Methane production from hydrate-bearing sediments

Gas hydrates are ice-like compounds of gas and water formed at high pressure and low temperature. The large amount of hydrocarbon gas trapped by hydrates provides an important potential energy resource for the future. A multiphase, multicomponent, thermal, 3D simulator was developed in our laboratory in the past. In the present work, we have used the simulator to simulate gas production from hydrates in porous media in the equilibrium/kinetic mode.;The simulator has been validated against other simulators in DOE code comparison study. The core scale experiments of hydrate formation and dissociation are history-matched with the simulator. Permeability and its spatial variation are used as parameters to match the experimental results. Conventionally, empirical correlations have been used for transport properties of sediments containing gas hydrates as in the simulator mentioned above. Using empirical correlation from oil reservoirs may not give accurate transport properties for hydrate bearing sediments. These transport properties are estimated here using pore scale modeling. Percolation theory is used to numerically calculate effective transport properties of the porous medium at different hydrate saturations. The transport properties calculated from these mechanistic models are expected to replace the empirical correlations in reservoir simulations of hydrate reservoirs.;The production scenarios for confined and unconfined gas hydrate reservoirs are assessed using the simulator. For confined reservoirs, at high injection temperature, gas production rate increases with injection pressure. If the production pressure is low, depressurization is better than warm water injection for confined reservoirs. For unconfined reservoirs, reservoir depressurization is ineffective; thermal stimulation is necessary for gas production. Production strategy is developed for the Gulf of Mexico reservoir dependent on reservoir confinement, reservoir dip and hydrate saturation. To assess the production potential of methane by injecting CO2 into methane hydrate reservoirs, another simulator is developed on the basis of the previous simulator. CO 2 hydrates are thermodynamically more stable than methane hydrates at pressures between the methane hydrate equilibrium pressure and CO2 hydrate equilibrium pressure. Using the CO2 injection method we can produce methane and sequester CO2 simultaneously in the reservoirs, if operated in such conditions.