Stability of Depletion Chamber Edges in Oil Sands Recovery Processes
Date
2021-04-22
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Many modifications to Steam-Assisted Gravity Drainage (SAGD) have been proposed to make the steam-based recovery process more efficient and profitable. A common approach is coinjection of additives with steam. There are two general classes of additives: first, solvents that dilute the bitumen leading to a higher mobility of oil phase and second, non-condensable gas (NCG) that provides an insulative effect in a reservoir to reduce heat loss and consequently raising the thermal efficiency. Solvents most used in oil sands processes are C3 to C7 solvents whereas NCGs typically consist of natural gas (methane) or carbon dioxide. Despite a lot of research on solvent and non-condensable gas additive processes, the underlying physical mechanisms of heat transfer, flow, and potential instability remain unresolved given the interplay of phase behavior, oil mobilization, heat transfer (conductive and convective), multiphase counter-current flow, and potential instabilities in steam-only, solvent-steam, and NCG-steam process are complex. This thesis documents research on these mechanisms and how they interact by using ultra-fine three-dimensional thermal reservoir models. The results of the analysis reveal that interfacial instabilities are observed in both pure-steam and steam-NCG (0.5 mol%) cases where the instabilities are evidenced by gas fingers that evolve above the top depletion chamber edge. The instability, triggered by dominant convective heat transfer, exhibits two types of fingers in the steam-only case: solution-gas fingers and thermally-stimulated oil viscous fingers, with consequently enhanced
heat transfer rate. In the NCG-steam case, only solution-gas fingers are present, and the length scale of the fingers is smaller than that in the steam-only case. In the steam-solvent case, the presence of solvent tends to suppress the onset of the instabilities. This is due to the rich solvent band present at the chamber edge which causes the mitigated temperature gradient and consequently lower tendency for solution gas ex-solved from oil sands.
Description
Keywords
oil viscous fingering, instability;, thermal-solvent recovery;, steam-assisted gravity drainage;, non-condensable gas, thermal viscous fingers
Citation
Zhou, Q. (2021). Stability of Depletion Chamber Edges in Oil Sands Recovery Processes (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.