Normalized ElectroMagnetic Imaging (NEMI) for Controlled Source EM Evaluation of Hydrocarbon Prospects

Marine Controlled Source ElectroMagnetic (CSEM) surveying is a powerful tool for mapping offshore electrical resistivity structure and in recent years has been developed as a DHI tool. Geophysical inversion and forward modeling are currently the standard methods of CSEM data analysis. However, due to non-linearity of the problem, these methods are computationally time intensive. We present a technique for fast imaging of thin resistive layers within a conductive background that enables a ‘first look’ at full CSEM datasets before imaging. The non-linear properties of the electromagnetic fields are used to determine the existence and lateral extent of thin resistive layers that may be associated with hydrocarbon-bearing layers. We present the results of synthetic datasets that show the imaging algorithm is successful at identifying the existence and lateral extent of a hydrocarbon bearing layer.