Three-dimensional modelling of controlled source electro-magnetic surveys using non-conforming finite element methods

ELÍAS, MATÍAS W; ZYSERMAN, FABIO I; ROSAS-CARBAJAL, MARINA; MANASSERO, MARÍA CONSTANZA

GEOPHYSICAL JOURNAL INTERNATIONAL

WILEY-BLACKWELL PUBLISHING, INC

Año: 2022 vol. 229 p. 1133 - 1151

0956-540X

The controlled source electro-magnetic (CSEM) method is increasingly used for in-land andoff-shore subsurface characterization. Given its complex dependence between data and theparameters of interest, there is a crucial need for performant numerical algorithms that cansimulate the CSEM response of 3-D geological structures. Here, we present two finite element(FE) algorithms for simulating the CSEM response in 3-D media with isotropic conductivity.A primary/secondary field approach is used to avoid the singularity introduced by the source.The primary field is computed semi-analytically for a horizontally layered model and differ-ent sources. The secondary field is obtained by discretizing the diffusive frequency-domainMaxwell?s equations with non-conforming FE. The two numerical algorithms are specificallydesigned to work on distributed-memory computers: (1) an iterative procedure with domaindecomposition and (2) a direct and global algorithm. We evaluate their performance by com-puting their speed up on parallel processors, and solving problems with realistic conductivitystructures. We also compare the accuracy of the solutions with published results on canoni-cal models. The results shown here demonstrate the functionality of the two methodologiespresented for specific cases when computing 3-D CSEM solutions.