The Experimental Research Of Improving Ice Conversion In Generating Methane Hydrate

Natural gas hydrate has been recognized as an important potential strategic resource that can replace traditional fossil energy because of its wide distribution, abundant reserves, high energy density and clean combustion. To better understand the physicochemical properties of gas hydrate, it is very necessary to conduct the study on the gas hydrate formation and dissociation. However, it is really uneconomical and uneasy to obtain natural hydrate-bearing samples from the seabed, and synthesizing gas hydrate in laboratory by simulating in-situ conditions has become a necessary way in the researches. Though there are many ways to synthesize gas hydrate in laboratory, studies on the effect of water form in the hydrate formation found that ice was much easier to generate the hydrate with methane than water. In fact, gas hydrate formed from ice and gas mixtures is one of the primary methods to simulate the gas hydrate formation in the cryolithozone and have comprehensive understanding of hydrate formation kinetics. Unfortunately, the saturation of methane hydrate synthesized in laboratory is not high enough to simulate natural storage conditions, so exploring methods to obtain hydrate with high saturation become very necessary.In this paper, a series of experiments of forming hydrate from ice powders in different conditions have been carried out with constant volume method to evaluate the effects of factors such as pressure, temperature, porous medium and chemical additives, hoping to come up with methods to obtain hydrate with high saturation. Based on the experimental results and the analysis, the following conclusions have been drawn. Initial pressure has a direct effect on the formation of gas hydrate, and this effect is more obvious when the temperature is closer to freezing point. Secondary pressurization can improve the saturation of gas hydrate to a certain extent. When the initial pressure is not high, the secondary pressurization has an obvious effect on improving the saturation of gas hydrate. Temperature is very important to the formation of methane hydrate, and low temperature is good for the hydrate generating. Heating will obviously increase the hydrate saturation. Heating has a more obvious effect on improving the methane hydrate saturation than that of secondary pressurization. Porous media has obvious effects on the hydrate formation from ice, the smaller particle is better for the hydrate formation from ice when the porous media is enough, and commonly, more porous media will lead to high saturation for hydrate. The thermal conductivity of porous media has tendency dual effects on hydrate formation from ice and they restrain each other in the process of hydrate formation. Chemical additives such as SDS and THF have promoting effects on hydrate formation from ice, and there is an optimal value for the concentration of SDS that can maximize this effect, but the effect of THF is relatively not very obvious, with the increase of THF, the promoting effect is more and more obvious.