清水压裂中支撑剂输送沉降行为的CFD模拟

CFD Simulation of Proppant Transportation and Settling in Water Fracture Treatments

清水压裂技术具有成本低、对地层伤害小等优点,在页岩气等致密气藏开采中得到广泛应用,压裂过程中的湍流效应、颗粒间及颗粒与壁面的相互作用等是影响支撑剂输送沉降行为的重要因素。针对传统支撑剂沉降计算方法没有考虑流固、固固间双向耦合的缺点,建立了欧拉–欧拉两相流模型研究支撑剂在清水压裂过程中的输运沉降行为,模型考虑了流动的湍流效应、高浓度下颗粒间的摩擦应力,并利用Johnson–Jackson边界条件考虑颗粒与壁面间的作用。利用该模型研究了不同进口速度及位置、砂粒密度等参数条件下平板裂缝中压裂液与支撑剂的两相流流动,模拟结果与实验符合度较高,验证了模型的有效性。同时文中也讨论了这些参数对支撑剂输送沉降规律的影响。

Water hydraulic fracture treatments are widely used in of exploitation for tight gas reservoirs such as shale gas because of its low cost and little damage to formation＇s permeability. In the process of fracturing, turbulence effects, particle-particle and particle-wall interactions are important factors which affect proppant transportation and settling behavior. Because conventional proppant settlement calculation methods don＇t consider the two-way coupling of fluid-solid and solid-solid, Euler-Euler two- phase flow model is established to study the proppant transportation and settling behavior in the process of water-fracturing. Turbulence effects and friction stress between high concentration particles are taken into consideration to study the particle- wall interaction, and Johnson-Jackson boundary conditions are also considered. By using this model, the two-phase flow of fracturing fluid and proppant in the slot under different inlet-velocity position, particle density are studied. The simulation results coincide with experimental results well, which verifies the effectiveness of the model used. In the meanwhile, the effect of these parameters to proppant transportation and settling law is also discussed in the paper.