页岩复杂裂缝支撑剂分流机制

Mechanism study on proppants’ division during shale complex fracturing of shale rocks

针对页岩水力压裂复杂裂缝支撑剂分流问题,研发复杂裂缝支撑剂分流运移评价试验系统并进行支撑剂分流规律研究。结果表明:支撑剂在压裂裂缝中存在悬浮运移和滑移滚动,其中支撑裂缝前缘主要以滑移滚动为主;次级裂缝角度、注入排量、加砂质量浓度、压裂液黏度、次级裂缝与主裂缝流量比等对分支后主次裂缝的支撑长度、支撑高度和支撑形态具有重要影响;分支后主裂缝支撑剂分流体积比与次级裂缝角度、注入排量、加砂质量浓度、主次裂缝宽度比成正比,与次级裂缝与主裂缝流量比、压裂液黏度成反比,影响因素由强至弱排序分别为主次裂缝宽度比、注入排量、压裂液黏度、加砂质量浓度、次级裂缝角度和次级裂缝与主裂缝流量比;分支后次级裂缝支撑剂分流体积比与次级裂缝角度、加砂质量浓度、主次裂缝宽度比、次级裂缝与主裂缝流量比成反比,与注入排量、压裂液黏度成正比。

An evaluation method via laboratory experiment of the flow behavior of proppants during complex fracturing in shale reservoir was proposed, in order to investigate the division and migration of proppants in the fractures. The experimental results show that there are two kinds of flow mode for the proppants: suspended migration and slip rolling in the fracture tips. The length, width and shapes of the propped fractures can be affected by many factors, including the angle between the main fracture and the secondary fractures, fluid displacement, proppant concentration, fluid viscosity and the flow ratio between the the main and the secondary fractures. The volume of proppants remaining in the main fracture after division to fracture branches are proportional to the angle between the main fracture and the secondary fractures, the fluid displacement, the proppant concentration, the width ratio between the main and the secondary fractures, but inversely proportional to the flow ratio of the secondary fractures and the main fracture and the fluid viscosity. The importance of the influencing factors on the volume ratio of proppants? division ranks from the width ratio between the main fracture and the secondary fracture, the fluid displacement, the fluid viscosity, the proppant concentration to the angle between the secondary to the main fractures.