Adsorption and Transport of Chemical Species in Laboratory Surfactant Waterflooding Experiments

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the Improved Oil Recovery Symposium of the Society of Petroleum Engineers of AIME, to be held in Tulsa, Okla., March 22–24, 1976. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and with the paper, may be considered for publication in one of the two SPE magazines. Abstract Important factors influencing adsorption of petroleum sulfonates from field brines onto reservoir sandstone surfaces include salinity, pH and presence of other anionic absorbing species in the water phase; equivalent weight of the petroleum sulfonate species; and specific surface area and mineralogical composition of the reservoir sand. Transport of petroleum sulfonate surfactants can be abetted by establishing conditions which reduce their adsorption and promote their desorption. Pretreatment of the sandstone with sacrificial anions such as carbonate and complex phosphates and inclusion of these additives in small concentrations in the surfactant slug and drive waters effectively reduce petroleum sulfonate adsorption. Use of a fresh water drive fluid effectively desorbs petroleum sulfonates adsorbed from a higher salinity brine, and helps maintain concentrations of surfactant in the low tension displacement front within necessary limits for producing low interfacial tensions over longer reservoir distances. Because of adsorption, the active displacement front in low tension waterflooding tends to advance more slowly than the microscopic frontal velocity of injected fluids. Polysaccharide biopolymers tend to move Polysaccharide biopolymers tend to move relatively faster than the frontal velocity, especially in sands containing a residual oil phase. There is, therefore, a tendency for biopolymer mobility control agents to move ahead of the active displacement front during low tension waterflooding. Care must be exercised in the design of field low tension waterflooding projects, to maintain concentrations of several important chemical species within necessary limits in the active displacement front and to maintain desired relative positions of displacement front and mobility control buffer as they are propagated across the oil reservoir. Introduction Foster has described a low tension waterflood process employing a petroleum sulfonate, inorganic salts, and a biopolymer as chemical flood water additives,. Essential features of the process are (1) propagation of a zone of ultra low oil/water interfacial tensions (about 10 to 10 dynes/cm) across an oil reservoir to mobilize residual oil, and (2) stabilization of the displacement of mobilized oil by a bank of lower mobility drive water.