Tertiary Recovery of the Bradford Crude Oil by Micellar Solutions, from Linear and Two-Dimensional Porous Media
Authors: Ali S.M. Farouq , Stahl C.D. 
Published: December 2007

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Abstract
Results of an extensive, five-year laboratory investigation of the tertiary recovery of Bradford crude oil, employing micellar solutions, are discussed. most of the experiments were carried out in linear sandstone cores, ranging in size from two inches diameter × 4 ft to nine inches diameter × 20 ft length, while a series of runs were conducted in two-dimensional porous packs representing a five-spot flood porous packs representing a five-spot flood pattern. pattern. The basic parameters studied were the micellar solution slug size, the polymer buffer size and mobility, and the flood advance rate, in relation to tertiary oil recovery, and to some extend sweep efficiency. Mobility control by polymer buffer was simulated by a comparable polymer buffer was simulated by a comparable viscous buffer in some of the experiments to study the essential features of slug protection. Two different micellar solutions (viscosities 19 and 38 centipoise), supplied by the Marathon Oil Company and Bradford crude oil were employed in the tests.
Particular attention was directed to mobility control at the rear end of the micellar solution slug. Polymer buffer concentrations ranged from 500 to 1500 ppm, while the buffer size was varied from 0 to 80% of pore volume. In both linear and two-dimensional tests, the oil recovery increased as the buffer mobility decreased, especially over the polymer concentration range of 500–1000 ppm. Glycerin solutions having comparable mobilities showed similar behavior. it was found also that in the linear systems investigated approximately 20% pore volume buffer is adequate to protect the micellar solution slug, for slug sizes as small as 2.5%, as regards oil recovery, and the maximum slug concentration in the effluent. The effect of isopropyl alcohol in the polymer buffer was also studied.
Oil recovery was found to increase with an increase in slug size, for slug sizes of 2.5 to 12% pore volume. The recovery was over 90% of the initial oil (waterflood residual) in place for a slug size of 5%, beyond which the gain in recovery with an increase in slug size was small. The recovery ratio (oil recovered to slug volume injected) was higher for smaller slugs, e.g. 8.6 for a 2.5% slug, as compared to 3.4 for a 10% slug. For a given slug, this ratio also increased with an increase in the polymer concentration.
The breakthrough sweep efficiency in a laboratory five-spot sand pack was found to be about 60%, based upon oil recovery, as well as visual observation.