Linear and non-linear approximations based integral equation method in marine EM field modeling

Electromagnetic induction (EMI) methods have an important role in modeling hydrocarbon reservoirs embedded in marine sediments. One of these methods is marine control source electromagnetic (MCSEM) technique. In comparison with other geophysical techniques like seismic methods, which model hydrocarbon reservoir with high accuracy, The MCSEM technique is comparatively less accurate but due to much less costs, this method may be recommended for modeling hydrocarbon reservoirs embedded in marine sediments. In addition, the sea water reduces the voltage resulting from magnetotelluric (MT) currents, thus the MT method is not efficient, and is not suitable for imaging marine hydrocarbon reservoirs. Hence, the MCSEM method is used for these reservoirs. In this research, for threedimensional (3D) forward modeling of a hydrocarbon reservoir with regular and irregular geometrical shape, and also, for four-dimensional (4D) forward modeling of a regular geometrical reservoir, integral equation (IE) method is used. The aim of the present study is to develop and apply several approximations to simulate the electromagnetic problems and to solve integral equation for 3D MCSEM synthetic data in order to avoid solving full integral equations, and also, to decrease the computational costs. In order to monitor small changes in electrical conductivity among increasing pressure inside the reservoir, the capability of time-lapse CSEM data has been discussed. It has been found that this method can detect the changes in the reservoir due to the fluid injection. In this study, T-matrix approximation (TMA), born approximation (BA) and extended born approximation (EBA) are applied to approximate 3-4D integral equations in the MCSEM method at low frequencies.