We investigate the effects of coupled multiphase flow and geomechanics in the hydraulically fractured reservoirs numerically. We account for poromechanics of flow within a discrete fracture for rigorous simulation, considering both fluid compressibility and fracture volume change. We newly propose a numerically stable sequential method for all-way coupled geomechanics and flow for the discrete fractured systems. The stabilization term is dynamic, depending on the fracture length, and the numerical results support good stability and convergence of the proposed sequential method for hydraulic fracturing simulation. From numerical experiments, we identify at the fracture tip the vacuum area where pressure is below the initial reservoir pressure as well as dry zone where gas saturation is high. The existence of vacuum area is fundamentally due to different time scales between flow and geomechanics, which can be considered as the Mandel-Cryer effect in the fractured systems. The dry zone is not necessarily identical to the vacuum area. The reservoir gas can be introduced into the fracture substantially when the reservoir is highly permeable. The vacuum area and the dry zone can be prominent in naturally or previously hydraulically fractured reservoirs. We study the system responses of the fracture propagation by varying parameters of flow and geomechanics. The hydraulic fracture propagates slowly when reservoir permeability or fracture toughness is high, when Young’s modulus is low, or when the initial total stress is higher than the initial reservoir pressure.

我们以数值方式研究了水力压裂储层中耦合多相流和地质力学的影响。我们考虑了流体可压缩性和裂缝体积变化，考虑了离散裂缝内流动的孔隙力学以进行严格模拟。我们新提出了一种数值稳定的连续方法，用于离散裂缝系统的全程耦合地质力学和流动。稳定项是动态的，取决于裂缝长度，数值结果支持所提出的用于水力压裂模拟的序列方法具有良好的稳定性和收敛性。通过数值实验，我们在裂缝尖端确定了压力低于初始储层压力的真空区域以及含气饱和度高的干区。真空区的存在从根本上是由于流动和地质力学的时间尺度不同，可以认为是裂缝系统中的 Mandel-Cryer 效应。干燥区不一定与真空区相同。当储层具有高渗透性时，储层气体基本上可以被引入裂缝中。真空区和干区在天然或以前水力压裂的储层中可能很突出。我们通过改变流动和地质力学参数来研究裂缝扩展的系统响应。在水力压裂中传播时慢慢储层渗透率 当杨氏模量低或初始总应力高于初始储层压力时，断裂韧性高。