Performance of ASP compound systems and effects on flooding efficiency

Based on practical needs of oil fields, the viscosity, interfacial tension, static absorption, phase behaviors, molecular clew dimension (D-h), molecular configuration and flooding effect of the alkali/surfactant/polymer (ASP) systems were studied by instrumental analysis and physical modeling. The mechanisms of enhanced oil recovery were also discussed. As alkali concentration increased, the viscosity, interfacial tension and D-h of ASP decreased. As surfactant concentration increased, the viscosity and D-h increased, while the interfacial tension first decreased and then rose. The viscosity, interfacial tension and D-h of weak-alkali ASP all surpassed those of the strong-alkali ASP. The saturated absorption quantity of ASP ranked as surfactant > alkali > polymer. The saturated adsorption quantity and the ability to reduce the surfactant adsorption loss of the strong alkali were both higher, but the ability to reduce polymer adsorption loss was lower, compared with the weak alkali. As the concentrations of alkali and surfactant rose, the stability of emulsions was enhanced. The effect of alkali on the polymer molecular aggregation surpassed that of the surfactant. Physical modeling showed as the viscosity of the flooding agent rose, the recovery rate of weak-alkali ASP increased by 22.0% under the conditions of 1.2 wt% alkali, 0.3 wt% surfactant and 2500 mg/L polymer. The contribution rate to the recovery efficiency of A compound flooding ranked as the extended swept volume effect of the polymer (alpha(p)) > displacement effect (beta) > the extended swept volume of emulsification (alpha(e)). The results were alpha(p) = 73.5%, beta = 19.9%, alpha(e) = 6.6% (weak-alkali ASP); alpha(p) = 68.5%, beta = 23.0%, alpha(e) = 8.4% (strong-alkali ASP).