可控源电磁法2.5维自适应有限元各向异性正反演

本文基于非结构化的三角单元网格的自适应有限元法进行各向异性介质的正演模拟，其优势在于对起伏地形和复杂地质构造的模拟，采用自适应策略的网格剖分在满足计算精度的前提下尽量减少了计算量；反演运用基于高斯牛顿法改进的Occam算法，在对初始条件要求不高的前提下能快速地搜索拉格朗日乘子、减少模型的搜索量。对一维VTI介质模型和经典二维各向异性海洋油气藏模型进行了正演计算，验证了程序的计算精度和效率；对海底起伏地形各向异性模型进行了反演计算，该算法能够比较准确地还原海底各向同性的围岩、基岩异常体的电阻率以及各向异性异常体的埋藏情况。最后对实测数据进行了反演，进一步验证了算法的可行性。

Modeling and inversion of the CSEM field in 2.5D anisotropic media with an adaptive finite element method

We conduct a forward calculation of anisotropic media with the adaptive finite element method based on unstructured triangular meshes.In the simulation of tough topography and complex geological structures, the adaptive mesh strategy can ensure not only computational efficiency but also computational accuracy.The improved Occam algorithm based on Gauss Newton method can find quickly and appropriately the Lagrange multiplier under the condition of little dependence on the initial conditions.The forward modelings of a 1D VTI model and a classical 2D anisotropic ocean reservoir model prove the computational accuracy and efficiency.For a complex 2D anisotropic seafloor model, the inversion algorithm shows resistivity and buried depth of surrounding rocks, bedrocks and anisotropic anomalous bodies.Finally, tests on measured data shows the feasibility of the proposed algorithm.