Finite element modelling of marine controlled-source electromagnetic responses in two-dimensional dipping anisotropic conductivity structures

Abstract

We present an adaptive finite element (FE) solution for the marine controlled-source electromagnetic (CSEM) forward problem in 2-D dipping anisotropic conductivity structures. Our code is implemented on an unstructured triangular mesh, which allows for arbitrary model geometries including bathymetry and dipping layers. We have verified the FE code using a layered 1-D model with anisotropy. For this model, the FE algorithm provides accurate results. The relative amplitude error between the analytical solution and numerical results for all electromagnetic components except Hz for large offsets is less than 1 per cent and the error in phase is less than 0.5°. We simulate the marine CSEM responses of a 2-D anisotropic model, and the numerical results show that the CSEM fields are affected considerably by anisotropy in both the reservoir target and the surrounding sediment, but to different extent.