【作者】 王磊；

【导师】 谭捍东；

【作者基本信息】 中国地质大学（北京） ， 地球探测与信息技术， 2008， 硕士

【摘要】 井地电阻率电法是指通过开发井的套管向井下供入大功率的电流,在地表测量由套管流入地层中的“漏电流”在非均匀电性变化的地下介质中形成的地表电位分布的方法,起源于俄罗斯,主要用于圈定已知油气藏边界和预测已知油气藏周边的含油气有利区块。这是目前油气勘探开发中一类重要而又急需的方法技术。论文简要介绍了井地电阻率法的基本原理及其发展与研究现状,以稳定场电流关系式为基础,推导出求解点源三维地电场的方程组。用有限差分法解决点电源三维地电场的正演问题,重点推导了关于网格节点系数的计算公式,并根据前人的研究成果开发了点电源井地电阻率法三维正演数值模拟软件。在开发过程中,为了避免计算量过大以及对计算机内存要求比较高的困难,引入了不完全Cholesky共轭梯度方法,从而大大提高了运算效率,为三维电阻率反演奠定了基础。对比均匀半空间和垂直接触带模型的数值解与解析解相对误差,结果表明正演算法具有较高的准确性。在此基础上通过对简单模型的三维数值模拟计算,分析低阻异常体在不同体积大小、不同埋藏深度等状态时所引起的异常响应,证明正演计算具有可靠性和稳定性,可以用于接下来的反演研究。在现有基础上进一步探索三维反演算法,使用最小构造反演的共轭梯度算法来解决求解雅可比矩阵G和GTG的逆矩阵的问题,避免存储G和GTG的逆矩阵,同时也节省了内存,加快了反演速度。由于反演参数较多,求模型光滑约束的最小构造反演能够有效消除多余的构造信息,得到稳定、可靠的反演结果。传统的最小构造反演通常需要数十次迭代才能收敛,文中借鉴前人方法对传统的最小构造反演进行改进,即用实验法确定相对最佳的拉格朗日乘子,并在反演迭代过程中保持不变直至收敛。对多个模型的试算结果表明,三维反演的结果能够较好的反映异常的赋存状态,表明该算法的反演结果是可靠的。更多还原

【Abstract】 The borehole-ground DC electrical resistivity method is one of electrical prospecting methods by placing an electric current electrode in a drill hole and measuring the distribution of electric potential on the surface of the earth. It stems from Russia, and is mainly used to delimit a known hydrocarbon reservoir and detect possible hydrocarbon-bearing blocks adjacent to the known reservoir. It is regarded as an important and urgent technique for hydrocarbon exploration.This paper introduces the basic principle and the research present situation of borehole-ground DC electrical resistivity method briefly. Taking the stable field current relationship as the foundation, we infer the equations of 3D electric field caused by point source. The numerical calculation software of 3D forward of point source borehole-ground DC charged-body potential method uses finite difference principle. And we study the formula of the grid node. In order to avoid the problem of the computation load oversized as well as the high computer memory, we chose the method of incomplete Cholesky conjugate gradient. This way could raise the operation efficiency greatly, and establish foundation for 3D inversion.After comparing the relative error of the numerical solution with the analytic solution, we could has the conclusion that algorithm is accurate. Then we do some 3D forward numerical calculations, and analyze the responses of low-resiistivity anomalous bodies with different size and depth. It verifies that the result is credible and steady.Further exploration of the 3D inversion algorithm has been done, when we solve the Jacobian matrix G and the reverse matrix GTG by the way of the smallest tectonic conjugate gradient algorithm, it could avoid the storage of the matrix G and the reverse matrix GTG, it also could save the memory and speed up the inversion. The smoothly restraint of the model could be solved by the way of the smallest tectonic inversion, and help us to eliminates the unnecessary structure information. We also have improved the traditional minimum structure inversion algorithm, because the traditional algorithm requires tens of inversion iterations. A new iterative technique has been developed by Xiaoping Wu. A relative proper value of Lagrange multiplier is given after we do some test, and it will be kept unchangeable until convergence.Some models have been computed by the 3D inversion software, and the result could reflect the condition of the anomalous bodies. It indicated that the inversion result is reliable.更多还原