三维任意各向异性介质中海洋可控源电磁法正演研究

由于海底介质受沉积环境的影响,层理发育呈现明显各向异性特征.对于海洋可控源电磁法各向异性的研究以往主要局限于一维和二维模型,为更深入了解复杂情况下海底各向异性对海洋可控源电磁响应的影响规律,本文开展三维任意各向异性介质中海洋可控源电磁法正演研究.采用交错网格有限差分技术,通过对任意各向异性介质电导率张量实行体积和空间电流密度平均,完成海洋可控源电磁二次散射电场的离散化,成功实现任意各向异性介质中海洋可控源电磁正演模拟.通过对几种典型各向异性电性模型条件下海洋电磁电场多分量响应及分布特征和各向同性情况的对比分析,总结电各向异性对海洋电磁响应的影响规律和识别方法.本文算法研究及算例可为海洋可控源电磁数据精细化处理解释提供技术支撑.

MCSEM 3D modeling for arbitrarily anisotropic media

Due to excellent sedimentary environment in the ocean, strong layering and stratificationscan be developed under the ocean, resulting in distinct electrical anisotropy. Traditional research on MCSEM anisotropic effects has been focused on 1D and 2D models. To deeply understand the influence of the electrical anisotropy on MCSEM responses, we study in this paper 3D marine CSEM modeling for an arbitrarily anisotropic earth. We utilize the staggered finite-difference algorithm, combined with volume average and volume current average method for handling the conductivity tensor elements, accomplish successfully 3D MCSEM modeling for an arbitrarily anisotropic earth. Through analyses and comparison of the MCSEM responses for isotropic and different anisotropic cases, we demonstrate the characteristics related to the influence of the electrical anisotropy on MCSEM responses and identification technique from the MCSEM survey for the electrical anisotropy of the media under the ocean. The algorithm and results from the numerical experiments in this paper offer the technical support to the detailed interpretation of the MCSEM data.