Research on two-dimensional inversion method of transient electromagnetic in whole-space based on particle swarm

In order to improve the detection accuracy, provide effective targets for drilling and provide reliable geological information for mine water damage prevention and control, a two-dimensional inversion method of transient electromagnetism in whole-space based on particle swarm is proposed for the complexity of actual mining conditions in coal mines. By establishing a Q-type geoelectric model and carrying out a two-dimensional forward simulation based on finite difference in the time domain, the magnetic field intensity values at each grid node at different times are obtained. The extracted magnetic field intensity values obtained from the forward simulation and the magnetic field intensity values from the measured data are inverted by the least squares method. The particle swarm algorithm is used to optimize the resistivity and formation thickness parameters, so that the fitting error of the inversion results meets the accuracy requirements. According to the measurement point number, the magnetic field intensity values after the least square inversion are calculated by the two-dimensional inversion method of transient electromagnetism in whole-space. Moreover, the transient electromagnetic field response law and inversion accuracy obtained after the two-dimensional inversion are analyzed. The practical application results show that the two-dimensional inversion method of transient electromagnetism in whole-space based on particle swarm is feasible. The low-resistance anomaly in the inversion result has layered characteristics and certain connectivity, which can better reflect the lithological structure characteristics and water-bearing characteristics of the layered formation that dominated by sand and mudstone and improve the detection accuracy and resolution.