A 3D finite-element modelling investigation into optimal survey parameters and direct imaging for marine controlled-source electromagnetic surveys

Relatively little is known about marine controlled-source electromagnetic surveys (MCSEM) used to detect hydrocarbon reservoirs. Typical MCSEM require the use of inversion to generate a model of the subsurface. We utilize a 3D finite-element forward model to simulate a MCSEM survey. With the results we were able to determine the strengths and weaknesses of each transmitter and receiver configuration that would best detect a shallow hydrocarbon target. Careful selection of the correct configuration is important as we have found that incorrect transmitter orientation, offset and receiver measurement component can yield misleading results. Using the ideal configuration we were able to directly image the hydrocarbon target without the use of inversion modeling. The direct image is able to show the hydrocarbon target's shape and edges without any ambiguity. The direct image of the target can potentially be used to refine 3D inversion modeling, or be used in conjunction with seismic profiles to refine seismic picks.