A Walkaway Vertical Seismic Profiling Modeling and Imaging Study and Combining Its Results with Migrated Surface Seismic Images

This paper presents and analyzes results from a Finite Difference Modeling (FDM), processing, and imaging study of a Walkaway Vertical Seismic Profiling (WVSP) survey, and discusses how the images from WVSP enhance those from the surface seismic data. It is shown that the results from the WVSP integrate well with the image from the surface seismic performed in the same line. For the study, a seismic model with vertically and horizontally varying velocities was built and a WVSP data set was generated. The surface seismic had difficulty showing clear images from the layers with steep dips and near vertical displacements on the model due to the lack of ray coverage. The study demonstrates that the WVSP geometry can record reflections from near vertical layers facing the borehole, which help with imaging the parts of the subsurface structure which were missing in the surface seismic. With the proper combination of the images from the WVSP and the surface seismic, a more complete image profile of the subsurface can be constructed around the borehole. However, while contributing to surface seismic, it is also seen that the WVSP introduces more migration artifacts related to source interval distance and interbed multiples than the surface seismic data.