A Comparison Of Sodium Orthosilicate And Sodium Hydroxide For Alkaline Waterflooding

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract Alkaline waterflooding has been extensively investigated over the past 50 years in laboratory and field testing situations as a method for increasing crude oil recovery. Alkaline salts such as sodium silicate, sodium hydroxide and sodium carbonate have been cited in various patents and investigations as useful agents for patents and investigations as useful agents for improving water flood performance. Laboratory measurements of interfacial tension (IFT) values between alkaline solutions of sodium orthosilicate and sodium hydroxide and several mid-continent and California crude oil samples have been obtained with a variety of types of injection water. In softened water with no Ca++ or Mg++ ions present, both alkaline salts exhibit similar reductions in interfacial tension with all the crude samples tested. When unsoftened water was used to prepare alkaline injection solutions, sodium orthosilicate was effective in significantly reducing IFT values at concentrations of 0.5% to 1.0% with mid-continent crudes. However, using sodium hydroxide, even up to 5% by weight, IFT values with these same crudes were not reduced as much as with sodium orthosilicate. Both alkaline salts were equally effective in reducing IFT values between the California crude oils tested and unsoftened injection solutions. The concentration of alkaline salt required to produce a minimum IFT value ranged from 0.01% to 0.5% by weight, depending upon the injection water used. This paper will review the laboratory data which has been accumulated, and present a comparison between sodium orthosilicate and sodium hydroxide as alkaline waterflood additives. Introduction A recent article by Johnson provides an excellent review of the historical background, proposed mechanisms and the state-of-the-art proposed mechanisms and the state-of-the-art in caustic and emulsion methods for improved waterflood recovery of oil. The addition of alkaline chemicals to injection water has been proposed by many workers over the past six proposed by many workers over the past six decades (Reference 1 and the references contained therein). Considerable laboratory data and a few field trials have suggested that alkaline waterflooding, or modifications thereof, can provide an incremental increase in oil recovery under the proper operating conditions in selected reservoirs. At the present time there are several field trials of alkaline waterflooding under way or proposed.