will need the following hardware and applications to perform the workflow: • A personal computer with a minimum of 2GB of RAM; however, we recommend 16GB of RAM for optimal performance. • For Petrel 32-bit: Microsoft XP 32. For Petrel 64-bit: Vista 64 and XP 64. • A graphic card compatible with Petrel • A Petrel license and license key Mapping and Geological Workflows

Introduction and Display Settings • 9

• Petrel Seismic to Simulation Software with the latest updates • Training datasets

What to Expect In this training material, you will encounter the following: • Overview of each module • Prerequisites to the module (if necessary) • Learning objectives • A workflow component • Lesson(s) • Scenario-based exercises • You will also encounter notes, tips and best practices

10 • Introduction and Display Settings


Icons Throughout this manual, you will find icons in the margin representing various kinds of information. These icons serve as at-a-glance reminders of their associated text. See below for descriptions of what each icon means.

Tips

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Best Practices

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you need to proceed with extreme caution.

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Workflow Diagram

Contents

Day 1:

Day 2:

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Display and color management

•

Isochore processing

•

Make Surface process

•

•

Overview of algorithms

Surface calculations and surface-surface operations

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Surface editing and operation

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Intersections

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Plotting and printing options



Lesson 1 Display and Color Management

Display objects in Petrel Most objects in Petrel contain a Style tab where the appearance in the active display window is controlled. The style options vary based on the object type and the type of selected display window.













Color templates

Introduction to color templates Each object in Petrel has a default color template associated with it. • These are based on standard industry colors Color templates are either standalones (applied to one object) or global (applied to all objects of that type). The global templates are located under the Templates pane in the Petrel Explorer. Color templates can have the following characteristics: • Linear or logarithmic • Continuous or discrete • HSV (Max) or HSV (Min) or RGB











Surface Displays

Continuous color templates - RGB

RGB

RGB is similar to HSV (Min) Uses the minimum amount of colors between the corner points of a cube. Along axis between the max and min values.

RGB color model

Note: Path along axis (shortest route) between two colors. 24 • Introduction and Display Settings


Exercise 1 – Display and Color management Purpose The purpose of this exercise is to become familiar with the display options of surfaces and polygons in Petrel. You will also learn to use and manipulate the different types of color templates. This exercise is separated into six parts: • Displaying a surface in a 3D window • Displaying multiple surfaces in a 3D grid • Other surface display techniques • Displaying a polygon in a 3D window • Restricted contouring • Color templates Exercise Data A Petrel project with the proper data for starting this exercise has been prepared for you. It is called Applied_Mapping_Cloudspin.pet. The project can be copied by first opening the original project and then saving it using Save as. Save it in your own Student folder.

Displaying a Surface in a 3D Window In this exercise, you will work with some of the display options available for surfaces. Data The HOUSTON struc grid surface (Input pane ->Surfaces(Depth)).

Contouring Exercise Steps 1. In an empty 3D window, display the HOUSTON struc grid surface. 2. Open the surface’s Settings dialog and go to the Style tab.



3. Turn off Grid lines and Solid. Under Contour lines, select Auto from the Color drop-down menu.



4. Change the Inc. to 10. 5. Change the contour range (that is, Top/Base) to -5100; -6500, respectively. 6. Turn on the Show Annotation -option and adjust the annotation parameters as desired. 7. Change the background to grey. 8. Experiment with various color settings to find what you like best. 9. Click the Make a contour object button displayed contours as an Input pane object.


to save the


Grid lines Exercise Steps 1. Turn off the contours and turn on Grid lines.

2. The Line style parameters are the same as for contours. a. Set Color to Auto.

3. Try the three available Resolutions. 4. Turn on the contours.

Solid Exercise Steps 1. Turn off Grid lines and Contour lines. Turn on Solid. 2. Set Color to Auto.



3. Experiment with the different color choices, materials and transparencies. 4. Turn the Contour lines back on.

Using Light Sources When a surface is displayed in a 3D window, it has a default light source, called the “Headlight”, which shines from the camera position in to the screen. Additional light sources can be added to enhance the display of the surface in a variety of ways. Exercise Steps 1. In an empty 3D window, display the HOUSTON struc grid (Input pane -> Surfaces (Depth)). 2. Select the Windows pane and expand the Light sources folder. You should see only Headlight. Turn Headlight off. What effect does that have on your map? 3. Right-click on Light sources and select Insert light source

4. A new source called Light Source 1 is created. What effect does it have on the map? 5. Open the settings for Light Source 1. You will see three types of light sources: Mapping and Geological Workflows


Directional: A directional light source is a light shining in a specific direction. It highlights parts of a surface facing the light and places in shadow those parts of the surface facing away from the light. The direction and intensity are adjustable. Below is the HOUSTON struc grid with the light facing west (below left) and east (below right).

Point: A point light source is a light shining in all directions from a particular point in space. This source tends to brighten parts of the surface nearest to it. The position and intensity are adjustable. Below, the light is above the surface over the northwest corner (left) and near the surface in the southeast corner (right).

Spot: A spot light source is a spotlight shining in a specific area from a position in a direction. The brightest light will shine where the light is pointed with darkening away from that point. Position, intensity, shade angle, and drop-off rate are adjustable. The maps below show the effect of changing the focus of the light. In the below left map, the light is pointed at the southeast corner. In the below right map, it is pointed to the west from the same position.



Multiple light sources can be applied to a single 3D window. In the map below, a directional light has been added in addition to the spot light we used in the rightmost map above.

Experiment with the three types of lights. Change the color of the light. Manipulate the sliders for Intensity, Drop-off rate and Shade angle. 6. Change the position of the light(s). It is best to do this in a separate 3D window. In a new 3D window, turn on the same light source(s) as in the original window. With the 2nd 3D window active, right-click on a light source and select Edit.

7. A 3D positioning widget appears. As with other similar widgets, you can move the ball in any direction (carefully, as it is very easy to get lost). The Directional and Spot light Mapping and Geological Workflows


widgets have arrows which are used to point the light. The Spot light widget also has a shade used to focus the light over larger or smaller areas. The Point light widget only has the positioning ball. The Spot light widget is shown in the figure below.

Practice using the widget watching the effects in the first 3D window while moving it in the second one.

Modify Surface Properties – Show Contours in Solid Surface appearance can be enhanced by turning on the Show contours in the solid option. This causes contours to be highlighted in the color surface. 1. Display the HOUSTON struc grid used earlier showing only the Solid coloring without Contour lines, as shown below.



2. Open the surface’s Style tab -> Solid sub tab. 3. Select the Show contours check box, and click OK.

Displaying Multiple Surfaces in a 3D Window Graphics from more than one surface may be displayed in a 3D window. There are several ways to do this. You can add saved contours to a surface’s display, drape a bitmap image on a surface, or you can superimpose an attribute on a surface.



Modify Surface Properties - Transparency To visualize two or more surfaces at once, make the top surface transparent so you can see surfaces or other objects beneath it. Data The HOUSTON struc grid surface and Houston phi data points found in the Input pane. Exercise Steps In an empty 3D window, display the HOUSTON struc grid, located in the Input pane / Surfaces (Depth) -folder. 1. Click on the View from Above button. 2. Grid the Houston_phi data points, located in Input pane / Porosity Data folder. 3. Use the HOUSTON struc grid surface to supply all gridding parameters by activating the HOUSTON struc grid and then press the Get limits from selected in the Make/edit surface process/Geometry tab. See picture below.

4. Specify the name of the new surface to be Houston_porosity. 34 • Introduction and Display Settings


5. Display Houston_porosity. Since it plots above the structure map, it completely hides the structure. 6. Open the settings for the new Houston_porosity surface and go to the Info tab. Change the Template from elevation depth to porosity. 7. Open the Style tab -> Solid sub-tab for Houston_porosity. Set the Transparency to 30% and click OK. You should now see a map similar to the map below on which the structure map appears through the porosity map.

8. Experiment with transparency settings until you are satisfied with the display.

Adding an Attribute to a Surface Attributes, such as porosity, can be added to an existing surface. As attributes, they can be displayed as the solid color under the structure contours to achieve the same effect as the previous exercise. Data Data for this exercise includes the HOUSTON struc grid and HOUSTON_Porosity surfaces. Exercise Steps You will add the HOUSTON_Porosity as an attribute of the structure surface. 1. Right-click HOUSTON_Porosity and select Copy as surface attribute. Mapping and Geological Workflows


2. Right-click HOUSTON struc grid and select Paste as surface attribute.

a. HOUSTON_Porosity now appears as an attribute of the structure.

3. In an empty 3D window, display HOUSTON struc grid. a. Open its Style tab and set the color to Z-values or Auto. b. In the Input pane, toggle the HOUSTON_Porosity attribute on and see the solid (colorfill) change to porosity.

Drape Bitmap on a Surface Draping an imported image on a surface is another effective display technique. Images in several formats (for example, bmp, jpg, tiff, gif, png) can be imported into Petrel and draped on a surface. Data For this exercise, images of Blue Castle mountain and any of the Cloudspin surfaces can be used. 36 • Introduction and Display Settings


Exercise Steps 1. Import the image. a. Right-click the Other Data folder and select Import (on selection). b. Navigate to the …\Import Data\Images directory and select Blue_Castle.jpg. c. Set file type to Bitmap image (*.bmp; *.jpg; *.tiff; *.gif; *.png).

d. Click Open 2. Register the image to the map so that it will drape over the surface correctly. a. Open the settings for Blue Castle.jpg b. Examine the image statistics. There should not be any X or Y values. The Z-values represent the image’s pixel values (e.g. color or shading). c. Open the Settings tab and select Located in world. The Settings dialog now has fields where the X-, Y- and Zcoordinates are entered as follows (see picture below).



d. Alternatively, click on the HOUSTON struc grid surface in the Surfaces (Depth) folder in the Input pane, and click on the Set from selected button in the Settings dialog. The coordinates from the HOUSTON struc grid surface are then transferred to the Blue Castle bitmap. e. Click OK f. Display the Blue_Castle.jpg in the 3D window 3. Drape the image on surface a. Turn off Blue_Castle.jpg from the 3D display. b. Open the Style tab for HOUSTON struc grid. c. Display the Contour lines d. In the Solid -sub tab, change the Color from Solid to Textured and insert Blue_Castle.jpg as the texture object.

Display Grid Nodes Grid nodes cannot be directly displayed; however, a surface can be converted into points where the points are at the grid node locations. The point object can then be displayed. Data You will continue using the HOUSTON struc grid surface. Exercise Steps 1. In the Input pane ->Surfaces (Depth) right-click HOUSTON struc grid and select Convert to points.



2. In an empty 3D Window, display the HOUSTON struc grid points. Adjust the Style parameters until you get a suitable display. The display below was created with the Style settings shown in the screen capture to the left.

Color templates Global and standalone color templates All objects in Petrel will be attached to a template from the list in the Template tab. The template will, in most cases, be attached during import, but can be changed at all times. In this exercise we will inspect the results of manipulating the templates. Data Make a copy of the Surfaces (Depth) folder. Exercise Steps 1. Tile two 3D windows and display DALLAS struc grid in one Mapping and Geological Workflows


window and HOUSTON struc grid in the other. a. Open the settings for DALLAS struc grid and go to the Info tab. b. Select the template: Elevation Depth. c. Click on next to the template filed to open the Global property template. d. Get the min and max value from the Dallas struc grid by clicking on the blue arrows. e. Click OK and note how the colors for both the Dallas and the Houston struc grids are changed. f. Go back to the Settings/ Colors -tab for DALLAS struc grid and select Override global property template.

This makes the color template for DALLAS struc grid accesible and all changes will be applied to this surface only. g. Select color interpolation type RGB. h. Click OK and note that only the colors in the Dallas struc grid are changing. The Houston grid is left unchanged, as it remains attached to the global template.



Summary How to use the different settings available for the different types of objects in Petrel has been covered in this module. You should now be able to display any of the objects as desired in 2D or 3D windows.



Module 2 – Surfaces and Grid Algorithms Introduction How to build 2D surfaces in Petrel using the Make/edit Surface process will be covered in this module. The different gridding algorithms available in Petrel will also be presented. Prerequisites No prerequisites required. Learning Objectives In this module the user will learn how to: • Make surfaces • Select the correct geometry settings • Select the best algorithm


Surfaces and Grid Algorithms • 43

Lesson 2 – Surfaces and grid algorithms

Surfaces in Petrel

Lecture and exercise purpose

Purpose: To learn how to build surfaces (2D Grids) in Petrel. You will learn: •

What determines a 2D grid

•

The source of 2D grids

•

What 2D grids are used for in Petrel

•

How to create a default 2D Grid

•

To define the X-Y limits and grid increments

•

To test algorithms and parameters and instantly see the effect

Make surfaces

Introduction (definition of a surface) 2D grid: A surface defined by points organized in an array of rows and columns. The intersection of these rows and columns define grid nodes. Z-values stored at the grid nodes represent the surface.

44 • Surfaces and Grid Algorithms








Make/Edit surface – Process Make the input from the Input pane active and click the blue arrow in front of the input data selection. Petrel will automatically name it ‘output name’ unless you select the check box in front of Name and specify an output name. If you are gridding Well Tops, select the “attribute” associated with the well top from the pull-down menu (Z, TWT picked, TWT auto, MD, Dip angle or Dip azimuth). When using point data as input, for all algorithms, select among the attributes for the point data (if they have attributes). If needed, activate a boundary polygon from the Input tab and select it as Boundary. It is also possible to use an existing surface as the boundary. Select the Run for all main input in the same folder check box for an automatic generation of all surfaces in the folder. They will be stored in a new folder with the same name as the original folder.



Algorithms: By clicking the Suggest settings from input button, you can choose the settings that will suggest interpolation methods and settings in the Algorithm tab. The Convergent interpolation algorithm (from CPS-3) is the default algorithm in the Make/edit surface dialog. It is a control point oriented algorithm, rather than grid point, which means it will honor details in areas with high point density and retain a general trend in areas with little data.



