A successful strategy for parameterizing anisotropic depth imaging in a Saudi Arabian unconventional exploration area

Abstract

Summary We developed a methodology that resulted in significant enhancements in defining the subsurface geology, in a survey over an unconventional exploration area, with high anisotropy in Saudi Arabia. The methodology included (a) anisotropic model building using walkaway VSP, (b) formation-guided interpolation and extrapolation along interpreted horizons to create the full anisotropic volumes and (c) prestack Kirchhoff depth migration from topography. Approximately 400 km 2 of wide azimuth land seismic data located in Saudi Arabia were imaged in which the target is a shale formation. We observed large anisotropy (~50%) for the shale through isotropic prestack migrations with both the seismic and checkshot calibrated velocity models. Significant imaging improvements were achieved by processing the data with the anisotropic depth imaging workflow, using anisotropic models derived from the walkaway VSP. Also, the anisotropic models produced a seismic depth image that calibrated to the well depth with less than 1% depth error.