分形裂缝中VES压裂液-颗粒多相流动及多尺度动态耦合机理

VES fracturing fluid is a new high-efficient and clean fracturing fluid. Proppants migration by fracturing fluid in fracturing fracture determines ultimate fracture formation and oil and gas recovery. There is a strong coupling between rheological properties of microscale micelles in VES fracturing fluid and macroscale multiphase flow behavior. The dynamic coupling mechanism is not only the way to accurately describe VES fracturing fluid-particles multiphase flow behavior but also the key to acquire the method to control particles migration. The research employs multiscale method to conduct experimental study on VES fracturing fluid-particles multiphase flow in fractal fracture and dynamic microscale structure of micelles based on visualization method, and elucidate the mechanism of influence of rheological properties of microscale micelles on macroscale flow. Dissipative Particle Dynamics method is employed to simulate rheological properties of fracturing fluid based on finite volume grid. Real-time stress-strain constitutive relations in entire fluid field are obtained and coupled with momentum equation, through which multiscale model and simulation method are built. The relationship between VES fracturing fluid-particles flow pattern and rheological properties of fracturing fluid and fracture characteristics is analyzed. Control methods of flow pattern and rheological properties of fracturing fluid are obtained. The research will not only provide support for predicting fracturing fluid-particles multiphase flow and controlling rheological properties of fracturing fluid but also enrich the research connotations of fluid-particles multiphase flow.

VES压裂液是一种新型高效清洁压裂液，压裂液携颗粒在裂缝中运移效果决定裂缝最终形态和油气采收率。在复杂裂缝形态和强壁面效应下，VES压裂液中微尺度胶束流变特性与宏观多相流动行为强烈耦合，其动态耦合机理既是准确描述VES压裂液-颗粒多相流动的前提，也是寻求控制颗粒运移手段的关键。本项目采用多尺度研究方法，基于可视化方法对分形裂缝中VES压裂液-颗粒多相流动特性以及动态胶束微观结构进行实验研究，阐明微观胶束流变特性对宏观多相流动的影响机理；基于有限体积网格，采用耗散粒子动力学方法模拟流体流变特性，获得实时全场离散应力-应变本构关系，与动量方程耦合，建立多尺度模型及数值模拟方法；分析VES压裂液携颗粒多相流型与流体流变性质、裂缝特征的相关关系，获得流型和压裂液流变性质调控方法。本项目的实施，既可为压裂裂缝中压裂液-颗粒多相流动预测及压裂液流变性质调控提供依据，又有望丰富流体-颗粒多相流研究内涵。