Abstract:

Injecting hot water is one of the effective ways to dissociate natural gas hydrate (NGH), and the movement of thermal front determines the dissociation rate of hydrate, which is a key parameter for thermal stimulation. A one-dimensional experimental system is designed to form NGH with different initial conditions in sand-packed tube, and then hot water with different thermal parameters was injected to analyze the movement of thermal front. Results show that the higher the NGH saturation is, the less the thermal front movement rate is; the thermal front movement rate increases slightly with the initial temperature increasing;the thermal front movement rate is larger with higher hot-water temperature and larger hot-water injection rate. Among the four parameters, i.e.NGH saturation,initial temperature,hot-water temperature and hot-water injection rate,the most sensitive parameters are the NGH saturation and hot-water injection rate, followed by the hot-water temperature, and the least sensitive parameter is initial temperature. In order to increase dissociation rate of hydrate, it is reasonable to increase the hot-water injection rate within the technical feasibility. Lowering the hot-water temperature can slightly decrease the dissociation rate of hydrate, while the economic feasibility will increase.

Key words: natural gas hydrate, injecting hot water, thermal front movement, influencing factor