Chromatographic Transport of Reverse-Wetting Agents and Its Effect on Oil Displacement in Porous Media

Abstract

Published in Petroleum Transactions, AIME, Volume 219, 1960, pages 150–157. Abstract A study of the effect upon oil recovery from an unconsolidated porous medium of chromatographic transport of selected reverse-wetting additives during water displacement is described. Flow tests were performed on hydrocarbon oil-saturated sand columns (containing connate water) into which small volumes of short-chain aliphatic amine solutions were introduced during water flooding. Concurrently, measurements of oil-silica contact angles, oil-water interfacial tensions and oil-water distribution coefficients were measured as a function of additive concentration. Certain treatments were found to cause a slight reduction in oil recovery, while others produced a significant increase (up to 50 per cent of the normal irreducible minimum oil saturation). Recovery efficiency was correlated most satisfactorily with the maximum degree of reverse wetting produced during additive transport; conditions which resulted in only mild oil wettability of the sand reduced recovery, while those favoring strong oil wetting increased recovery. A mechanism of reverse-wetting additive action during chromatographic transport is developed which ascribes the results to transient changes in oil-solid contact angle during flow, with consequent release of oil trapped by capillary forces. implications of these observations with regard to improved waterflood efficiencies are discussed. Introduction The need for finding improved methods of oil production is amply illustrated by the large volume of oil considered economically unrecoverable by existing production practice. Water flooding has long been an excellent method of secondary recovery. However, even in those areas of a formation which are well swept by a water flood, 20 per cent or more of the oil remains trapped within the formation and is not recovered. This trapping of oil within the pores of the rock structure results primarily from interfacial forces. If these interfacial forces were altered, it is possible that the trapped oil could be released and recovered.