Experimental Study on the Distribution Characteristics of CO2 in Methane Hydrate-Bearing Sediment during CH4/CO2 Replacement

CH4/CO2 replacement is of great significance for the exploitation natural gas hydrate resources and CO2 storage. The feasibility this method relies on our understanding efficiency mechanism. In study, experiments were carried out to study distribution characteristics CH4 in hydrate-bearing sediments during after replacement. Similar previously reported data, also implied that process could be divided into two stages: fast reaction slow reaction, representing hydrate-gas interface bidirectional diffusion caused replacement, respectively. After content gradually decreased, methane increased with increase sediment depth. Higher percentage can achieved higher temperature lower initial saturation hydrate. Based calculation consumption amounts, it was found mainly took place stage while formation by gaseous water almost runs through whole experimental process. Thus, pore scale summarized following steps: injection, diffusing sedimentary layer, occurrence formation, wrapping mixed CH4-CO2 hydrate, continuous stagnant