What is Next for SAGD?: Evaluation of Low GHG and High-Efficiency Tertiary Recovery Options

Steam injection has been widely applied in different forms to recover heavy-oil and bitumen for decades. Even though this method is a proven and effective technology, the steam generation process itself may lead to environmental issues and low economic viability. Also, many worldwide steam projects, including SAGD projects in Canada, have already reached their maturity with a severe decline in production despite continuous steam injection. Escalating greenhouse gas (GHG) emissions is another crucial downside of steam injection application, contributing to an emission growth rate of about 1.1% worldwide and 0.8% annually in Canada. This requires us to search for different techniques to deplete the remaining (conditioned) oil efficiently and in an eco-friendly manner. This paper focuses on the testing of a new technique to minimize GHG emissions resulting from steam generation while enhancing the ultimate recovery post-SAGD. ~50,000 cP heavy crude and processed oil (for visual models) samples were used as an oleic phase in this experimental research. Condensable gases as single and multiple (mixed with methane) components were included as potential solvents to be applied to the already steamed models. Visual Hele-Shaw and glass-bead-pack models were employed to investigate the displacement mechanism, displacement efficiency, and phase distribution in porous media. All experiments were performed at currently existing temperatures in matured SAGD reservoirs to further evaluate the sensitivity of phase behavior of condensable solvents in a heavy-oil/steam system, as well as existing condensed water of which is not compatible with hydrocarbon solvents. We observed that condensable solvents could improve the displacement efficiency/incremental heavy-oil recovery over 30% by mobilizing residual oil and providing favorable conformance to the steam chamber. More importantly, the steam usage was able to be entirely cut off, and the energy efficiency could be ramped up to almost 100%. Additionally, the type (and composition) for applying condensable solvents were determined at a given post-SAGD temperature. Also, the retrieval potential of the condensable solvent with oil was investigated for an efficient process. Condensable gases with different compositions were introduced as potential solvents to recuperate heavy-oil and bitumen recovery and reduce or even completely cut off the steam injection at late-stage SAGD, diminishing its GHG emission and improving energy efficiency. Valuable findings present beneficial recommendations for low-emission and high-efficiency late-stage heavy-oil recovery as post-SAGD applications, as well as other types of steam injection processes.