The Acquisition Design Committee was responsible for integration between all technical committees and proposing the seismic acquisition plan. They began work in September 2007 by examining the trade-offs between the type of simulations, number of shots, number of receivers, size of computation aperture, quality of numerical calculations (fidelity), and frequency content. They discussed many possible simulation and acquisition scenarios: variable density acoustic, elastic, multicomponents, ocean bottom receivers, 3D (vertical seismic profiling [VSP]), and 4D. Early estimates of acquired data volume ranged from 100 to 2000 terabytes (TB) of data.
As with field acquisition, there are economic and practical (operational) limitations, as well as the geophysical considerations as discussed in “Design Considerations.” Ray-trace modeling, 2D-acoustic modeling, and limited 3D modeling were carried out to establish some of the geophysical parameters and to understand the time and cost implications for the project, as summarized in “Acquisition Design Modeling.” The preliminary results in the PPT files and published articles referenced in this chapter provided a baseline for the initial test runs. The acquisition and simulation specifications changed over time as more details were developed by the technical committees, as more knowledge was gained about the capabilities and limitations of numerical modeling and data storage, and through discussions with the simulation vendor once they were under contract; finally, they were approved by the SEAM Management Committee. The final specifications, listed in Appendix B of Chapter 5, are somewhat different than those in the various PowerPoint presentations referenced in this chapter and the initial vendor contracts.
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.”