Utilizing 3-D wave-equation migration for seismic imaging is a new approach that has shown great promise imaging the complex deep Gulf of Mexico structures.

Previously, only Kirchhoff methods could be used to generate common-reflection point (CRP)

Comparison of standard Kirchhoff depth migration (top) versus wave-equation depth migration. In the standard depth migration, the sediments under the salt body are not imaged correctly by Kirchhoff migration due to multipathing. In the bottom image, the wave-equation depth migration focuses accurately the multiple arrivals under the salt. (Images courtesy of 3DGeo)
gathers in offset domain and iteratively improve the velocity model used for imaging. Recent research has established a new approach to generate angle-domain common image gathers directly from 3-D wave-equation methods. The angle-gathers can be used to update the initial velocity model, and they form the basis for a novel method of 3-D migration velocity analysis.

This technology can be used for oil and gas exploration in deep, complex structures more than 15,000 ft (4,573 m) where conventional single traveltime arrival Kirchhoff imaging (shown on the top) fails to provide an accurate structural image. Wave-equation imaging (shown on the bottom) provides much higher structural resolution and amplitude fidelity. This in turn allows the geophysicist to obtain higher-resolution petrophysical information, linking the accurate seismic amplitude to reservoir properties like porosity, sand/shale content, water/oil saturation, compressional and shear velocity ratio, etc.

3DGeo has been one of the pioneers in researching common image angle gathers technology and holds the patent (US6546339) for using the moveout of the angle gathers for computing the velocity update. The current work is focused on wave-equation ultradeep illumination and accurate amplitudes in conjunction with wave-equation imaging and velocity model building. A project sponsored by the US Department of Energy developed, tested and prepared for commercialization a novel, next-generation technology designed to enhance seismic resolution and imaging of ultradeep complex geologic structures by using wave-equation depth migration and wave-equation velocity model building technology for deeper data penetration and recovery and steeper dip and ultradeep structure imaging along with accurate velocity estimation for imaging, pore pressure prediction, and accurate illumination and amplitude processing for extending the amplitude vs. offset prediction window. The advanced imaging methodology may improve the success rate and cost-effectiveness for new deepfield discoveries, and it also has applications in increasing recovery efficiency for the development of existing fields.

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