Browsing by Author "Irani, Mazda"

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    On Stability in Gravity Drainage Oil Sand Recovery Process
    (2017) Irani, Mazda; Gates, Ian; Natale, Giovanniantonio; Maini, Brij; Larter, Stephen; Zeng, Fanhua
    The controlling feature of steam-based recovery processes is heat transfer from the steam chamber to the formation – the greater the heat flux, the larger the oil volume heated and the higher the oil drainage rate. Stability phenomena in SAGD occur both at the edge of the chamber and at the liquid pool that exists above the production well. Previous studies have demonstrated that instability at the steam chamber edge can enhance heat transfer there by creating limited-amplitude steam fingers which enlarge the heat transfer area thus leading to greater thermal efficiency of the recovery process. In the research documented in this thesis, the stability between steam condensate and bitumen at the edge of the chamber is explored by deriving a new steam pressure diffusion equation. The results show that the stability is controlled by the interface velocity and water-phase hydraulic diffusivity. Also, the results demonstrate that at typical SAGD operation conditions, the chamber edge is unstable. In the liquid pool, the key measurement to maintain its stability is associated with steam trap control. The main objective is to keep subcool higher than set value which varies between 0 to 40° and even higher values. This study presents a new method to calculate the liquid pool level from temperature profile in observation wells, and liquid pool shrinkage as a function of time. Using this method, envelopes are suggested to differentiate three different regimes: “stable production”, “liquid pool depletion” and “steam breakthrough limit”. In solvent-based liquid pool trap control, analysis of the Nsolv field results and stability analysis suggests that vapour breakthrough is part of the process but can be minimized by operating at temperatures greater than second subcool limit.