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A novel hybrid FEM-BEM method for 3D eddy current field calculation using current density J

Science China(Technological Sciences) 2003年第1期46卷 41-48页

作者：刘志珍王衍章贾智平孙英明 School of Electrical Engineering Shandong University Jinan 250061 China Department of Science and Technology Shandong University Jinan 250061 China School of Computer Science and Technology Shandong University Jinan 250061 China Center of Computer Jinan University Jinan 250002 China Correspondence should be addressed to Liu Zhizhen

This paper introduces a novel hybrid FEM-BEM method for calculating 3D eddy cur-rent field. In the eddy current region, the eddy current density J is solved by the finite element method (FEM) which is discretized by brick finite element mesh, while in the eddy current free re-gion, the magnetic field intensity H is solved by the boundary element method (BEM) which is dis-cretized by rectangular boundary element mesh. Under the boundary conditions, an algebraic equation group is obtained that only includes J by eliminating H. This method has many advan-tages over traditional ones, such as fewer variables, more convenient coupling between the FEM and the BEM and wider application to multiply-connected regions. The calculated values of two models are in good agreement with experimental results. This shows the validity of our method.

关键词： conductor eddy current density magnetic field intensity 3D eddy current field FEM BEM coupling. To solve a large eddy current field is one of the most difficult problems in the numerical

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Propagation effects of low frequency electromagnetic waves in production well

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Petroleum Science 2012年第2期9卷 182-191页

作者： Song Xijin Guo Baolong Dang Ruirong Wang Xuelong Institute of Intelligent Control and Image Engineering Xidian UniversityShaanxi 710071China Key Laboratory of Photoelectric Logging and Detecting of Oil and Gas Ministry of EducationXi'an Shiyou UniversityShaanxi 710065China College of Computer Science&Technology Shaanxi University of TechnologyShaanxi 710048China

The frequency domain electromagnetic method has already been widely used for tomographic imaging or electromagnetic well logging. However, different from open hole logging, the metal casing existing in production well logging has a strong shielding effect on the electromagnetic waves, thus bringing some difficulties to the application of the frequency domain electromagnetic method in production well logging. According to the relation of the field source geometry to the ring around the mandrel, the general expressions of frequency domain electromagnetic responses in axially symmetrical layered conductive medium are deduced. The propagation effects caused by the low-frequency electromagnetic waves in cased hole are also analyzed. The distribution curves of eddy current density and magnetic flux density along the radial direction in the mandrel indicate that the eddy loss within the mandrel is proportional to the transmission signal frequency and the mandrel conductivity. The secondary field responses of different casing materials show that the transmission frequency has an important effect on the ability of electromagnetic waves penetrating the metal casing. The transmission frequency should be ultra-low in order to enable the electromagnetic signal to penetrate the casing easily. The numerical results of frequency responses for different casing physical parameters show that the casing thickness has a significant impact on the choice of the transmission frequency. It is also found that the effect of the casing radius on the transmission frequency can be neglected.

关键词： Propagation effects eddy current density magnetic flux density production well frequency response

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