频率域井地电磁法的物理模拟和数值模拟研究

Borehole to surface electromagnetic method (BSEM) is a high precision electromagnetic exploration method which excites in well and measure on the ground. BSEM has wide application prospects on the aspects of deep minerals exploration and monitor of oil and gas reservoir, but so far there is no significant improvement in the processing and interpretation of real data because of the deficiency of BSEM relative theory and the difficulty of 3D forward and inversion problem. This project plans to adopt physical modeling and numerical simulation to carry out fundamental research on the response feature of BSEM trapping abnormal boundary and how the target influences the field component. Complete the response analysis of geoelectric model of BSEM systematically. On the aspect of physical modeling, this project designs homogeneous half model and marine sediment two layers model based on the similarity criterion. Improve the existing transmitting and receiving system physical modeling. Measure the background before burying the model and total field after burying model. Research the space distribution of BSEM. On the aspect of numerical simulation, this project adopts staggered-grid finite difference method、sparse storage and ILU precondition QMR method which is embedded divergence correction to compete 3D numerical simulation of BSEM in frequency domain. Through the comparison analysis and mutual authentication of two simulation results, we can improve the simulation method and discuss the efficiency and practicality of BSEM so that to promote the application of BSEM on resource exploration and reservoir evaluation.

井地电磁法是一种井中激发、地面观测的高精度电磁勘探方法，在深部矿产资源勘探、油气储层检测等方面应用前景广阔。但是，由于井地电磁法相关理论和方法研究不足、三维正反演问题难度较大，资料处理解释至今没有突破性进展。项目将采用物理模拟和数值模拟，开展井地电磁圈定异常边界响应特征和目标体电性参数变化对场分量的影响规律等基础研究，系统完成井地电磁地电模型响应分析。在物理模拟方面，根据相似准则，设计均匀半空间模型和海洋沉积双层模型，改进已有的物理模拟发射和接收系统，测量填埋异常体前后的背景场和总场，研究频率域井地电磁场空间分布特征。在数值模拟方面，采用交错网格有限差分方法、稀疏存储和嵌入了散度校正的ILU预处理QMR算法，实现频率域井地电磁三维响应的数值模拟。通过两种模拟结果的对比分析、相互验证，改进模拟方法，论证井地电磁勘探方法的有效性和实用性，推动井地电磁方法在资源勘查和油储评价方面的应用。

本项目根据电磁法物理模拟相似准则和室内物理模拟实验环境，通过对不同石墨、水泥及沙、盐水配比制作的模型小样的测量，挑选出能满足相似准则的高阻异常体和沙盐水层等的配比；按照项目计划完成了井地电法模拟实验设施设备的安装调试工作，设计建设了陆地及海洋井中垂直双极源电磁物理模拟平台，制作不同背景模型及异常模型，通过水槽开展了多个实验。实现了考虑散度校正及ILU预处理的井地电磁三维数值模拟，优化了井地电磁模拟技术，开展了多个模型的井地电磁三维数值模拟，为快速和准确计算井地电磁三维正演提供了更好的工具；通过对物理和数值模拟结果的对比研究与分析，通过陆地、海洋的物理模拟及数值模拟的相互验证和对比分析以及改进，获得了频率域井地电磁场从水面至水下的空间分布特征，进一步深入研究分析了频率域井地电磁空间分布特征，验证了井地电磁勘探方法的有效性和实用性，进一步推进井地电磁方法在资源勘查和油储评价方面的应用。相关成果发表SCI论文2篇，获国家发明专利授权1项和德国新型使用专利授权1项。