Paper Summary
In recent years, marine controlled source electromagnetics (CSEM) has found increasing use in hydrocarbon exploration due to its ability to detect thin resistive zones beneath the seafloor. It is the purpose of this paper to evaluate the effect of an electrically-thin ocean on the physics of CSEM using the towed streamer in-line configuration through examination of the electric field and the time-averaged energy flow depicted by the real part of the complex Poynting vector, and for an isotropic and transversely anisotropic sedimentary sequence. The observable electric field following excitation by a horizontal electric dipole (HED) source can be understood through the energy flow within the entire structure caused by the competing influences of guided energy flow in the reservoir layer and the air interaction. The influence of transverse anisotropy in a sedimentary sequence is to enhance the effect of guided energy flow as compared to an isotropic structure, yielding a response that is analogous to that in deeper water for an isotropic medium.