Enzyme Penetration Tests on Carbonaceous Rocks for Application to Enhanced Oil Recovery

Abstract

Abstract Many different Enhanced Oil Recovery (EOR) methods have been applied on reservoirs with declining oil production. Currently there is a demand for new and green technologies in order to increase oil recovery. One of the technologies in focus is Enzymatic EOR (EEOR). One of the newest proposals for the application of enzymes utilizes their ability to alter the wettability of the reservoir rock. Both laboratory experiments and pilot plant tests have been carried out (although mainly for sandstone rocks) to study this effect. However little is known about the applicability of enzymes on carbonate reservoirs. The aim of this paper is to outline the penetration behavior of two different enzymes on carbonate cores, in order to check whether the enzymes get irreversibly adsorbed in the rock and, thus, would "get lost" close to injection sites if injected for EOR. This is an important study in order to investigate the feasibility of EEOR application in the North Sea carbonate reservoirs. Two enzymes, an esterase and a lipase, were selected based on their ability to change the wettability and adhesion properties and also desorption rates on cleaned cleaved chalk surfaces. The penetration tests were conducted on North Sea chalk reservoir cores. The tests showed that the esterase does not penetrate chalk whereas the lipase does. When the core is previously unused a recovery rate of up to 35% of the lipase is achieved.