基于CFD-DEM方法的迂曲裂缝中支撑剂运移关键影响因素分析

Analysis on Key Influencing Factors of Proppant Migration in Tortuous Fractures Based on CFD-DEM Method

裂缝中支撑剂的运移和铺置是维持裂缝开放和增强裂缝导流能力的关键,但支撑剂在迂曲裂缝中的运移机理尚不明确。为此,基于计算流体力学原理,利用离散单元法建立支撑剂在迂曲裂缝中运移的数值模型,研究携砂液注入速度、压裂液砂比、支撑剂粒径等因素对迂曲裂缝中支撑剂运移铺置规律的影响。结果表明:裂缝迂曲度越大、支撑剂铺置距离越短,流速损失越大;在距裂缝入口20 mm处,与迂曲度为1.0的裂缝相比,迂曲度为1.2、1.5、2.0的裂缝中的流速损失率增大2.2、3.7、4.5倍;迂曲裂缝内支撑剂铺置距离随支撑剂注入速度的增大而增大,随压裂液砂比、支撑剂粒径的增大而缩短。该研究可为支撑剂在迂曲裂缝中运移的相关研究提供理论指导。

The migration and displacement of proppant in fractures is the key to maintain fracture opening and enhance fracture conductivity,but the mechanism of proppant migration in tortuous fractures remains unclear.According to the principle of computational fluid dynamics,a numerical model of proppant migration in tortuous fractures was established by the discrete unit method to study the effects of proppant-carrying fluid injection rate,fracturing fluid-proppant ratio,proppant particle size and other factors on the migration and displacement of proppant in tortuous fractures.The result shows:The greater the tortuosity of the fracture,the shorter the proppant displacement distance and the greater the flow rate loss;at 20 mm from the fracture entrance,the flow rate loss rate in the fracture with tortuosity of 1.2,1.5 and 2.0 was increases by 2.2,3.7 and 4.5 times compared with that in the fracture with tortuosity of 1.0;the proppant displacement distance in the tortuous fracture increased with the increase of proppant injection rate,and decreased with the increase of fracturing fluid-proppant ratio and proppant particle size.This study can theoretically guide the study of proppant migration in tortuous fractures.