Research And Implementation Of Forward Modeling Of Marine Controlled-Source Electromagntic Method

Recently, the application of controlled-source electromagnetic method (CSEM) to seafloor detection has become the study hotspot overseas. CSEM has been used to study marine lithosphere, investigate seafloor sediments distribution and explore mine resource in seafloor. Among these applications,CSEM has shown great success in hydrocarbon exploration in deep sea environment. This paper use the horizontal electric dipole source for the emission, present the methods and principle of CSEM. Achieved the two-dimensional numerical simulation of forward model through adaptive finite element method. We establish some simple geological models to find out sever key factors which affect the results of CSEM.Through analysis we summarize the response rules. The main contents of this paper can be summarized as followings:1.According to Maxwell's equations, we obtained the analytical solution of air, sea and underwater formation of three different media. Come to any point in the seabed at frequency domain electromagnetic field equation. According to the electromagnetic field formula, simulate models'electromagnetic response.2. Improved MARE2DCSEM software program and ported it to windows system, developed forward finite element 2D electromagnetic simulation software.3. By numerical modeling, we obtained the major factors which affect the results of marine controlled-source electromagnetic are seawater depth, seabed resistivity, format- ion thickness, seafloor topography, and transmitter-receiver geometry and transmission frequencies. The relationship between those factors and Response curve is showed as fallows: Marine CSEM exploration has well effects in the deep sea; The response curve amplitude increases as formation resistivity and thickness increaseing;Compare with broadside geometry, Inline geometry has well effect; emission frequency is generally used in 0.01 Hz ~10 Hz .4 Construction of two typical reservoir (anticlines and fault) and numerical simulation, analysis the response curve of each component. Model results show The results show that the marine CSEM method can distinguish between the existence of oil and gas. But it can not determine the size and number of oil and gas location and other information by simply normalized curves.It requires to do electromagnetic data processing.5. This paper first use of a certain area of WC-15 region to establish the true stratigraphic section that corresponds with the actual model, model results show that marine CSEM method requires a combination of integrated geological and seismic data. In this way ,it will provide more useful informations.