Kirchhoff Prestack Depth Migration of 3D VSP Data in Offset and Angle Domains

Shallow unconsolidated sediments, irregular refractors, rapid surface elevation changes and hidden karsts are geologic features in the Middle East that can significantly degrade the quality of recorded seismic data. Accurate handling of these complexities is critical for seismic interpretation as low relief structures, stratigraphic traps and fractures have become important exploration targets. Vertical Seismic Profiling (VSP) not only generates higher fidelity data when compared with surface seismic surveys, but VSP data can also be analyzed for reservoir properties via imaging, modeling and inversion for various seismic attributes. This paper describes a Kirchhoff prestack depth migration (PSDM) technique for 3D VSP data to produce common image gathers (CIGs) in both offset and angle domains. The offset domain CIGs are for use in migration velocity analysis (MVA) and the angle domain CIGs (ADCIGs) are for use in modeling and elastic inversion for reservoir properties. This extended Kirchhoff PSDM technique was applied for both synthetic and real data examples and the initial results are promising.