水面等值反磁通瞬变电磁法矢量有限元三维正演研究  

Study on Three-Dimensional Forward Modeling for Opposing Coils Transient Electromagnetic Method by Vector Finite Element on Water Surface

作　　者：蓝金星 孙娅[1] 席振铢[1] 龙霞 

机构地区：[1]中南大学地球科学与信息物理学院,湖南 长沙 [2]湖南五维地质科技有限公司,湖南 长沙

出　　处：《地球科学前沿（汉斯）》2023年第4期421-432,共12页Advances in Geosciences

摘　　要：等值反磁通瞬变电磁法(OCTEM)在浅水域探测中应用前景广阔,为研究其探测能力,采用矢量有限元法进行浅水域水面等值反磁通瞬变电磁法三维正演模拟。首先,从频率域麦克斯韦方程组出发,利用Galerkin法推导了基于电场的矢量有限元方程,再通过余弦变换变换将频率域响应转换至时间域;然后采用三维矢量有限元法计算了浅水域典型地电模型响应,与数值滤波解进行对比,验证了算法的正确性,并分析了不同水深、不同基底围岩电阻率下等值反磁通瞬变电磁响应规律;最后,采用矢量有限元法计算了浅水域水面等值反磁通瞬变电磁三维响应,正演结果表明等值反磁通瞬变电磁法对低阻异常体响应强烈,异常清晰明显,对浅水域低阻异常体具有较高的探测能力。本研究可为浅水域等值反磁通瞬变电磁法数据处理解释提供一定理论参考。The opposing coils transient electromagnetic method (OCTEM) has broad application prospects in shallow water detection. In order to study its detection ability, the vector finite element method was used to simulate the three-dimensional forward modeling of the opposing coils transient electromagnetic method in shallow water. Firstly, starting from the Maxwell equations in frequency domain, the vector finite element equation based on electric field was derived by Galerkin method, and then the frequency domain response was transformed into time domain by cosine transform. Then, the three-dimensional vector finite element method was used to calculate the response of typical geoelectric model in shallow water. Compared with the numerical filtering solution, the correctness of the algorithm was verified, and the opposing coils transient electromagnetic response law under different water depths and different base rock resistivity was analyzed. Finally, the vector finite element method was used to calculate the three-dimensional response of the opposing coils transient electromagnetic method in shallow water. The forward results show that the opposing coils transient electromagnetic method has a strong response to the low-resis- tance abnormal body, the anomaly is clear and obvious, and has a high detection ability for the low-resistance abnormal body in shallow water. This study can provide a theoretical reference for the data processing and interpretation of opposing coils transient electromagnetic method in shallow water.

关 键 词：浅水域探测 等值反磁通瞬变电磁法 矢量有限元 三维正演 

分 类 号：TP3[自动化与计算机技术—计算机科学与技术]