Enhanced Oil Recovery of Acidic Crudes by Caustic Cosurfactant-Polymer Flooding

A laboratory study of alkaline flooding behavior of three viscous acidic crude oils has been carried out. Optimum flooding formulations have been selected by constructing 'activity maps' of the phase behavior of the crude oil-NaOH mixtures as a function of oil fraction and NaOH concentration. Crude oil-NaOH mixtures demonstrate Optimum phase behavior within a very narrow range of NaOH concentration. Addition of nonionic surfactant Triton X-100, as cosurfactant, has been found to enlarge the optimum region of the activity map very considerably. The results obtained from a series of one-dimensional core flow experiments using Berea sandstone cores indicate that simple application of dilute NaOH solution does not recover any significant amount of additional oil as compared to waterflooding. Optimum caustic-cosurfactant solutions with adequate mobility control, using polyacrylamide Cyanatrol 960, recovered upto 96% of oil in place. Caustic consumption appeared to be a significant factor and unfavorable mobility ratio precludes high oil recovery even when caustic solution initiates oil mobilization.