Effects of flow rate and alkali-to-acid ratio on the displacement of acidic oil by alkaline solutions in radial porous media

Alkaline flooding is a method of enhanced oil recovery that relies on the f ormation of surface-active substances in situ by a chemical reaction betwee n acidic components in the oil and an alkaline reagent. As the injected alk ali advances through the porous medium, it keeps contacting fresh oil. At s ome moment dependent on the alkali/acid concentrations and the velocity, th e alkali at the advancing front may become depleted and the flood becomes i nterfacially nonreactive. The present study is aimed at investigating the a bove-mentioned phenomena. Displacement studies were conducted in radial cel ls containing sintered glass beads as a porous medium. Light paraffin oil a cidified with 10 mmol/L of linoleic acid served as the displaced (oil) phas e while the displacing aqueous solution contained 0-25 mmol/L of sodium hyd roxide, The highest oil recovery was obtained under the conditions of low f low rate and high alkali concentration. Increasing the flow rate at high Na OH concentration resulted in decreasing oil recovery up to a certain thresh old flow rate. Conversely, the amount of oil recovered by waterflooding onl y (no alkali) initially increased with increasing how rate up to the same t hreshold flow rate beyond which there was no difference between the alkalin e flood and a waterflood. (C) 2000 Academic Press.