Fracturing process using a viscosity stabilized energizing phase

摘要

Hydraulic fracturing process in which a normally gaseous energizing phase is incorporated into an aqueous fracturing fluid in a manner to effect good dissemination and stabilization of the energizing phase in the fracturing liquid. A normally gaseous energizing phase is incorporated into an aqueous fracturing fluid having a viscosity at wellhead conditions within the range of 10-300 centipoises. The fracturing fluid containing the energizing phase is introduced into the well and displaced from the wellhead down the well to the vicinity of the subterranean formation. During the displacement of the fracturing fluid from the wellhead to the vicinity of the formation, the viscosity of the fracturing fluid is increased by a factor about 2 or more. The higher viscosity fracturing fluid is displaced from the well into the formation in the course of the fracturing process. The energizing phase is provided by incorporating a substantial amount of liquid carbon dioxide into the aqueous fracturing fluid. Nitrogen gas may also be incorporated into the fracturing fluid. Mixing of a cross-linking agent within the fracturing fluid and cross-linking of a polymeric thickening agent causes viscosity enhancement of the fracturing fluid as it moves down the wellbore.