Sensitivity analysis of marine Controlled-Source Electromagnetic data

Electromagnetic sounding methods represent one of the few geophysical techniques that can provide information about the state and the properties of deep continental crust and upper mantle. In particular, marine Controlled-Source Electromagnetic (mCSEM) method is being applied to offshore hydrocarbon exploration and providing encouraging results, as it can complement the information obtained from seismic elaborations, mainly the position of the elastic discontinuities, with a map of electrical conductivity, the principal "discriminator" between conductive water-bearing rocks and non-conductive hydrocarbon accumulations. The processing of mCSEM data can be problematic due to the non-uniqueness of the solution, the environmental and equipment noise, and the high computational power required when dealing with 3D inversion. This paper proposes a simplified procedure to study and rank the sensitivity of mCSEM in a canonical 1D scenario, with a single resistive anomaly embedded in a homogeneous background. We analyze the sensitivity of the data with respect to the most important test parameters, namely the frequency, target depth, thickness, and resistivity. In addition, this procedure is also utilized to validate the so-called T-equivalence theorem. The results of this study could assist the interpreter to highlight the reliability of the inverted parameters in a complex inversion environment.