Fast, accurate imaging of complex, oil-bearing geologies, such as overthrusts and salt domes, is the key to reducing the costs of domestic oil and gas exploration. Geophysicists say that the known oil reserves in the Gulf of Mexico could be significantly increased if accurate seismic imaging beneath salt domes was possible. A range of techniques exist for imaging these regions, but the highly accurate techniques involve the solution of the wave equation and are characterized by large data sets and large computational demands. Massively parallel computers can provide the computational power for these highly accurate imaging techniques.

The portable code, Salvo, performs wave-equation-based, 3D, prestack, depth imaging and currently runs on the Intel Paragon, the IBM SP2, the Cray T3D, and SGI Challenge and Origin 2000, using a massively parallel algorithm for frequency-space migration. It uses MPI for portability, and has sustained 22 Mflops/sec/proc (compiled FORTRAN) on the Intel Paragon. Salvo's capabilities include:

• Migrating 2D and 3D data
• Migrating Poststack and Prestack data
• Depth migration
• Filtering with Li or Graves & Clayton phase correction
• Implicit finite-difference migration
• Frequency and/or Spatial Parallelism
• Compute and I/O Partitions
• Parallel I/O
• Correlation, deconvolution imaging or derivative imaging
• Phase Encoding

Sandia National Laboratories and its partners propose to greatly reduce the time and cost required to perform 3D, finite difference, prestack depth migrations. General deliverables for the project are summarized below:

• High performance finite-difference algorithm that is scalable and portable;
• A scalable/portable seismic software development system including templates;
• Efficient parallel I/O and data management techniques for optimizing depth imaging performance and throughput.

Curtis C. Ober

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