Numerical simulation of gas production from permafrost hydrate deposits enhanced with CO2/N2 injection

Jing-Yu Kan, Yi-Fei Sun, Bao-Can Dong, Qing Yuan, Bei Liu, Chang-Yu Sun and Guang-Jin Chen

Energy, 2021, vol. 221, issue C

Abstract: A new numerical simulator was developed from the widely used CH4 hydrate simulator TOUGH + HYDRATE to realize the simulation of hydrate exploitation by CO2/N2–CH4 replacement. Focusing on actual hydrate reservoir, CO2/N2 injection combined with depressurization in a practical continuous injection-production mode was applied for gas production. The influence of feed gas composition and injection pressure on CO2 sequestration and CH4 production was investigated. Moreover, we conducted a fair comparison and revealed the advantages of CO2/N2 injection over two traditional methods in gas/water production performance. During gas injection, a continuous CO2/N2 separation process under stratum environment was observed, and the whole gas replacement process can be roughly summarized as a continuous cycle of CH4 hydrate dissociation and CO2/N2 hydrate formation. Increasing N2 mole fraction from 30% to 50% significantly enhanced the CH4 production efficiency, while its increase from 50% to 100% mainly resulted in more N2 production and higher injection-production ratio. Raising the injection pressure from 4.5 to 5 MPa improved CH4 recovery by 1.5 times, while increase from 5 to 7 MPa reduced CH4 recovery by 8.3%. A favorable CH4 recovery with relatively low cost can be achieved by finding an appropriate balance between CH4 release and CO2 sequestration.

Keywords: Permafrost hydrate; Numerical simulation; CO2/N2 continuous injection; CH4 production; CO2 sequestration; CO2/N2–CH4 replacement (search for similar items in EconPapers)
Date: 2021
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Citations: View citations in EconPapers (7)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:221:y:2021:i:c:s0360544221001687

DOI: 10.1016/j.energy.2021.119919

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