3D simulation of transient electromagnetic field for geosteering horizontal wells

The article discusses numerical simulation of the transient electromagnetic field. The field source is an induction coil. We consider the situation when a logging tool is in a horizontal well in a medium with horizontal and vertical boundaries. The specific features of this problem are the metallic mandrel of the tool, 3D geometry, and distant boundaries. The method of separate computation of normal and anomalous fields is proposed. The finite element method is used for spatial approximation of the field, and the implicit finite-difference scheme is used for approximation of the field in time. Correctness and advantages of the method are shown. Some numerical results are demonstrated. The method proposed can be used when designing tools for geosteering.