页岩气水平井复杂缝网压裂模拟

Complex fracture network fracturing simulation of shale gas horizontal well

为了更真实地模拟页岩储层水平井体积压裂,采用擅长处理非连续结构问题的离散元方法,利用三维离散元程序(3DEC)及其内嵌Fish语言建立表征天然裂缝的离散裂缝网络(discrete fracture netuork,DFN),并考虑流固耦合建立水力裂缝与复杂DFN相互作用的页岩水平井体积压裂数值计算模型。在缝网模型的理论基础上通过模拟计算,观察水平应力差异系数、杨氏模量、泊松比和天然弱面胶结强度等影响因素对于复杂缝网模型所形成的影响,结果表明:水力裂缝会沟通天然裂缝产生分支缝,储层内部容易形成充分裂缝网络的条件是具有较小的水平应力差异系数、较大的杨氏模量以及较小的泊松比,同时杨式模量对裂缝在各方向上的延伸有着促进作用,泊松比则是决定裂缝破裂所需能量大小。模拟结果为进一步认识页岩气水平井体积压裂裂缝行为研究提供了技术指导。

To simulate the horizontal well volume fracturing of shale reservoirs more realistically, a discrete element method is used to deal with the problem of discontinuous structures. A three-dimensional discrete element program (3DEC) and its embedded Fish language are used to establish discrete fracture networks (DFN) that characterize natural fractures, and considering the fluid-structure interaction, a numerical calculation model of shale horizontal well volume fracturing considering the interaction between hydraulic fracture and complex DFN is established. Based on the theory of the slotted mesh model, the impact of factors such as the horizontal stress differential coefficient, Young’s modulus and Poisson’s ratio, and the strength of the natural weak-face cement on the complex mesh model was observed through simulation. The results show that hydraulic fractures will communicate with natural fractures to produce branching joints; reservoirs that are easy to form an adequate fracture network have smaller horizontal stress difference coefficients, larger Young’s modulus, and lower Poisson’s ratio, while Young’s modulus The extension of cracks in all directions has a catalytic effect, and Poisson’s ratio is the amount of energy needed to determine cracks.The simulation results provide technical guidance for further understanding of the behavior of horizontal fracturing fractures in shale gas horizontal wells.