Make surfaces

Creating Surfaces: Geometry • • • •

Geometry AOI: xmin/xmax, ymin/ymax Increment: xinc, yinc Rotation Boundary Column

Ymax

AOI Boundary

Cell Yinc

Row Xinc


Node

Ymin

Xmin

Xmax


Geometry: Once the algorithm is specified from the Suggest settings from input list, the grid increment and X-Y limits need to be specified. Go to the Geometry tab. In most cases, the initial parameters are poorly defined, so select the User defined -option. The grid size and position can then be selected by highlighting an object (Input pane) to extract grid info and limits. A boundary polygon can also be selected from the Input pane to be put in the Boundary selection window. Click Get from selected. You can specify these settings manually and there is also the option to get grid and position automatically from input data and boundary.



Additional inputs: Additional inputs allow multiple, simultaneous input data sets. This is to support workflows where the user wants to make surfaces using combinations of data such as 3D and 2D seismic interpretation, isochore points, zero lines, dummy wells, etc. Any data type that can be used as the main input, can also be used in the Additional inputs tab. Additional inputs are supported with the following interpolation algorithms only: • Convergent • Isochore • Minimum curvature • Moving average When using the convergent interpolation algorithm, relative weights can be applied to the additional input data. The main input automatically gets a weight of 1, and the user can choose weights for the additional inputs of greater than 0 and less than or equal to 2. 52 • Surfaces and Grid Algorithms


Gridding methods in bold text is discussed in this course. Please see the Appendix for information about other algorihms and methods.



Minimum Curvature Overview

The minimum curvature algorithm will try to produce a surface that passes through all the data points with a minimum amount of bending. This will give you a smooth surface attempting to honor your input data. This is a good general algorithm which works well with most data.

The settings for the Minimum curvature interpolation are divided into two steps: Local interpolation and Global extrapolation. Local Interpolation You must choose: • Influence radius: • ½ or 1 cell. 54 • Surfaces and Grid Algorithms


• Interpolation method: • Moving average: Calculates an average weight on distance of the points near the grid node. This method is best for a low density of points and/or poor data quality. • Plane: Makes a linear plane, which represents the points near the grid node. • Parabolic: Makes a 3D parabolic surface to represent the points near the grid nodes. It is the preferred method for high point densities and/or good data quality. • Point weighting: • Equal: All points have equal weighting. • Inverse distance:  Points nearest the grid node have a heavier weighting. • Inverse distance squared:  Same as inverse distance but with heavier weighting. • Inverse distance quadrupled:  Same as inverse distance but with heavier weighting.



Global extrapolation Defines global extrapolation algorithms which are used when the local algorithm does not apply. There are three available options: • Minimum curvature: This algorithm uses a smoothing operator which will maintain the trends and keeps the surface smooth. • Full tension: This algorithm uses a linear operator, which will keep the surface as flat as possible. • None (test only): Only values from the local interpolation will be defined for the grid, and no global extrapolation will be performed. These areas of the grid will be absent. A number of settings for Minimum Curvature are set globally under project settings and used in a number of processes. Click on Min. Curvature settings for direct access to these global settings.



Minimum curvature using dip and azimuth Is an amended form of Minimum Curvature which allows dip and azimuth data attached to well tops to influence the grid locally around well tops. Defines the range of influence of each well top (in grid nodes) under the local interpretation settings.  The global extrapolation settings are the same as for the normal minimum curvature. This method requires that the dip and azimuth data have been attached to well tops as an attribute.





Dip and Azimuth Data (only available for well tops) Choose between: • None: Both dip and azimuth data are ignored. • Azimuth only: Only azimuth data is considered in the calculation. • Dip and Azimuth: Both dip and azimuth are honored in the calculation. As a default, the effect of the dip and azimuth will be considered globally; however, its influence can be restricted locally. Z-Values There are two options for controlling the Z-values during the extrapolation. Allow Residual: Resulting surface must be within a maximum specified vertical distance of the input data. This is useful for extrapolating noisy data. Restrict Extrapolation: The resulting surface will be smoothly truncated towards the specified limits (in absolute values or as a percentage of the input data). See also: Post processing (Make surface). Fault Polygons Fault influence: This option can be used to remove the effect of the fault polygons during early iterations. This ensures that segments with little or no data still get a value. The default (100%) will use the fault polygons during all the iterations, decrease this number to allow the first iterations to run without fault polygons. Use z-values of fault polygons: With this checked the z-values of the fault polygons will be used as a secondary input during the extrapolation. Fill inside the fault polygons: Deselecting this option will leave nodes inside closed fault polygons undefined, resulting in holes in the grid within the fault area. Initial coarsening factor – the start interval in the XY plane. Number of nodes to snap to – this is only used in the first pass. Use smaller values for denser data.



Order of projection – determines how the calculation is extrapolated in areas with no data. A higher order gives more complexity. After the first run, the gridder will take over these settings.



Exercise 2 – Surfaces and grid algorithms Purpose The purpose of this exercise is to become familiar with gridding (i.e., the creation of surfaces from data) in Petrel, and editing surfaces (directly or by editing and re-gridding contours). This exercise is separated into three parts: • Make/edit surface • Gridding with boundaries • Gridding with faults Exercise Data A Petrel project with the proper data for starting this exercise has been prepared for you, and is named Applied_Mapping_Cloudspin.pet. The project can be copied by first opening the original project and then saving it using Save as. Save it in your Student folder.

Make/Edit Surface The Make/edit surface process is used to build surfaces using data, such as well tops and 3D seismic data, as input. This process is equivalent to gridding in CPS-3 and ZMAP Plus. A full explanation of gridding in Petrel can be found in the Online Help Manual (Open by pushing F1).

Gridding: 3D and 2D Seismic Interpretation Seismic interpretations are among the more commonly gridded data types. The process of gridding 3D seismic is equal to gridding 2D seismic, but some of the settings may differ due to the density of the data. In this segment, you will grid data for interpreted surfaces. Data Data for this exercise is the HOUSTON depth interp 3D interpretation data (Input pane ->Seismic Interpretations Depth folder). This interpretation could be considered to be dense, and as such, may require different gridding parameters than one which has been more sparsely interpreted.



Exercise Steps 1. Display HOUSTON_depth_interp interpretation in a 3D window. Set the style parameters appropriately. It should look similar to this:

2. Open the Make/edit surface process. 3. When the Make/edit surface dialog opens for the first time, it should have all fields blank. If there are any entries, they must be cleared before proceeding by performing the following steps: a. Click in the Result surface box (it will highlight) b. Press the Delete key.

c. Click Yes when you are prompted to reset the settings in the dialog:



The top section of the Make/edit surface dialog pertains primarily to data being input to and output from the gridding process.

4. Input data: a. Main input: highlight HOUSTON_depth_interp and click the Main input arrow to paste the selected interpretation into the Main input box.

b. Boundary: None. c. Faults: None. d. Result Surface: Select Name and enter Houston Depth Surface. e. Run for all Main input in the same folder: Accept the default selection which is off. 5 a. Click the Suggest settings from input button and select Seismic lines (high density).

b. Petrel automatically opens the Algorithm tab. The Convergent Interpolation is the default gridding algorithm for most data types. In this exercise, use default settings.



6. Go to the Geometry tab. a. Select the User defined radio button and make sure HOUSTON_depth_interp is highlighted and click Get limits from selected to set the area of interest parameters. The grid increment will always have the default values of 50. For now, accept these defaults. b. The Geometry tab should look like this:

By default, Petrel will always use 50 by 50 as the grid increment, regardless of the data or area of interest. While this default may work well in many instances, it may cause problems in other surface linearity corresponding to the input data. It is advisable to try different increment settings before deciding on the final version of a surface.

7. Click OK. 8. Insert a new folder into the Input pane (Menu -> Insert ->New folder) and rename it to My surfaces (Depth). Drag Houston Depth Surface into this folder. Display the surface in a 3D window. Adjust the min / max color range as appropriate. Do you see any problems with this surface? Two things may stand out which will be addressed subsequently: • Surface extends too far beyond the data in some areas • Fault zones gridded through

Gridding: Well Tops (or other point data) Scattered data, such as well tops and point data, are other commonly gridded data types. The procedure is similar to gridding interpretations. Data The data for this exercise is the Well Tops 1 (Input pane ->Well Tops 1 folder -> Stratigraphy folder). In this folder, you will find tops for



several formations, as well as a variety of other attributes computed in association with the tops. Exercise Steps 1. Clear the 3D window and display the Houston tops in it. Set the style parameters appropriately. It should look similar to this:

2. Open the Make/edit surface process dialogue and clear all parameters. 3. Set up the following gridding parameters: a. Main input: Houston Welltops b. Attribute: Z c. Boundary: none d. Faults: none e. Name: Houston Z f. Algorithm: Convergent g. Geometry: Get limits from selected: Houston Mapping and Geological Workflows


h. What is the grid increment? Is this appropriate for this data? 4. Click OK to create the surface. Drag it into the My Surfaces (Depth) folder in the Input pane. Display the surface. Set the display parameters appropriately.

5. Compare this with the surfaces created from 3D and 2D interpretations created earlier. What general comments can you make?



Gridding with Boundaries In the previous exercise, the surface extended well beyond the data in several places. While some of this may be controlled though use of the advanced gridding parameters, the best way to prevent an unwanted surface is through the use of a boundary (a polygon encompassing the area you want gridded). Boundary while Gridding The easiest way to grid with a boundary is to allow the Make/edit surface process to create a temporary boundary as it grids. You will repeat the process from the previous section with one difference. Data Data for this exercise is the HOUSTON Well Tops (Input pane ->Well Tops 1). Exercise Steps 1. The Houston Z surface should still be displayed. 2. Start the Make/Edit Surface process and clear the Result Surface, but not the parameters. 3. Use the following input and results parameters: a. Main Input: HOUSTON_Welltop b. Attribute: Z c. Boundary: none d. Faults: none e. Result Surface: [empty] f. Name: Houston Z bound 4. Select the Convergent Interpolation algorithm 5. In the Geometry tab, select Make boundary from Main input. Make sure to expand the bundary by 1 cell. 6. Click OK, and then display the new surface. Drag the new surface into My Surfaces (Depth).



In most places, the surface now only extends one grid cell beyond the data.



Boundary from Data The boundary used in the preceding method is not saved as an object. If a boundary object is needed for display, modification or other purposes, two alternatives are available. One of these methods is to create a boundary from the input data prior to starting the Make/edit surface process. 1. Right-click the HOUSTON struc grid object in the Input pane (Input pane -> Surfaces (Depth)) and select Create surface edge.

A Boundary of HOUSTON_struc_grid object appears at the bottom of the Input tab. Display the boundary along with the interpretation. 2. Use this boundary as input to the Make/edit surface process and create a new surface named Houston Depth Surface (inc=200) bound2 with all other parameters the same. 3. Drag the new surface into My Surfaces (Depth) and display it together with the boundary.

Digitize a Boundary Another alternative is to manually create a boundary using the Make/ edit polygons process. 1. Display only the HOUSTON_depth_interp interpretation data in a 2D window. 2. Activate the Make/edit polygons process. 3. Notice that on the function bar (right side of the window) the Make/edit polygon button

and the Start a new set of

polygons button are pressed indicating that the next polygon created will be in the Input pane as a new object. 4. Also, the Add new points button may be depressed, if it is not, click it. With these buttons selected, digitize in the 2D window where you want your polygon points to be. Mapping and Geological Workflows

If you do not see the boundary being drawn as you click points, make sure the Z-Domain is set to Any and zoom out by clicking

.


It is not necessary to make the first and last points the same as Petrel will do that for you when you click the Close the selected polygon button

.

5. Rename the polygon object found at the bottom of the Input pane(Input pane -> Polygons xx) to Houston Depth_ Boundary. a. Insert a new folder into the Input pane. Name it Data - Other. b. Drag the two boundary objects and the point object into it. 6. Repeat the previous gridding exercise using the new boundary. (Name the output surface Houston Depth Surface (inc=200) bound3. Drag the new surface into My surfaces (Depth) and display it.



Edit an existing Boundary (Optional) Another alternative is to edit the boundary created from the points. This method also uses the Make/edit polygons process. 1. Make a copy of the Boundary of HOUSTON_depth_interp polygon created earlier and rename it Edited Boundary of HOUSTON_depth_interp. HINT: Use CTRL and C, CTRL and V to copy the polygon. 2. Display the HOUSTON_depth_interp interpretation data and the Boundary of HOUSTON_depth_interp polygon created earlier. 3. Activate the Make/edit polygons process. 4. Since you are editing an existing polygon, turn off the Start a new set of polygons button by highlighting the polygon to be edited. 5. Display the points (vertices) which make up the boundary by clicking the Show points in polygons button (or SHIFT and P). 6. Use the following buttons to edit the polygon: a. Select and edit points: i. drags an existing point to a new location; also ii. inserts new point if clicked and dragged on the line connecting existing points b.

Select multiple points: drag the rubber band box to select points within. Points can then be treated as a group by other functions. c. Delete selected items: select single or groups of points. 7. When all edits have been made, make sure the polygon is still closed by clicking the Close the selected polygon button .



Gridding with Faults The 2D gridding (Make/edit surface) process in Petrel, as in most other gridding programs, does not automatically detect and account for faults. The user must provide fault information for the gridding algorithm to use. The Make/edit surface process recognizes two kinds of fault objects: centerline faults and fault polygons (with or without z-values). In the next exercise, you will create fault polygons and use those polygons as input into gridding. Creating Fault Polygons Data Data for this exercise is the: • HOUSTON_depth_interp interpretation (Input pane ->Seismic Interpretations Depth) • Houston Depth Surface (inc=200) (Input pane ->Surfaces (Depth) -folder) • Edited Houston fault polygons (Input pane ->Edited Fault Polygons). Exercise Steps 1. Display the HOUSTON_depth_interp interpretation and the Edited Houston fault polygons in the same window. Your map shows that, in addition to the four faults contained in the file, there is one more. Your task is to add the last faults to the fault object.



2. Before adding the additional faults, make a copy of Edited Houston fault polygons (CTRL and B/ CTRL and V) and rename the copy Houston fault polygons Complete. Display the Houston fault polygons Complete. 3. Activate the Make/edit polygons process. 4. Click the Start a new polygon in the active set button and digitize the points which make up one of the new faults. When you have added the last point, click the Close the selected polygon button . 5. When you are done, you should have a map similar to the following.



