DSG Data Loading

R5000 3D地震数据格式山定子

注释

3D Seismic Data Formats in Software Version 5000.0.0.1 © 2008 Landmark Graphics Corporation

Software Version 5000.0.0.1

June 2008

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Landmark

3D Seismic Data Formats in Software Version 5000.0.0.1

3D Seismic Data Formats 3D地震数据格式 Overview

简介 Landmark’s Release 1998.5 introduced two new 3D seismic data formats, bricked and compressed, to supplement the time-series (.3dv) and time-slice (.3dh) formats. Advantages of these formats include improved overall performance for some workflows, access to both vertical and horizontal views in a single volume, and the option for better preservation of the fidelity of 32-bit floating point data than 8-bit .3dv files. An additional advantage of the compressed data format is a significant reduction in file size relative to .3dv files. Applications that read seismic files, including SeisWorks® software, SeisCube™ software, and StratWorks® software, were upgraded to read all of the new formats. Other applications and utilities that were enhanced to read and/or write the new data formats include 3D Batch Control Monitor, ZAP!® software, Batch ZAP!, and PostStack™ software. The .3dv (3D vertical time-series) and .3dh (horizontal timeslice) formats are still supported by all of Landmark’s interpretation applications.

What’s in this Help Document 本文档内容 This document describes Landmark’s seismic data formats, possible conversions between formats, and tools to evaluate and manipulate the resulting files •

“.3dv/.3dh Seismic Data Formats” on page 2

•

“Bricked Seismic Data Format” on page 4

•

“Compressed Seismic Data Format” on page 11

•

“Selecting the Appropriate 3D Seismic Data Format” on page 13

•

“Summary of Landmark’s 3D Seismic Data Formats” on page 16

•

“Converting Seismic Formats” on page 17

•

“Seismic Format Tools” on page 18


Overview

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.3dv/.3dh Seismic Data Formats

.3dv/.3dh地震数据格式

Prior to Landmark’s Interpret2000 release, SeisWorks® software only read .3dv seismic data files for vertical displays and .3dh files horizontal displays (timeslices or depthslices). For these seismic volumes, all of the data for the seismic traces is contiguous in a file. The location of each trace is maintained in an index. Seismic data loaded into .3dv/.3dh files use one of the four formats listed below. Format 格式

Range of Values 数值范围

32-bit floating point

5.4E-79 to 7.2E+75

32-bit integer

-2,147,483,648 to +2,147,483,647

8-bit integer

-128 to +127

16-bit integer

-32,768 to +32,768

8-bit data requires about 1/4 of the disk space required by 32-bit data. 16-bit data requires about 1/2 of the disk space required by 32-bit data.

File Naming Conventions 文件名约定 Starting with Release 5000.0.0, you no longer have control over the actual name of the seismic dataset on disk. You now identify seismic datasets via the dataset and version name that is stored in the OpenWorks database.

Extent Files 扩展文件 The physical 3D vertical (.3dv) and timeslice (.3dh) files on disk have at least two parts, called “extents.” The 01 extent contains the header information for the seismic file. This includes reference information as to the total number of extents in the file, their sizes, and revision status. The 02 extent contains trace data. If the seismic data exceeds the space available for the 02 extent, additional disk files are created as required. All of the filenames for these additional “extent files” are the same, except that the number of the extent increases by one for each new file.



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For example: mig32b01.3dv - trace header information mig32b02.3dv - trace data mig32b03.3dv - trace data When you archive or restore your files, you must save and restore all of the extents together.

Seismic File Size Limits 地震文件大小限制 In Release 5000.0.0., each SeisWorks .3dv or .3dh extent can store more than 2 GB per extent. You can have up to 32 extents for each file. The total theoretical (not tested) storage capacity for a .3dv/.3dh file (all extents) is therefore greater than 64 GB.

