Study On Forward And Inverse Methods For Marine Controlled-Source Electromagnetic Exploration

With China’s marine exploration technology advancing rapidly,previously unknown areas of the ocean are being discovered and yielding vast amounts of energy and resources.As a result,the world’s focus on energy and resource competition has shifted from land to sea.The Marine Controlled-Source Electromagnetic Methods(MCSEM)have proven to be highly effective in detecting energy and resources on the seabed,both theoretically and practically.The significance of this discovery cannot be overstated,as it has enormous implications for marine energy and resource exploration.In this paper,the MCSEM method,its principles,detection devices,and the electrical characteristics of the ocean are reviewed briefly.The optimization parameters and devices of the MCSEM method,as well as the depth of the detection target,are discussed in detail.The paper then presents an approach based on a three-dimensional staggered grid finite difference method to discretize Maxwell’s equations,which are used to derive iterative relations for the forward modelling of the response of MCSEM in the time domain.The numerical stability and boundary conditions of the finite difference method are also analyzed.Finally,the paper presents three models designed to represent different types of detection targets in the shallow,medium,and deep seabed: a metal sulfide model,a combustible ice model,and a deep oil reservoir model.These models are used to evaluate the optimization parameters and detection effects of MCSEM for detecting different targets.Overall,this paper provides valuable insights into the MCSEM method and its potential for detecting energy and resources in the ocean.This paper presents an in-depth analysis of the MCSEM method for detecting seafloor resources.And includes a testing phase where the electric field response intensity obtained by the MCSEM method is compared and analyzed for changes in target body thickness,burial depth,and other conditions,using previously designed models of metal sulfide,combustible ice,and oil reservoir seafloor resources.These tests provide a theoretical basis for practical exploration.In addition,the paper evaluates the inversion algorithm by discussing the degree of matching between the resistivity inversion distribution and the model results of high-resistivity and low resistivity anomalies models in the marine environment.The inversion algorithm is based on the regularization constraint in the time domain,and the results show that the regularization inversion method implemented in the paper can accurately obtain the shape and location of the anomalies.Overall,this paper provides valuable insights into the MCSEM method and its applicability for the detection of seafloor resources,paving the way for further research and practical exploration in this field.