Experimental Studies For Formation And Decomposition By Depressurization Of Natural Gas Hydrate

As a greatly potential alternative energy resource, natural gas hydrate (NGH) is of high quality and burns clean. The studies about the formation and decomposition technologies of NGH have great significance in view of theory and practice. Through experiments, analysis and calculation technology, the relationship between permeability and NGH saturation, the law of formation in porous medium, and decomposition of NGH by depressurization in porous medium were discussed in this paper.On the base of others'articles, many NGH formations in porous medium were carried out. The initial pressure was changed by three ways, injecting water and gas in certain proportion, the amount of gas, and the amount of water. The higher the initial pressure was, the more NGH formed. However, it took more for the formation. The effect of temperature on formation of NGH was analyzed by changing the environment temperature. It demonstrated that, the lower temperature was, the more the NGH formed. It also took more for the formation. NGH was also formed in two porous medium, in lager ceramsite and smaller quartz sand. After calculation, it was easy to find that NGH formed slowly in smaller quartz sand with two speed crests while NGH formed fast in lager ceramsite with one speed crest. Many empirical formulas were validated by the experimental data, which described the relationship between the permeability and the saturation of NGH. And an exponential formula was given which could match the experimental data perfectly. Thus all could be used in the NGH exploitation and numerical simulation.Decomposition experiments of NGH were carried out at different conditions, including the same depressurizing range and the different flows. The former experiments demonstrated that the depressurizing range should be smaller at lower initial temperature while it should be lager at higher initial temperature for the NGH self- reservation. And the flow of gas produced had an important effect on the pressure and the temperature of NGH reservoir. Therefore, the flow should be set in a proper range avoiding the obvious self-preservation.