A novel CO2 and pressure responsive viscoelastic surfactant fluid for fracturing

Hydraulic fracturing is playing a more and more important role in rapid shale oil and gas recovery development. Meanwhile, damage to the reservoir fracture and environmental contamination caused by fracturing fluid flowback water has raised serious concerns. In this study, a CO2-responsive surfactant, erucamidopropyl dimethylamine (EA), was synthesized and used as the thickening agent to develop a novel viscoelastic surfactant (VES)-based fracturing fluid. This fluid was responsive to the presence and pressure of CO2. It was not only rock formation friendly and environment benign but also readily reusable attributed to a gelling-breaking process that can be easily controlled by manipulating CO2 gas conditions. The viscoelastic behaviors of this VES fluid were investigated through rheological measurements under ambient and elevated temperature and pressure. The fluid-rock interaction was studied in core flooding tests. Results showed a good CO2-responsiveness, switchable viscoelastic performance, high shear tolerance, thermal stability, good salinity tolerance, and low core damage of the fluid. The switchable rheological behavior implies this fracturing fluid can readily be reused. It is expected that this fluid finds applications not only in enhanced oil and gas recovery, but also in other areas such as CO2 sequestration reservoir leakage sealing.