不同注热水温度下水合物开采实验研究

Experimental Investigation of Gas Hydrate Dissociation by Hot Brine Injection with Different Temperatures

天然气水合物(NGH)是目前备受关注的新型洁净优质能源,注热法是其有效开采方式之一。为了经济有效地进行注热开采,采用自制的一维天然气水合物开采模拟实验装置,在填砂模型中生成相同初始条件的天然气水合物藏,然后注入热盐水进行开采模拟实验,分析不同注热水温度对开采动态的影响。结果表明:注热水温度越高,水合物开始分解的越早,注热阶段的平均产气速率也越大;不同注热水温度下,热前缘的移动接近于线性,注热温度从40℃到100℃时,平均热前缘移动速度从0.15 cm/min增加到0.2 cm/min,说明注热水温度对热前缘的移动影响不大。注热前期,注热水温度越高,能量效率越高,但注热后期,注热水温度越高,能量效率反而越低。在本组实验条件下,注热水温度从40℃增加到100℃时,注热开采的能量效率由6.7减小到2.4,而平均热前缘移动速度并没有明显降低。因此,为保证注热开采的经济有效,建议在注热前期注高温水,在中后期采用低温水驱替。

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 line-ar.When the temperature increases from 40 ℃ to 100 ℃,the average speed of thermal front movement increa-ses 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 effi-ciency 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-tem-perature brines should be injected in middle and later periods.