Mathematical Modeling of the Fate of the Injected and In-Situ Generated Gases in Subsurface Geological Formations

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Risk of leakage of carbon dioxide (CO2) injected into subsurface geological formations and solvents used in solvent-aided thermal recovery of bitumen from shallow oil sands is one of the major environmental challenges. Permanent trapping of these chemicals in subsurface may occur by several trapping mechanisms such as dissolution, residual phase, and mineralization. Recently, bio-derived chemicals such as dimethyl ether with mutual solubility in oleic and aqueous phases have gained interest in solvent-aided thermal recovery of bitumen. In addition, significant volumes of methane, carbon dioxide, and hydrogen sulfide are generated or liberated from oil sands as a result of steaming of bitumen at high temperatures greater than 200oC. While injected solvents for bitumen recovery are partially recovered with the produced fluids, a fraction of these chemicals along with the generated gases will remain in subsurface with potential risk of leakage to the groundwater in long term. The focus of my research is to develop models to study the long-term fate of the injected or in-situ generated chemicals in subsurface. While progress has been made in the past decade, further research is required to develop a better understanding of the trapping mechanisms and gain insight into the long-term fate of the injected CO2 and other chemicals. My research program aims to advance the knowledge of fundamental trapping mechanisms such as convective dissolution and long-term fate of CO2 and injected chemicals or in-situ generated chemicals in subsurface. Of particular interest is the development of computational tools that can be used by oil sands industry, governmental organizations, and policy makers for risk assessment of CO2 and environmental impact assessment of solvent injection for in-situ extraction of bitumen from oil sands. Recently, models have been developed for estimation of the rate of leakage of pressurized brine and CO2 from storage sites. However, development of tools for estimation of the rate of leakage of the injected and in-situ generated chemicals is still very much in its infancy. In particular, leakage models with applications to in-situ oil sands extraction processes are lacking. In addition, finding ways to accelerate solubility trapping of CO2 and reduce risk of leakage by acceleration of convective dissolution requires further research. This research develops knowledge and provides tools that help safe implementation of CO2 and acid gas sequestration as well as informed application of solvents for in-situ bitumen extraction from oil sands. In particular, new insights into the long-term fate of injected chemicals, determination of potential leakage pathways and mechanisms, and strategies to accelerate solubility trapping will be novel contributions of this research. In addition, this program provides training for 5 Undergraduate, 2 MSc, and 2 PhD students.