6. What is the range of Z-values for the five faults (Settings -> Statistics)? 7. Look at the interpretation and faults in a perspective view. You should see that the four imported faults fit on the interpretation while the new fault is floating above it. 8. Before using these faults for gridding, you must “correct” the Z-values of the two new faults. Do this by assigning the Z values from the unfaulted Houston Depth Surface (inc=200). Do this by opening the settings for the Houston fault polygons Complete -> Calculations and fill in as illustrated in the figure below and Assign Z=A.



9. Display the corrected fault polygons together with the surface in a 3D window to QC the operation.

Gridding using fault polygons The Make/edit surface process can make use of fault polygon Z-values as additional data input into the gridding process. Gridding in this manner will usually result in better surfaces in the vicinity of faults than if fault Z-values are not used, especially with sparse main input data. To use fault Z-values advantageously requires that the Z-values make sense; otherwise, the resulting surfaces will have problems. 1. Create two more Houston Depth Surfaces, one using the faults Z-values and the other using the faults but not their Z-values. Name them Houston Depth Surface fltd using z and Houston Depth Surface fltd no z, respectively. Set the gridding parameters as follows: a. Main Input: HOUSTON_depth_interp. b. Boundary: none. c. Faults: Houston fault polygons Complete. d. Result Surface: [empty]. e. Name: as stated above. f. Method: Convergent Interpolation. g. Fault Polygons: Influence: 100%. i. Fault Polygons: Use Z-values: on; off, respectively. j. Fault Polygons: Fill inside: on; off, respectively. k. Geometry: Get limits from selected: Houston Depth Surface(inc=200) but change the inc to 50. l. Place these surfaces in the My Surfaces (Depth) folder. The dialog should look like those below for the two faulted surfaces.





The resulting surfaces are displayed below.



Gridding using additional inputs Some of the algorithms available in the Make/edit surface process support the use of additional inputs for gridding surfaces. These algorithms are: • Convergent interpolation • Isochore interpolation • Minimum curvature interpolation • Moving average interpolation In addition, the Convergent interpolation also gives you options for individually weighting the influence of each additional data in the gridding process. In this workflow, you will learn how to use additional inputs in the Make/edit surface process. 1. Open the Petrel project Applied_Mapping_Cloudspin.pet 2. Create isochore points from the Dallas - Dallas base stratigraphic interval: Click on the Dallas well top once so it becomes active (bold), then right-click on the Dallas base well tops and select Convert to isochore points.

3. Open the dialog window for the Make/edit surface process. 4. Drop in the main input data: The DALLAS BASE - DALLAS isochore points created in step 2. 5. In the Geometry tab, select Grid size and position Automatic (from input data/boundary). 6. Suggest settings from input: Isochore points/residuals. 78 • Surfaces and Grid Algorithms


7. Drop in the Model Boundary in the Boundary field.

8. Click Apply to run the process. Do not close the dialog window. A new isochore grid is stored in the Input pane Mapping and Geological Workflows


9. Activate the Name field and enter Dallas with zero line. 10. In the Additional inputs tab, append as many rows as there are additional inputs. Here, append 1 row. 11. Drop in the Input data. Use Dallas zero line to adjust the isochore map for the current zone.

12. Click Apply again. A new isochore grid named Dallas with zero line is stored in the Input pane. 13. Display and compare the two isochore grids in two 3D windows. What is the influence of the additional data?



Summary In this module, we covered how to build 2D surfaces in Petrel using the Make/edit surface process and associated parameters where changed. We also presented an overview of the different gridding algorithms available in Petrel.



Module 3 – Surface Editing and Operations Introduction How to perform editing and operations on surfaces will be covered in this module. Prerequisites • Basic knowledge of how to build surfaces in Petrel Learning Objectives In this module the user will learn how to: • Use the pre and post processing tools in the Make/edit surface process • Subtract surface maps from a 3D model • Surface operations and cleanup


Surface Editing and Operations • 83

Lesson 3 – Surface editing and operations

Surface editing and operations Lecture and exercise purpose

Purpose: To learn methods for adjusting and cleaning a 2D grid and the order of implementation and operations for incorporating stratigraphic relationships. You will learn how to: •

Perform Pre processing

•

Perform Post processing

•

Lightly smooth the entire grid

•

Locally smooth parts of a grid

•

Fill holes in a grid

•

Blank portions of a grid

•

Interactively edit a grid

•

Tie a grid to the points it represents

•

Truncate one grid by another

•

Baselap one grid onto another

84 • Surface Editing and Operations












Create fault polygons and map is an operation available for seismic interpretations at both the horizon and survey level. The operation can be accessed from the Operations tab in the Settings dialog, under Convert points/polygons/surfaces. The inputs are: • A folder containing the correctly assigned fault stick interpretation. • An optional geometry for the final map, which can be either a seismic survey or a regular surface. If no input is supplied, Petrel uses a geometry based on the seismic survey. Optional outputs: • To “clean” fault segments. This option should be used if the interpretation is done on a combination of inlines and crosslines. For example, if the interpretation cannot be converted directly to pillar based faults. If the interpretation is already ”clean,” you can achieve better results by turning this option off. • To keep intermediate results. The intermediate results include a single horizon 3D grid. The primary objective of this functionality is to create a high quality set of correctly intersected fault polygons together with an associated map of the seismic data. The fault polygons will be much more accurate than those normally available from a seismic system as they are created by fault interpretation accurately intersecting the horizon interpretation. However, a seismic interpretation which is poorly done will result in bad polygons. The tool set allows the interpreter to improve both the quality of the polygons and the interpretation.



The result of the operation is a folder in the Input pane named by the horizon interpretation. It contains the resulting polygon and surface together with the data boundary and clipping surfaces. In the Models pane, a model is created with the name of the input horizon when the Keep intermediate results option is selected. The 3D grid has only a single horizon, which is also named after the input horizon.





General Smooth To smooth a surface, double-click on the surface name and go to the Operations tab. Expand the Surface Operations folder and select Smooth. An option to specify smoothing Iterations and/or filter width appears. More iterations will give a smoother result, while filter width specifies the width in cell numbers that will be influenced by smoothing - the more cells, the smoother the result. Click Run.


There is one level of undo. By selecting For all similar objects in folder, the same smoothing operation will be executed on all objects in the folder.


Peak Removal Display the surface and make the Make/edit surface process active. Click the Peak to be removed button from the function bar to the right of the display window. Go to the bottom toolbar and click the Use influence radius button. Adjust size of feature to remove in units (= grid cells). Select to use full tension (powerful linear smoothing) or minimum curvature (more curved smoothing) for the operation. These options are located to the right on the bottom toolbar. Click on the Peak to be removed button.



Smooth Local Area Display the surface and make the Make/edit surface process active. Click the Smooth area button from the function bar to the right of the display window. Go to the bottom toolbar and click on the Use influence radius symbol. Adjust the size of the feature to remove as in the previous example. Drag the mouse pointer over the area to be smoothed (contours disappear). Click the Refresh button to re-display contours.



Fill Holes Open the settings for a surface and go to the Operations tab. Expand the Surface operations folder and select Extrapolate. Once you click Run, Petrel will extrapolate the grid to fill undefined areas. By default, the Minimum curvature interpolation (maintains trend) is used, otherwise full tension (tends to flatness) is used if you deselect the Min. curvature option. Click Run to fill holes. All holes are filled at once. There is only one level of undo.



Poor extrapolations and fault gaps are the most common areas for grid blanking. Open the settings for a surface and go to the Operations tab. Expand the Eliminate where folder and select Eliminate inside (or Eliminate outside). A polygon defining the area you want to blank must be made beforehand in the Make/edit polygon process. Highlight this polygon in the Input tab and click the blue arrow for closed polygon input. Click on Run. There is only one level of Undo.



Tools Display the surface and make the Make/edit surface process active. There are four main operations associated with the icons in the function bar: Pick and drag Z-value (touched contour). Pressing down the left mouse button will drag the z-value you initially picked along the surface to give the other values the same Z-value. Assign Z-value to selected node. Specify in the bottom toolbar, for example, Z=40. This will give all the nodes a value of 40. Add Z-value to selected node. If Z=40 from the lower toolbar and the selected node is –200, this will assign the value –200+40= -160. Subtract Z-value from selected node. If Z=40 from the lower toolbar and the selected node is –200, this will assign the value –200-40= -240. Go to the bottom toolbar and click on the Use influence radius button: Adjust the size of the feature to smooth in units (= grid cells). If applicable, also select the shape for the edit; curved, triangular or square. 98 • Surface Editing and Operations


Surface editing and operations Edit surface form - examples

3D surface editing is contour editing taken to a higher level. 1. Click and Drag Z-value

2. Push up specified amount


3. Push down specified amount


Tie to Points After editing, the surface should be retired to its data. Grids that have been cleaned and edited will seldom tie back to their original data. This is OK if this original data was the cause of the noise that was cleaned up (seismic). However, if the cleaning/editing was done in the betweendata areas, and the data is to be honored, then the grid will need to be re-tied to that data. The workflow will be as follows: 1. Double-click on the Make/edit surface process 2. Set up the primary parameters a. Main input = Grid to be tied 3. Click on Suggest settings from input and specify Surface as input type. Petrel will choose Surface Resampling. 4. Go to Geometry tab and click on Automatic. This will specify the grid size and position (X-Y limitations) from the original grid (from the input data). 5. Go to Well Adjustment Tab a. Select Global adjustment b. Input points to tie surface to (blue arrow) c. Optional: Request well error report 100 • Surface Editing and Operations


The residual surface will be interpolated by the methods from the drop-down menu (default Convergent). It will be found by creating a surface from the error at each well. The error is the difference of the horizon and the corresponding well top. Algorithms for creating the residual are: Convergent, Cos expansion, Moving average and Minimum curvature. Click Apply when the desired settings are specified. The surface will be inserted at the bottom of the Input pane.





Exercise 3 – Surfaces editing and operations Purpose The purpose of this exercise is to become familiar with the surface editing tools and the operations associated with the surfaces. • Perform a general smoothing on the entire surface. • Perform local smoothing where needed. • Fill any holes that exist in the grid • Blank undesired nodes. • Edit surface form where other methods have not worked. • Tie the surface to the well data if appropriate. The following exercises will walk you through some of these steps. Data Use the project you have saved to your Student folder. If necessary, you can open a secondary project from the Projects folder, called Applied Mapping Cloudspin.pet and drag and drop the Grid folders into your existing project.

Create fault polygons and map This workflow demonstrates how to create fault polygons and maps from a specific seismic horizon without having a 3D grid ready in Petrel. Exercise Steps 1. Expand the Seismic/Horizon interpretations folder and open the setting for the CARACAS horizon. 2. In the Operations tab, open the Convert points/polygons/ surfaces folder and activate the Create fault polygons and map process.



3. In the Faults folder -field; drop in the Fault interpretations folder in the Seismic main folder in the Input pane. This folder contains fault sticks that will be converted to fault polygons. Only fault sticks will be accepted as inputs here. 4. In the Get surface geometry from field; drop in the mig seismic volume. 5. Deselect the option; Clean fault segments. This option performs a preprocessing by creating a copy of the input data without any crossing fault sticks. Use this option if the sticks are interpreted both in inline and crossline directions. This option is not necessary to use when the data is “clean”. 104 • Surface Editing and Operations


6. Select the Keep intermediate results check box to save the 3D grid that was used to generate the polygons. The grid is stored in the Models pane. Petrel deletes this 3D grid automatically if the options is deselected. 7. Click Run. A new folder containing a boundary, fault polygons and surfaces is stored in the Input pane. 8. Display and quality check the result. The figure below displays the CARACAS horizon from the 3D grid together with the fault polygons. The colors for the fault polygons are adjusted for better visibility.



Prepare grid for exercises The data for this exercise is the HOUSTON phi grid (Input pane -> Porosity Surfaces folder). This grid ranges from 0 to 1, and as such, does not show much relief, even with an exaggeration of 50. For these exercises, you will multiply this grid by 100 to make the surface features easy to see and edit. Exercise Steps 1. Copy the HOUSTON phi grid and rename it “to be edited” grid. To do this: a. Highlight the grid (make it bold) in the Petrel Explorer. b. Go to the Edit option on the Main menu and select copy and then paste (or use CTRL and C/CTRL and V). The resulting grid is placed at the bottom of the Input pane. c. Next, double-click on the grid and go to the Info tab. d. Change the name to to be edited. 2. Display the to be edited grid in a 3D window. 3. Multiply all Z-values in the grid by 100. To do this: a. Double click on the grid and go to the Calculations tab. b. Toggle on the A= a constant parameter. c. Enter 100 for the A parameter:

d. In the Assign section, click the Z=Z*A button.

Note how the surface changes in the display and how the form of the surface is easily seen.


e. Turn on the Automatic legend . You might have to adjust the color scale by clicking on the Adjust color table on selected button 4. Increase the vertical exaggeration to 50. Do this by clicking on the pull-down menu containing numbers above the display area. Mapping and Geological Workflows

Lightly smooth entire surface The input data will often, especially if it is seismic, contain a noise component. This noise creates high frequency chatter over the entire surface. This exercise shows you how to remove this high frequency noise from your grid. Exercise Steps 1. Copy the to be edited grid and rename it lightly smoothed. Do this by using the same procedures used to create the to be edited grid. 2. Display the lightly smoothed grid in a 3D window. 3. Perform a general smooth on the lightly smoothed grid: a. Double-click on the grid’s name and go to the Operations tab. b. Expand the Surface operations folder and select Smooth. c. Click on Run and observe the amount of smoothing that is done. d. Click on the Undo button . Change the number of Iterations or Filter width and click on the Run button. Note the change in the smoothing. e. Repeat this undo-adjust-run process until you are satisfied with the result.



Remove local features Sometimes, the original data used to create a grid will contain points that are dramatically different from the neighboring points. The resulting grid will contain a peak (positive or negative) that is incorrect. Normally, you should fix the problem in the data and rebuild the grid; however, sometimes this is not possible and the grid itself must be corrected. This exercise shows you how to remove peaks from a grid. Exercise Steps 1. Copy the lightly smoothed grid and rename it to remove peak. Do this using the same procedures used to create the edit input grid 2. Display the remove peak grid in a 3D window. 3. Remove undesired peaks (positive or negative) from the remove peak grid. a. Activate the Make/edit surface process. b. c. d. e.

