125 / 2023-06-21 10:57:15

Influence of liquid saturation in coal on the synthesis and decomposition of gas hydrate

gas hydrate ; dissociation rate ; impedance ; saturation ; THF hydrae

As an important energy source in China, its main energy status will not change in a certain period of time. Coal and gas outburst is a geological disaster induced by the comprehensive action of gas, earth stress and other factors in the process of coal mining, which is highly destructive and seriously threatens the safety of coal mine. The direct cause of most coal and gas outburst accidents is the destruction of the gas coal seam, resulting in a large amount of gas instantaneous gushing, resulting in a large number of casualties and property losses. Therefore, the prevention and control of coal and gas outburst accident more reasonable method is to delay the coal and gas concentrated , hydration curing outburst is effective to prevent coal and gas outburst technology, its mechanism lies in the coal seam gas hydration curing hydrate form, thus reduce the coal bed gas pressure, and eliminate high pressure gas flow to achieve the purpose of prevention and control of coal and gas outburst. In order to further study the impedance characteristics and dynamic rules of gas hydrate in coal, using the high pressure gas hydrate formation and decomposition experiment device with impedance measurement function, the dynamics of hydrate synthesis and decomposition (20%, 40%, 60%, 60%, 80% and 100%). The impedance change in this process was measured, the gas consumption, reaction rate of the hydrate synthesis experiment were calculated under different saturation conditions were calculated, and the influence of liquid saturation in coal on the generation and decomposition of gas hydrate in coal was clarified.The results show that the impedance change can reflect the hydrate generation and decomposition in coal, according to the pressure curve of coal hydrate synthesis and decomposition process, the hydrate synthesis and decomposition reaction process can be divided into four stages, respectively: hydrate rapid synthesis stage, hydrate slow synthesis stage, hydrate rapid decomposition stage and hydrate slow decomposition stage. The decomposition rate of hydrate in coal increases and then decreases with the increase of liquid saturation, while the heat absorption effect of decomposition increases with the increase of liquid saturation. The average percentage of gas production in gas hydrate with liquid saturation of 20% is 73%. Under the temperature condition of 303.15K, the hydrate will be completely decomposed, and the incomplete recovery of the gas may be related to the methane adsorption of the coal gas. Under the condition of liquid saturation of 60%, 80% and 100%, the recovery rate and duration of gas hydrate decomposition in the coal body are roughly the same, and the final percentage of gas production is close to 100%. This indicates that the effect of high liquid saturation content on the recovery of hydrate decomposition in coal body is reduced, and it also indicates that the increase of liquid content in coal body has no significant effect on the decomposition time of gas hydrate within a certain range of liquid saturation. At the beginning of gas hydrate decomposition, the decomposition rate of 20% liquid saturation was the lowest at 80% liquid saturation. Moreover, in the middle stage of gas hydrate decomposition, the maximum rate of hydrate decomposition at 60% liquid saturation was the highest in all experiments. However, the maximum value of the hydrate decomposition rate is the lowest at 40% saturated liquid. This indicates that the gas production rate at 40%; in the experiment at 60%, 80% and 100%.