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Soaking Process for the Enhanced Methane Recovery of Gas Hydrates via CO2/N2 Gas Injection

Seo, Young-ju, Kim, Daeok, Koh, Dong-Yeun, Lee, Joo Yong, Ahn, Taewoong, Kim, Se-Joon, Lee, Jaehyoung, Lee, Huen
Energy & Fuels 2015 v.29 no.12 pp. 8143-8150
energy, gas hydrate, greenhouse gases, methane, sediments, soaking, vapors
Replacement technique is known as a promising method for potential energy extraction from gas hydrate deposits and greenhouse gas sequestration into deep ocean sediments. When it comes to the utilization of the replacement method in field applications, the soaking duration or the frequency of CO₂/N₂ gas injection becomes an important process variable. In this study, the influence of soaking duration and frequency on the CH₄ replacement efficiency was quantitatively investigated for the first time by imitating the gas hydrate-bearing sediments. The CH₄ replacement process with CO₂/N₂ was performed through two consecutive stages: dynamic replacement and soaking process. While any additional soaking process after the dynamic process enhanced the CH₄ replacement efficiency from 35–36 to 52–60%, several replenishments of a fresh CO₂/N₂ gas mixture into the vapor phase were considered more effective than solely increasing the soaking time. The present study will help in establishing the basic process variables for obtaining an enhanced CH₄ replacement efficiency during the well design and operation of the replacement technique in field production tests.