Anisotropic Full Waveform Inversion of Walkaway VSP data from the Arabian Gulf

Full waveform inversion (FWI) is a powerful technology for the estimation of subsurface elastic parameters. Recently, an elastic FWI method was applied to a Walkaway VSP dataset that was extracted from a larger 3D VSP survey located in the Arabia Gulf, offshore Saudi Arabia. This work is part of a larger feasibility study to detect and map very thin sand stringers located in a sand-shale geologic environment where the P impedance contrasts are low. The ultimate objective of this study is to derive high resolution P, PS and Vp/Vs images from the larger 3D VSP survey for the placement of horizontal wells. This paper presents interim results from this feasibility study using only frequencies up to 40 Hz for the FWI. We will discuss the results of using a vertically transverse isotropic (VTI) anisotropic elastic model of the Earth that reproduces the data fairly well, and is geologically consistent when compared to other independent measurements, such as sonic logs.