An offshore Field A located at the Gulf of Mexico has shown a low recovery factor by primary production. The wettability was evaluated by the Amott method and it was found that the porous media is preferentially oil-wet.
Experimental work was undertaken in order to define the feasibility of injecting alkaline solutions to the field in order to improve the oil recovery. The purpose of these experiments was to produce surfactants in-situ to low the interfacial tension and also to react with the reservoir rock surface to modify the wettability of the porous media. The experimental work considered the injection of sea water and sodium hydroxide mixtures into cores from field A. Experimental cores were previously saturated with the field oil which has a density of 0.8928 gr/cm and an acid number of 1.2 mg KOH/gr oil. The alkaline solution was injected at the rate of 25 ml/hr in order to insure velocity displacements about one feet per day, and also reservoir conditions were achieved; displacement pressure of 1,500 psi and temperature of 100°C were kept constant.
The experimental results show that the oil recovery can be higher than 50% when the alkaline solution was injected as compared whith injection of sea water. The effect of the alkali concentration over the recovery factor is also analyzed.