Click on the Peak remover button . Click on a peak to be removed (select any peak). If too little or too much of the feature was removed then: Click on the Undo button.

f. Adjust the Size of feature button at the bottom of the screen (units are grid cells). You may have to increase up to 10 to see a good effect. g. Click on the Peak Remover button . 4. Repeat the process for several peaks. 5. Use the Undo button to remove any undesired smoothing.



Smooth local features Often, the light smoothing that was performed on the entire grid is not aggressive enough to remove noise in specific areas. In these situations, an interactive local smoother is needed. This exercise will apply a local smoother to specific areas of a grid. Exercise Steps 1. Copy the remove peak grid and rename it to local smooth. Do this by using the same procedures used to create the to be edited grid. 2. Display the local smooth grid in a 3D window. 3. Smooth specific areas of the local smooth grid: a. Activate the Make/edit surface process. b. Click on the Smooth area button . c. Click in the center of the area to be smoothed (select any area). d. If too little smoothing was done, then click again. e. If the area being smoothed is too small, then adjust the Size of the feature button at the bottom of the screen (units are grid cells). 4. Use the Undo button to undo undesired smoothing.


You may need to zoom in to clearly see what you are editing.


Edit surface Sometimes, sparse data does not contain enough information to create a grid that effectively displays the interpreted geologic feature, hence, you will have to edit the grid to add a form that represents your geologic interpretation. This exercise will allow you to add shapes to the grid using the Make/edit surface tools. Exercise Steps 1. Copy the local smooth grid and rename it to edited. Do this using the same procedures used to create the to be edited grid. 2. Display the edited grid in a 3D window. 3. Add or alter shapes on the edited grid. a. Make the Make/edit surface process active by clicking on it in the Processes pane. b. Add a positive feature: i. Click on the Add Z-value to grid node button ii. Adjust the Z-value button be added. iii. Adjust the radius button the edit.

.

to the amount to to alter the width of

iv. Select the shape button to define the edit form. v. Click and drag the cursor to make the edit.

c. Add a negative feature: i. Click on the Subtract Z-value from grid node button . ii. Adjust the size and shape of the edit feature. iii. Click and drag the cursor to make the edit. 110 • Surface Editing and Operations


d. i. ii. iii.

Create a feature by dragging an existing contour value: Click on the Pick and drag Z-value button . Adjust the size and shape of the edit feature. Click and drag the cursor to make the edit.

You may need to zoom in to clearly see what you are editing.

4. Use the Undo button smoothing.

to remove any undesired

Tie to points Grids that have been cleaned and edited will seldom tie to their original data. This is OK if this original data was the cause of the noise that was cleaned up (seismic). However, if the cleaning/editing was done in the between-data areas, and the data is to be honored, the grid will need to be re-tied to that data. This exercise will re-tie the edited grid to the original porosity points. Exercise Steps 1. Copy the edited grid (or local smooth grid if edited is messy) and rename it to tied. Do this using the same procedures used to create the to be edited grid. 2. Display the tied grid in a 3D window. 3. Make the grid’s range match that of the HOUSTON phi data file (0-1). Do this by: Mapping and Geological Workflows

Since the HOUSTON phi data file is in percent (0-100) you will have to divide the edited phi grid by 100.


a. Double-clicking on the grid’s name and going to the Calculations tab. b. Checking the statistics at the top of the tab to see if the range is 0-1 or 0-100. c. If the range is 0-100, then set A=100 d. Clicking on the button Z=Z/A in the Assign section. e. Checking the statistics again: 4. Tie the tied grid to the original data (HOUSTON phi data): a. Double-click on the Make/edit surface process to see its dialog. b. i. ii. iii.

Clear any parameters by: Clicking on the Output data: Surface box. Clicking on the Delete key. Answering YES to the question.

c. i. ii. iii.

Specifying the primary parameters: Selecting tied grid as the Main input. Clicking on Suggest settings from input. Specifying Surface as the Input data from the pull-down menu.

d. Define the grid shape: i. Go to the Geometry tab. ii. Click on Get limits from selected. e. i. ii. iii. If the surface is altered too much then you may want to click on Use influence radius and use a small radius.


Select data to tie to: Go to the Well Adjustment tab. Select Global adjustment. Highlight the points to tie to in the Petrel Explorer (HOUSTON phi data) iv. Input the points using the blue arrow. f. Select Set name to change the name of the output. Tie to the data by clicking Apply. 5. Display the resulting surface (at bottom of the Input pane) in a 3D window.


Surface Operations Fluid Contact Polygons Intersect an elevation with a structural surface and capture the trace as a polygon. This polygon can be displayed on that structural surface to show the intersection of the fluids. Exercise Steps 1. Display the Houston struc grid. a. Open its settings and go to the Operations tab b. Open the Convert points/polygons/surfaces folder. c. Select Create intersection with plane and enter the elevation –5700, and click Run.

The polygon intersecting –5700 with the Houston struc grid surface will appear at the bottom of the Input pane with the name Intersect Houston Depth Surface and -5700.



2. Display the polygon and change its line style parameters so that it can be easily seen.

Blank surface inside polygons In this exercise, you will blank a surface inside polygons. Data The data for this exercise is the Austin struc grid Surface (Input pane ->Surfaces (Depth) folder) and the Edited Austin Faults polygons (Input pane ->Edited Fault Polygons folder). Exercise Steps 1. Open a 3D window and display the Austin struc grid Surface. Display the Edited Austin Faults polygon also (adjust Style as appropriate).



2. Open the Settings window for the Austin struc grid and go to the Operations tab. 3. Expand the folder Eliminate where and select Eliminate inside. 4. Highlight the Edited Austin Faults in the Input pane and add it to the operation by clicking on the blue arrow in the lower part of the panel.

5. Click the New object button . This will create a new version of the surface rather than overwriting the original. 6. Click the Run button. The resulting surface should be similar to the figure below.



Grid and Contour Editing Often, surfaces will not be exactly the way you envisioned them or they may exhibit problems. Surfaces can be corrected through the use of the following processes, either individually or by using a combination of both. • Minor changes can be easily done by directly editing grid nodes in the Make/edit surface process. • Major changes are better made through contour editing and gridding.



Surface resampling The grid increment(s) of an existing surface can be increased or decreased using this Make/edit surface process. Data The data for this exercise is the Houston Depth Surface(inc=200). Exercise Steps 1. Display the subject surface in an empty 3D window. If texturing is still on, reset Solid Color to Z-values. 2. Display the grid lines (Settings -> Style -> Grid lines) at high resolution. 3. Start the Make/edit surface process and set the following parameters: a. Main input: Houston Depth Surface(inc=200) b. Name: Houston Depth Surface_Rfnd c. Geometry tab: Get limits from selected from Houston Depth Surface(inc=200). Accept the default increments (50). 4. In the Algorithm tab set the method to Surface Resampling and accept the default settings. 5. Click OK to resample the surface from its original increment of 200 to 50. 6. Compare the two surfaces. How do they differ?



Summary How to perform various editing and operations on surfaces have been covered in this module, including the use of the pre and post processing tools in the Make/edit surface process, extracting surface maps from a 3D model and different surface operations and cleanup.



Module 4 – Isochore Processing Introduction In this module, how to calculate isochore data in Petrel will be covered. Prerequisites No prerequisites are required Learning Objectives In this module, the user will learn how to: • Create isochore points • Handle deviated well situations • Use dip and azimuth information to calculate TVT and TST • Make isochore surfaces


Isochore Processing • 119

Lesson 4 - Isochore Processing

Isochore processing

Lecture and exercise purpose Purpose: To learn methods for building isochore data and grids and to use those grids to create structures.

You will learn to: •

Create isochore data

•

Build isochore grids

•

Create structures by adding or subtracting isochores to existing structures

Isochore processing Sources of isochores

120 • Isochore Processing

•

From an existing 3D model

•

Isochore points

•

Calculated between two well tops

•

Calculated between a well top and a surface

•

Apply dip and azimuth data to calculate TVT and TST


Isochore processing

Isochore and isopach – definitions Isochore: Thickness between two horizons measured vertically Isopach: Thickness between two horizons measured normal to horizon surfaces

Isochore

Isopach

Isochore processing Definitions

Well Thickness TST

TVT



The Thickness attribute will always be calculated. To calculate the TVT and TST, Petrel requires that dip and azimuth data are present.


When you are creating isochore points, a list of predefined attributes will appear. The ones related to thickness are: • TST – True Stratigraphic Thickness. This is the thickness between two layers measured 90 degrees on the layers. This equals the isopach. • TVT – True Vertical Thickness. This is the thickness between two layers measured vertically. This equals the isochore. • Thickness – This attribute represents the TVD between the well markers. In the case of a vertical well, or if the layering is horizontal, the Thickness = TVT.


Isochore processing

Create isochore values - methods Simple case – No dip/azimuth data needed , Thickness = TVT Vertical well

Well

Z-top – Z-base


Deviated well and horizontal surface

Well

Z-interpolated – Z-base


Isochore processing

Create isochore values - methods

Complex case – TVT must be calculated

Deviated well and deviated surface

We need to have: •

Dip/azimuth data

Well

Z-interpolated – Z-base

Or •

An existing surface





Deviated Wells

Check the statistics. If the thickness values are negative you will need to multiply by –1.


The Deviated wells technique (or mixed deviated and vertical) requires that a structure grid exist for either the top or base of the zone for which isochore data is to be generated. 1) Create a structure grid for the top or base of isochore 2) Convert the non-gridded horizon’s top picks to points. Make sure the Z-attribute is active in the Attribute folder under the Well Tops folder. Go to the base horizon and right-click to select Convert the active attribute to points. 3) The well top horizon is converted to points and put at the bottom of the Input pane. Rename the points to ISOCHORE 4) Calculate the difference between the points and the structure: a. Open the settings for the ISOCHORE point dataset b. Go to the Calculations tab c. Set A = The structure surface d. Set Z=Z-A






Create Structure by Hanging Isochore Generating an isochore is an intermediate step in the structural grid building process. In this exercise, you will create the base of a zone structure by subtracting the isochore from the top of zone structure. 1. Check the isochore for negative values and clip to min of zero if needed. 2. Copy the top structure grid. 3. Rename the copied grid to BASE. 4. Subtract the isochore grid from the renamed grid: a. Open the settings for the BASE grid. b. Go to the Calculations tab. c. Set A= The isochore grid. d. Set Z=Z-A





Note: For more info and instructions regarding isochore processing and isochore to isopach conversion, please please see the Appendix.

Exercise 4 – Isochore Processing Purpose The purpose of this exercise is to become familiar with calculating isochores in Petrel directly from well cuts, existing 2D surfaces, and 3D grids • Vertical wells technique • Deviated wells technique • Building isochore grids Exercise Data For this exercise, you will continue with the Applied_Mapping_ Cloudspin.pet project (or the name you have given it).

Build isochore data points Isochore data are generated in one of two ways. The first method is used when all wells are vertical or TST/TVT is recorded at the well tops. The second method is useful when all, or some of the wells, are deviated and there is no access to the dip\azimuth data required to calculate TST\TVT.

Vertical wells technique This technique works directly on the top pick files and requires only two steps. It is only appropriate when all wells are vertical or dip/azimuth data are recorded for the well tops. The data set you will use has some deviated wells but also has the dip/azimuth data. Exercise Steps 1. Go to the Input pane and expand the Well Tops folder and the Stratigraphy folder under that (you can hide the zones by right-clicking and turn off the Show zone buttons). 2. Create isochore data for the Dallas zone (DALLAS to DALLAS BASE). Do this by: a. Highlighting the top marker (DALLAS) by clicking on it. b. Right-clicking on the base marker (DALLAS BASE) and selecting Convert to isochore points. Mapping and Geological Workflows


c. The resulting points will be placed at the bottom of the Input pane and named DALLAS BASE – DALLAS. d. Open the settings for these isochore points and check their statistics. Show the Axis in top toolbar to see the extent of the isochore points (you can also increase the point size in Settings – Style)

3. Create isochore data for the Houston zone (HOUSTON to HOUSTON BASE) using the same technique as used for the Dallas zone. The resulting data will be named HOUSTON BASE – HOUSTON. 4. Turn on the HOUSTON BASE – HOUSTON isochore points in a 3D window and turn on the axis to display the values. The axis is turned on by clicking on the Show/hide axis button in the top toolbar. 5. Open the settings dialog for the HOUSTON BASE – HOUSTON and change the size of the points in the Style tab to make them easier to see. Select Show number annotations and adjust the font size. 6. Expand either of the new isochore points datasets and also expand the Attributes folder as in the figure below. Each of the folders hold their own settings including statistics, info, colors, and operations.



7. Compare the statistics for the Thickness, TST and TVT attributes.

Are there any differences? Why? 8. Right-click on the Thickness attribute under the posted points set and select Use as visual vertical position. Notice the change in the display in the 3D window.


By default, the Z attribute is used as the visual vertical position (the attribute deciding the position in the coordinate system)


Deviated wells technique (or mixed deviated and vertical) and missing Dip/Azimuth data This technique is useful if you have the combination of deviated wells and missing dip or azimuth data. It requires that a structure grid exists for either the top or base of the zone for which the isochore data is to be generated. You will create isochore data for two zones. One is the same Houston zone for which you generated isochore data in the previous exercise steps, and the other is the Austin zone. Both have grids existing for the top of zone structure. Exercise Steps 1. Go to the Input pane and expand the Well Tops folder and the Stratigraphy folder below. Make the Z attribute active in the Well Tops and Attribute folder. 2. Create point data for the Houston Base horizon by rightclicking on the base of zone pick (HOUSTON BASE) and selecting Convert the active attributes to points. The resulting points will be placed at the bottom of the Input pane. 3. Open the settings dialog for the points just created and change the name to Isochore HOUSTON and the template to Thickness general. The point set will be converted to an isochore thickness set representing the Houston zone in the next step. 4. Calculate the thickness of the Houston zone by subtracting the Isochore HOUSTON points from the HOUSTON struc grid: a. Go to the Calculations tab of the Isochore HOUSTON settings dialog. b. Set A = HOUSTON struc grid. c. Assign Z=Z-A



5. If the thickness values are negative, you will need to multiply them by –1 (assign Z = -Z in the calculator). 6. Create isochore data for the Austin zone by using the same method used for the Houston zone in the previous steps. Name the data Isochore Austin. 7. Compare the results of the Vertical Wells Technique and the Deviated Wells Technique. a. Double-click on the Thickness attribute under the HOUSTON BASE – HOUSTON isochore points. Leave the dialog box open. b. Open the settings for the Isochore Houston point dataset. 8. Compare the statistics of each. Note which is larger, the magnitude of difference, and their means.

