New Results on the Application of Alkaline Waterflooding to High Acidity Crude oil

Abstract

The main objective of this work was to study the enhanced recovery of a high acidity crude oil (South Geisum crude) by alkaline solutions. Different properties of South Geisum crude oil, namely acidity, interfacial tension, and contact angle were investigated. Displacement tests were carried out to study the effect of alkaline slug concentration, slug size, alkali type, temperature and viscosity on recovery.South Geisum crude oil is a highly acidic crude (4.38 mg KOH/g). It was found that the interfacial tension between this crude oil and formation water decreases with increasing alkaline concentration until it reaches a minimum, after which it increases again with further increase in alkaline concentration. Interfacial tension between crude oil and displacement water also decreases with increasing alkaline concentration. Contact angle measurements indicated oil-wetting conditions which increase by the addition of alkaline solutions. Displacement floods in a 5-spot quadrant showed that, at the early stages of displacement oil recovery increases with increasing alkaline concentration until it reaches a maximum at 4% by weight NaOH concentration. Also, at such early stages, an excessive increase in alkaline concentration results in lower oil recovery. On the other hand, after the injection of many pore volumes of water, oil recovery is almost the same regardless of the alkaline concentration. It was found also that the oil recovery increases with increasing alkaline slug size until it reaches; a maximum at 15% PV after which increasing slug size results in decreasing oil recovery (this result has not yet been reported in the literature). Sodium hydroxide slugs produce more oil recovery than sodium carbonate slugs. Oil recovery increases with increasing temperature and decreasing oil viscosity.