The Alcohol Slug Process for Increasing Oil Recovery

Abstract

Published in Petroleum Transactions, AIME, Volume 219, 1960, pages 46–53. Abstract This study defines the basic mechanism of the miscible displacement of oil and water from porous media by various water-driven alcohol slugs. Three distinct alcohol slug processes were studied. Considerable data concerning the quantity of alcohol required for oil recovery were also obtained. All data were obtained in a 1-in. diameter, 100-ft long, unconsolidated core. The porosity of this system was 35 per cent, and the permeability was approximately 4 darcies. Total core pore volume was 5,716 cc. All displacements were conducted at a constant injection rate of 5 to 6 cc/min, which correspond to a frontal advance of 5 to 6 ft/hr. The first portion of this paper is concerned with the use of one alcohol-isopropyl-as the slug material. Isopropyl alcohol (IPA) is completely miscible with both oil and water; however, miscibility of the three-component systems, oil-water-IPA, requires a relatively high concentration of IPA. Hence, the displacement is not of the miscible type unless the IPA concentration is maintained above some critical value. A slug of IPA equal to only 13.5 per cent of the pore volume was found to be sufficient to obtain complete recovery of residual naphtha. In later studies two distinct process variations were developed. The first of these utilized methyl alcohol (MA) and IPA as slug materials. It was shown that methyl alcohol may be substituted for IPA at the front and rear of the slug with no loss of oil recovery. A slug of 4 per cent MA–4 per cent IPA–4 per cent MA was sufficient for complete oil recovery. Because MA is considerably cheaper than IPA, this represents an important step toward economic application. A second process variation used normal butyl alcohol (nBA) and MA as the composite slug, the nBA segment being injected first. This technique requires the smallest total slug size (approximately 10 per cent) of all processes studied. The high cost of nBA, however, precludes commercial application. It is possible that this basic process, subject to changes of alcohol type, may lead to a commercial process.