榆林地区浅埋煤层采空区电法综合勘探技术

为探明榆林地区浅埋煤层不明采空区,分析了其浅埋煤岩层垂向、横向正常电性特征以及存在采空区时的异常电性差异特征,从而确定榆林地区具备使用瞬变电磁法和高密度电法探测采空区的电性基础。然后开展了瞬变电磁法和高密度电阻率法探测的施工参数试验,建立相应的施工技术体系,实现了榆林地区浅埋煤层采空区的有效综合勘探。结果表明:(1)榆林地区正常地层垂向电性呈稳定的"低阻-高阻-低阻"趋势特征,而当煤层中存在地质异常体时,横向差异明显,出现不连续的高阻或低阻特征;(2)瞬变电磁法采用240 m×240 m发射线框、14 A发射电流、25 Hz发射频率、2048次叠加次数,高密度电阻率法采用20 m接收极距,这些施工参数可以满足榆林地区浅埋煤层采空区的电磁法探测要求;(3)瞬变电磁法、高密度电阻率法探测的异常区范围基本一致,在两种方法重合异常区打钻揭露采空区,说明两种方法可互相补充、验证,为应用于榆林地区煤层采空区综合物探的合理手段。

Comprehensive exploration technology based on the electric methods for the goaf of the shallow coal seams in the Yulin area

The purpose of this work was to clarify the unknown goaf of shallow buried coal seams in the Yulin area. Analysis reveals normal features of electricity of shallow coal seams in the vertical and horizontal directions as well as abnormal electrical characteristics when existing the goaf. Thus it is determined that the transient electromagnetic and high-density electrical methods can be used to detect the goaf in this area. Then the parameter test for the two methods was conducted and a feasible work scheme was established. Finally a comprehensive survey was conduced in the goaf area of coal seams in Yulin. The results show that 1) the vertical electrical properties of the normal strata in the Yulin area exhibit a stable trend of low resistance-high resistance-low resistance. And when there are geological anomalies in the coal seam, the lateral difference is obvious with discontinuous high-resistance or low-resistance features. 2) The transient electromagnetic method adopts a 240m×240m transmitting wire frame, 14A transmitting current, 25Hz transmitting frequency, 2048 times of superposition; and the high-density resistivity method adopts 20m receiving pole distance. These work parameters can meet the requirements of electromagnetic detection to the shallow coal goaf in the Yulin area. 3) The ranges of abnormal areas detected by the transient electromagnetic and high-density resistivity methods are largely consistent, as evidenced by drilling verification at the overlapped places of the two methods, implying they can complement and verify each other and serve as a comprehensive geophysical survey in the coal goaf of the Yulin area.