Calculating .3dv and .3dh File Size 计算.3dv和.3dh文件大小 To get an approximate estimate of how much space will be required for a .3dv file, use the formula: (# lines) x (# traces) x (# samples/trace) x N

where N is the storage factor. N为存储系数

Data Format

Storage Factor (N)

Floating Point

4

32-bit Integer

4

16-bit Integer

2

8-bit Integer

1

To calculate the space required for a .3dh file, use the formula: (# lines in input .3dv) x (# traces in input .3dv) x [(total time to be sliced, in ms)/ (time slice sampling interval)] x N

(# 在输入.3dv中的测线数) x (在输入.3dv中的道数) x [(以ms为单位的做切片的总时间)/(时间切片样点间隔)] x N



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Bricked Seismic Data Format

块地震数据格式

In the bricked format file, seismic data is grouped into threedimensional “bricks” of data that allows users to optimize performance along any single dimension or to normalize performance across several dimensions. 联络测线 Crossline

In l

ine 纵测线

Time/Depth

时间/深度

Each brick contains data for a user-specified number of crosslines by inlines. Time or depth makes up the third dimension.

Advantages of Bricked Seismic Format 块地震数据格式的优点 Improved Interpretive Workflow Performance 改进的解释流程性能 Interpretive workflows that step randomly through a series of inline, crossline, or arbitrary line views will benefit with the new bricked file format. In the traditional SeisWorks environment, trace data is written in a .3dv file that optimized display speeds only for the inline direction. As a result, users have often constructed crossline-oriented files for use in their crossline views. Neither file could produce fast arbitrary line views. Bricked files can be designed to optimize performance for a particular display orientation similar to .3dv files. However, bricks can also be created such that they normalize display performance for a variety of views. Although the performance of the inline and crossline displays will not be as good as if they had come from separate inline-optimized or crossline-optimized volumes respectively (although still quite acceptable), users will notice substantial improvements in crossline and arbitrary line displays as compared to a .3dv file. The improvements in display performance with the bricked file format are achieved by creating a file that reduces the number of disk seeks and reads necessary to obtain the requested data. The file is indexed so that Software Version 5000.0.0.1


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only the data necessary to construct the desired view is delivered. This also tends to minimize the amount of network traffic necessary to deliver the data to the end-users workstation. Crossline and arbitrary line display performance have been improved with minimal impact on primary display orientation performance. Greater Flexibility from a Single Volume 来自单个数据体的更大灵活性 Creating bricks with dimensions designed to normalize the display time of any vertical seismic view demonstrates best how bricks can help. The same bricked volume can be used as a source for inline, crossline, and arbitrary line access. In the past, some users have chosen to create two volumes (inline-optimized and crossline-optimized) to get both acceptable inline and crossline display performance.

如果做大量时间切片解释，Landmark建议创建一个时间优化块文件或一个.3dh文件。

Another distinct advantage of the bricked file format is that any bricked file can be used to construct timeslice views; separate .3dh files are no longer required. Display performance for timeslice views from bricked volumes optimized for inline or crossline or normalized any vertical view is sufficient for occasional timeslice interpretation (if doing a lot of timeslice interpretation, Landmark recommends creating a timesliceoptimized brick file or a .3dh file).

Better Preservation of Amplitude Values 更好地保留振幅值 The float8 and float16 sample formats preserve the amplitude range of the original data far more accurately than the current method of clipping and scaling to an 8- or 16-bit integer value. As these files maintain the original range of values, you do not set the scaling and clipping values when constructing the seismic volumes. Since these values are set for each seismic view in SeisWorks® software, you are not locked into a single clipping or scaling value. Another advantage is that original amplitudes rather than the 8-bit value used to construct the color display can be reported in the Seismic View status area while tracking with the cursor.



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Brick Dimensions 块范围 Landmark’s PostStack seismic data loaders and the 3D Batch Control Monitor and Seismic Converter utilities allow users to create bricked data volumes whose individual brick dimensions can be designed to suit the end user’s environment and workflow needs. The brick dimension selected, along with the order that the bricks are written to the file, determine the direction of best display performance. For example, if you work primarily with inlines during interpretation, you can create a bricked volume that optimizes inline display by designating a small dimension in the inline direction. On the other hand, if you work equally with inlines, crosslines, and arbitrary lines, you can create a bricked volume where display times for all vertical sections is normalized. This type of volume would have equal dimensions in the inline and crossline directions and would be larger in the time/depth dimension. Landmark provides four standard choices for creating bricked volumes (also see the diagram on the next page): • • • •

Inline - optimized for inline displays Crossline - optimized for crossline displays Horizontal - optimized for timeslice displays Any Vertical - display performance is normalized for any vertical view (good performance for retrieval of lines (inlines), traces (crosslines), and arbitrary lines).

