Experimental investigation of alkali-surfactant-polymer flooding forcarbonate reservoirs

This paper presents a systematic study of laboratory tests for Alkali-Surfactant-Polymer (ASP) floodingapplication for carbonate reservoirs.The performance of the selected chemicals was first screened through interfacial tension and viscosity measurements with Dulang crude oil. The selected chemicals concentration were then assessed by natural imbibition tests, and core flooding experiments using carbonate core samples at 80 oC.These experiments were performed to investigate the effect of thealkali, alkali-surfactant, and alkali-surfactant-polymer on the rock wettability and subsequent effect on the oil recovery. Results from the imbibition tests indicated that 33.1% of original oil in place can be recovered in the presence of 0.6% alkali and 0.8% surfactant as compared with the use of brine alone. Additional results obtained from the core flooding test showed significant improvement in the oil recovery with the use of ASP flooding. Injection of 0.5PV of the formulated ASP slug followed by chase water produced an additional 24.7% OOIP over water flood, accomplishing a total oil recovery of 88.7% OOIP. This makes the ASP flooding an attractive method for carbonate reservoirs and significant amount of the residual oil can be recovered. No issues of reservoir heterogeneity or related sweep efficiencies were included in this study.