Enhancing VSP Imaging Quality by an Efficient Dip Filter Consistent with Velocity Model
M. Lou and H. Simpson
Event name: 81st EAGE Conference and Exhibition 2019
Session: Poster: Borehole Seismic Methods A
Publication date: 03 June 2019
Info: Extended abstract, PDF ( 1008.86Kb )
Price: € 20
VSP data usually provides a higher resolution seismic image than surface seismic data, but its imaging result often suffers severe migration artifacts due to the fact that there are fewer, and vertically-fixed, borehole receivers and therefore low and uneven CDP folds in VSP survey. A common method to suppress VSP migration artifacts is to reduce migration aperture to a small angle. However, a small aperture angle can fail to image significantly dipping structures. Here, we develop an efficient dip filter consistent with the local velocity model in VSP migration, which preserves true dip structures and in the meantime suppresses migration artifacts. The dip filter consists of two major parts: (1) we first efficiently calculate the wave propagation angles from both source and receiver positions to each image point based on a travel time table computed by an Eikonal solver in conventional Kirchhoff migration, and (2) we then accordingly perform the dip filtering for each image point based on the possible dip angles defined by the bisects of the source and receiver propagation angles to the image point. Both synthetic and field VSP data demonstrate that the dip filter consistent with the local velocity model effectively enhances VSP imaging quality.