Depending on the direction which the well penetrates the zone, it is possible for either technique to produce larger or smaller values than the other. The deviated well technique will always produce correct results. The vertical well technique will only produce correct results for vertical wells, perfectly flat structures or those combined with the dip/ azimuth data.



Build isochore grids Isochore grids are built in the same manner as structure or fault surfaces. However, the extrapolation often seen and considered acceptable for structures and faults is seldom acceptable for isochore grids. The Isochore Interpolation algorithm is a specialized version of the Convergent Interpolator. It will always produce a surface with Z-values equal or greater than 0. You can also use the post processing tools to restrict isochore extrapolation and the Well Adjustment tool to re-tie to the isochore data. Default gridding Often, the default parameter settings produce acceptable results when building grids. Build default grids for the Dallas, Houston, and Austin zones by using the isochore data you generated in the previous exercises. Exercise Steps 1. Double-click on the Make/edit surface process in the Processes pane to see the dialog for building surfaces. 2. Clear any parameter settings in this dialog. Do this by: a. Highlighting the contents of the box to the blue arrow associated with Result Surface. b. Pressing the Delete key. c. Clicking YES when asked if you want to reset the settings. 3. Build a default isochore grid for the Dallas zone by inputting the standard parameters: a. Main input = DALLAS BASE-DALLAS. b. Attribute = TVT. c. Name: Dallas Isochore d. Boundary = DALLAS struc grid. e. Click on Suggest settings from input. f. Input data = Isochore Points. g. Algorithm = Isochore Interpolation. h. Go to Geometry tab, select Automatic (from input data / boundary). i. Click Apply to create the grid.



4. Display the resulting grid along with the input data in a 3D window. 5. Build a default grid for the Houston zone. You can use either the Isochore Houston point data or the HOUSTON BASE – HOUSTON isochore points with the TVT attribute. View the result in a 3D window. 6. Build a default grid for the Austin zone using the Isochore Austin data. Notice how the Attribute options below the Main input in the Make/edit surface process disappear when you use the Isochore Austin points as input. View the result in a 3D window. 7. For the Austin isochore grid (and the Houston grid if you used the Isochore Houston points as input), open the settings and change the template to thickness (Settings ->Info tab). 8. If you want to check the isochore input data with the isochore grids, toggle both on in a 3D window. Make sure to use TVT as Mapping and Geological Workflows


the visual vertical position. Go to Dallas isochore points, expand the Attributes folder and right-click on TVT. Select Use as visual vertical position.

Post processing Regardless of the algorithm used, the grid will often project significantly higher and lower than the isochore data. Post-processing tools allow you to clip the grid, preventing this extrapolation (by truncation or elimination). Exercise Steps 1. If not displayed, display Isochore Austin in a 3D window. Make sure that a significant number of contours are displayed and that the color range looks good. a. Adjust contours by going to the grid’s Settings dialog -> Style tab and select the Show check box for Contour lines, set the increment to the desired number, and click Apply.



b. Adjust colors by going to the grid’s Settings dialog, Colors tab. Select the Override global property template check box. In the appearing color template, click Get max from data, Get min from data, and then Apply to update. 2. If the Make/edit surface dialog is not open, double-click on the Make/Edit Surface process. To display the exact parameters you used to build the Isochore Austin grid, highlight Isochore Austin in the Input pane and use the blue arrow to insert it into the Result surface field. Also, check the parameters to be sure they correspond with the grid.



3. Go to the Post Proc tab and select Truncated from the drop-down menu (clips Z-values, but keeps the data). Accept the default values (10%).

4. Click Apply. Note how the surface is clipped at the 10% above and below these limits (try also Eliminated and then back to Truncated to see the difference).

Surface before clipping

Surface after clipping

Note the flat clipping plane.



5. Toggle on the smoothing iterations found below the clipping parameters and set the number of iterations to 50. Note how the sharp ledge is smoothed out.

Well adjustment If you smoothed during Post Processing, then you will need to re-tie the surface to the data that was used to build the surface. Exercise Steps 1. If not displayed, display the Isochore Austin you created and post-processed in a 3D window. Make sure a significant number of contours are displayed and the color range looks good. 2. Open the Make/Edit Surface process. 3. To display the exact parameters you used to build the Isochore Austin grid, highlight Isochore Austin in the Input pane and use the blue arrow to insert it into the Result surface field. Also, check the parameters to be sure they correspond with the grid. Mapping and Geological Workflows


4. Go to the Well Adjustment tab: a. Select Global adjustment. b. Input the isochore points that were used to build the grid. c. Try all of the algorithms in the Residual surface by: pull-down menu, clicking Apply after each to see the effect.

5. Note that each algorithm has some over-projection problems or shape problems. Try the Use influence radius parameter and set its value to 1000 or 2000. 6. After you have settled on an algorithm and the post-processing techniques that are suitable to you, repeat the process for the other two isochore grids you have generated. 7. Insert a new folder into the Input pane and name it Isochore Grids. Drag and drop the three updated isochore grids into the folder. 142 • Isochore Processing


Build structures by hanging or stacking isochores The primary reason for generating an isochore is that it is an intermediate step in the structural grid-building process. In this exercise, you will create the base of zone structure by subtracting the isochore from the top of zone structure. Example: Houston struc grid – Houston Isochore = Houston base grid Exercise Steps 1. Make a copy of Austin struc grid (this is the top structure of the Austin zone). 2. Rename the copy to Austin base. 3. Go to the Calculations tab for Austin base surface and subtract the isochore (Isochore Austin), built in the previous exercise steps (make sure it has positive thickness) from your Austin base grid. a. Set A=Isochore Austin by highlighting the grid in the Input pane and using the blue arrow to drop it in. b. Click on Assign Z=Z-A.

Now you have two grids with the exact same values. We will shift the surface called Austin base downwards using the isochore values for the Austin zone.

Check to see that the thickness is positive, if not, multiply by –1 (assign: Z=-Z).

4. In a 3D window, display the top (Austin struc grid) and the Austin base grids with their well tops and wells. 5. Repeat the steps for the Houston and Dallas Base grids. Place all of the grids in the Structure Grids folder.



Summary In this module, you have learned different methods to calculate isochore values in Petrel. How to create isochore points, how to handle deviated well situations, how to use dip and azimuth information to calculate TVT and TST and how to make isochore surfaces were also covered.



Module 5 – Surface Operations Introduction How to perform surface operations including, volume calculation, creating rock gross thickness grids and combining two or more surfaces, will be covered in this module. Prerequisites There are no prerequisites for this module Learning Objectives In this module, the user will learn how to: • Manipulate surfaces using surface operations • Perform volume calculations between surfaces • Build rock gross thickness grids


Surface operations • 145

Lesson 5 – Surface operations

Surface operations

Lecture and exercise purpose Purpose: Learn how to perform operations on surfaces and between surfaces. You will learn to: •

Manipulate a surface using Surface Operations

•

Calculate azimuth and dip values from a surface

•

Use the surface calculator

•

Calculate volume between surfaces

•

Areal calculations

– Build rock gross thickness grids

– Inside polygon – For defined nodes in a grid

146 • Surface operations


Surface operations 2D Volume processing; General procedure 1. Given top and base structure grids 2. Incorporate fluid contacts into top and/or base grids 3. Build gross rock thickness grid 4. Discount gross rock thickness by N:G, Phi, and (1-Sw) 5. Calculate volume for positive thickness 6. Calculate area for positive thickness

4

3 1

2

5 6

Volume processing (2D Grids) Top and base structure grids

1. Should define the zone of interest 2. Should not contain missing node values over area of interest •

No volumes for missing nodes

•

Fault gaps should be filled with nodes

3. Should be tied to the top picks 2

3

Well

1





Volume processing (2D Grids) Build hydrocarbon pore thickness

1. Gross thickness * Net-to-gross = net thickness 2. Net thickness * Porosity = pore thickness 3. Pore thickness * (1 – Water saturation) = hydrocarbon pore thickness 1

Gross

3

2

Net

Pore

Hydrocarbon

Note: For each step, copy the input thickness grid, rename it to the output thickness, and then perform the calculation. Mapping and Geological Workflows


Calculate volumes

There are three methods for calculating volumes

Between two surfaces


Between a surface and a plane

Volume/area versus depth


When you are using fault polygons in the volume calculation, Petrel will subtract all volumes inside the polygons. This will produce more accurate volumes.


Remember that you have only one undo!


Calculate areas There are two methods for calculating areas for an isochore grid.


Un-blanked grid cells

Inside a polygon

Approximate area

Precise area (requires closed polygons)






The workflow in the example above is calculating the volume below a surface to four specified depths and the sending the result to a spread sheet with four entry lines. Simple settings for output columns and text can be specified.

Exercise 5 – Surface Operations Purpose The purpose of this exercise is to become familiar with the Surface calculator and learn how to create petrophysical grids. This exercise is separated into seven parts: • Surface volumetrics with fault polygons • Combine fluid contacts and structures • Build gross thickness grid • Prepare petrophysical grids • Build net, pore and hydrocarbon thickness grids • Calculate volumes for hydrocarbon thickness • Calculate area for hydrocarbon thickness Mapping and Geological Workflows


Data Continue to use the project you from the previous exercises. In this exercise, the volumes will be calculated for the Houston zone. Locate the Houston Base surface you created in the previous exercise. If this grid was not created or is not correct, use the Houston Base grid that came with the class project which can be found under the Other Data folder in the Input pane.

Surface volumetrics with fault polygons The volumetrics operations on regular surfaces allow you to use fault polygons. It improves the accuracy of surface volumetrics, as the volumes on either side of the fault polygons will be calculated without the so-called smearing effect of the fault zone. Exercise Steps 1. Open the project Applied_Mapping_Cloudspin.pet 2. Open the Settings -> Operations tab for the HOUSTON struc grid. This is a regular surface. The surface is located in the Input pane -> Surfaces (depth) folder. 3. In the Calculations -folder select the Volume below surface (constant level) -operation. 4. Specify the base level -6000 m 5. Drop in the fault polygon to use. Here: HOUSTON fault polys located in the Input pane -> Fault Polygons folder. 6. Optionally, drop in a boundary to use, for example the Model Boundary located in the Input pane. 7. If the option Create attributes is selected, the operation will create area and volume attributes for the surface. 8. Click the Run button to execute the calculation.



8. Calculated volumes appear in the Petrel message log.


If the log is not appearing after running the process make sure the option Message log is selected in the View drop-down menu.


Combine fluid contacts and structures The top and base of zone structure grids must be combined with the top and base fluid contacts, if they exist. In this exercise, only the base fluid contact exists and it is at an elevation of –6010. It must be combined with the HOUSTON base structure grid to create the HOUSTON base hydrocarbon surface. Exercise Steps 1. Make a copy of the HOUSTON base grid and rename the copy to Houston base hydrocarbon. 2. Combine the structure grid with the fluid contact by: a. Going to the Calculations tab. b. Setting A = -6010. c. Clicking on the Set Z=A where: Z
Build gross thickness grid The gross thickness represents the total thickness of the hydrocarbon bearing portion of the zone, including hydrocarbon, other fluids, and rock. In this exercise, you will create a grid representing this thickness. There are two ways of making the gross grid.



Method one: Make a copy and adjust values on copy Exercise Steps 1. Copy the HOUSTON struc grid and rename the copy to HOUSTON gross thickness. 2. Calculate the gross thickness by: a. Open the settings for the Houston gross thickness b. Go to the Calculations tab. c. Set A = HOUSTON base hydrocarbon. d. Click on the assign: Z=Z-A button. 3. Check the statistics near the top of the Calculations tab. You will see that the grid contains some very large negative numbers. Clip the negative numbers to 0 by: a. Go to the Calculations tab. b. Set A=0 c. Clicking on the Set Z=A where: Z
Method two: Using the surface calculator to create new grids You will now perform the same operation as in the previous step, this time using the Surface calculator to create the Houston Gross grid. 1. Right-click on the Houston struc grid and select Calculator. 2. Type in Houston_Gross= in the input field of the calculator. 3. Subtract the Houston base hydrocarbon from the Houston struc surface. The full statement should read as follows: Houston_Gross=HOUSTON_struc_grid-HOUSTON_ Base_hydrocarbon 4. Click Enter and the new HOUSTON Gross surface will appear in the Input pane. It is up to you to decide which method you think is easier for similar operations in the future. Mapping and Geological Workflows




Preparing petrophysical grids Petrophysical grids and/or constants should represent ratios ranging from 0 to 1. Often data are represented in percentages and must be divided by 100. Other times, grids will project above and/or below 1 and 0 and need to be clipped to those limits. Exercise Steps 1. Check the petrophysical grids to be used for volumetrics to be sure they have acceptable values and ranges. a. The net-to-gross grid is called Houston net to gross – ratio and is located in the Net/Gross Data folder. b. Make sure the grid has: i. Proper values (numbers in the 0-1 range). ii. Proper limits (clipped to minimum of zero and maximum of 1.0).

c. The porosity grid is stored in the Porosity Surfaces folder and is called HOUSTON phi. Make sure the grid has the: i. Proper values (numbers in the 0-1 range) ii. Proper limits (clipped to minimum of zero and maximum of 1.0).



d. The Sw parameter to be used is 0.18; therefore, no processing is needed.

Build net, pore and hydrocarbon thickness grids A hydrocarbon pore thickness grid is created by successively reducing the thickness of the gross rock grid by the portions that are non-net, rock, and water. Remember, it is possible to use the Surface calculator for all of the operations below. Exercise Steps 1. Create a HOUSTON net thickness grid by multiplying the HOUSTON gross thickness grid by the HOUSTON n:g grid that you checked and possibly modified. To do this: a. Open the Surface calculator. (Right-click on any surface and select Calculator) Type in HOUSTON_net_ thickness =HOUSTON_gross_thickness*Houston_ net_to_gross_ratio. b. Display the HOUSTON net thickness grid in a 3D window to see if it is acceptable.



