A Hybrid Grid‐Based Finite‐Element Approach For 3D Steel Casing Forward Modeling

Abstract

Steel casing forward modeling often requires considering the slender casing in the study area to study the influence of this casing on the underground electromagnetic field, which can be implemented by the unstructured finite-element (FE) method based on tetrahedra. However, the calculation efficiency of applying the unstructured FE method directly to the steel casing model is poor. To this end, this article develops an FE approach based on a hybrid grid by using slender prismatic elements to mesh the steel casing area, while the remaining areas are still discretely meshed with tetrahedra. By showing numerical examples of the vertical single steel casing and L-shaped steel casing models, the advantages of the method are tested by evaluating the response curves and the degrees of freedom. The results show that prismatic elements are suitable for discretizing steel casing areas. This approach can maintain the high accuracy of the numerical solution and reduce the number of elements required for discretizing the steel casing area. Hybrid grids can greatly increase the computational efficiency of the FE method for steel casing forward modeling.