3D CSEM modeling and inversion for hydrocarbon reservoir mapping: The bathymetry problem

Abstract

The effects of bathymetry on controlled‐source electromagnetic (CSEM) responses cannot be neglected when aiming for reliable and accurate modeling and inversion results, owing to the high seawater conductivity, 3.3 S/m on average, and thus potentially high contrasts in the electrical properties between water and seabed. In the presented study, we further make use of the possibilities of the finite‐difference method to allow 3D inversions with a high degree of model discretizations in order to simulate a 3D seafloor surface. At the same time, we separate the computational mesh for the forward operator from the model discretization mesh, through usage of a proper conductivity‐averaging scheme, limiting the computational requirements. Reliability of the method is demonstrated through a modeling and an inversion study for a marine survey scenario.