基于非结构化有限元海洋可控源电磁法2.5维各向异性反演

2.5D Anisotropic Inversion of Marine CSEM Data Based on Unstructured Finite Element Method

目前海洋可控源电磁法(CSEM)数据的反演解释大多是基于海底地层为规则且各向同性的情况,反演的效果往往不能真实反映海底地层的电性分布,为油气储层的辨别带来较大的偏差。针对这一问题,利用非结构有限元方法实现了2.5维电阻率各向异性介质海洋可控源的电磁响应反演。文中采用非结构化网格对模型计算域进行剖分可以模拟海底起伏地形和非规则异常体;同时针对海洋可控源电磁多频点、多场源的特点,采用MPI并行技术加速反演,极大地提高了反演计算效率。理论模型反演测试表明算法的可靠性和稳定性。通过复杂各向异性模型,讨论了起伏地形下海洋可控源电磁2.5维各向异性的反演规律,为准确解释CSEM实际数据提供理论依据和指导。

Currently, the inversion of marine controlled-source electromagnetic(CSEM) data is mostly based on the regular and isotropic earth media, and it often cannot reflect the underground electrical distribution, which results in a large deviation for the oil and gas reservoir identification. Aiming at this problem, we realize the marine CSEM 2.5 D anisotropy inversion based on unstructured finite element method. In order to simulate the seabed topography and irregular anomalies, the computational domain is divided into unstructured grids. Considering the multi-frequency and multi-field sources characteristics of marine CSEM data, this paper adopts MPI parallel technology to accelerate and improve the efficiency of the inversion. We validate the accuracy and effectiveness of our algorithm by a theoretical model. Then through tests from synthetic models, we analysis the 2.5 D anisotropic inversion of marine CSEM data under undulating terrain, providing theoretical basis and guidance for the accurate interpretation of the real CSEM data.