Experimental Studies And Numerical Simulations For Depressurizing Production Of Natural Gas Hydrates

Natural Gas Hydrate (NGH) is new energy resource of abundant reserves, high quality and clean. Researches on its production technologies have the great significance in the view of theory and practice.By using the experimental system for NGH formation and production, experiments on NGH depressurization production were conducted in sand-packed models. The transition of CH4 in the process of NGH formation was analyzed. The effect of pressure drop and initial temperature on gas production, water production, pressure difference during NGH production was compared. On this basis of this, by using the mathematical model for depressurization production of NGH, the fitting of experimental results of NGH production was conducted. The effect of permeability, the initial temperature, the NGH saturation, outlet pressure on NGH production was analyzed.Experiments show that in the process of NGH formation, there are three stages for CH4 transition, including slow increasing, fast increasing and fast decreasing. The production of NGH by depressurization method is controlled by the processes of decomposition and production of NGH. The in-situ gas production changes rapidly with higher gas production rate, which is mainly controlled by depressurizing rate and temperature. The influence factors include permeability,the initial temperature, the initial NGH saturation and outlet pressure. The production time becomes is shorter with the increase of permeability,the initial temperature and the initial NGH saturation. The higher the outlet pressure, the higher the peak gas production. The research can provide basis for the depressurization production of NGH in theoretical and experimental aspects.