Each of these choices maps to a set of predefined brick dimensions, listed below, used to create the appropriate bricked volume Dimensions for Default Brick Sizes Volume Type

Line dimension

Trace dimension

Time/Depth dimension

Inline optimized

1

32

32

Crossline optimized

32

1

32

Horizontal optimized

32

32

1

Vertical access normalized

8

8

16

For horizontal optimized files, Landmark recommends using the command line utility Brickreorder to improve display performance. See “Bricked Seismic Format Reordering Utility” on page 19.



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标准块类型示意图

Schematic Diagram Showing Standard Brick Types 纵测线优化

横测线优化

Optimized for Inlines

Optimized for Crosslines

Crossline

Crossline

In lin e

In lin e

Time/Depth

Time/Depth

时间切片优化

任意垂直视图优化

Optimized for Timeslices

Normalized for Any Vertical View

Crossline

In l

Crossline in e

In lin

e

Time/Depth

Time/Depth

In addition to these 4 choices, an expert option (User Defined) allows users to create volumes with any brick dimension. Advanced brick dimensions are three integer values describing the following: • • •


number of samples in the crossline dimension number of samples in the inline dimension time/depth dimension


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Bricked Filenames 块文件名 Starting in Release 5000.0.0, users no longer have control over the actual name of the seismic dataset on disk. Users will identify datasets via the dataset and version name that is stored in the OpenWorks database. The bricked file on disk may be made up of more than one physical file (called “extents”). If an additional extent is needed, a five-digit number is appended to the basename of the original file. For example, the second extent of a file with a system-supplied name of S_FLOUNDER.bri will be S_FLOUNDER00001.bri.



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Bricked File Output Sample Formats 块文件输出样例格式 Bricked seismic data can be created using one of five different sample formats: •

Float32 — maintains original input sample values using a 32-bit floating point format.

•

Float16 — input samples are converted to 16-bit integers (-32768 to 32767) on a brick-by-brick basis. The values for the group of samples within each brick are biased such that the range is arranged equally about a zero value. Next, each sample is scaled and stored. Since the bias and scale factors are stored for each brick as 32-point floating point numbers, shifting and scaling are reversible to within the precision of 32-bit floating point arithmetic. Essentially the full range of the original 32-bit source data is maintained for use within SeisWorks® software.

•

Float8 — input samples are converted to 8-bit integers (-128 to 127) on a brick-by-brick basis. The values for the group of samples within each brick are biased such that the range is arranged equally about a zero value. Next, each sample is scaled and stored. Since the bias and scale factors are stored for each brick as 32-point floating point numbers, shifting and scaling are reversible to within the precision of 32-bit floating point arithmetic. Much of the full range of the original 32-bit source data is maintained for use within SeisWorks® software.

•

Int16 — equivalent to the 16-bit .3dv file format. Input samples are converted to 16-bit integers by clipping the data to a userdefined range and then scaling these values to the range -32768 to 32767. Data stored in this way cannot be restored to the original 32-bit floating point values.

•

Int8 — equivalent to the 8-bit .3dv file format. Input samples are converted to 8-bit integers by clipping the data to a user-defined range and then scaling these values to the range -128 to 127. Data stored in this way cannot be restored to the original 32-bit floating point values.



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Bricked Volume Cache 块数据体缓存 The SeisWorks® software environment provides a bricked volume cache for use during the reading and writing of bricked data. When data is requested by the application, SeisWorks® software first examines the bricked cache. If the data is not there, it will retrieve for the necessary data from the source file on disk. This process takes place on a brick-bybrick basis. For some applications, such as PostStack™ software and bcm3d, the most appropriate cache size can easily be calculated. Thus, the application sets the cache size; there is no user option for these applications. For a detailed description of how SeisWorks® software handles cache memory for bricked volumes, refer to the manual titled Data Display in SeisWorks® Software Version 5000.0.0.1.



