Computing dip-angle gathers using Poynting vector for elastic reverse time migration in 2D transversely isotropic media

Abstract

Angle-domain common-image gathers (ADCIGs) have wide applications in seismic imaging. For isotropic elastic reverse time migration (ERTM), we can produce dip-angle ADCIGs by using conventional Poynting vectors. Seismic anisotropy widely occurrs in Earth materials, such as in the shales and fractured reservoirs. ERTM based on the isotropic elastic wave equation is unable to accurately image anisotropic structures, leading to noise, discontinuous reflection events and mispositioning in migration results. Hence, conducting ERTM and generating dip-angle ADCIGs for anisotropic media require solving the anisotropic elastic wave equation. However, it is challenging to compute the gathers using the conventional Poynting vector for anisotropic elastic media. In this study, we derive the group and phase Poynting vectors, in which we use the optical flow method to stabilize the phase-related Poynting vectors. This approach admits efficient calculation of dip-angle ADCIG in anisotropic media. It also suppresses noise in anisotropic ERTM. The results of numerical experiments demonstrate the effectiveness of the proposed method.