The Marine Controlled Electromagnetic Source (MCSEM) is a geophysical method that has
been occupying its space in the oil industry as an indicator of the presence of hydrocarbons.
Because of this, it is necessary to improve it as an interpretation tool through research
related to modeling and inversion. In this aspect, the influence of bathymetry is one of the
points that needs attention, since the effect it causes in the MCSEM data can mask the
presence of resistive bodies that may be related to reservoirs or indicate false positives and
lead to misinterpretations. In this work, we used the 3D nodal finite element method to
model MCSEM responses in the presence of bathymetry. Finite element meshes were made
using Tetgen software and we chose two models of bathymetry. The first one describes an
elevation of the ocean floor and the another one represents a depression in it. We analyzed
the amplitude and phase of the electrical inline field for both models with and without
bathymetry and also analyzed the effect of the reservoir’s presence in these situations. We
also observe the influences for different frequencies. Another aspect that should be mentioned
is the MCSEM 3D response for situations without the air waves in the data, represented here
by models with 10 km of water depth. These models, by separating the influence of the air,
although unrealistic, give us a better dimension of the effects that we want to study.
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