压裂液侵入对页岩储层导流能力伤害

The Damage of Fracturing Fluid Intrusion to the Conductivity of Shale Reservoir

大规模水力分段压裂是页岩气等非常规资源高效开发的关键技术。页岩气井返排率一般较低,大量的压裂液长期滞留地层对储层岩石、支撑剂强度等造成一定的伤害,影响页岩储层压裂改造长期效果。针对该问题,通过室内试验模拟研究现场压裂前后气测导流的变化规律,对压裂液伤害程度进行表征。结果表明:压裂液侵入降低了支撑剂、页岩岩石强度,导致支撑剂破碎率、岩石嵌入程度加剧,导流能力伤害达到60%以上;使用大粒径支撑剂、较高铺砂浓度,优选破胶性能好、低残渣、防膨性强的压裂液,能有效提高导流能力,降低压裂液伤害程度。研究结果对页岩地层压裂设计,降低压裂液伤害提高产量提供参考。

Large-scale hydraulic fracturing is a key technology for efficient development of unconventional resources such as shale gas. Generally speaking, the flowback rate of shale gas wells is relatively low. A large amount of fracturing fluid stays in the formation for a long time, which causes certain damage to the reservoir rocks and proppant compressive strength, and affects the long-term effect of shale reservoir fracturing transformation. To solve this problem, the variation rule of gas conductivity before and after field fracturing was studied by indoor test simulation, and the damage degree of fracturing fluid was characterized. Results show that the intrusion of fracturing fluid reduced the strength of proppant and shale rock, and increased the fracture rate of proppant and the degree of rock embedding, in which the damage of flow conductivity reached more than 60%. Using large particle-sized proppant, high sand concentration, and choosing quality fracture fluid with good gel-breaking performance, low residue, and strong anti-swelling, could effectively improve the conductivity and reduce the damage degree by fracturing fluid. This research could provide a reference to the fracturing design for shale formation, reducing the fracturing-fluid-induced damage, and increasing the production.