致密气井间歇泡排注剂后关井时间探究

Shut-in time after intermittent injecting foam agent into tight gas wells

X井区部分气井生产中后期产气量低于临界携液流量时会产生积液。间歇泡排(泡沫排水采气)是一种有效的排水采气措施。但是泡排剂从井口注入井筒之后,经过多长时间到达井底积液位置并扩散反应,对这个问题的研究较少,行业内一直没有形成准确易行的方法与认识,在一定程度上影响了泡排效果的正常发挥。因此,通过研究带环空气井在注入泡排剂之后井口油压、套压、气量和温度的变化趋势,以判定泡排剂下行时间和扩散时间,进而确定加注泡排剂后的关井时间,并探究了泡排剂流道横截面积以及压力对泡排剂下行时间的影响。结果表明:①泡排剂下行时间与泡排剂泵入速率、井温、井压、泡排剂黏度、管壁粗糙度、管径(流道横截面积)大小、井斜、井深等因素有关;②X井区泡排剂平均下行速度为577 m/h,当油管鞋下深3072~3588 m时,泡排剂下行至油管鞋处平均需要6 h,泡排剂到达井底之后的平均扩散时间为2.5 h,综合起来所需要的关井时间为8.5 h;对于水平井,其井斜更大,建议关井10 h以上;③采用探究结果来指导加注泡排剂后的关井时间,优化泡排作业,可提升泡排作业的增产效果。

In X well block,liquid accumulation may be occurred at the time of gas production lower than critical liquid-carrying flow rate during the middle to late development stages.Intermittent injection of foam agent(so-called foam drainage gas recovery)is effective for these gas wells.However,how long the foam agent travels to bottomhole to be dispersed is less studied,or no method has been developed to measure the time.As a result,a normal foam injection may be affected to some extent.Plenty of production data(containing wellhead tubing pressure,casing pressure,gas flow rate,and temperature)of the wells with annulus were adopted to estimate the foam-agent travelling and dispersing time,then the shut-in time,and finally the effect of both cross-sectional area and pressure of foam agent on the travelling time.Results show that(1)for one typical well,the travelling time is related to such factors as pumping rate,well temperature and pressure,agent viscosity,dogleg,tubing diameter(cross-sectional area),and well inclination and depth;and(2)for the foam agent used in X well block,the downward travelling velocity is 577 m/h on the average.When the shoe depth varies from 3072 m to 3588 m,the foam agent roughly takes 6 h to reach the shoe,the average dispersing time of 2.5 h,and the average shutin time of 8.5 h,individually.For one horizontal well with larger deviation,the shut-in time over 10 h is recommended.These results are conducive to estimating the shut-in time,optimizing the foam-agent injection process,and improving the effectiveness of injecting foam agent into gas wells.