Performance of Urea and Pyrrolidine as Additives in the ES-SAGD Process

We present an experimental investigation comparing the recovery performance, steam utilization efficiency, and environmental metrics of urea and pyrrolidine as coinjected additives in the Expanding Solvent Steam-Assisted Gravity Drainage (ES-SAGD) process for in situ bitumen recovery. Despite the exploration of various solvents for ES-SAGD, a systematic comparison of thermally decomposing agents and stable organic amines in terms of their distinct mechanistic impacts on bitumen mobilization and comprehensive environmental footprints remains a critical research gap. This study addresses these gaps by providing a systematic experimental evaluation of both urea and pyrrolidine, integrating the recovery performance evaluation with chemical stability analysis. Laboratory experiments were conducted using a comprehensive screening apparatus under controlled conditions of 220 °C and 336.4 psia (2.3 MPa) to evaluate the effectiveness of additives at different concentrations: urea at 1.5, 3.0, and 5.0 wt % and pyrrolidine at 1.0, 2.0, and 3.0 wt %. The evaluation included a systematic analysis of bitumen recovery, oil production rate, cumulative steam-to-oil ratio, gas production, and additives’ solubility characteristics. The results demonstrate that both additives significantly enhanced oil recovery compared to conventional SAGD, which recovered 66% of the original oil in place (OOIP). Optimal performance was achieved with 3.0 wt % urea and 2.0 wt % pyrrolidine, yielding maximum oil recoveries of ∼93% and ∼91% of the OOIP, respectively. These concentrations also improved steam efficiency, reducing the average steam-to-oil ratio by 35% relative to baseline SAGD. Consequently, energy consumption decreased by 11.6–11.7 GJ/m 3, accompanied by a substantial reduction in CO 2 emissions. The associated carbon tax recovery potential ranged from $27.50 to $27.74 per tonne of CO 2, highlighting significant economic benefits. Gas chromatography analysis revealed distinct additive behaviors: urea underwent thermal decomposition, generating NH 3 and CO 2, whereas pyrrolidine preserved its chemical structure, enhancing emulsification and solubility. The study demonstrates that low concentrations of urea and pyrrolidine have the potential to improve operational efficiency, positioning ES-SAGD as a promising technology for bitumen production, offering substantial environmental and economic advantages.