3-D Marine Controlled-Source Electromagnetic Modeling in Electrically Anisotropic Formations Using Scattered Scalar–Vector Potentials

Abstract

Marine controlled-source electromagnetic (CSEM) method has become a popular technique for offshore hydrocarbon exploration. It has been well recognized that marine CSEM data are strongly affected by electrical anisotropy of geologic formations in practice. Here, we present a robust and efficient finite volume algorithm for simulating marine CSEM responses in 3-D arbitrarily anisotropic formations. The algorithm is based on scattered scalar–vector potentials which improve the ill-conditioning of the resulting linear system by deflating the null space of the curl operator, and a conservative volume averaging scheme is utilized for the discretization of arbitrary electrical anisotropy. The accuracy of our algorithm is validated against quasi-analytic solutions for a layered vertical transverse isotropic reservoir model. It is then demonstrated by numerical results that the marine CSEM fields are significantly affected by the anisotropic conductivity tensor, and neglect of the full anisotropy of geologic formations may cause misleading data interpretation.