Technical Papers
A Statistical Workflow to SeismicBalance
When balancing various 2d datasets it is imperative that
relationships between lines within any particular survey are not distorted.
This paper will discuss an efficient workflow, using tools available to
all SeisWorks 2d users to, quickly and accurately, calculate vintage shifts.
The displays presented will show clearly the need for altering default
calculation parameters and the pitfalls of basing any decisions on single
locations. There is a real danger when basing mistie corrections on any
single location. It is common to chose a single intersection between two
lines or between one line and a well to determine time, phase and amplitude
shifts. Using simple UNIX commands we can take the report file generated
by Automatic Computations within SeismicBalance to produce a crossplot
of each of the three parameters against the correlation coefficient. This
process allows the interpreter to quickly determine which value to use
to correct a particular survey. It also helps identify surveys that contain
subsets of differing lines. The statistical approach presented has been
tested in production on many datasets totalling more than 60000 kilometres
and proved to be a very cost-effective way of improving the interpretability
of regional data.
Seismic Balancing to Improve Interpretation Results - A Case Study from the Joseph Bonaparte Gulf
Keith Woollard GeoCom
Services Australia
Audrey Leonard Woodside Energy Limited
Amanda Panting Woodside Energy Limited
Woodside Energy Limited and Shell Developement Australia were recently awarded 3 exploration permits in the southern Bonaparte Basin. 6500 kms of 2d data has since been acquired and processed. A dataset consisting of 577 2d seismic lines, totaling over 20000km, had previously been loaded to SeisWorks as 8 bit integer. The original processing, and reprocessing, of these lines had used widely varying parameters, as had the workstation load. It was decided to use SeismicBalance, along with statistical analysis tools, to match the time, phase and amplitude of the existing project. Landmark's Release 98+ version of SeismicBalance was used as it contained several significant improvements over previous version. The technique employed was instrumental in identifying dataloading errors in the original dataset, thus increasing the reliability of the final project.
Presentation
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The Use of compression Technology to Aid Seismic
Interpretation in the North West Shelf, Australia
Keith C Woollard GeoCom Services
Australia
Landmark's upcoming SeisWorks Release (1998.5) incorporates
new storage formats for seismic data that include compression. Whilst this
compression is not "loss less", it is vastly superior to 8 or 16 bit integerisation.
The software was tested on a 170 square km 3d survey
from the North West Shelf of Western Australia to determine optimum compression
parameters. The amount of loss generated by the compression was analysed
in several domains. This was compared and contrasted with the loss caused
by the integerisation in conventional loading. Interpretation was carried
out to final map stage on conventionally loaded 8 and 16 bit data. These
maps were compared to those obtained via the compressed dataset. The cost-benefit
of such compression was also analysed.
Presentation
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Increases in Dynamic Range Through Trace Dependent
Scaling in IESX
Keith C Woollard GeoCom Services
Australia
IESX is unique amongst UNIXseismic interpretation systems
due to the application of a trace dependent scalar. This simple technology
allows better amplitude preservation when loading data to integer format.
This paper analyses, both quantitatively and qualitatively,
the improvement in dynamic range and looks at the implications to the interpretation
workflow.
Presentation
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Using Landmark Utilities to Merge 3D Surveys
Keith C Woollard GeoCom Services
Australia
Stewart Bayford British-Borneo Australia
The release of 3d/3d merge a number of years ago has improved dramatically the Geoscientists ability to interpret multi survey projects. In some cases, however, there is a need to deal with multi surveys as one dataset. In this case study a shallow target was identified at the overlap between two older 3d surveys. As the prospect relied heavily on time slice interpretation it was decided to attempt a post-stack 3d/3d merge. The surveys were first matched using SeismicBalance and then merged to a new survey using bcm. A rudimentary “bin-borrowing” technique was used to augment the sparsely sampled older survey. The results achieved were surprisingly good from what can only be described as worst case input data.
Presentation
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