Miscible Fluid Displacement in Porous Media

Abstract

Published in Petroleum Transactions, AIME, Volume 213, 1958, pages 76–79. Abstract An experimental investigation of miscible fluid displacement has been made in linear porous media under highly adverse mobility ratio conditions. Various refined oils were displaced at field rates by liquid propane in both horizontal and vertical models 9 to 36 ft in length. In horizontal tests, mixed zones or transition zones form between the two liquids early in the displacements. Initially, the zones grow rapidly. In 2-in. diameter models, the mixed regions become nearly stable zones from 6- to 20-ft long. From then on these quasi-stable zones apparently grow only by molecular diffusion. The lengths of the quasi-stable zones appear to be almost independent of the core material in which displacements are made and increase with increasing rates of injection and oil/solvent viscosity ratios. The lengths of the quasi-stable zones measured in 2-in. diameter models at viscosity ratios and injection rates anticipated in the field indicate that essentially piston-like displacements of oil by solvent would occur. However, the mixed zone lengths increase markedly as the model diameter increases. In vertical displacements controlled by gravity drainage, only short transition zones form. The entire lengths of these zones can be accounted for by molecular diffusion. Therefore, in reservoirs having characteristics allowing a high degree of gravity drainage, nearly complete oil recovery should be attainable by miscible fluid displacement. Introduction The oil industry is faced with an ever increasing cost for finding new oil reservoirs. This, coupled with the fact that conventional methods of oil recovery usually leave from 1 to 3 bbl of oil in the ground for every barrel produced, has aroused considerable interest in developing more efficient methods. An integral part of the mechanism of many of these new methods of recovery is a miscible fluid displacement in which oil is displaced by a much less viscous material such as liquid propane. A number of investigators have explored the mechanics of miscible fluid displacement but in the experiments reported many of the important factors have been varied only over a limited range far removed from normal oilfield values. This paper presents the results of an experimental study of oil displacement by liquid propane at field rates from linear, natural-sandstone models of various sizes. Both horizontal and vertical flow tests were made.