2. Create a HOUSTON pore thickness grid by multiplying the HOUSTON net thickness grid by the HOUSTON phi grid that you checked and possibly modified. Do this in the same way using the calculator. a. Display the HOUSTON pore thickness grid in a 3D window to see if it is acceptable.

3. Create a HOUSTON hydrocarbon thickness grid by multiplying the HOUSTON pore thickness grid by 1 – Sw (where Sw = .18) Mapping and Geological Workflows


a. Display the HOUSTON hydrocarbon thickness grid in a 3D window to see if it is acceptable.

Calculate volumes for hydrocarbon thickness Volumes for a hydrocarbon thickness grid can be calculated under the Input pane in two ways: volumes between two structures or volumes below an isochore grid and above a plane. Incorporating petrophysical conditioning parameters requires isochores; therefore, the isochore method is used. Exercise Steps 1. Calculate the volume of the HOUSTON hydrocarbon thickness grid. To do this: a. Open the setting dialog for the HOUSTON hydrocarbon thickness grid (double-click on the name). b. Go to the Operations tab->Calculations folder, and select Volume below surface (constant level). c. Specify zero for the Base level parameter. d. Click on Run to calculate the volume. 2. Convert the cubic feet parameter to barrels. You will need to use a calculator and the conversion number 1.781076E-1 (ft3 * 1.781076E-1 = barrels). Your number should be somewhere around 1,085,062 barrels.

Calculate area for hydrocarbon thickness The areas for a hydrocarbon thickness grid can be calculated under the Input pane in two ways: Blank the non-positive portions of the grid and calculate the area of the remaining nodes, or draw a polygon around the positive thickness and calculate the area of the polygon. The polygon method sometimes requires editing to close the polygon, but it is more accurate. The blanking method always requires the same number of steps, but it is less accurate by a few percentage points. In this exercise you will use the blanking method for area calculation. Exercise Steps 1. Calculate the area of the positive portion of the HOUSTON hydrocarbon thickness grid. To do this: a. Copy the HOUSTON hydrocarbon thickness grid and rename the copy HOUSTON blanked hydrocarbon. b. Blanking the grid where it is less than .01: 164 • Surface operations


Go to the Calculations tab, Set A = .01 Click on the button Eliminate where: ZCalculations folder, and select 2D and 3D area of surface. 2. Convert the square feet parameter to acres. You will need to use a calculator, the 2D area, and the conversion number 2.295684E-5 (ft2 * 2.295684E-5 = acres). Your number should be somewhere around 149 acres. If you do not have a calculator, go to the Units tab under Project settings and set area to acre and redo the calculation. Reset the units afterwards. 3. Display the blanked thickness grid in a 3D window to be sure that you are calculating area for the correct portion of the grid. 4. At this point, place all of the grids into a folder: a. Insert a new folder (make it a top level folder) b. Rename it Pay Maps. c. Drag and drop Houston hydrocarbon thickness, Houston blanked hydrocarbon, Houston pore thickness,Houston net thickness and Houston gross thickness grids into the folder. c. d. e. f.



Summary How to perform surface operations, including calculating volumes, creating rock gross thickness maps and combining two or more surfaces, has been covered in this module.



Module 6 – Intersections Introduction How to use the various types of intersections in Petrel to inspect your model, and how to set up an intersection window for plotting by using a General Intersection, will be covered in this module. Prerequisites No prerequisites are required for this module Learning Objectives This module will cover the use of the following: • General intersection • Polygon intersection • Well path intersection • Plane settings • Intersection window


Intersections • 167

Lesson 6 - Intersections

168 • Intersections




Intersections Well Intersection

Intersection along coordinates of well path. Helps to QC a digitized (proposed) well or to visualize data along existing well path(s). 1. Select Create Vertical Well Intersection for a well or a folder of wells. 2. Display any or all available data on the new vertical intersection.


1

2


Users can lock a fault intersection perpendicular to a fault surface for detailed structural quality control during fault modeling. By using the intersection player, users can step through all the fault pillar intersections for a given fault, as indicated in the image above. Seismic data, horizon lines, horizon edges and properties can be displayed on these intersections.





Style tab (General intersection) Defines how the General Intersection is displayed in the Display window. The Reset option at the top of the window sets the options back to default, while Color sets the color of the General Intersection and its icon in the Petrel Explorer. Plane Settings When the Show check box is selected, the plane will be seen as more or less transparent. The plane will only be defined by its frame when Show is cleared. If you have the Only when active option selected, the plane will only be shown when the plane is active (bold) in the Petrel Explorer. This is useful if several intersections are made in the current project. Transparency of the General Intersection is also user controlled. Clip offset is an option to add an offset limit to the clipping tools (clip in front/behind) in the function bar below the Display window. The clipping will clip (remove) displayed objects in front of or behind the General Intersection. Data such as surfaces will be removed from the display either in front of or behind the plane depending on selection. Map/Intersection line settings are only available when in a Map or an Intersection window. Use these settings to change the color and/or width of the intersection line in the Map window.



Input Settings Surfaces: This option allows the user to view selected surfaces in the Input window as lines in the General Intersection. Select the Show check box for input surfaces. Select color and width for the surfaces. Wells: This option allows the user to show selected well trajectories on the General Intersection. The wells will be projected towards the General Intersection within the user defined maximum distance (Distance limit). Show name and symbol allows you to view the well name and symbol of the well on the plane. Define font size and color. Seismic: This option gives you three options which can be changed for seismic. The first option is controlled from the Style -tab -> Input settings -sub tab for the General intersection while the two last options are controlled from the Style -tab -> Intersections -sub tab for a seismic volume. 1. Depth offset will move the intersection a bit further away from the user than it really should be (useful if there are difficulties in observing polygons displayed along traces). 2. Interpolate will interpolate values between traces for a smoother display. 174 • Intersections


3. Decimate will decrease data display when moving the intersection (may be turned off if the graphics card is extremely good). Polygons: This option allows you to view polygons with a user defined Ghost limit. Is useful, for example, when interpreting seismic in a Seismic Intersection. It allows you to decide how many traces to see away from the plane. Note that the interpreted polygons should then be viewed on the plane and that they fade away the further away they are from the plane.

3D-Grid Settings Horizons: This option allows you to set the color and width of the horizons that are displayed on the intersection. Faults: This option allows you to set the color and width of the faults that are displayed on the intersection. Zones: This option allows you to set the color and width of the zones that are displayed on the intersection. The transparency can also be adjusted on the zones. Filter property: When this check box is selected, the filter on properties will be activated in the intersection. Mapping and Geological Workflows


Grid lines: When this option is selected, the grid lines of the 3D model will be visualized on the intersection when this option is checked. Under this option, is also the ability to change the line color and thickness.



Exercise 6 – Intersections Exercise Data A Petrel project with the proper data for starting this exercise has been prepared for you. This project is called Applied_Mapping_gullfaks. pet. Open the project and save it by using Save As from the File menu. Give the project an appropriate name and save it to your own Student directory.

Intersections (Cross Sections) Petrel offers a number of different types of intersections or crosssections: • General Intersection – intersection defined by 2 points. • Well Intersection Fence – intersection snapped to wellbores. • Vertical Intersection – intersection defined using a polygon which can contain more than 2 points with multiple turning points. • Vertical Well Intersection – intersection defined by a deviated well trace. Mapping and Geological Workflows


Most data objects in the Input and Models panes can be displayed on these intersections. They can be viewed in a 3D window, an intersection window (for plotting) and an interpretation window (if seismic is displayed). In the following exercises we will focus on the General Intersections; however, most of the settings will be identical for the different types of intersections.

General Intersection A general intersection is a plane cutting through the data in a display, equivalent to a cross-section. Data can be displayed on this plane independently of the data displayed in the 3D volume of interest. The plane can also be used to restrict the display of data in the 3D view by cutting away data on one side or the other of the plane. Exercise steps: 1. Display only the Top Tarbert surface (in the Depth Surfaces folder) in a 3D window. Check the display mode, if it is TWT, change it to TVD.

. 2. Adjust the display to use full color range (Hint: Use the Adjust color table on selected icon ). 3. Right-click on the folder containing the surfaces and select Insert General Intersection. A transparent blue plane will be inserted running north-south through your model. Its extent is based on the minimum and maximum X, Y, and Z-values for all objects in the folder.



4. You can change the color and the transparency of the plane: a. Open the Settings dialog for the General Intersection. b. On the Info tab, change the color by selecting an alternate color from the pull-down menu. c. On the Style tab->Plane Settings sub-tab, decrease the Transparency to 40%.



Other parameters of interest: • Show – This option controls the display of the plane (for example, the green transparent fill). If deselected, only the outline or frame of the General Intersection will be displayed. • Only when active – This option assists in managing the display of multiple general intersections. If this check box is selected, the general intersection must be active (bold in the Input pane) to be displayed. d. Click Apply. Move the General Intersections’ Settings dialog out of the way, but leave it open. 5. The plane can be adjusted in a number of different ways: a. Move and rotate the plane: i. Click M or the Manipulate plane [M] button on the function bar, ii. Click on the plane and drag it.

b. Rotate the plane in any direction: i. With the Manipulate plane [M] button active, press the CTRL key while dragging the plane.



ii. Click the right or left arrow keys a couple of times. What happens? As long as the General Intersection is active and displayed in the 3D window and the Manipulate plane tool is active, the arrow keys can be used to manipulate the plane. The right and left arrow keys will rotate the plane; the up and down arrow keys will tilt the plane from the vertical position. 6. When the general intersection was inserted, the player bar became available on the bottom left of the Petrel window, and, as with the seismic lines, it can be used to control movement of the plane, the display of the data intersected by the plane and the display of data on the plane.

The axis of the rotation’s position depends on where you point at the plane when you start the movement.

a. You have probably noticed that the plane tilted from the vertical position when you were rotating it. Click the Align plane vertically button on the toolbar to constrain the plane to the vertical position. There is a complementary option to align the plane horizontally, Align horizontally (timeslices) Mapping and Geological Workflows

. Intersections • 181

b. Click the Align north to south (inlines) button . This prevents the plane from rotating. There is a complementary option to limit the plane to an east-west orientation, Align east to west (crosslines) . Click the icon again to turn off the align option. c. Align the plane so that it is centered on the Top Tarbert surface and runs roughly SW to NE. Rotate the display so that you are looking from the SE.

7. Clip behind the plane by pressing Clip behind the plane button . What happens to the display? In front and behind are “relative”; just use the one that creates the desired result. a. In the Settings dialog for the General Intersection, go to the Style tab, Plane settings sub-tab. Set the Clip offset to 100. Click Apply. What happens to the display? Hint: Zoom in. This parameter works in conjunction with the “clip plane” options. Enter a value to create a buffer around the general intersection plane. Data falling inside this buffer will always be displayed, regardless of the clip plane setting. 182 • Intersections


Note this only affects data posted in the 3D window, not data posted just on the General Intersection. The values will be in the project units (e.g. feet or meters). 8. Press CTRL and B or use the Toggle visualization on plane button . The data display is controlled by this icon (also known as the “magic blue button”) located in the player bar in the lower left portion of the window. What happens in the Input pane to the boxes next to some of the objects/folders? If a check box is blue, the object can be displayed on the General Intersection. Otherwise, the data can be displayed in the 3D window but not projected onto the Well Intersection Fence. The same process is used for all intersection types: general, vertical, and well. a. What types of objects can be displayed on the General Intersection? Intersection planes act as separate windows displayed within the 3D window. As with the other window types, the object display (and style settings) is independent between the intersection and the 3D window; hence, the “magic blue button”. It performs a role similar to activating different window types from the Windows pane. 9. In the Input pane, in the Depth Surfaces folder, click on the blue boxes in front of the Base Cretaceous, Top Etive and Top Ness surfaces. What happens to the display? 10. Once you have selected the objects to post, the limits of the General Intersection will change, reflecting the extents of the selected data. 11. Display parameters for objects posted on the General Intersection are controlled from its Settings dialog. a. Go to the Style tab, Input settings sub-tab. Change the line thickness of the displayed surfaces on the plane by selecting a different width from the pull-down menu for Surfaces.


The Base Cretaceous, Top Etive, and Top Ness profiles are displayed on the General Intersection, but the surfaces are not displayed in the 3D window.


b. Review the options for adjusting the color of the surfaces. c. Click Apply. 12. In the Input pane, notice that the check box next to the Wells folder is blue, indicating that wells can be displayed on the General Intersection. Turn on the Wells. What happens to the display? The wells have a larger Z-range than the 2 surfaces currently displayed, so the boundaries of the General Intersection have expanded to encompass the wells. 13. Increase the width of the line displaying the well trace to 2. Click Apply. 14. Notice that some of the well traces fade in and out of the plane of the General Intersection. These are the portions of the well bores that fall within a certain distance of the General Intersection. The solid portion of the line represents the portion of the bore hole in front of the plane; while the dashed portion of the line represents behind the plane. Rotate the display. What happens? 15. The distance within which the bore holes are displayed is controlled by the Distance limit: parameter on the General Intersection Style tab, Input settings sub-tab. Change the default value of 1000 to 200 and click Apply. What happens in the display? 184 • Intersections


16. The player bar at the bottom left of the window can be used to step or play the plane through the displayed data. a. Change the plane step parameter to 500. You can either type in the value to use or select from the pull-down menu. The number is in the project’s units (for example, feet or meters). b. Practice using the Step plane forwards plane backwards

and Step

buttons to move the plane.

c. Practice using the Play plane forwards Mapping and Geological Workflows

The Show well name and Show well symbol parameters do not work for general intersections viewed in a 3D window.

Step plane Intersections • 185

backwards , Stop buttons. 17. There are two additional tools for manipulating the plane: Snap intersection plane to point and Snap intersection plane to 2 Points. Both of these options require an object posted in the 3D display to use as reference. a. Turn off the Clip plane option. b. Adjust the display so you are viewing the Top Tarbert surface from the top . c. Click the Snap intersection plane to 2 points button and click on two points on the surface. The orientation of the General Intersection is now based on the points you selected. d. Turn off the “magic blue button” (deselect the Toggle visualization on plane [Ctrl + B] icon) and turn on the Wells (turn off Well Tops 1). e. Click the Snap intersection plane to point button and click on a well that penetrates the surface. The location of the General Intersection now passes through the selected point. 18. Close all Settings dialogs and save your project.

