In order to determine the distribution of the residual oil and the position of the watenflood front during the exploration of hydrocarbon reservoir, 3D FEM modeling of the borehole-sufface DC method with arbitrary shape line current source in the semi-underground space of the continuous variation of conductivity within each block is put forward. The singularity in the vicinity of the electrical source is eliminated by computing the anomalous potential. The continuous conductivity among the nodes can simulate the complex geologic body. Arbitrary shape casings of the pumping well or injection well widely exist in oil field, such as vertical, inclined,horizontal, multiple branch well et al, so the normal potential formula of any point drived by the arbitrary shape line current sources in the semi-underground space is established. The slow speed of 3D modeling is solved by symmetrical super relaxation preconditioned conjugate gradient method, and the practical and effective program is programmed. The influence of the bond quality of the cement mantle, the distance of return well to surveying well and the depth of target stratum on the surveying result of the borehole-surface DC method is analyzed through simulating three geoelectrical models, providing reference for oil reservoir engineering.%为了更好的研究油藏开发过程中剩余油的分布情况以及注水前沿的推进位置,给出了三维空间任意线电流源且电导率连续变化的井-地电位三维有限元数值模拟方法.在模拟过程中,采用异常电位法消除线电流源奇异性的影响,并且将网格节点间的电导率设计为连续变化,使其能够模拟实际中更为复杂的地质情况;考虑到采油井或注水井可能存在垂直、倾斜及水平等任意情况,推导了任意线电流源正常电位的计算公式;采用对称超松弛预条件共轭梯度法解大型线性方程组,解决了井-地电位三维模拟速度慢的问题,并编制了实用、高效的井-地电位三维模拟软件.通过对3例地电模型进行模拟计算,分析了水泥环胶结质量、回流井到观测井的距离以及目标层的深度对井-地电位观测结果的影响.
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