Experimental study on incremental synthesis of gas hydrate based on temperature oscillation

The formation of homogeneous gas hydrates with high saturation in porous media is the basis of hydrate exploitation simulation experiments. " Wall-climbing effect” and " armor effect” are important factors that restrict the formation quality of hydrate to be lower than the theoretical value, the method of temperature oscillation is a necessary means to improve the formation saturation of hydrate. The current method which based on temperature oscillation had increased the formation saturation of natural gas hydrate, however, the limitation of its temperature oscillation interval under the freezing point caused the uniformity of hydrate formation cannot be resolved better. In this paper, starting from increasing the gas-water transition region in the induction stage, it is proposed that temperature oscillation above freezing point which can effectively overcome the heterogeneity of hydrate synthesis in the oscillation range of 1 ℃~17 ℃. A total of three times of incremental hydrate synthesis experiments were carried out, the results show that the incremental hydrate synthesis can be achieved by multiple times of temperature oscillation above freezing point, however, with the increase of the number of oscillation continuously, which has obvious secondary effect, the number of temperature oscillations should not exceed three.