Intersection Window Cross sections created in the Intersection window (or in an Intersection viewport in a Plot window) are essentially the same as General Intersections, except they are in a format suited for printing/ plotting. This exercise walks you through using the Intersection window. Exercise Steps 1. Create a new general intersection by highlighting Intersections, right-clicking on the Intersections folder in the Models pane, and selecting Insert general intersection or use the one you created in the previous exercise. 2. In the 3D window, give the intersection the desired orientation. Click on the blue button at the bottom of the Petrel window. 3. Open a new Intersection window by going to Window in the menu bar and selecting the new Intersection Window. 4. Turn on the General intersection. 186 • Intersections


5. Turn on the horizons in your 3D Grid Model (Models pane) by selecting the check box next to the Horizons folder. 6. Display the Porosity between the horizons by selecting the check box next to Porosity (located in the Properties folder). 7. Display the faults (select the check box next to the Faults folder). 8. To change the orientation, switch between Align NorthSouth

, Align East-West

, or flip the view around

the vertical axis by using Align camera with plane . 9. To choose a different location of the intersection, use the player toolbar at the base of the Petrel window and either step through or play through the model. 10. To change the colors of the zones, change the color under the Zone filter folder in the Models pane (deselect Porosity and select Edges). 11. To display grid lines or change thickness of horizon and fault lines, double-click on the General Intersection in the Intersection folder to open the Settings dialog, and change the settings under 3D-grid settings for items from the 3D Grid, or under the Input settings for items from the Input pane. 12. When you have created the intersection you want, you can create an index map, in bitmap form, of where the intersection has been cut: a. In the 3D window, display the General Intersection together with one of the horizons to show where it goes. b. Go to the Edit menu and select or click on the Copy

Changes done in the Intersection window are reflected in the 3D window.

bitmap button . c. Go to the Edit menu and select Paste bitmap. d. The bitmap will now be placed under the Input pane. e. While in the Intersection window, toggle on the bitmap. You can move it around anywhere you like (remember to choose viewing mode), and change the size of it. Just remember that the bitmap is not interactive, that is, changing the location of the intersection will not automatically update the bitmap inset. Mapping and Geological Workflows




Summary How to set up an intersection window and how to use the various intersections available in Petrel to inspect the model, have been covered in this module.



Module 7 – Plotting and Model Maps Introduction In this module plots in general will be covered. How to annotate, scale and prepare for printing is key for successful output and presentation. Various plots related to a 3D grid and associated properties will also be covered. Prerequisites There are no prerequisites required for this module. Learning Objectives In this module the user will learn about: • Plot setups • Print setup • Annotations and styles • Make various plot types from 3D grid


Plotting and Model Maps • 191

Lesson 7 – Plotting and Model Maps

Plotting

Lecture and exercise purpose Purpose: Learn tips and tricks to help improve your maps You will learn to:

192 • Plotting and Model Maps

•

Set a fixed scale

•

Use the Set home function

•

Link to coordinate group

•

Link to visual group

•

Annotations

•

Printer setup

•

Print using the Workflow Editor








The paper size specifies the paper size for the printer and is tied to the printer. When selecting Automatic paper size, Petrel will attempt to find a paper size supported by the selected printer that best matches the plot size specified above. The user may also specify the size of the paper directly by selecting Manual paper size. • If the plot size is larger than the paper size, the plot will be panned across multiple sheets of paper. • If the plot size is smaller than the paper size, the plot will be printed in the upper left corner of the paper.



The Petrel print dialog is accessible from File->Print or from the CTRL and P command. It gives you options for page scaling (for example fitting to page), orientation (for example portrait or landscape) and roll plotter. The print dialog has options for directly generating CGM and PDF files. If you prefer to use the original printing and plotting sub system, you can still do so by using the Print method option available from the Page setup menu.





Exercise 7 – Plotting and Model Maps Purpose How to generate reservoir maps representing a variety of parameters will be covered in this exercise. These maps include: structure maps from the 3D Grid, layer and slice maps through property models, isochore maps, average property maps, property thickness maps for specific zones, pay maps for zones and fluids, and fluid contact maps. Each of these is generated in a different way and the following exercises will guide you through each method. This exercise is divided into several parts: • Structure Maps (for display and export) • Isochore Maps • Layer Maps • Slice Maps (Elevation) • Average Property Maps • Property Thickness Maps • Volume Thickness Maps (Pay) • Fluid Contact Maps Data A Petrel project with the proper data for starting this exercise has been prepared for you. This project is Applied_Mapping_Gullfaks.pet. If you have not already done so, make a local copy in your student folder. You may want to rename the project.

Structure Maps – For Display Structure maps generated from 3D models make the final result much cleaner than simply displaying a 2D surface in the Map window. Data Data: Models pane -> Class Model ->3D Grid-> Horizons.



Exercise Steps 1. Open a new Map window. 2. Expand Class Model>3D Grid>Horizons.

3. Select the check box in front of Top Tarbert to display it in the Map window. 4. Click View all items to fit the horizon into the viewport. 5. Place Well Tops in the map. To do this: a. Expand the Input pane -> Well Tops folder. b. Within the Well Tops folder, expand the Attributes folder. c. Toggle Well on. d. Expand the Stratigraphy folder. e. Toggle Top Tarbert on and all others off. f. Select the check box next to the Well Tops folder. g. Set well symbol style. Open Well Tops -> Settings -> Style and: i. Set Symbol to As Well ii. Set Size to 12 h. Expand the Model pane -> Class Model -> 3D Grid -> Fault Filter. i. Turn off all of the faults by clicking the check box next to the Fault Filter folder. Turn on the Top Tarbert fault by selecting the check box next to it. j. Select the check box next to the Model pane -> Class Model -> 3D Grid -> Faults folder. This will turn on the Top Tarbert faults. 200 • Plotting and Model Maps


k. Open Settings -> Style for Horizons. l. Set an appropriate contour interval. m. Turn on Show contours in the faults 6. Open Settings -> Style for Faults. a. On the Lines tab set Horizon lines to Show, and Color to Black. b. On the Solid tab, set Color to Z-values. The resulting Top Tarbert map is shown below.

7. Rather than displaying contours in the faults, you can turn them off by opening Settings -> Style for the horizons and turning off Show contours in the faults . The faults will still be color filled according to your faults’ style settings. To fill the faults with a solid color, open Settings -> Style for Faults and on the Solid tab set the Color to anything but Z-values. Mapping and Geological Workflows


a. The map below has the faults colored As Fault.

b. To change the color fill: Check the Z min and max (Horizons -> Settings -> Statistics).

c. Access the global color template to set the color Max and Min values. (Horizons -> Settings -> Info, then click on the button: statistics. 202 • Plotting and Model Maps

) to rounded values based on the


d. Click Apply.

Structure Maps - For Export Petrel horizons are not directly exportable for use in other programs such as Z-MAP Plus or CPS-3. Horizons must be converted to surfaces which can be exported for import into other programs as grids. Data Data: Models pane -> Class Model -> 3D Grid -> Horizons. Exercise Steps 1. Open the Class Model -> Horizons -folder.

2. Open Settings -> Operations for Top Tarbert. Mapping and Geological Workflows


a. Insert a Template surface (Input pane -> Template Grids -> Template Grid 50x50). The Template surface provides the grid geometry with which the new surface is built. b. Select Fill in faulted areas. c. Click the Make surface button when the Operations tab looks like this:

3. The new surface appears at the bottom of the Input pane and is named Top Tarbert.

Isochore Maps Three types of isochore maps can be constructed in Petrel: • Pillar Isochore: displays thickness along pillars. This is used for evaluating growth characteristics across faults. • TVT Isochore: displays TVT thickness on nodes that do not cross faults. This is used for conformable mapping. • Faulted Isochore: displays TVT thickness on all nodes. This is used for structural mapping.



Pillar Isochore Map – Automatic Method It may be desirable to build an isochore grid and map which will show abrupt changes in thickness across a fault due to growth characteristics. This automatic process in Petrel calculates thickness along pillars. Since pillars parallel faults, pillars dip the same as the faults. This will show sharp changes in thickness when crossing faults if growth characteristics are present. Because pillars follow faults, the thickness is exaggerated when fault dips are shallow, but are close to true thickness on steeply dipping faults. Data Data for this exercise include Zones in a 3D model (Models pane -> Class model -> 3D Grid -> Zone Filter).

Exercise Steps

1. Expand 3D Grid . 2. Open Settings -> Convert zone(s) to isochore for Zone filter to create isochores for all zones. If you want to restrict isochores to specific zones/subzones, expand the Zone filter and open only Settings -> Convert zone(s) to isochore for the zone or sub-zone for which you want an isochore. 3. Select the second Make isochore button to make an isochore along the pillars.



4. The isochores will appear in a new folder at the bottom of the Input pane, as shown below:

5. In a new Map window, display one of the isochores (Input pane -> Isochores from 3D Grid -> Tarbert-2 (Along Pillar)). 6. Change the contour interval to 5. 7. Display the well locations and well names.



TVT Isochore Map A TVT isochore displays TVT thickness on nodes that do not cross faults. This is used for conformable mapping. Data Data: Models pane -> Class model -> 3D Grid -> Zone Filter. Exercise Steps 1. Expand 3D Grid. 2. Open Settings -> Convert zone(s) to isochore for Zone Filter to create isochores for all zones. If you want to restrict isochores to specific zones/sub-zones, expand the Zone Filter and open only Settings -> Convert zone(s) to isochore for the zone or sub-zone for which you want an isochore. a. Insert a Template surface (Input pane -> Template Grids -> Template Grid 50x50). The Template surface provides the grid geometry with which the new surface is built. b. Select the Fill in faulted areas check box. c. Click Make isochore in the Convert Zone(s) to isochore [TVT] section when the output tab looks like this:

3. The isochores will appear in a new folder at the bottom of the Input pane, as shown below. Mapping and Geological Workflows


4. Next, you will compare the Pillar and TVT isochore maps by placing them side by side in a Map window. a. Go to File -> Page Setup and set the Size to A4 and Orientation to Landscape. When you click Apply, your active map window will change to the new settings.

b. Go to the Setup multiple viewports tab. c. In the Layout section set Number of Rows to 1 and Number of Columns to 2. Click the Setup viewports button.



5. The Tarbert-2 (Along Pillar) map is in the left viewport. The right viewport is empty. If the right viewport has a red border, it is active, if not, click in it to make it active. 6. Display one of the isochores (Input pane -> Zones from 3D Grid -> Tarbert-2 (TVT)) in the right viewport a. Set the contour increment to 5. b. Post the well names and locations. c. Turn off all marginalia (Info box, scale bar, legend, etc.)



Optional: Faulted Isochore Map – Manual Method An isochore represents the true vertical thickness of a zone (gross rock). Isochores should never be used for conformable mapping. They are generally used to show the “true isochore” for structural purposes. They can also be used to show growth characteristics across faults. In Petrel, the process of construction is not automatic. It involves subtracting one surface from another, and then operating on the result using the calculator. Data Data for this exercise include Zones in a 3D model (Models pane -> Class model -> 3D Grid -> Zone Filter). Exercise Steps 1. Expand Class Model until the individual horizons are visible.



2. Right-click on Tarbert2 and select Convert to structured surface. Repeat for Tarbert1.

3. The structured surfaces appear at the bottom of the Input pane. Select the Input pane -> Tarbert 2, and create a copy using CTRL and C, CTRL and V. Rename the Copy of Tarbert 2 to Tarbert 1-2 Isochore. 4. Make a 2D isochore grid by subtracting the top surface from the bottom surface: a. Double-click on Tarbert 1 -2 Isochore to open the settings dialog and choose the Calculations tab. b. Insert the Tarbert 1 surface by selecting it from the Input pane and clicking on the blue arrow next to A=. Mapping and Geological Workflows


c. Click on Z=Z-A in the Assign section (see figure above). Where Z is the Tarbert 1-2 Isochore and A is the Tarbert1 surface. 5. There can be negative values, especially at the faulted areas. We want these negative values to be considered zeros on the map, so toggle on . Leave the value as zero(0). Click on Set Z=A where Z < A. 6. Click OK. The new map (2D grid) is stored under the name Tarbert 1-2 Isochore. 7. Display Tarbert1-2 Isochore in a new Map window.



Layer Maps A layer map is the display of all the cells of a model having the same layer index (K value). Additional material can also be displayed on the map to aid in understanding its content. Data Data needed for this exercise includes: • The properties in the depth converted 3D grid (Models pane -> Class model -> 3D Grid -> Properties). • The zones statistics in the depth converted grid (Models pane -> Class model -> 3D Grid -> Zone Filter) Exercise Steps 1. Find the layer information for Zone Tarbert-1 (Models pane -> Class Model -> 3D Grid -> Zone Filter -> Zone 2 -> Tarbert-1). a. Open the Statistics tab and check the Cover zone indices (K layer) information. Note that Tarbert-1 is comprised of K layers 52-58.

2. In a new Map window, display Porosity (Class Model -> 3D Grid -> Properties -> Porosity) 3. Open Properties -> Settings -> Style. a. Click Jump to Top of Zone and select Tarbert-1. K-index 52 appears. b. Click Apply and observe the porosity values at the top of the Tarbert-1 zone.



c. Click on the up arrow (located to the right of the K Index field). This will change the K index to 53 automatically.



Slice Maps (Elevation) A slice map is a horizontal cut through the model. Any feature intersected by that horizontal cut can be displayed in the picture. This is equivalent to a time slice. Data The data for this exercise include Zones (Models pane -> Class model -> 3D Grid ). Exercise Steps 1. Right-click on 3D Grid -> Intersections and select Insert General Intersection. 2. Display the new intersection in a new Intersection window. 3. An Intersection toolbar is displayed in the lower left-hand corner. Click on the Align horizontally button

.

4. Turn on the Edges, Faults and Horizons by selecting the check boxes next to each of them.

5. Click on View all in the function bar. 6. Use the player to play through different slice positions. You can change the slice increment (the default is 100) in the Intersection toolbar (next to the player).



