Novel Pore Scale Visualization during CO₂ Injection into CH₄ Hydrate Saturated Porous Media

CO₂ capture in sediments through CO₂-rich gas injection into methane gas hydrate reservoir is a recently proposed technology for methane recovery and simultaneously storing CO₂ in deposits. CO₂ capture and storage in CH₄ hydrate formations located at low-temperature, high-pressure conditions, is an attractive proposition as technical and economic costs are lower and it is safer option to store as hydrates, since it offer confined storage, presence of elevated pore pressure, very low CO₂ leakage rates and long-term storage potential. The current literature lacks visualization studies that could improve our understanding of fluid migration and hydrate rearrangement during CO₂ injection into CH₄ hydrate. This experimental study is the first to provide pore-scale visualization (using high-pressure micromodel) when CO₂ is injected into CH₄ hydrates. Our study shows that the CO2 richness in the invading liquid phase controls the CO₂ injectivity and the redistribution of the hydrates. The CO₂ content in the liquid phase is controlled by the CO₂ injection scheme. The resulting CH₄/CO₂ mixed hydrates were stepwise depressurized to visualize the hydrate reformation below the CH₄ hydrate phase that would improve the recovery of CH₄ while reforming the CO₂ hydrate, thus keeping the hydrate mass intact. This research would help improve our understanding of an effective CO₂ injection scheme for improved CH₄ recovery and CO₂ storage.