The research on the natural gas hydrate dissociation kinetic from hydrate-sediments/seawater slurries

Due to the weak cementation of natural gas hydrate (NGH) reservoir in the seabed, during both the drilling and development processes, a multiphase (gas hydrate-sediments-seawater-natural gas mixture) flow is more likely to exist in the NGH reservoir and development wells, understand the natural gas hydrate particle dissociation kinetic in the hydrate-sediments/seawater slurries is important. In this work, first, a new NGH phase behavior research experimental apparatus contains a strong magnetic stirrer was built. By using this, we for the first time proposed to form NGH reservoir in the water saturated sands under stirring in the laboratory, which showed a much higher hydrate formation rate and water to hydrate conversation ratio than the usual static formation method. After that, the CH 4 hydrate-sands/seawater slurries were produced, the influence of pressures, temperatures, the size of sands, and stirring rates on CH 4 hydrate dissociation kinetic in the slurry were investigated. The dissociation rate of CH 4 hydrate-sands mixed particles markedly increased with decreasing operation pressure from 3 MPa to 0.1 MPa. The average dissociate rate reached 1762.57 mL/min at 0.1 MPa. It is interesting that unlike to the single NGH reservoir, no hydrate secondary formation and ice formation phenomenon arose in the hydrate-sands/seawater slurries during the CH 4 hydrate dissociation process. The increase of temperature and stirring rate substantially stimulated the dissociation of CH 4 hydrate particles in the slurry, while the sands’ size showed little effect. In addition, a high precision kinetic model for describing the dissociation of CH 4 hydrate in hydrate-sands/seawater slurries was built, in which the influence of pressure, temperature and stirring rate on the hydrate apparent dissociation rate constant was considered at the same time.