CO2 -Foam Fracturing With Methanol Successfully Stimulates Canyon Gas Sand

Summary Successful stimulation using CO2 foam with methanol has revived the economically marginal Canyon gas-sand reservoir of Sterling County, TX. Field experience in the Conger (Penn) field demonstrated that CO2 foam (1) lessened the water required in the fluid and (2) provided a gas assist to help remove water and lower interfacial tension (IFT). The low pH of the fluid, combined with additional clay stabilization, iron control, and enhanced water recovery additives, proved helpful in initial well response and subsequent performances. Since the CO2-foam fracture treatments were administered, production from Sterling County Canyon gas sands met or surpassed initial rates, even though formation pressure in the field declined 33.2%. Stimulation is essential for commercial production in these sands. However, water blockage, caused by stimulation, was encountered in designing an effective completion technique for a tight formation with reduced bottomhole pressure (BHP). Production in tight, low-pressure gas wells can be completely blocked if formation pressure does not exceed the capillary pressure increase caused by injected fracture fluid. Original stimulation techniques consisted mainly of gelled-water fracture treatments containing 65, 000 lbm of 20/40-mesh sand with a maximum concentration of 2½ lbm/gal. In many cases, several weeks of swabbing were required to ensure continuous flow. After the fracture treatments, about 40% water recovery was realized throughout the field. This paper discusses CO2-foam fracture treatments and job design and presents case histories from several Conger (Penn) field CO2-foam fracture treatments.