基于三维分形裂缝模型的页岩气井智能化产能评价方法

A smart productivity evaluation method for shale gas wells based on 3D fractal fracture network model

基于分形理论多次信息叠加算法设计了三维天然裂缝生成方法,人工裂缝模型与天然裂缝模型耦合可表征页岩压后复杂多尺度裂缝系统。采用马尔科夫链-蒙特卡洛智能化历史拟合算法,结合嵌入式离散裂缝技术耦合数值模拟器预测页岩气井产能,形成了一体化页岩气井产能评价模型。研究表明:三维天然裂缝生成方法可利用分形参数控制裂缝网络的整体分布,与人工裂缝耦合可表征页岩压后复杂的跨尺度裂缝系统;嵌入式离散裂缝模型具有裂缝网格数量少、运算耗时短的优点,能够灵活表征天然裂缝及人工裂缝属性,在有效降低计算量的同时能够精确地模拟流体在基质-裂缝中的交换过程;嵌入式离散裂缝模型与智能化历史拟合算法相结合能够降低裂缝、储集层等未知参数计算的不确定性,实现储集层、裂缝关键参数的有效反演,并实现气井产能量化预测。经实际应用验证一体化井产能评价模型预测结果具有较高的可信度。图13表7参26。

The generation method of three-dimensional fractal discrete fracture network(FDFN)based on multiplicative cascade process was developed.The complex multi-scale fracture system in shale after fracturing was characterized by coupling the artificial fracture model and the natural fracture model.Based on an assisted history matching(AHM)using multiple-proxy-based Markov chain Monte Carlo algorithm(MCMC),an embedded discrete fracture modeling(EDFM)incorporated with reservoir simulator was used to predict productivity of shale gas well.When using the natural fracture generation method,the distribution of natural fracture network can be controlled by fractal parameters,and the natural fracture network generated coupling with artificial fractures can characterize the complex system of different-scale fractures in shale after fracturing.The EDFM,with fewer grids and less computation time consumption,can characterize the attributes of natural fractures and artificial fractures flexibly,and simulate the details of mass transfer between matrix cells and fractures while reducing computation significantly.The combination of AMH and EDFM can lower the uncertainty of reservoir and fracture parameters,and realize effective inversion of key reservoir and fracture parameters and the productivity forecast of shale gas wells.Application demonstrates the results from the proposed productivity prediction model integrating FDFN,EDFM and AHM have high credibility.