The Effects of Alcohols and Crude Oil Composition on the Performance and Mechanisms of Alkaline Flooding of Oil Reservoirs.

Alkaline flooding for enhanced oil recovery was investigated and methods were developed to increase the efficiency and predictability of the process. The problems associated with current alkaline flooding technology were addressed in three ways. The effect of alcohol additives on alkaline flooding was studied since alcohols have benefited related surfactant procedures. Crude oil composition was correlated with flood behavior to provide better predictions of alkaline flood performance. Finally, alkaline flood recovery efficiencies of oxidized crudes were measured to determine the benefits of in-situ air oxidation. The alkaline flooding process was studied through the use of interfacial tension measurements, microscopic examination of floods in thin flow cells, and sandpack floods. Five acidic crudes and four low acidity crudes were investigated. Alcohol additives were found to significantly improve the alkaline recovery of certain crudes. The improvement in flood performance was found to increase with increasing water solubility of the alcohol. Water miscible alcohols had little effect on the crude oil/water interfacial tension; whereas less soluble alcohols exhibited a high crude oil/water interfacial tension which was detrimental to oil recovery. Recovery also depended on the emulsion behavior of the crude. Crudes which did not readily emulsify on contact with alkaline water did not show more efficient recovery with alcohol. Microscopic studies of alcohol-augmented alkaline floods showed that alcohols destabilized emulsions thereby improving oil drop coalescence which aided the formation of an oil bank. Alcohols also reduced the viscosity of emulsions which resulted in improved sweep efficiency. Two acidic crudes (Tullos and MG3) which represented the extremes in emulsion behavior were fractionated by ion exchange chromatography and analyzed for chemical composition. The interaction of the fractions with alkaline water was observed in thin flow cells. Only carboxylic acid fractions formed emulsions. However, phenolic fractions curtailed this emulsification. Emulsification behavior was attributed to changes in the crude oil/water interfacial viscosity. Finally, sandpack floods showed that one oxidized oil yielded 10% higher recovery than the unoxidized oil. It was concluded that air oxidation of the crude yielded surface active material capable of improving oil recovery by alkaline flooding