2.5D self-potential forward modeling by natural-infinite element coupling method

The self-potential method is an effective method for time-lapse monitoring of underground fluxes, in particular of contaminants. High efficiency and precise forward modeling are necessary for data interpretation and inversion. The natural element method is a new meshless numerical modeling method based on Voronoi diagram, Delaunay triangulation, and natural neighborhood interpolation, where the model nodes are arranged flexibly without grid constraints. However, adding boundary conditions is cumbersome for multi-source models. The infinite element method is an effective numerical method for truncated boundary problems without loading boundary conditions. A new numerical modeling approach is proposed by the coupling of natural elements and infinite elements and applied to redox self-potential models which are multi-source models. The numerical result shows the global stiffness matrix of the new coupled method is sparse, symmetric and independent of the position of field sources, which is helpful to improve forward modeling efficiency. The new method has high precision and is suitable for multi-source models.