Anisotropic three-dimensional inversion of CSEM data using finite-element techniques on unstructured grids
Anisotropic three-dimensional inversion of CSEM data using finite-element techniques on unstructured grids
复制标题
DOI：
10.1093/gji/ggy029
复制
发表时间：
2018-05
影响因子：
2.8
通讯作者：
Feiyan Wang;J. P. Morten;K. Spitzer
中科院分区：
文献类型：
--
作者：
Feiyan Wang;J. P. Morten;K. Spitzer
在本文中，我们提出了一个最近开发的各向异性三维反演框架解释可控源电磁（CSEM）数据在频率域。该框架集成了高阶有限元正演算子和高斯-牛顿反演算法。使用参数变换应用电导率约束。我们在非结构网格上离散连续的正问题和反问题，以灵活处理任意复杂的几何形状。此外，一个非结构化的网格是更可取的相比，一个单一的直线网格的多尺度问题，因为局部网格细化不会显着影响感兴趣的区域以外的网格密度。非均匀的空间离散化有助于在合适的尺度上对反演域进行参数化。为了快速模拟多源EM数据，我们选择使用并行直接求解器。我们进一步加快反演过程中分解的整个数据集到子集的频率（和发射机，如果内存需求是负担得起的）。与每个数据子集相关联的计算任务被分布到不同的进程并并行运行。我们验证了该方案使用合成海洋CSEM模型与粗糙测深，最后，将其应用到一个工业规模的3-D数据集，从巨魔油田石油省在2008年获得的北海检查其鲁棒性和实用性。
In this paper, we present a recently developed anisotropic 3-D inversion framework for interpreting controlled-source electromagnetic (CSEM) data in the frequency domain. The framework integrates a high-order finite-element forward operator and a Gauss–Newton inversion algorithm. Conductivity constraints are applied using a parameter transformation. We discretize the continuous forward and inverse problems on unstructured grids for a flexible treatment of arbitrarily complex geometries. Moreover, an unstructured mesh is more desirable in comparison to a single rectilinear mesh for multisource problems because local grid refinement will not significantly influence the mesh density outside the region of interest. The non-uniform spatial discretization facilitates parametrization of the inversion domain at a suitable scale. For a rapid simulation of multisource EM data, we opt to use a parallel direct solver. We further accelerate the inversion process by decomposing the entire data set into subsets with respect to frequencies (and transmitters if memory requirement is affordable). The computational tasks associated with each data subset are distributed to different processes and run in parallel. We validate the scheme using a synthetic marine CSEM model with rough bathymetry, and finally, apply it to an industrial-size 3-D data set from the Troll field oil province in the North Sea acquired in 2008 to examine its robustness and practical applicability.