Surface-related multiple wave imaging of marine Walkaway VSP data

Abstract

Walkaway VSP and 3D VSP are usually utilizing the upgoing reflected p-wave imaging to solve the geological tasks such as borehole side structure and reservoir research. The surface-related multiples are usually attenuated as the interference wave. Compared with the upgoing reflection, the surface-related multiple is featured with legibility, wide illumination, small angle of reflection, and long propagation path. Based on the Walkaway VSP data from a well on the sea, we research the pre-stack depth migration imaging of surface-related multiple, with major technical thread as follows. Firstly, arrange the Walkaway VSP data of Z component into a common receiver point gather. Secondly, extrapolate the source wavelet from the receiver point to the free surface using ω − x field explicit one-way wave operator according to the reciprocity principle of shot-point and receiver-point. Thirdly, extrapolate the common receiver point wave field and source wave field respectively from the free surface, using the related imaging conditions to extract the imaging value, to realize pre-stack depth migration. The test via model and example showed that the proposed method realize accurate imaging.