Numerical simulations were done by Tierra Geophysical, now part of Landmark Graphics Corporation. SEAM did not specify a specific approach to perform numerical simulations. Instead, SEAM developed quality requirements for the simulations and allowed vendors to meet those requirements using any numerical approach, whose specifics may remain unknown to SEAM. Hence, this chapter does not attempt to describe the specifics of the simulation computation. Rather, it focuses on
run parameters so that the data can be reproduced;
artifacts from postsimulation filtering to apply the SEAM far-field wavelet;
global amplitude scaling process;
use of ghost source and receivers so that absorbing upper surface data have the same wavelet as the free surface data;
the degree of variation in the data caused by factors such as a change to the simulation code, use of multiple compute clusters, and elimination of numerical problems that occurred on a very small percentage of the shots; and
problems that occurred, and how they were identified and corrected.
There are significant connections between this and Chapter 3 for topics of source wavelet, trace scaling, absorbing upper surface, and verification. Chapter 3 also covers vendor qualification procedure, requalification using the production model, and verification of production simulations.
The SEG-Y header definitions that were actually used are listed in Appendix A. The simulation specifications as actually implemented are listed in Appendix B. These evolved over time in response to knowledge gained and as more details were developed by the technical committees,
Figures & Tables
SEAM Phase I: Challenges of Subsalt Imaging in Tertiary Basins, with Emphasis on Deepwater Gulf of Mexico
“SEAM is a collaborative industrial research effort dedicated to largescale, geophysical numerical simulation projects. The projects are designed to provide the geosciences exploration community with earth models and simulated data that represent significant geophysical challenges of high business value to the petroleum resource industry. The Phase I project produced a deepwater subsalt earth model designed to capture as much physics and realism as possible in a 3D model that was relevant to oil and gas exploration. The 3D model covers a 40 õ 35 õ 15 km area and includes a complex salt intrusive in a folded Tertiary basin. The primary deliverable was the seismic data set of variable density acoustic simulations consisting of 200 TB of uncompressed traces for over 60,000 shots. Also delivered to the participants were several smaller compressed subsets of these data (“classic” data sets) intended for easier handling, simpler distribution to third parties, and easier comparison of imaging tests results. This report covers how the prime objectives of Phase I were met. Details are outlined in chapters on Model Development, Numerical Design and Vendor Qualification, Acquisition Design, Production Simulations, Quality Control, and Data Storage and Distribution.”