SOTEM法深部探测关键问题

The loop-source TEM method is widely used though, but it cannot meet the demand for large scale, three dimensional data acquisition; the LOTEM method is limited by its weak signal, it cannot meet the requirement of high resolution. Based on the superiority of near-source investigation, short-offset TEM (named SOTEM by authors) will be proposed in this project. The several key technology ,such as theory,method and technology will be conducted. Based on the theoretical study of the infinitesimal integration of current carrying point charge, the exact formula of SOTEM response will be derived. The study of SOTEM deteting abilty will be finishes after the anaysese to EM field compnents distribution and response of SOTEM, the coupling effect of EM field with the layered earth, as well as the sensitivity to conduct and resistance target.The suitble configuration and detecting method of SOTEM will be arrived after study on the relashionship between the parameters of field components,detedtion depth,surveying time delay range,and geo-electric structure.The interpreting accuracy will be improved by using the technology of curves high-resolution iteration.With the integration of mathematical physics modeling, the processing and analysis of the field data, it is expected to effectively detect the minerals at 500 m -- 2000 m depth with high resolution. and to bring the breakthrough to traditional method and make fundamental contributions to the development of electromagnetic method.

回线源瞬变电磁应用虽然相对较广,但还不能满足大面积三维数据采集需求,长偏移瞬变电磁法接收信号往往较弱,不利于深部精细探矿；基于时域电磁场近源测深的优越性，本项目提出电性源短偏移瞬变电磁法(SOTEM),并对其深部探测的理论、方法、技术等关键问题进行研究。根据时变点电荷载流微元积分理论，推导出SOTEM响应的精确表达式；通过分析SOTEM电场、磁场各分量的响应及分布特征、以及各分量与地层相互作用特点、对高低阻层的敏感度等，研究SOTEM深部探测能力；通过对各场量、探测深度、观测时长、地层电性等参数之间的关系研究，形成SOTEM探测方法；采用曲线精细拟合技术，提高定量反演精度;结合实际测试资料的处理与分析，实现对地下500 m--2000 m目标矿体的高精度有效探测。项目的研究成果将在传统瞬变电磁法探测研究的基础上取得新突破，对电磁法的发展做出原创性贡献。

瞬变电磁法是矿产资源勘探的有效手段。随着找矿空间逐渐向深部延伸，传统瞬变电磁装置不能满足探测需求。回线源瞬变电磁装置探测深度较浅，一般不超过500米；电性源长偏移距瞬变电磁装置虽然具有较大探测深度，但是其精度较低，不利于深部精细探矿。基于时域电磁场近源测深的优越性，本项目提出电性源短偏移瞬变电磁法(SOTEM),并对其探测的理论、方法、技术等关键问题进行研究。. 项目首先从麦克斯韦方程组出发，推导了任意位置水平电偶极子在层状大地产生的瞬变电磁场计算公式，实现了SOTEM一维正演；利用有限差分方法，计算了无限长线源在二维大地结构中的电磁场，实现了SOTEM二维正演；利用COMSOL多物理场仿真模拟平台实现了SOTEM三维正演。基于上述不同维度的正演模拟，计算了典型地电断面的电磁响应，分析了多分量的分布、扩散特性，以及对不同地层的灵敏度，为野外实际探测中最佳观测分量和观测区域的选择提供了指导。结合数值模拟与野外观测，研究了激发极化、静态偏移应和发射源阴影等附加效应问题，获得了其影响机制和现象规律的系统认识。利用多种反演算法，开展了SOTEM数据一维反演研究，实现了半定量的镜像源方法、拟MT反演方法，定量的OCCAM反演方法、阻尼最小二乘反演方法（DLSM）、基于截断奇异值分解的广义逆矩阵方法（TSVD）。同时研究了一维反演算法应用于三维模型带来的误差问题，并提出了采用多源、多分量联合反演的方法来提高复杂地质构造的反演精度。最后，项目在国内多处矿区进行了SOTEM探测试验和应用推广，在深部金属矿探测、煤田水文地质调查领域取得了显著的效果。. 项目取得了丰硕的研究成果，发表一系列论文，授权多项专利和软件著作权，获得多项科技奖励，培养多名硕士和博士研究生。