Stabilization and performance of a novel viscoelastic N2 foam for enhanced oil recovery

Abstract

A novel viscoelastic N2 foam (0.12% sodium dodecyl sulfate + 0.18% erucyl dimethyl amidopropyl betaine) with ultra-low interfacial tension and alkali-free was developed. With the conditions of Xinjiang Oilfield (45℃, c (salinity) = 7880 mg/L), the foam performances were investigated by the modified Rose-Miles method. The modified Rose-Miles method is in non-shear action, in which N2 enters a porous media and pumps into the solution to produce foam. The stability mechanism was explained based on the dilatational surface viscoelasticity and liquid viscoelasticity. The EOR effect was evaluated by the displacement experiment. The results showed that the foam volume of viscoelastic N2 foam was five times compared with the initial solution. The foam half-life and the drainage half-life were 6.5 and 6.2 times higher compared with that of stabilized by the polyacrylamide, respectively. The surface of N2 foam possessed high elasticity modulus, and the solution had high viscoelasticity, so the particle size and drainage of liquid film changed slowly. Finally, the viscoelastic N2 foam flooding (0.4PV surfactant + 0.4PV N2) enhanced oil recovery by 22.95%, compared with the surfactant flooding (0.8PV surfactant) by 4.06%. The viscoelastic N2 foam could greatly reduce the amount of surfactant and had an excellent EOR application in the Xinjiang Oilfield.