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Compressed Seismic Data Format

压缩的地震数据格式

By providing amplitude-range-preserving compression ratios of 20-to-1 or greater, the compressed seismic file makes storage and management of large original and attribute volumes practical. Compressed volumes are also bricked; however, the dimensions are not specifiable. All bricks in compressed volumes have the dimensions of 8 x 8 x 8 samples. Landmark’s 3D Batch Control Monitor and Seismic Converter utilities allow users to convert .3dv and bricked files to compressed volumes. Landmark’s PostStack/PAL™ and PostStack Data Loader applications allow users to output to compressed volumes.

Advantages of Compressed Data Format 压缩的数据格式的优点 Using Landmark’s fully integrated compression tools, users can achieve higher fidelity files by compressing 32-bit data than by scaling and clipping that same data to 8-bits integers while saving disk space. In many cases, it may be unnecessary to access the original 32-bit floating point data in order to perform detailed amplitude and attribute analysis workflows. The compression algorithm compresses small blocks of the volume independently. This enables SeisWorks® software to selectively decompress the data rather than requiring that the entire volume be decompressed before any data can be accessed. The algorithm also uses overlapping blocks. During compression, each sample contributes up to 8 blocks, minimizing blocking artifacts. Compressed data can be accessed along inline (line), crossline (trace), arbitrary lines, and timeslice views as needed. Alternatively, subsets of these compressed volumes can be loaded into such 3D applications as OpenVision for high-performance visualization and interpretation.



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Controlling Compression 控制压缩率 Compression ratios are not specified directly. Instead, a fidelity factor is specified by the user when the compressed volume is created. The fidelity factor controls the amount of compression by specifying how closely, on average, the compressed data must match the original data. The equation for fidelity is Fidelity = (1 - (RMS Error)/(RMS Signal)) x 100 By specifying fidelity, the RMS (root mean square) is indirectly indicated. The higher the fidelity, the lower the RMS Error. The actual fidelity is typically higher (and the RMS Error is lower) than the specified value. In general, higher fidelity values (from 1 to 99, where 99 is the highest amount of fidelity) correspond to lower compression ratios.

Compressed Volume Cache 压缩的数据体缓存 The compression toolkit manages two caches during the reading and writing of compressed data: an uncompressed cache and a compressed cache. For some applications, such as PostStack and bcm3d, the most appropriate cache size can easily be calculated. Thus, the application sets the cache size; there is no user option for these applications. For specific guidelines pertaining to cache control in SeisWorks® software, please refer to the Data Display in SeisWorks® Software Version 5000.0.0.1, which is available from the SeisWorks Help menu.



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Selecting the Appropriate 3D Seismic Data Format 选择合适的3D地震数据格式 The best format(s) for a given dataset is a function of many factors including the size of the volume, data quality, type of work to be done with the volume, interpreter’s workflow preferences, system configuration, available hardware, plus those factors that are sitespecific. In general, there is a need to balance disk space needs, display performance in SeisWorks® software, and data quality when determining the best seismic data format. Since there will be differences in the factors listed above from site to site, along with differences in how these factors are prioritized, it is not possible to give a set of rules for choosing seismic data formats. Rather, a listing of observations for each of the seismic data formats is listed below to help in the decision-making process. Please note that any observations regarding display times are conservative generalizations. Since display times are a function of variety of factors, actual results vary. For this discussion, very small datasets are defined as those less than 1 Gigabyte in size, small datasets are from 1 to 5 Gigabytes in size, medium datasets are from 5 to 15 Gigabytes, and large datasets are those over 20 Gigabytes in size. Datasets in the 15 to 20 Gigabyte size range may behave more similarly to medium-sized datasets in some settings, whereas in other settings they may have characteristics more in common with large datasets.


Selecting the Appropriate 3D Seismic Data Format

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Advantages

Advantages and Disadvantages of Each Format 每种格式的优缺点 .3dv/.3dh format

Bricked format

Compressed format

Fastest inline display times for inline-optimized .3dv files for very small to medium-sized seismic volumes.

Can access any seismic view from a single volume.

Datasets can be significantly reduced in size.

Can get a 2:1 reduction in file size with minimal data loss when loaded as float16 format.

