Three-dimensional finite difference time domain simulation for down-hole transient electromagnetic method
XU Xin-Gang1, XU Zheng-Yu2
1. School of Resources and Geosciences, China University of Mining & Technology,Xuzhou 221116,China;; 2. School of Nuclear Engineering and Geophysics, East China Institute of Technology, Nanchang 330013,China
Abstract：As one of the effective methods used in geological prospecting, the down-hole transient electromagnetic method is a geophysical survey method in search for mineral resources, which measures the transient electromagnetic field in a borehole by placing the receiving coils in the borehole. In this paper, based on time domain finite difference algorithm, the authors used a loop source and non-uniform gird, developed a 3D simulation program, and simulated the response of the uniform medium half space, inclined conductor, and inclined conductor with overburden. According to the comparative analysis, the maximum value of response decreases with delay time in uniform half space; in the early period of transient electromagnetic survey, it mainly reflects the response of the surrounding rock; in the late period, abnormal response of the conductor can be obviously displayed. When the source is in the central position, the abnormal response conductor can be reflected, and when the source is in the right position, the need to extend the observation time can be observed in response to abnormal conductor. The impact on overburden conductor is reflected in the entire observation time, making the abnormal response of the conductor ambiguously displayed. The authors studied the work and provide the reference for the down-hole TEM abnormal response characteristics and data interpretation.
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