Research On Forward Modeling And Inversion Of3D Resistivity Method Based On Finite Volume Method

DC resistivity methods has increasingly become shallow hydrology, engineering, environment, archaeology and human social life,that is closely related to an important means of detecting areas. Geological targets were presented as three-dimensional electrical structure, if only1-D or2-D data inversion interpretation inevitably uneven nature of electricity will be3D effect. Therefore, it is necessary to study and explore3-D forward and inversion technology of DC resistivity methods.In this paper, the finite volume method was used to solve the forward problem of point sources3-D electric field. With this method not only the discrete technology of FDM is adopted, but also the flexibility of finite element grid is inherited. The primary advantages of this method are numerical robustness through its discrete principles, applicability on very general unstructured meshes, and the intrinsic local conservation properties of the resulting schemes. Using bi-conjugate gradient stabilized method algorithm with incomplete LU factorization to solve the system linear equation,that avoid direct interpretation problems, making resistivity3-D inversion is performed within the demand drastically reduced, and greatly improving the speed of processing for resistivity3-D inversion laid the foundation.3-D resistivity inversion, actually, is large-scale optimization problem, which costs a lot of computation and memory storage, it will encounter many uncertainties. In this paper, the Gauss-Newton method was used to solve the3-D resistivity inversion problem. In the process of iteration, we don’t need to calculate the Jacobian matrix J directly, this approach improves the speed of inversion and reduces the memory storage. Choosing a fixed value for the regularization parameter, so that it reduces the computation greatly, but also can get better results. Some models have been computed by the3D inversion software, and the result could reflect the condition of the anomalous bodies. It indicated that the inversion result is reliable.