深井低阻体电性源短偏移距瞬变电磁探测技术研究

Study on short offset transient electromagnetic detection technology for low-resistance electrical sources in deep mine

煤矿深部开采是一种趋势,但是相随的复杂水害问题给安全造成了巨大威胁,煤层顶板以上巨厚砾岩层中的含水层表现为浅薄深厚、发育不规则的特性,常规地面瞬变电磁探测深度不够,深部探测体积效应大,低阻屏蔽效应明显。为保障深部煤层安全回采,高精度、高分辨率的探测煤层顶板以上巨厚砾岩层的富水性及富水范围,基于电性源短偏移距瞬变电磁法的相关理论,分析了电性源短偏移距瞬变电磁探测技术的垂直磁场强度、视电阻率值及探测深度计算表达式,研究总结了现场类地震的一发多收探测方法,探讨了基于改进阻尼因子的最小二乘法反演方法,在华北某矿区深部巨厚砾岩层富水性探测中应用。研究结果表明:电性源短偏移距瞬变电磁探测技术增大了探测深度,实现了深度超过1000 m的低阻含水异常体有效探测,缩小了深部探测的体积效应,有效压制了低阻屏蔽影响,反演计算明显提高了深部巨厚砾岩层的富水性及富水范围的探测精度,经过38次迭代后H型理论模型的反演误差为7×10^-7,经过50次迭代后实际资料的反演误差为0.05%,针对低阻异常区进行钻探验证,出水情况与强含水异常区及中等含水异常区相吻合,探测精度和分辨率明显提升。该方法探测研究为深部煤层安全回采提供了有效的地质技术资料,具有较高的推广应用价值。

Deep mining in coal mines is a trend,but the accompanying complex water hazards pose a huge threat to safety.The aquifer in the super-thick conglomerate above the coal seam roof is characterized by shallow,deep and irregular development.The conventional ground transient electromagnetic detection depth is insufficient,and the volume effect of deep detection is large,and the low resistance shielding effect is obvious.In order to ensure safe mining of deep coal seams,the water content and water-rich range of the super-thick conglomerate above the coal seam roof were detected with high precision and high resolution.Based on the short offset transient electromagnetic method of electrical sources,the electrical properties were analyzed and the calculation expressions of the vertical magnetic field strength,apparent resistivity value and detection depth of the short-distance transient electromagnetic detection technology of the source were summarized.The research summarized the detection method of on-site multiple earthquakes and discussed the least squares based on the improved damping factor.It has been applied to the water-rich exploration of the thick conglomerate deep in a mining area in north China.The research results show that the short offset transient electromagnetic detection technology of electrical source increases the detection depth,realizes the effective detection of low-resistance water bearing anomalies with a depth of more than 1000 m,reduces the volume effect of deep detection,and effectively suppress the influence of conductive shielding,and it obviously improves the detection accuracy of the deep thick conglomerate layer and the rich water range.After 38 iterations,the inversion error of the H-type theoretical model is 7×10-7,and the inversion error of the actual data is 0.05%after 50 iterations.According to the drilling verification of the low-resistivity anomaly area,the water output is consistent with the strong and medium water-bearing anomaly area,and the detection accuracy and resolution are significantly improved.This method provides effective geological technical data for safe mining of deep coal seam and has a high value of popularization and application.