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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。
Affected by the sedimentary environment, the stratification of the sea floor is developed, and the anisotropic medium is closer to the real marine geological conditions. Research on ocean anisotropy can better understand the structural features of the seafloor and effectively carry out seafloor resource exploration. Based on the anisotropic Maxwell electromagnetic equation, this paper introduces the scalar function according to the passive characteristics of the electromagnetic field. The continuity of the electric field and the magnetic field respectively extends to the seafloor and deep sea. The extended electromagnetic potential function is coupled to the sea floor Emission source, so as to realize the recursion solution of the seafloor electric field and the magnetic field. We first explore how to use the marine resistivity method to identify and solve the anisotropy of the seafloor. The study found that the anisotropy of seabed can be solved from the apparent resistivity sounding curve and the sea bottom apparent resistivity polar diagram. Furthermore, through the forward modeling of the high resistivity (reservoir) model in the anisotropic submarine formation, we found that the apparent resistivity of the marine electrical method has obvious anomalous response to the high resistivity thin layer in the shallow water area. Compared with the ocean controlled electromagnetic method, the marine direct current method is not influenced by the air wave, and has a good advantage in the exploration of oil and gas resources in the shallow sea area. However, most predecessors have done research based on the isotropic model. In this paper, one-dimensional oceanic DC resistivity Anisotropy forward modeling method, the algorithm has high computational accuracy, which can provide theoretical reference for 2D and 3D forward modeling.