摘要
针对复杂起伏地形问题,从总场满足的方程出发,推导2.5维广域电磁法满足的微分方程,采用有限元技术实现2.5维广域电磁法有限单元法正演计算。设计层状地电模型,验证本文开发的2.5D广域电磁法算法的正确性,分析广域视电阻率与Cagniard电阻率曲线特征。同时,构建广域视电阻率的正则化反演目标函数,采用非线性共轭梯度算法开展目标函数最优化求解,对直接带地形条件的2.5维广域电磁法反演非线性共轭梯度进行研究。研究结果表明:广域视电阻率在近区的利用率得到提高,从而提高了该方法的勘探深度。与Cagniard视电阻率相比,广域视电阻率受静态效应的影响较小,而Cagniard视电阻率在近区和过渡带出现严重畸变特征。开发的反演算法能够反映异常所在的位置,异常体的边界平滑过渡,反演结果准确。另外,无论是广域视电阻率的反演还是Cagniard电阻率的反演,异常体深部电阻率的收敛相对较慢。
The partial differential equations of 2.5D wide field electromagnetic were derived based on the total field equations for models with complicated topography,and a fast and accurate 2.5D forward modelling procedure was presented using the finite element method.The layered geoelectric was designed to verify the correctness of the 2.5D wide field electromagnetic algorithm,and the characteristics of the wade field apparent resistivity and the Cagniard apparent resistivity were analyzed.At the same time,the objective function for the regularization inversion using numerically calculated values of wide field apparent resistivity was established,and the non-linear conjugate gradient(NLCG)method was used in the inversion to obtain a reliable resistivity model.The results show that the utilization of wide-area apparent resistivity is increased in thenear zone,which increases the exploration depth of this method.The wide field apparent resistivity is less effected than the Cagniard apparent resistivity for static effect geoelectric model.The Cagniard apparent resistivity data show serious distortion characteristics in the near and transition region for static effect geoelectric model.The inversion results of the model show that the developed inversion algorithm can reflect the location of the abnormal body,the boundary of the abnormal body is smooth.And the last example is a complicated topographic model with 2D conductive anomalous bodies,which is used to show the performance to deal with complicated topographic for the developed inversion algorithm in this paper.In addition,the deep resistivity values of the inverted model convergence is relatively slow in both inversion of the wide field apparent resistivity and Cagniard resistivity data.
作者
周峰
张志勇
汤井田
李勇
ZHOU Feng;ZHANG Zhiyong;TANG Jingtian;LI Yong(Fundamental Science on Radioactive Geology and Exploration Technology Laboratory,East China University of Technology,Nanchang 330013,China;Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,Ministry of Education,Central South University,Changsha 410083,China;Key Laboratory of Geophysical Electromagnetic Probing Technologies of Ministry of Natural Resources,Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang 065000,China)
出处
《中南大学学报（自然科学版）》
EI
CAS
CSCD
北大核心
2021年第9期3273-3283,共11页
Journal of Central South University:Science and Technology
基金
国家自然科学基金资助项目(41830107,42004061)
江西省科技厅计划项目(S2019ZRMSB0661)
有色金属成矿预测与地质环境监测教育部重点实验室(中南大学)开放基金资助项目(2019YSJS20)
自然资源部地球物理电磁法探测技术重点实验实验室开放课题(KLGEPT201903)
东华理工大学博士启动基金项目(DHBK2019080,DHBK2019085)。
关键词
广域电磁法
2.5维
有限单元
正则化反演
wide field electromagnetic
2.5D
finite element method
regularization inversion
