3D OBC PP/PS prestack depth migration

Accurate PP/PS depth imaging at the reservoir level

Presented at EAGE 68th Conference & Exhibition in Vienna, Austria, 12 - 15 June 2006, this talk outlined a workflow for advanced anisotropic modeling and depth imaging of an OBC PP/PS seismic survey.

Ocean-bottom cable (OBC) methods record both compressional (PP) and converted shear-wave (PS) data. PS data have successfully been used to image through gas clouds (Xiang-Yang Li et al., 2001) and image reflectors that are weak on PP data ( MacLeod et al., 1999), and can help constrain rock property estimates (Özdemir et al., 2001). Thus, in principle, the use of PS data can significantly mitigate risk in hydrocarbon exploration and production. However, imaging of PS data relies upon accurate compressional and shear velocity estimates, as both the moveout and offset of the imaged point depend upon these parameters.

Velocity anisotropy is also a critical factor. Previously used processing flows have not adequately comprehended this, and the results have often been of poor quality and difficult to tie with the PP volumes. This can preclude their use for lithology prediction. WesternGeco has implemented an imaging workflow that can resolve many of these issues.

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