Forward modeling of marine DC resistivity method for a layered anisotropic earth  

海洋直流电阻率法各向异性正演模拟研究（英文）

作　　者：殷长春[1] 张平[1] 蔡晶[1] 

机构地区：[1]吉林大学地球探测科学与技术学院,吉林长春130026

出　　处：《Applied Geophysics》2016年第2期279-287,417,共10页应用地球物理（英文版）

基　　金：financially supported by the National Hi-tech Research and Development Program of China(863 Program)(No.2012AA09A20103)

摘　　要：Since the ocean bottom is a sedimentary environment wherein stratification is well developed, the use of an anisotropic model is best for studying its geology. Beginning with Maxwell＇s equations for an anisotropic model, we introduce scalar potentials based on the divergence-free characteristic of the electric and magnetic （EM） fields. We then continue the EM fields down into the deep earth and upward into the seawater and couple them at the ocean bottom to the transmitting source. By studying both the DC apparent resistivity curves and their polar plots, we can resolve the anisotropy of the ocean bottom. Forward modeling of a high-resistivity thin layer in an anisotropic half-space demonstrates that the marine DC resistivity method in shallow water is very sensitive to the resistive reservoir but is not influenced by airwaves. As such, it is very suitable for oil and gas exploration in shallowwater areas but, to date, most modeling algorithms for studying marine DC resistivity are based on isotropic models. In this paper, we investigate one-dimensional anisotropic forward modeling for marine DC resistivity method, prove the algorithm to have high accuracy, and thus provide a theoretical basis for 2D and 3D forward modeling.受沉积环境影响,海底地层层理发育,各向异性介质更接近于真实海洋地质条件。对海洋各向异性研究可更好认识海底构造特征,有效地进行海底资源勘查。本文从各向异性麦克斯韦电磁方程出发,根据电磁场的无源特征引入标量位函数;利用电场和磁场的连续性分别向海底深部和海水中延拓,并将延拓后的电磁位函数在海底耦合到发射源上,从而实现海底电场和磁场的递推求解。我们首先探索如何利用海洋电阻率法识别和求解海底电各向异性特征。研究发现海底各向异性可从视电阻率测深曲线和海底视电阻率极性图进行求解。进而,我们通过海底各向异性地层中高阻体(油气藏)模型进行正演模拟,发现海洋电法视电阻率在浅水区对地下高阻薄层有明显的异常反应。相比海洋可控源电磁法,海洋直流电法不受空气波影响,在浅海区油气资源勘查有着较好的优势,而前人大多基于各向同性模型进行研究,本文实现一维海洋直流电阻率法各向异性正演模拟,算法计算精度高,能很好的为二维、三维正演模拟提供理论参考。

关 键 词：Electrical anisotropy Marine DC resistivity method Forward modeling Field continuation algorithm 

分 类 号：P631.322[天文地球—地质矿产勘探]