Zou Guodong, Pan Bin, Zhu Weiyao, Liu Yuwei, Ma Shou, Liu Mingming
School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China.
SinoFTS Petroleum Services Ltd., Beijing 100083, China.
Polymers (Basel). 2023 Mar 21;15(6):1560. doi: 10.3390/polym15061560.
Fracturing fluids are widely applied in the hydraulic fracturing of shale gas reservoirs, but the fracturing fluid flowback efficiency is typically less than 50%, severely limiting the shale gas recovery. Additionally, the mechanism and main influencing factors of fracturing fluid flowback are unclear. In this study, microscopic experiments are conducted to simulate the fracturing fluid flowback progress in shale gas reservoirs. The mechanism and factors affecting fracturing fluid flowback/retention in the fracture zone were analyzed and clarified. Results show that the ultimate flowback efficiency of fracturing fluid is positively correlated with the fracturing fluid concentration and the gas driving pressure difference. There are four kinds of mechanisms responsible for fracturing fluid retention in the pore network: viscous resistance, the Jamin effect, the gas blockage effect and the dead end of the pore. Additionally, the ultimate flowback efficiency of the fracturing fluid increases linearly with increasing capillary number. These insights will advance the fundamental understanding of fracturing fluid flowback in shale gas reservoirs and provide useful guidance for shale gas reservoirs development.
压裂液广泛应用于页岩气藏水力压裂中，但压裂液返排效率通常低于50%，严重限制了页岩气采收率。此外，压裂液返排的机理及主要影响因素尚不清楚。本研究通过微观实验模拟页岩气藏压裂液返排过程。分析并阐明了影响压裂液在裂缝带返排/滞留的机理和因素。结果表明，压裂液的最终返排效率与压裂液浓度和气驱压差呈正相关。孔隙网络中导致压裂液滞留的机制有四种：粘性阻力、贾敏效应、气锁效应和孔隙死端。此外，压裂液的最终返排效率随毛细管数的增加呈线性增加。这些认识将加深对页岩气藏压裂液返排的基本理解，并为页岩气藏开发提供有益指导。
