The objective of this study is to examine the impact of polarity on surfactant-steam flooding performance in the recovery of a Canadian bitumen sample.
10 laboratory-scale core flood experiments were used to investigate the interaction between the polar head of surfactants and polar fractions of the bitumen sample (resins and asphaltenes) in the presence of steam. A Canadian bitumen from Alberta with high polar fraction content; resins (17 wt%) and asphaltenes (29 wt%), was selected. The bitumen sample was first characterized in terms of viscosity at reservoir temperature (10,000 cP) and API Gravity (12°). Then, coreflood tests were conducted by coinjecting steam with an anionic, a cationic, or a nonionic surfactant. The performance of three anionic, three cationic, and three nonionic surfactants was tested. Each core flood result was evaluated in terms of the cumulative oil recovery, the residual oil content, the produced oil quality, and the asphaltenes content of produced and residual oil samples. Then, bitumen's polar fractions (resins and asphaltenes) and bitumen itself were subjected to each surfactant solution under steam and liquid water conditions, and simultaneously their interactions were captured by an optical microscope. Analysis of microscopic images was used to explain the performance differences in each flooding test.
Every surfactant-steam flooding process resulted in higher recovery than steam flooding alone. The greatest oil recovery was observed with the longest tail length anionic surfactant. It has been observed that the presence of asphaltenes in displaced oil inhibits the formation of microemulsions and consequently reduces the amount of produced oil. Further, we observed that the microemulsions are successfully formed between the resins fraction of bitumen sample and surfactant solution under steam condition. Hence, to maximize the effectiveness of surfactant processes in high asphaltenes content reservoirs, we highly recommend the use of asphaltenes precipitants prior to injection of any surfactant solutions.