基于格子—玻尔兹曼方法的裂缝导流能力流固耦合

Fluid-solid coupling of the fracture conductivity based on Lattice-Boltzmann method

为了定量研究不同类型支撑剂填充裂缝的导流能力及其影响因素,借助离散元方法构建了不同粒径范围内支撑剂在不同缝宽裂缝中的堆积模型,利用耦合的固体力学和格子—玻尔兹曼方法,分析了在闭合压力作用下支撑剂在水力裂缝中的嵌入程度及缝宽变化,并以此为基础研究了支撑剂粒径和裂缝缝宽对水力裂缝渗透率和导流能力的影响。通过与实验数据进行对比验证了模型的准确性。模拟结果表明,随着初始缝宽的减小和支撑剂粒径的增大裂缝缝宽的减小程度不断增大,最大减小了31.95%,且初始缝宽对其影响较支撑剂粒径更为显著;水力裂缝的渗透率随着缝宽的减小和支撑剂粒径的增大而增大,但是随之应力敏感性更强,闭合压力作用下裂缝渗透率最大减小了93.37%;具有较高渗透率的窄裂缝,其导流能力相对于宽裂缝反而更小,说明相对于裂缝渗透率,裂缝宽度是影响裂缝导流能力的主要因素。

In order to quantitatively study the conductivity of the fractures filled with different types of the proppants and its influencing factors,with the help of the discrete element method,the model of different-size proppant packing in the fractures with different widths was established.By means of Lattice-Boltzmann method and the coupled solid mechanics,the variations of the proppant embedment and fracture width under the action of the closure pressure were analyzed.And moreover based on that,the effects of the proppant size and the fracture width on the permeability and conductivity of the hydraulic fractures were investigated.The accuracy of the model was verified by comparing with the experimental data.The simulation results show that with the decrease of the initial fracture width and the increase of the proppant grain size,the reduced degree of the fracture width increases with the maximal decrease of 31.95%,and furthermore the effects of the initial fracture width on it are more significant compared with those of the proppant grain size;the permeability of the hydraulic fracture increases with the decrease of the fracture width and the increase of the proppant size,but with the more increase of the stress sensitivity,the maximal permeability decreases by 93.37%under the action of the close pressure;the conductivity of the narrow fracture with pretty higher permeability is smaller than that of the wide fracture,which indicates that corresponding to the fracture permeability,the fracture width is the main factor effecting the fracture conductivity.