No clipping or scaling is used when data is loaded.

Fastest crossline display times for crossline-optimized .3dv files for very small to medium-sized seismic volumes. File size can be reduced by 2:1 (16-bit integer format) or 4:1 (8bit integer format).

Can get a 4:1 reduction in file size with little data loss when loaded as float8 format. Float16 and Float8 are displayed as 32-bit floating point data in SeisWorks® software. For medium or larger-sized datasets, a volume with a normalized brick size (e.g., 8x8x16) can result in an overall faster workflow, particularly when changing among displaying inlines, crosslines, and arbitrary lines frequently.

Only one volume is required to access all seismic views. Data displays in SeisWorks® software as 32-bit floating point values. For 20 Gigabyte or larger datasets, display times are generally better for compressed data than for the other data formats. The larger the dataset, the better the performance of compressed data relative to bricked and .3dv/.3dh files. Fidelity level is specified when data is loaded.

For large datasets, optimized bricked file performance equals or exceeds the performance of similarly optimized .3dv/.3dh files.



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Disadvantages

Landmark Need two volumes to see both vertical and horizontal views of the seismic data. Crossline and arbitrary line display times are slow for inlineoptimized medium-sized or larger .3dv files. Similarly, inline and arbitrary line displays are slow for cross-line optimized .3dv files. There is a permanent loss of amplitude data due to scaling and clipping when data is loaded in 16-bit integer and 8-bit integer formats.

3D Seismic Data Formats in Software Version 5000.0.0.1 Display times for optimized bricked files for medium or smaller datasets are slower then similarly optimized .3dv files. With a normalized bricked file for medium or smaller datasets, the display time for an inline can be significantly slower than for an inline-optimized .3dv file (the crosslines and arbitrary lines will typically display faster with the bricked file, however).

Random errors are introduced into the data during compression. Display performance in SeisWorks® software for very small to medium-sized datasets is commonly slower than for .3dv/.3dh files and some bricked files. Decompression is CPU-intensive. Enough RAM is required to enable effective cache utilization.

16- and 8-bit integer data are displayed as 16-bit and 8-bit data respectively in SeisWorks® software.



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Summary of Landmark’s 3D Seismic Data Formats Landmark 3D地震数据格式小结 The diagram below summarizes Landmark’s seismic data formats. 老格式 Old Formats

新格式 New Formats

Data not bricked Specific views accessible

Data bricked All views accessible

.3dv

.3dh

Bricked

Compressed

Only vertical views

Only horizontal views

User controls brick size

All bricks 8 x 8 x 8

8-bita

8-bita

8-bit (int8)a

16-bita

16-bita

16-bit (int16)a

32-bita

32-bita

float8b

float32c

float32c

float16b

compressed formatc

float32c a. data

may require scaling and clipping before loading to this format; data displayed at same scale as stored b. scale and bias factor determined automatically and stored with data; data displayed as float32 c. data displayed as float32


Summary of Landmark’s 3D Seismic Data Formats

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Converting Seismic Formats

转换地震格式

Bricked, .3dv, and .3dh formats are bidirectionally convertible to one another. Compressed formats can also be converted bidirectionally to any of the other formats. Conversions between various seismic formats can be performed using the Seismic Converter utility or bcm3d. Not all conversions are supported. The available output formats are dependent on the input seismic data set. Supported conversions are listed below. Although supported, Landmark does not recommend compressing 8-bit .3dv or .3dh files. Overall, compression of 8-bit data introduces a lot of error with little savings in disk space.

支持的格式转换

File Type

Format

Supported Conversions

3dv

3dv 8bit

Bricked int8 Compressed

3dv 16bit

Bricked int16 Compressed

3dv 32bit int

Bricked float32, bricked float16, bricked float8 Compressed

3dv 32bit float

Bricked float32, bricked float16, bricked float8 Compressed

Bricked float32

All 3dv & 3dh formats Bricked float16, bricked float8 Compressed

Bricked float16

All 3dv & 3dh 32-bit formats Bricked float8 Compressed

Bricked float8

All 3dv & 3dh formats

Bricked float16 clipped

3dv 8-bit, 3dv 16-bit 3dh 8-bit, 3dh 16-bit Compressed

Bricked float8 clipped

3dv 8-bit 3dh 8-bit Compressed

Compressed

All 3dv & 3dh formats Bricked float32, bricked float16, bricked float8

Bricked

Compressed


Converting Seismic Formats

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Seismic Format Tools

地震格式工具

Conversions Between Formats 格式转换 Two utilities perform conversions between the seismic data formats: •

Seismic Converter, which is described in detail in the Seismic Utilities manual. Information is also available from the Help menu in the Seismic Converter toolbar.

