任意方位电偶源的MCSEM电磁场三维正演  

3D marine controlled-source electromagnetic forward modeling with arbitrarily orientated dipole source

作　　者：严波 李予国[3] 韩波[3] 梅晓勇 贺少波 许思维 

机构地区：[1]长江大学油气资源与勘探技术教育部重点实验室,湖北武汉430100 [2]湖南文理学院国际学院,湖南常德415000 [3]中国海洋大学海底科学与探测技术教育部重点实验室,山东青岛266100

出　　处：《石油地球物理勘探》2017年第4期859-868,共10页Oil Geophysical Prospecting

基　　金：油气资源与勘探技术教育部重点实验室(长江大学)开放基金项目(2015-22);国家自然科学基金重点项目(41130420)和国家自然科学基金青年基金项目(41604063)联合资助

摘　　要：在海洋可控源电磁(MCSEM)勘探中,在深水中被拖曳的电偶源很容易受到洋流的影响而偏离预先设定的方位,从而对观测电磁场造成影响,因此有必要研发能够模拟符合实际情况的任意方位的电偶源MCSEM响应的数值计算方法。首先求出任意方位的发射源激发背景模型产生的一次电磁场,然后将一次电磁场作为三维异常体模型的新场源,再求出异常体引起的二次电磁场,实现了MCSEM的三维正演算法。该方法不仅可以提高发射源附近区域的数值解精度,还可以减少正演模拟网格的剖分数目,从而提高计算效率。采用直接法求解有限差分离散形成的大型线性方程组,不仅便于对多个发射源做并行计算,还可以避免迭代误差。与一维模型的解析解和前人三维模型的数值解对比验证了本文算法的正确性,并分析了电偶源的方位、长度对MCSEM三维数值模拟结果的影响。In practical marine controlled-source electromagnetic(CSEM)surveys,the electric dipole dragged in deep seawater is easily deviated from the preset position due to the influence of ocean currents,and impacts on electromagnetic data.Therefore we develop a numerical calculation method for arbitrarily orientated dipole source.First we calculate the primary electric field activated by arbitrarily orientated dipole source on the background model.Then taking this primary electric field as a new source for 3D target,we calculate the secondary electric field and achieve 3D CSEM forward modeling.This method can not only considerably improve the numerical solution accuracy in the vicinity of the source,but also improve calculation efficiency by reducing the grid number.The direct method used to solve the large linear equations formed by the finite-difference discrete is very appropriate for parallel processing for multi-dipole sources and avoids iteration errors.Comparing with analytical solutions of 1D model and conventional numerical solutions of 3D model,our tests prove the correctness of the proposed method.Furthermore we analyze dipole source position and length impacts on 3D marine CSEM numerical simulations.

关 键 词：海洋可控源电磁法 三维正演 有限差分 任意方位电偶源 直接法 

分 类 号：P631[天文地球—地质矿产勘探]