Abstract:In middle and deep subsurface layers, complex wavefield, low fold, low S/N, and weak reflection may cause poor accuracy of velocity model building, thereby affecting depth migration quality. We propose in this paper a new tomography velocity model building method for middle and deep structure. Using angle domain common imaging gathers (ADCIGs) in velocity analysis, we deduce tomography model building equations based on residual curvature, and back project the residual curvature of ADCIGs along ray paths to get velocity update. This method avoids both difficult event picking from low S/N prestack data in conventional reflection tomography and ray tracing to fit source and receiver coordinates. So it can obtain high inversion accuracy. Model and real dataset test results verify the correctness and validity of the proposed tomography method.
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