Successful Field Applications of CO2 Foam Fracturing Fluids In the ARK-LA-TEX Region

The CO2 foam fracturing fluid provides a gas drive to assist removal of the treating (load) fluids after the proppant has been placed in the formation, establishes permeability to gas within the formation volume that has been saturated by load fluids, and minimizes the actual water volume that is required to place a given volume of proppant in the formation. Due to the high density of the liquid CO2 mixture, the CO2 foam can be utilized on deep, high pressure formations without experiencing prohibitive wellhead treating pressures. The CO2 also reacts with the water in the foam to form carbonic acid, so that the overall pH of the system is reduced (thus reducing the damaging effect of the fluids), and it lowers the surface tension of the load fluids so that they can be recovered more rapidly and efficiently. Field experience in the Ark-La-Tex area has demonstrated that the CO2 foam system can be used successfully in low permeability oil and/or gas sands and carbonates, at depths ranging from 2900' to 14,000 ', reservoir temperatures of 120_F to 370_F, and reservoir pressures of 1000 psi to 13,200 psig. Treatment histories and pressure transient tests have demonstrated that many of these formations are sensitive to some fluids utilized in conventional gelled water fracture treatments. A comparison of CO2 foam with several other stimulation methods demonstrates its overall success. In many instances the production results obtained with CO2 foam fluid are superior to more conventional systems that have been used in the past.