Browsing by Author "Wang, Jingyi"

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    Energy Recovery from Oil Sands Reservoirs
    (2021-01-04) Wang, Jingyi; Gates, Ian Donald; Chen, Shengnan; Hu, Jinguang; Hubbard, Stephen M.; Zeng, Fanhua
    Alberta's oil sands are the third largest proven crude oil reserve in the world, after Saudi Arabia and Venezuela. The proven reserve is ~165.4 billion barrels. At original reservoir conditions, for in-situ methods, the bitumen is too viscous to extract directly with viscosities of the order of hundreds of thousands to millions of centipoise. To extract bitumen via in-situ recovery processes, the bitumen's viscosity must be lowered to less than 20 cP. In all current commercial oil sands recovery processes, this is done by injected high pressure and temperature saturated steam into the reservoir. One such process, Steam-Assisted Gravity Drainage (SAGD), has been proven to produce bitumen, but due to steam generation has high emissions intensity with large energy requirements. The research presented here studied the SAGD process from multiple angles. The first study is focused on the edge of steam chamber where both SAGD and Steam and Gas Push (SAGP) processes were compared to understand the impact of non-condensable gas on heat transport at the edge of the chamber. The second approach uses a detailed compositional model to exam the time scales for steam and bitumen flow within the depletion chamber. The approach used for multiple steam and multiple bitumen components is novel. The third study examined the instantaneous steam-to-oil ratio behavior when the steam chamber was exposed to different reservoir features. The last study explored the recovery of heat energy from post-SAGD chambers. The analysis reveals the following results. 1. non-condensable gas does improve the thermal efficiency of SAGD, but it changes the behaviour of the edge of the chamber by creating a more extensive depletion zone at the edge of the chamber. 2. the time scales for steam flow and bitumen mobilization, drainage, and production can be weeks to months to years depending on the stage of the process. This speaks to the 'thermal momentum' that is established in the reservoir during the process. 3. The SOR, in particular, the instantaneous SOR provides a signal that can be used to identify reservoir features. This could be used with multiple SAGD well pairs to determine reservoir features across pads. 4. A large fraction of the injected heat energy in the reservoir remains in the reservoir rock (sand grains) and the overburden and understrata. However, it is possible to extract a significant fraction of the energy remaining in the reservoir after SAGD operations have finished. This should be explored in the field since this provides a means to raise the overall energy efficiency of SAGD.
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    ItemOpen Access
    Evaluation of closed-loop U-Tube deep borehole heat exchanger in the Basal Cambrian Sandstone formation, Alberta, Canada
    (2022-10-01) Chong, Qinwan; Wang, Jingyi; Gates, Ian D.
    Abstract Closed-loop deep borehole heat exchanger (DBHE) systems for producing heat from geothermal sources have the advantage that the heat transfer fluid is contained within the loop. In this study, for the first time, a U-configuration closed-loop DBHE was examined to evaluate the energy produced per unit energy invested from a 2330-m-deep geothermal reservoir in central Alberta, Canada. A detailed earth model where the system is modeled from the surface to the geothermal source is used in a numerical simulation model to understand the efficiency of the process. The results reveal that the fluid flow reaches its highest temperature in the ascending section of the U-loop rather than the bottom section which implies that the insulation on the working fluid should start in the ascending section of the U-loop. The results demonstrate that the closed-loop system can achieve ratios of the energy produced and energy invested of 7 GJ/GJ. Although this efficiency is promising, the absolute amount of heat energy harvested is limited by the loop’s heat transfer area in the geothermal reservoir.