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井地电位成像是通过套管向井中供电或将电源放在井中,在地表观测电位异常的一项技术,其供电源有线源和点源两种类型。为了研究这两种电源对地下异常体产生的电位异常特征,本文针对不同激励源,采用有限差分方法进行数值模拟研究,在线性方程组求解电位时引入不完全Cholesky共轭梯度(ICCG)迭代方法,分别实现了点源和线源井地电位成像技术的三维正演。最后,基于阻尼最小二乘法实现了井地电位成像技术的电阻率三维反演。设计不同地电模型分别进行正演和反演试算,正演结果表明,供电电源的类型不同,异常体在地表的电位异常特征也不同;反演结果表明,低阻体的反演结果要好于高阻体,点源置于异常体下方时反演的电阻率对异常体边界的识别比线源更加准确。
Well-to-ground potential imaging is a technique of supplying power to a well or placing a power source in a well through a casing, and observing anomalous potential on the surface. The power source is provided both as a cable source and a point source. In order to study the potential anomalies produced by these two kinds of power supplies on underground anomalies, this paper studies the numerical simulation of different excitation sources by using the finite difference method. When the linear equations solve the potential, an incomplete Cholesky conjugate gradient (ICCG) iteration method Respectively, to realize the three-dimensional forward modeling of the point source and source-source ground potential imaging technologies. Finally, the resistivity 3D inversion of well ground potential imaging technique is realized based on the damping least square method. The results of forward modeling show that the types of power supply are different, and the anomaly bodies have different potential anomalies on the surface. The inversion results show that the inversion result of low-resistivity body is better In the high resistivity body, when the point source is placed below the anomalous body, the resistivity retrieved from the anomalous body boundary is more accurate than the line source.