基于LBM的粗糙裂隙内两相驱替渗流特性模拟研究  

STUDY ON TWO-PHASE DISPLACEMENT FLOW BEHAVIOR THROUGH ROUGHWALLED FRACTURES USING LBM SIMULATION

作　　者：周新 盛建龙[1] 叶祖洋[1] Zhou Xin;Sheng Jianlong;Ye Zuyang(School of Resources and Environmental Engineering,Wuhan University of Science and Technology,Wuhan 430081,China)

机构地区：[1]武汉科技大学资源与环境工程学院,武汉430081

出　　处：《力学学报》2024年第5期1475-1487,共13页Chinese Journal of Theoretical and Applied Mechanics

基　　金：国家自然科学基金资助项目(42077243)。

摘　　要：岩体粗糙裂隙两相驱替渗流普遍存在于许多工程应用中,而裂隙开度分布特征与壁面润湿性是影响两相驱替特性的关键因素.基于分形理论生成三维粗糙裂隙面并分别构建开度分布一致的均质模型和不一致的非均质模型,通过LBM伪势模型模拟粗糙裂隙准静态排水过程,研究了裂隙开度分布特征与壁面润湿性对两相驱替渗流特性的影响规律及细观机制.研究结果表明:均质模型驱替前缘基本保持平稳推进,而非均质模型出现优先驱替阻力较小的大开度区域的优势驱替路径现象,润湿性增强可加剧该现象致使驱替前缘更快突破,对均质模型无明显作用;残余捕获可分为孤立的“圈闭”模式和吸附在裂隙壁面的“水膜”模式,非均质模型中圈闭捕获明显多于均质模型,强润湿性有利于水膜捕获增多;当驱替压力增大至进入压力后,非均质模型中部分小开度区域润湿相被逐步排驱,而均质模型大多数润湿相被快速驱替,因此非均质模型P_(c)-S_(w)曲线比均质模型更加平缓,润湿性增强使得两种裂隙模型驱替开始发生时的进入压力更大,施加相同驱替压力时驱替效率更低.Two-phase displacement flow in rough rock fractures is prevalent in many engineering applications,and aperture distribution characteristics and wettability of rough-walled rock fractures are the two significant factors that affect two-phase displacement flow behavior.Three-dimensional rough surfaces of fracture were generated based on fractal theory and the homogenous model with homogenous aperture distribution and heterogeneous model with heterogeneous aperture distribution were established respectively.Quasi-static drainage process through rough fractures was simulated using LBM pseudo-potential model,accordingly the effect of aperture distribution and wettability of fracture and its microscopic mechanism on two-phase displacement flow behavior were studied.The displacement front of homogenous model basically maintained stable movement,while the phenomenon of dominant displacement path that preferentially invading larger-aperture area with smaller displacement resistance occurred in heterogeneous model.Enhanced wettability can exacerbate this phenomenon,leading to faster breakthrough of the displacement front,which has no significant effect on the homogenous model.Residual capture can be divided into isolated“trapped”pattern and“water-film”mode that adsorbed on the fracture wall,heterogeneous model obviously had more trapped capture than homogenous model,and strong wettability was beneficial for increasing water-film capture.When the displacement pressure increases to the entry pressure,some wetting phases in small-aperture regions of heterogeneous model are gradually displaced,while most of wetting phases in homogenous model are rapidly invaded,thus the Pc-Sw relation curves of heterogeneous model were gentler than that of homogenous model,and increasing wettability resulted in higher entry pressure at the beginning of displacement for both two fracture models and lower displacement efficiency when the same displacement pressure was imposed.

关 键 词：粗糙裂隙 两相驱替 开度分布 润湿性 格子BOLTZMANN方法 

分 类 号：O357.3[理学—流体力学]