Comparison of structured and unstructured grids in marine controlled source electromagnetic inversions for offshore hydrocarbon exploration

The grid chosen for marine controlled-source electromagnetic forward modeling and inversion is important because it affects the accuracy and efficiency of the latter. Providing these kinds of results is particularly difficult for offshore exploration. In this study, we compared a structured and unstructured grid using three models. Complex geometry, accuracy, and convergence central processing unit (CPU) time were considered to compare the different grids based on the inversion results. These showed that the structured grid provided an accurate resistivity model and a complex geometry model no worse than the unstructured grid. Furthermore, if the number of the iterations was the same CPU calculations took less time using the structured grid. Sometimes, the structured grid sometimes needed more iterations than the unstructured grid, but the CPU time costs still less than the unstructured grid. These results show that the structured grid is a better choice to invert marine controlled source electromagnetic data for offshore exploration.