The Role of Surfactant Additives In the In-situ Recovery of Bitumen From Oil Sands

Abstract

Abstract The experimental results reported in this paper are part of a study designed to examine the benefits of using surface-active chemicals with steam-based processes for obtaining additional bitumen recovery from the oil sands. Results are included, mainly from the following three stages of the work:the effect of temperature and concentration on the stability of a commercial petroleum sulfonate surfactant;displacement experiments conducted in laboratory cells (0.16 kg and 1.6 kg oil sand capacity) at 100ºC;simulation runs carried out on the 45-cm Alberta Research Council Test Bed (75 kg oil sand capacity) at saturated steam conditions of 3.5 MPa and 250ºC. Measurements of bitumen/aqueous interfacial tensions and surfactant retention in porous media are also briefly described. Based on this work it appears that surfactants have considerable potential; a two- to three-fold increase in bitumen recovery was often realized when compared to baseline experiments in the absence of surfactant. Introduction Bitumen contained in oil sands has virtually no mobility at reservoir temperatures and pressures. The primary means to reduce the viscosity and improve mobility is to provide thermal energy; bitumen undergoes a very steep reduction in viscosity with increasing temperature. In-situ recovery methods using steam injection either in cyclic or drive processes, have been widely used(l). However, they are often inefficient and leave behind substantial amounts of oil. The use of volatile additives, such as solvents(2. 3), gases(4, 5) and combinations of gases and solvents(5), in conjunction with steam to increase bitumen recovery has been promoted. At present, the commercial feasibility of these processes cannot be estimated with certainty. Alkali additives with steam were applied in both laboratory(6) and field(7) tests with little success. The use of surfactant additives in combination with steam has also been suggested(8, 9). A recent laboratory study of a surfactant-steam flood using 30ºAPI crude at 180ºC showed (Figure in full paper) that a significant reduction in residual oil saturation is possible(10). Studies of the stability(l0, 11) and retention(12) of surfactants have pointed out the problems associated with their use at elevated temperatures. In this work, the potential for increased bitumen recovery from oil sand formations by using a surfactant additive was investigated. A commercially available surfactant was used in all experiments reported here. This surfactant is typical of a class known as petroleum sulfonates. Both economic and technical considerations have led to their use in enhanced oil recovery from conventional reservoirs. A method which could be used to rapidly evaluate the effectiveness of large numbers of commercially available surfactants for oil sands research was recently presented(13). Experimental Details Materials Bulk samples of rich oil sands (14–15 wt. % bitumen) were obtained from the Suncor mine site of the McMurray formation and frozen in sealed 20-kg pails until use. The commercial petroleum sulfonate, Petronate TRS 10–80, was obtained from Witco Chemical Corporation. Analysis by the two-phase titration method(14) showed an active sulfonate of 86 wt. % based on an average equivalent weight of 418.