Simulation of CH4 production from subsea gas hydrate deposits coupled with CO2 storage

Natural Gas hydrates found worldwide in subsea sediments can be used as future energy resources. To increase their potential for energy applications today new technological approaches for the extraction of natural gas from gas hydrate deposits are being discussed and developed. The combustion of hydrate-based natural gas can contribute to the energy supply but the coupled CO2 emission causes climate change effects. To develop a sustainable hydrate based energy supply system the sequestration of CO2 has to be coupled with the CH4 production from the hydrate deposit. Due to this demand the simultaneous storage of CO2 in hydrate deposits has to be developed. From the thermodynamic point of view this process seems to be applicable because CO2 hydrate is more stable than CH4 hydrate. Regardin g technological implementation many problems have to be overcome. Especially mixing, heat and mass transfer in the reservoir are limiting factors causing very long process times. Using numerical models for dynamic system simulations and analysis different technological approaches are evaluated and compared. Therefore, detailed mathematical models for most relevant chemical and physical effects are developed and implemented into simulation programs like CMG STARS and UMSICHT HyReS. By means of abstract scenarios, the effects occurring during gas production and CO2 sequestration within a hydrate reservoir are identified and described. Relevant parameters such as pressure, temperature and hydrate saturation are discussed and compared for three cases: depressurization, CO2 injection after d epressurization and simultaneous methane production and CO2 injection.