Appraisal of an Array TEM Method in Detecting a Mined-Out Area Beneath a Conductive Layer

作者：Li, Hai^*; Xue, Guo-qiang; Zhou, Nan-nan; Chen, Wei-ying

来源：Pure and Applied Geophysics, 2015, 172(10): 2917-2929.

DOI：10.1007/s00024-015-1075-0

• transient electromagnetic method
• array configuration
• mine-out area
• OCCAM inversion

The transient electromagnetic method has been extensively used for the detection of mined-out area in China for the past few years. In the cases that the mined-out area is overlain by a conductive layer, the detection of the target layer is difficult with a traditional loop source TEM method. In order to detect the target layer in this condition, this paper presents a newly developed array TEM method, which uses a grounded wire source. The underground current density distribution and the responses of the grounded wire source TEM configuration are modeled to demonstrate that the target layer is detectable in this condition. The 1D OCCAM inversion routine is applied to the synthetic single station data and common middle point gather. The result reveals that the electric source TEM method is capable of recovering the resistive target layer beneath the conductive overburden. By contrast, the conductive target layer cannot be recovered unless the distance between the target layer and the conductive overburden is large. Compared with inversion result of the single station data, the inversion of common middle point gather can better recover the resistivity of the target layer. Finally, a case study illustrates that the array TEM method is successfully applied in recovering a water-filled mined-out area beneath a conductive overburden.

• 出版日期2015-10
• 单位中国科学院地质与地球物理研究所兰州油气资源研究中心; 中国科学院地质与地球物理研究所