中文摘要：

地-井瞬变电磁（TEM）方法是在地表发射，探头沿钻孔（井）测量瞬变响应的一种井中物探方法．由于接收探头沿钻孔深入地下，因此能够获得更加可靠的地下目标体信息，尤其当存在低阻覆盖层、浅部矿化等地质干扰，或者勘查深部规模不大之良导矿体时，地-井TEM方法的优势更加明显．相对于磁性源系统，电性源系统发射功率大，辐射面积广，更适合地形复杂地区之深部找矿．本文的目的是研究电性源地-井TEM的近似解释方法，首先给出了层状介质电偶极子在地下的TEM响应，进而通过电偶极子叠加的方式获得了电性源条件下的TEM响应．利用感应磁场与均匀半空间电阻率的单调关系通过反函数定理进行了全域视电阻率定义．理论模型的视电阻率计算结果显示，不同深度测点的视电阻率曲线首支不同，而尾支基本一致．这说明了全域视电阻率是测点周围有限范围内介质的综合反映，所以不同深度测点的视电阻率曲线首支所反映的范围是不同的．绘制了不同时间道视电阻率剖面曲线，以期显示地下电性分布规律．计算结果表明全域视电阻率定义能够基本可靠地反映地下信息，从而为该技术在矿区深部找矿的应用提供有力支持．

英文摘要：

The surface-to-borehole transient electromagnetic method （TEM） is a borehole exploration method, in this method a transmitting source is deployed on the surface while a receiving coil is moved down a borehole in order to detect conductive bodies in the vicinity of the borehole. The power of surface-to-borehole TEM method is that the receiver is placed in the exploration drill hole, generally located closer to the target than to most of the interfering bodies, particularly in areas where the ability of surface EM to define a target is limited either by large depths or by interfering conductive bodies such as overburden shallow sulphides and peripheral mineralized horizons. The electric source system is more suitable for the deep exploration in the complex terrain area with higher power and larger effective working area than magnetic source system. The purpose of this paper is to study the approximate processing method of electric source borehole TEM. In this paper, the TEM response of the electric dipole in the ground layer is first presented, and the borehole TEM response of the electric source is obtained by the electric dipole superposition. The global apparent resistivity is defined by inverse function theorem based on the monotonic relationship between induced B field and homogeneous half space resistivity. Calculation results of apparent resistivity of theoretical model show that the apparent resistivity curves of different depth are different in the first part and basically the same in the last part. This reflects that the global apparent resistivity is a comprehensive reflection of the medium around the measuring point and the range of first part of apparent resistivity curves is changing with position. Therefore, the apparent resistivity curves were drawn with depth of different time channels in order to show the underground electrical distribution. The calculation results show that the global apparent resistivity given in this paper can reliably reflect the underground information, so as to provide s