•

3D Batch Control Monitor, which is described in detail in the 3D Batch Control Monitor manual

Evaluate Formats 估算格式 Two easy-to-use utilities help users evaluate seismic formats. seisMath adds, subtracts, multiplies, or divides two input data sets of any format, creating an output .3dv file with 32-bit floating point samples. seisRMS computes the actual fidelity preserved during volume generation, using the original and new volumes as input. Input and output files must have the same time or depth range. 输入和输出文件必须拥有相同的时间或深度范围

When running both seisMath and seisRMS, the input and output files must have the same time or depth range. If you specify files that do not have the same range, the programs issue an error and exit.

seisMath seisMath allows you to compare two volumes mathematically. You can compare the entire volume or only a part of the volume. Subtraction of a compressed volume from the original volume is a useful way to assess the effects of compression. There are a variety of ways that seisMath can be used to evaluate the seismic formats. Here are a few suggestions based on early testing of the effect of compression on seismic data files: •

Subtract the compressed volume from the original volume.

•

For a more normalized evaluation, take the resultant volume from the first suggestion (original - compressed) and divide it by the original volume.



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seisRMS seisRMS allows you to calculate the actual fidelity level of a newly generated seismic trace file by comparing the new file to the file from which it originated. There are a variety of ways that seisRMS can be used to evaluate the seismic formats. Here are a few suggestions based on early testing of the new seismic data format files: •

When a compressed volume is being generated, a statistical analysis is first performed on the data to estimate the degree of error that can be introduced to keep the fidelity level above the designated value. Since this calculation is conservative, the actual fidelity level in the compressed seismic data file generally will be greater than that set by the user. seisRMS allows calculation of the actual fidelity.

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To get an estimate of the fidelity that is preserved when 32-bit data is converted to 8-bit integer data (either .3dv or bricked). This can be compared with the fidelity preserved when the same 32-bit data set is compressed.

Bricked Seismic Format Reordering Utility 块地震格式重整工具 The bricked format for 3D seismic data provides the flexibility to create volumes with different performance properties by allowing the dimensions of the bricks to be defined in a variety of ways. As an example, tall and thin brick along the line direction provide best access performance along a line. Flat and wide bricks would provide best access for a horizontal slice. However, brick dimensions are not the only determining factor in the performance of a bricked file along a given dimension. How the bricks are distributed in the file also affects performance. Bricked files are read most efficiently when all of the bricks needed for a given request are consecutive in the file. That way the data can be read very quickly. When creating bricked files optimized for inline or crossline display, Landmark’s seismic data loaders, PostStack and the 3D Batch Control Monitor (bcm3d), write bricks such that all of the bricks needed for a display along a particular dimension are together in the file. However, when PostStack and bcm3d generate a brick volume optimized for horizontal slice displays, all of the bricks for a horizontal slice are not grouped together in the file. Although the brick Software Version 5000.0.0.1


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dimensions are optimally defined, the order that the bricks have been written to the file is not optimal. In order to maximize display performance, brick files generated for optimal horizontal slice display performance should have their bricks “reordered” in the file. The Brickreorder utility should be run on horizontally optimized brick files generated by PostStack and/or bcm3d (including those generated by the Seismic Converter). Brickreorder will generate a new brick file with the bricks reordered to provide the best performance possible for horizontal access. After Brickreorder has been run, the original brick file produced by PostStack or bcm3d can be deleted manually; Brickreorder does not delete any files. Brickreorder allows users to reorder bricks along any dimension; however, it should only be necessary to use it to reorder along the ”z” dimension for horizontally optimized brick files.



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