Density-Driven CO<sub>2</sub> Dissolution in Depleted Gas Reservoirs with Bottom Aquifers
Depleted gas reservoirs with bottom water show significant potential for long-term CO<sub>2</sub> storage. The residual gas influences mass-transfer dynamics, further affecting CO<sub>2</sub> dissolution and convection in porous media. In this study, we conducted a series of...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-07-01
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| Series: | Energies |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1996-1073/17/14/3491 |
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| Summary: | Depleted gas reservoirs with bottom water show significant potential for long-term CO<sub>2</sub> storage. The residual gas influences mass-transfer dynamics, further affecting CO<sub>2</sub> dissolution and convection in porous media. In this study, we conducted a series of numerical simulations to explore how residual-gas mixtures impact CO<sub>2</sub> dissolution trapping. Moreover, we analyzed the CO<sub>2</sub> dissolution rate at various stages and delineated the initiation and decline of convection in relation to gas composition, thereby quantifying the influence of residual-gas mixtures. The findings elucidate that the temporal evolution of the Sherwood number observed in the synthetic model incorporating CTZ closely parallels that of the single-phase model, but the order of magnitude is markedly higher. The introduction of CTZ serves to augment gravity-induced convection and expedites the dissolution of CO<sub>2</sub>, whereas the presence of residual-gas mixtures exerts a deleterious impact on mass transfer. The escalation of residual gas content concomitantly diminishes the partial pressure and solubility of CO<sub>2</sub>. Consequently, there is an alleviation of the concentration and density differentials between saturated water and fresh water, resulting in the attenuation of the driving force governing CO<sub>2</sub> diffusion and convection. This leads to a substantial reduction in the rate of CO<sub>2</sub> dissolution, primarily governed by gravity-induced fingering, thereby manifesting as a delay in the onset and decay time of convection, accompanied by a pronounced decrement in the maximum Sherwood number. In the field-scale simulation, the injected CO<sub>2</sub> improves the reservoir pressure, further pushing more gas to the producers. However, due to the presence of CH<sub>4</sub> in the post-injection process, the capacity for CO<sub>2</sub> dissolution is reduced. |
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| ISSN: | 1996-1073 |