HR: 0800h
AN: GP41B-0880    [Abstracts]
TI: An Adaptive Finite Element Algorithm For 2-D Marine Controlled-Source Electromagnetic Modeling
AU: * Li, Y
EM: yuguo@ucsd.edu
AF: Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093 United States
AB: We develop an adaptive finite element algorithm for forward modeling of the frequency domain, marine controlled-source electromagnetic (CSEM) response over a two-dimensional (2D) conductivity structure excited by a horizontal electric dipole source. We transform the governing equations for the secondary electromagnetic fields into the wavenumber domain. A coupled system of two partial differential equations results for the strike-parallel components of electric and magnetic fields. They are numerically solved by the finite element method. The system of linear FE equations is solved using a matrix-free iterative approach based on the quasi-minimal residual (QMR) method. This approach requires only the product of the system matrix with a vector, but not explicit storage of the matrix itself. Hence our algorithm requires less memory storage. We use an unstructured triangular FE mesh which readily allows complex 2D bathymetry and other seabed features to be included in the model. An adaptive mesh refinement scheme based on an a posteriori error estimator has been implemented to improve efficiency and accuracy of numerical simulation. Our algorithm has been validated by comparisons with both a 1D analytical solution and a fully 3D finite difference solution. We compare the responses of 1D, 2D and 3D versions of a canonical oil field model to illustrate how dimensionality effects the CSEM responses. We also present a 2D model study for the oil field model that shows the complicating effects of seafloor bathymetry and diffusion through air.
DE: 0619 Electromagnetic theory
DE: 0644 Numerical methods
DE: 3006 Marine electromagnetics
DE: 3225 Numerical approximations and analysis (4260)
DE: 4255 Numerical modeling (0545, 0560)
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005