A Laboratory Investigation of Oil Displacement From Porous Media by a Liquified Petroleum Gas

Abstract

Abstract The results of a series of laboratory flood tests using liquid iso-butane to displace refined oils from test cores are presented and interpreted on an empirical basis. The study revealed the similarity of the miscible liquid displacement to that of the immiscible-fluid displacement mechanism. The efficiency of the iso-butane flood decreased markedly as the oil viscosity increased, but the effect of injection rate on the effectiveness of the primary production stage was negligible over the range investigated. The presence of free-gas saturation prior to iso-butane breakthrough increased the volume of isobutane required to recover a given percentage of the oil present. Injection of liquid iso-butane prior to water flood resulted in a marked improvement in oil recovery by the water flood. Introduction The production of petroleum is often enhanced by the injection of extraneous fluids into the reservoir. It has been suggested that the injection or cycling of a wet gas or a liquefied petroleum gas would be instrumental in increasing the efficiency of oil recovery to a greater degree than the commonly injected fluids, dry gas and water. Although instances of injection of light liquid hydrocarbons are not unknown, a systematic recording of the results is unavailable; and superficially, the practice gives the impression of being economically unsound. For specific types of displacement, analytic solutions have been advanced which aid in understanding the physical mechanisms involved. However, there is no generalized theoretical concept which permits adequate prediction of displacement efficiency from a knowledge of readily measured reservoir rock and fluid properties. The Buckley-Leverett approach to oil displacement by an immiscible phase is an admirable analysis of that type of mechanism. Dykstra and Parsons have introduced a useful concept in their evaluation of the role of the mobility ratio and its merit in rationalizing displacement phenomena. Everett, Gooch and Calhoun in their report on the effect of viscosity ratio and miscibility have pointed out the lack of a comprehensive theoretical approach and the desirability of investigating the mechanism of miscible-miscible displacement. In lieu of a well-developed theory concerning miscible-miscible displacement and in view of the scarcity of engineering information on actual LPG injection trials, the limited program of laboratory experimentation described below was undertaken.