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Large quantities of natural gas hydrates are present in shallow marine sediments as well as in arctic regions. This research is aimed at assessing production of natural gas from unconfined marine hydrate deposits. A multiphase, multicomponent, thermal, 3D simulator is used to simulate production of hydrates in the equilibrium mode. Three components (hydrate, methane, and water) and four phases (hydrate, gas, aqueous-phase, and ice) are considered in the simulator. Depressurization and warm water flooding of unconfined, horizontal and dipping reservoirs have been simulated. Production of methane from gas hydrate reservoirs depends on reservoir confinement, injection temperature, injection pressure, and production pressure. For unconfined horizontal reservoirs, depressurization is ineffective; thermal stimulation is necessary for gas production. Even warm water (temperature ≈ 30 °C) injection improves the gas production from hydrate reservoirs. Lower vertical permeability helps the gas production by heating a larger area of the reservoir for hydrate dissociation. As the well spacing decreases, the gas production rate increases. Depressurization alone is effective in dipping unconfined reservoirs, but much slower than warm water injection. As the injection point of the warm water moves down the reservoir, the start of the high gas recovery phase gets delayed, but the time for completion of gas recovery becomes shorter.

Axial variations in geometry and presence of viscous displaced fluid are known to alter the diffusive-dynamics of capillary imbibition of a wetting liquid. We here show that the coupled effect of axially varying capillary geometry and finite viscosity of the displaced fluid can lead to significant variations in both short and long time dynamics of imbibition. Based on a theoretical model and lattice Boltzmann simulations, we analyze capillary displacement of a viscous liquid in straight and diverging capillaries. At short times, the imbibition length scales proportionally with time as opposed to the diffusive-dynamics of imbibition of a single wetting liquid. Whereas, at long times, geometry-dependent power-law behavior occurs which qualitatively resembles single liquid imbibition. The distance at which the crossover between these two regimes occurs depends strongly on the viscosities of the imbibing and the displaced liquid. Additionally, our simulations show that the early time imbibition dynamics are also affected by the dynamic contact angle of the meniscus.

Capillary driven displacement of viscous liquids in a layered porous medium is dependent on the arrangement of the layers and the permeability contrast between the layers.

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