复杂管网线源井地电位三维有限元模拟

为更真实地模拟油气田井地电位法中由复杂管网线电流源供电的实际情况,本文给出了复杂管网线源在地下半空间中的正常电位表达式,导出了地下点电源异常电位边值问题,详细推导了地下点电流源异常电位变分问题,进而用有限元法求解了复杂管网线电流源异常电位的变分问题。编写了三维有限元正演程序对垂直、地下水平二分支油井钢套管与注水、输油钢管组合形成的复杂管网线源井地电位进行了模拟。结果表明,复杂管网线源激励下的井地电位异常响有其独特的特征和规律。这些结果将对利用复杂管网线源井地电位法探测剩余油的空间分布和注水前沿位置提供有力的指导,也为复杂管网线源井地电位三维反演奠定了良好基础。

3D FEM modelling of the borehole-to-surface potential method with complex pipe network linear current source

In order to model the actual situation about the borehole-to-surface potential excited by complex pipe network linear current source in oil field, this paper proposes a borehole-to-surface potential 3D FEM modeling method with complex pipe network linear current source and continuous variation of conductivity of the semi-underground space.In the paper, the normal potential formula of the complex pipe network linear current source in the semi-underground space and the variational problem of anomalous potential with point source is fetched in turn.Then the the variational problem of anomalous potential with the complex pipe network linear current source is presented, and it is solved by 3D FEM.The 3D FEM forward model software is programmed.A linear current source consisted of vertical and horizontal water pipes and oil pipes is modeled, and its special anomalous characteristics and rules are obtained.Results can privrne references for identifying the distribution of residual oil and the frontier of water injection, at the same ttme, a good foundation for 3D inversion of the borehole-to-surface potential.