Research progress in three-dimensional forward modeling for transient electromagnetic method

Abstract The transient electromagnetic (TEM) method is a valuable tool for detecting the structure of underground geological targets. However, TEM survey environments are complex and varied, with significant variation in the electrical properties of underground layers and ore bodies, as well as rugged topography. This study comprehensively reviews the progress of 3D forward modeling methods for TEM, including integral equation, finite difference, finite volume, and finite element approaches. Key issues in 3D modeling for TEM are then explored, such as transmitting waveforms, grid generation, iterative schemes, air layer treatment, and boundary conditions. A comparative analysis of existing 3D forward modeling techniques was then conducted, focusing on grid generation, iterative schemes, and memory usage. It is further highlighted that the key to improving the efficiency of TEM simulation is to develop parallel computing and improve the solving speed of large equation systems. The key to improving computational accuracy is to optimize time discretization, grid generation schemes, and boundary conditions. Finally, the authors suggest that the future development direction of forward modeling should focus on simulating complex geological and anisotropic models.