Abstract:

As a new clean energy, natural gas hydrate (NGH) has attracted much more attention in recent years. Thermal stimulation is one of the effective ways to dissociate natural gas hydrate. To dissociate NGH by hot brine injection economically, a onedimensional experimental system is designed to form NGH with the same initial conditions in sandpacked tube, and then hot brine with different temperatures was injected to analyze the NGH dissociation performance. The results show that the higher the hot brine temperature is, the earlier the NGH dissociation begins, and the higher the average gas production rate is during the hot brine injection stage. With hot brines in different temperatures injected, the relationship of the thermal front vs. time is close to linear. When the temperature increases from 40 ℃ to 100 ℃, the average speed of thermal front movement increases from 015 cm/min to 02 cm/min, indicating that the hot brine temperature has a little effect on the thermal front movement. Early in the heat injection period, the higher temperature results in higher energy efficiency; however, later in the heat injection period, the higher temperature results in lower energy efficiency. Under these experimental conditions, with the hot brine temperature increasing from 40 ℃ to 100 ℃, the energy efficiency decreases from 67 to 24, while the movement speed of thermal front stays stable. It is proposed that, to dissociate NGH economically, hot brines with high temperature should be injected in early stage and lowtemperature brines should be injected in middle and later periods.

Key words: natural gas hydrate (NGH), hot brine injection, thermal front, energy efficiency