7. You can also show the Property -> Porosity by selecting the check box next to it in the Properties folder. The new view will be of porosity values where they exist at a depth of 2029 meters.



8. Change the color of the horizons and faults as they are displayed in the Intersection window: a. Double-click on the General Intersection in the intersections folder. b. Go to the 3D grid settings tab from under the Style tab. i. Change the color of the horizon to As horizon, like the following figure. The same can be done with the faults. ii. This is also the area where you would change the width of the horizon and fault lines.



Average Property Maps An average property map is normally created for a specific zone and represents the thickness weighted average property of that zone. These maps are used to evaluate the lateral variation of the property and to compare the general character of the property in one zone to the same property in another zone. Average porosity is a commonly used version of this map type. Data Data for this exercise are the properties in the Depth Converted 3D grid (Class model -> 3D Grid -> Properties). Exercise Steps 1. Open the Properties -> Porosity -> Settings -> Operations tab. 2. Expand Make Map from Property, and select Make average map. 3. Insert a template grid (Input pane -> Template Grids -> Template Grid 50x50). 4. Select Tarbert-2 from the Zone drop-down menu. 5. Set Expand result to 1 node. 6. Select the Smooth result check box. 7. Click on Run. The result (Average Map for PorosityTarbert-2) is stored under the Input pane. 218 • Plotting and Model Maps


8. Display Average Map for Porosity/Tarbert-2 in a new Map window. 9. Place Well Tops for Tarbert2 on the map.



Property Thickness Maps A property thickness map is normally created for a specific zone and represents the thickness of the zone multiplied by the property in the zone. This is actually done on a cell-by-cell basis and the results are summed to get the value for the zone. Like the average property map, it is used to evaluate the lateral variation of a property and to compare the general character of that property in one zone to the same property in another zone. Porosity thickness is a commonly used version of this map type. Data The data for this exercise are the properties in the Depth Converted 3D grid (Models pane -> Class model -> 3D Grid -> Properties). Exercise Steps 1. Open the Properties -> Porosity -> Settings -> Operations tab. 220 • Plotting and Model Maps


2. Expand Make map from property, and select Make net map. 3. Insert a template grid (Input pane -> Template Grids -> Template Grid 50x50). 4. Select Tarbert-2 from the Zone drop-down menu. 5. Select the Smooth result check box. 6. Click on Run. The result (Net Map for Porosity/Tarbert-2) is stored in the Input pane.

7. Display Net Map for Porosity/Tarbert-2 in a new Map window and adjust the colors, if necessary. 8. Display well symbols and names on the map.



Volume Thickness Maps (Pay) A volume thickness map is a property thickness map generated for only that portion of a zone found in the hydrocarbon volume of a particular fluid type (for example, oil, gas, tar). Typical examples of these maps are: gross pay, net pay, porous pay, and hydrocarbon pore thickness. The 2D grids, used to generate these maps, are created by the Volume calculation process. The Volume calculation process creates only one set of these grids. So, if you want a grid representing gross pay oil and another representing gross pay gas, you will need to make two separate volumetric runs. If there are more than two zones, and you want separate maps for each zone, then you must make additional volume runs using the Zone filter during each run. Be sure to rename the grids after each run to prevent mixing them up. Data The data for this exercise includes: • Fluid Contacts in the 3D Grid (Models pane -> Class model -> 3D Grid -> Fluid Contacts). • Properties in the 3D grid (Models pane -> Class model -> 3D 222 • Plotting and Model Maps


Grid -> Properties). These will automatically be applied to the map making process if you indicate to do so. Exercise Steps 1. Open Properties -> HCPV oil -> Settings -> Operations. 2. Select Make volume height map. 3. Insert a template grid (Input pane -> Template Grids -> Template Grid 50x50). 4. Select Tarbert-2 from the Zone drop-down menu. 5. Select the Smooth result check box. 6. Click Run. The result (Volume Height Map for HCPV oil/ Tarbert-2) is stored on the Input pane.

7. Display Volume Height map for HCPV oil/Tarbert-2 in a new Map window, adjusting the colors if necessary. 8. Display well names and symbols on the map. Mapping and Geological Workflows


Colorizing a depth surface with a Pay Map It is often helpful to view the distribution of pay thickness in the context of the structure surface immediately above the pay zone. This can be done by using the colors from the pay thickness map onto contours of the structure map. Data The data for this exercise includes the Top Tarbert (Input pane -> Top Tarbert) surface made during part B of this exercise and a STOIIP (Input pane -> Volume Maps (Case_1) -> STOIIP (Case_1) created by running Volumetrics. Exercise Steps 1. Right click on the Input pane -> Volume Maps (Case 1) -> STOIIP (Case1) and select Copy as surface attribute.

2. Right-click on the Top Tarbert surface and select Paste as surface attribute. 224 • Plotting and Model Maps


3. The STOIIP (Case 1) attribute is now available for Top Tarbert surface. Expand the Top Tarbert surface folder and select STOIIP (Case 1) while displaying the surface in any Petrel window.



Fluid Contact Maps In Petrel, fluid contacts are created and stored separately from 2D Grids and from the horizons of the 3D Grid. This is because they are given special attributes and need to be accessed often. The contact surfaces cannot be mapped directly onto a Map window; however, they can be viewed in a 3D window. Fluid contacts are viewed in a Map window as draped lines or color on a structure surface. This type of display allows quick evaluation of the distribution of each fluid in the zone under the displayed horizon. Data The data for this exercise include: • Fluid Contacts (Models pane -> Class Model -> 3D Grid -> Fluid Contacts). • Horizons (Models pane-> Class Model -> 3D Grid -> Horizons). Exercise Steps 1. In a new Map window, display the Tarbert 2 horizon. 2. Rename the Map window to Map Window – Tarbert2 with Contacts 3. Expand the Fluid Contacts and display both the Gas Oil and the Oil Water Contacts. 4. Adjust the Lines on the map: a. Go to Settings -> Style for the Gas Oil Contact. If necessary, change: i. line color to Black ii. annotation interval to 1000. iii. annotation font to 8 point. b. Click OK.



c. Repeat for the Oil Water Contact. The map of fluid contacts as they intersect with the Tarbert 2 Horizon is shown below.



Summary In this module you have learned how to set up plots for printing with associated styles and parameters. I addition various plot maps were created from a 3D grid and related properties.



Appendix


Appendix • 229

230 • Appendix


The Kriging interpolation does not have the option of co-kriging but has been retained because it can work in real coordinates rather than simple simbox space and is usually quicker. The Kriging is the fastest in terms of performance. In Petrel 2009 there were considerable improvements; performance improvement through parallelization, the addition of a fast Collocated co-kriging algorithm as well as some additional options in the Expert tab to extend user control over the style of Kriging. The Kriging by Gslib version uses the external executable and is therefore slower, but it has the option for Collocated co-kriging.


Appendix • 231

Z(Xo) = Value at location Xo. If the weights (lambda) approach zero, the mean will get more and more influence. For Simple Kriging, the mean is a global mean (more stable algorithm than the Ordinary Kriging).

232 • Appendix


The kriging algorithm is not fast compared to other algorithms like the Convergent Interpolation.


Appendix • 233

234 • Appendix



Appendix • 235

236 • Appendix



Appendix • 237

During the simulation, local highs and lows will be generated between input data locations which honor the variogram. The positions of these highs and lows will be determined by a random number supplied by the user or the software. Due to this, multiple representations are recommended to gain an understanding of uncertainty. In the absence of other information, the input distribution will be given by the input data. In this case, the result will not give values above the maximum or below the minimum of the input data.

238 • Appendix



Appendix • 239

240 • Appendix



Appendix • 241

Gaussian Random Function Simulation was introduced in Petrel 2009.1. Compared to SGS, this Schlumberger developed algorithm has some advantages: it is faster to run and it has a fast on-the-fly tabulator to update the model as we change the correlation coefficient.

242 • Appendix



Appendix • 243

244 • Appendix



Appendix • 245

Isochore processing - Extra

Isochore-to-isopach conversion – theory

Isochore

Dip angle

Isopach

Cos (angle) = Side Adjacent / Hypotenuse Cos (Dip angle) = Isopach / Isochore Isopach = Cos (Dip angle) * (Isochore) Isochore = Isopach / Cos (Dip angle)


Isochore-to-isopach conversion – theory

246 • Appendix

•

When dips are zero, isochore = isopach.

•

When dips > zero, isochore is greater than isopach.

•

In folded terrains, isochore thickness varies from the crest and trough of folds to their sides.

•

For steep (> 35 to 40 degrees) and highly variable dips the isopach will have a more uniform thickness than the isochore and be easier to model.

Dip in Degrees

Isochore thick

Isopach thick

0

1

1.00

10

1

.98

20

1

.94

30

1

.87

40

1

.77

50

1

.64

60

1

.50

70

1

.34

80

1

.17

90

1

.00

Table: Thickness differences as dip varies



Build isochore data using isopach processing – general procedure 1. Given: picks for zone base and structure grid for zone top 2. Calculate isochore data from picks and surface 3. Convert isochore data to isopach data 4. Build isopach grid 5. Convert isopach grid to isochore grid (for use in structure building) 2 1

4 + 0

isochore

3 + 0


5

isopach

Appendix • 247

248 • Appendix



Appendix • 249


Build isochore grid using isopach processing – convert isopach to isochore (grid) 1. Use COS(DIP) grid built when converting data from isochore to isopach 2. Copy isopach grid and rename to ISOCHORE 3. In ISOCHORE grid’s Operations Tab, Arithmetic Operations, set A = COS(DIP) grid and perform Z=Z/Surface(xy). 2

3

1

250 • Appendix


Index A Algorithms euler, 56 for make surfaces, 49 kriging, 231 kriging by Gslib, 231 kriging interpolation, 231 laplace, 56 Allow residual, 59 Attributes adding to a surface, 35 Average property maps, 218

B Boundaries digitizing, 69 editing an existing boundary, 71 from data, 69 gridding with boundaries, 67

E Euler, 56 Exporting structure maps, 203

F Faulted isochore maps, 210 Fault polygons, 59 creating, 72, 90, 103 fault influence, 59 fill inside the fault polygons, 59 gridding using fault polygons, 75 initial coarsening factor, 59 number of nodes to snap to, 59 order of projection, 60 use z-values of fault polygons, 59 Fill holes, 96 Fluid contact maps, 226

G

Color management, 13

General intersection 3D grid settings, 175 clip offset, 173 defined, 178 input settings, 174 plane settings, 173 style tab, 173 transparency, 173

Color templates, 39

Global extrapolation, 59

Create fault polygons and map for seismic interpretations, 90

Gridding using additional inputs, 78 using fault polygons, 75 well tops, 64 with boundaries, 67 with faults, 72

C Clip offset, 173

D Deviated wells, 126 Dip & azimuth data, Displaying a surface in 3D window, 25 grid nodes, 38 multiple surfaces in 3D window, 33 objects, 13

Grid lines, 28 Grid nodes displaying, 38 Gross thickness, 158

I Intersections, 168 creating intersection plane perpendicular to a fault, 171


Index • 251

Intersection window, 186

slice maps (elevation), 215 structure maps for display, 199 structure maps for export, 203 TVT isochore maps, 207 volume thickness maps (pay), 222

Isochore maps, 204 Isochore processing, 120 building isochore data points, 131 building isochore grids, 135 building structures by hanging or stacking isochores, 143 creating structure by hanging isochore, 129 deviated wells, 126 deviated wells technique and missing dip/azimuth data, 133 post processing, 138 stacking, 122 vertical wells technique, 131 well adjustment, 141

Minimum curvature global extrapolation, 59 local interpolation, 54 settings, 54 using dip and azimuth, 57 Model maps, 192

P

K

Paper size, 196

Kriging, 231

Pay map colorizing a depth surface, 224

Kriging by Gslib, 231 Kriging interpolation, 231

L Laplace, 56 Layer maps, 213 Light sources, 29 directional, 30 point, 30 spot, 30 Local interpolation, 54

M Make/Edit Surface, 61 Make surfaces, 44 additional inputs, 52 algorithms, 49 geometry, 51 process, 48 Maps average property maps, 218 colorizing a depth surface with a pay map, 224 faulted isochore maps, 210 fluid contact maps, 226 isochore maps, 204 layer maps, 213 pillar isochore maps, 204 property thickness maps, 220 252 • Index

Petrophysical grids preparing petrophysical grids, 161 Pillar isochore maps, 204 Plotting, 192 Post processing, 138 well adjustment, 141 Printing, 196, 197 Property thickness maps, 220

R Restrict extrapolation, 59

S Seismic interpretations create fault polygons and map, 90 Sequential Gaussian simulation, 238 Show contours in solid, 32 Slice maps, 215 Smoothing, 93 local features, 108 smooth area, 95 Stochastic methods sequential Gaussian simulation, 238 Structure maps for export, 203 Mapping and Geological Workflows

Surface operations, 146 blanking surface inside polygons, 114 blank undesired nodes, 97 building gross thickness grid, 158 building net, pore and hydrocarbon thickness grids, 162 calculating area for hydrocarbon thickness, 164 calculating volumes for hydrocarbon thickness, 164 combining fluid contacts and structures, 158 creating fault polygons and map, 103 editing, 84 editing surface form, 110 fill holes, 96 fluid contact polygons, 113 grid and contour editing, 116 lightly smooth entire surface, 107 preparing petrophysical grids, 161 removing local features, 108 smooth area, 95 smoothing, 93 smoothing local features, 108 surface resampling, 117 surface volumetrics with fault polygons, 156 tie to points, 100 tools, 98

W Well adjustment, 141

Z Z-values, 59

Surface properties modifying, 32 transparency, 34 Surfaces adding an attribute, 35 displaying multiple surfaces in 3D window, 33 drape bitmap on a surface, 36 editing, 61

T Thickness, 122 Transparency of general intersection, 173 True stratigraphic thickness, 122 True vertical thickness, 122 TVT isochore maps, 207

V Vertical wells technique, 131 Volume thickness maps, 222 Volumetrics, 155, 156 Mapping and Geological Workflows

Index • 253

2010_Mapping & Geological Workflows

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