基于夹角断层边界的煤层气井压力动态响应

Dynamic response of CBM well pressure based on interacting fault boundary

考虑到断层对油气井压力及压力导数的动态响应有较大的影响,首先构建在无穷大外边界条件下且考虑井筒储集效应和表皮效应的煤层气渗流模型,并引入求解该类模型的相似构造法进行求解,再利用镜像反映原理得到煤层气井在夹角断层边界下的镜像解,根据叠加原理可得到基于夹角断层边界条件下的煤层气井的解析解,最后绘制无因次井底压力的双对数曲线、半对数曲线、一阶压力导数(PPD)曲线和二阶对数压力导数(SLPD)曲线,并分析夹角断层边界对煤层气井井底压力的影响规律。所得结论可为试井解释人员提供便利,同时也为断层的识别方法提供了进一步的补充和完善。

In view that faults have greater effect on the dynamic response of oil/gas well pressure and its derivative, a coalbed methane(CBM) seepage model taking wellbore storage effect and skin effect into account under the condition with infinite outer boundary was established firstly in this paper. In addition, the elementary method for solving this type of model was introduced to get the solution, i.e., similar constructive method. Secondly, the mirror image solution of CBM well at the interacting fault boundary was calculated according to the mirror reflection principle. Thirdly, the analytical solution of CBM well based on the condition of interacting fault boundary was obtained according to the superposition principle. Finally, dimensionless log-log plot, semi-log plot,primary pressure derivative(PPD) plot and second-order log pressure derivative(SLPD) plot of bottom hole pressure were prepared,and the influential laws of interacting fault boundary on the bottom hole pressure of CBM well were analyzed. The conclusions can provide the convenience for logging interpreters and supplement and complete the fault identification methods further.