Experimental Study of the Formation Rate and Distribution of Methane Hydrate in Layered Sand.

The geological structure and gas hydrate occurrence are stratification-dependent in the vertical direction. It is necessary to explore the formation processes and distribution characteristics of methane hydrate in layered porous media. The sand sample consists of two equal parts in a testing cylinder. The upper part is 0.5-1 mm sand in particle diameter, and the lower parts are 0.075∼0.5, 0.5∼1, and 1∼2 mm. The experimental results show that the formation rate of methane hydrate gradually decreases as the reaction goes on, and it is higher in layered sand than in nonlayered sand in the beginning. With the increase of the sand size in the lower part, saturation of methane hydrate gradually decreases in the upper part and increases in the lower part. In the layered sand, saturation of methane hydrate is higher in the sand layer whose particle size is bigger. The abovementioned results can be used to predict the favorable area where methane hydrate may appear in different stratigraphic structures in nature.