【摘要】 基于流固耦合理论,在基于渗透率的水力压裂(PHF)模型基础上建立了扩展渗透率的水力压裂(extended permeability-based hydraulic fracture,EPHF)模型.该模型假设岩石材料在开裂过程中渗透率的改变为平均有效应力的函数,采用多孔介质弹性本构关系和Drucker-Prager塑性模型描述岩石材料开裂前后的力学行为,孔隙流体采用达西定律描述.引入LET模型和混合黏滞系数考虑等效开裂区域内由压裂液与原液体混合引起的渗透率修正.分析了抗拉强度对关键位置的水压力和应力路径发展过程的影响,以及等效开裂区域和裂缝高度随注水时间的变化过程.结果表明:裂缝路径上的点(不含注水点)的水压力先降低后增加至传播压力;当有效应力差和初始水压力同时保持不变时或当总应力不变时,起裂压力随有效应力比的增加而降低.更多还原

【Abstract】 Based on a coupled fluid-solid theory,an extended permeability-based hydraulic fracture(EPHF) model was developed according to the permeability-based hydraulic fracture(PHF) model.The proposed EPHF model assumed that the permeability of porous rock was a function of mean effective stress when a rock was fractured.The porous elastic constitutive law and Drucker-Prager plastic model were adopted to model the pre-failure and post-fracture process of rock material,respectively.The Darcy’s law was used to describe the liquid phase.To consider the influence of injection fluid,the LET model was integrated to modify the permeability of fracture zone with the mixed viscosity of injection and original fluid being used.The development of pore pressure,stress path,equivalent fracture zone and fracture height for different tensile strength were studied by using the proposed model.The simulation results indicated that the pore pressure in fracture path(except injection point) first decreased and then increased to propagation pressure.If the effective stress difference and pore pressure were kept the same or if the total stress was constant,the breakdown pressure decreased when the effective stress ratio increased.更多还原