井下地电阻率观测中地表电流干扰影响计算

Calculation for the influence from the surface disturbance current in the deep-well geoelectrical resistivity observation

本文把地电阻率台站地下介质简化为水平三层均匀介质模型,以点电流模拟地表干扰电流,针对对称四极观测装置,计算了在不同电性结构中的不同深度观测时,地表电流干扰源对对称四极装置地电阻率观测的影响,计算得到:地表干扰源对电阻率观测的影响取决于电性结构的类型和层参数、供电电极和测量电极的埋深以及避开干扰源的距离.本文研究结果对实施井下电阻率观测中台址电性结构的选择、电极埋深、干扰源避让距离等有参考意义.

The mediums below the geoelectrical resistivity station are simplified as a model of horizontally homogeneous 3-layer medium,and the disturbance current on the earth＇s surface is substituted with a point current source. Then, the influence quantity, for the geoelectrical resistivity measurement, which was caused by the disturbance current, was calculated for a symmetrical four-electrode resistivity observation configuration（a fixed quasi Schlumberger sounding array）when the configuration is set in the underground different depths of different geoelectrical structures,and we also calculate the influence quantity when the location of disturbance current was changed on surface. The calculated results suggested that the influence quantity caused by the disturbance current of the earth＇s surface is determined by the type of geoelectrical structure and its parameters, the buried depth of both current electrodes and measuring electrodes, the distance from these electrodes to the disturbance current. The calculated results could be used as a rderence for choosing a geoelectrical structure under stations, and can determine the buried depth of the electrodes and the distance off the disturbance current.