电性源地-井瞬变电磁法深部精细探测技术研究

The conventional ground based TEM devices are easily influenced by the surface noise and their detection precision is exponentially reduced with the increase of buried depth of targets. The surface-to-borehole TEM can significantly improve the detection precision because of the receivers are closer to the targets and avoiding the surface noise that obtain more obvious anomaly. In view of the advantages of slow signal attenuation, large exploration depth and distinct anomaly of the electrical source TEM, this project will carry out the study on the electric source surface-to-borehole TEM method. We will conduct the calculation and modeling of the underground transient EM field of 1-3 dimensional models due to an electrical source by using the numerical algorithm such as FETD; and will analyze the response characteristics in the borehole based on the numerical simulation and physical simulation results to build the qualitative understanding of the target anomaly; and will use the method of OCCAM and regularized scheme to realize the one-dimensional accurate inversion of the electrical source surface-to-borehole TEM data as well as the joint inversion with the ground TEM data; we will also research the optimal field work techniques and the field test in the typical mining area. The research results of the project will have certain theoretical significance to supplement the theory of transient electromagnetic filed and enrich the working system of TEM method. It is of great practical significance for the deep mineral exploration and the detection of blind ores at nearly exhausted reserves mines.

传统地面瞬变电磁法（TEM）随探测深度增大，分辨率呈指数降低，且易受地表各种噪声影响，因此探测深度和精度具有较大局限性。地-井TEM的接收点更靠近目标体，因而可获得更加明显的异常反映，并可有效避免地表噪声的影响，能够显著提高深部电性结构的探测精度。目前，广泛研究和应用的地-井TEM都是基于磁性源。与磁性源相比，电性源具有信号衰减慢、探测深度大、异常形态简单等优点。因此，本项目拟开展电性源地-井TEM法研究。利用时域矢量有限元等数值算法，进行电性源地下瞬变场的正演模拟与计算，并分析典型地电模型响应的静态和动态特性；利用OCCAM、正则化等反演算法实现电性源地-井TEM数据的一维反演以及与地面数据的联合反演；研究最优施工技术，并在典型矿区进行探测试验。项目研究对完善瞬变电磁场理论、丰富瞬变电磁法工作体系有一定的理论意义，对深部金属矿、危机矿山盲矿的精细电性结构探测具有重要的实践意义。

传统地面瞬变电磁法（TEM）随探测深度增大，分辨率呈指数降低，且易受地表各种噪声影响，因此探测深度和精度具有较大局限性。地-井TEM的接收点更靠近目标体，因而可获得更加明显的异常反映，并可有效避免地表噪声的影响，能够显著提高深部电性结构的探测精度。目前，广泛研究和应用的地-井TEM都是基于磁性源。与磁性源相比，电性源具有信号衰减慢、探测深度大、异常形态简单等优点。因此，本项目拟开展电性源地-井TEM法研究。.针对该研究目的，本项目开发了电性源地-井瞬变电磁法一维、二维和三维正演程序，分析了地下电磁场多分量响应特性，厘定了不同电磁场分量对高低阻目标体的探测能力，研发了基于多种方法的地-井电性源瞬变电磁数据一维反演技术，并实现了多分量、多源、井地数据的联合反演，基本形成了系统的地-井电性源瞬变电磁数据采集和处理技术体系，并将该方法在淮北朱仙庄煤矿进行了示范应用，取得了良好效果。项目研究成果对完善瞬变电磁场理论、丰富瞬变电磁法工作体系有一定的理论意义，对深部金属矿、危机矿山盲矿的精细电性结构探测具有重要的实践意义。