水锁效应广泛存在于火山岩气藏中,是火山岩气藏的损害类型之一,严重影响着火山岩气藏的开发效果.本文结合核磁共振技术通过室内实验研究,探讨低渗透火山岩气藏自吸作用下的水锁伤害机制及伤害程度,通过气驱反排实验模拟了火山岩气藏水锁解除过程.研究表明:各渗透率级别的火山岩岩心自吸吸入水饱和度与吸水时间并非呈线性关系,自吸开始的2h之内,岩心含水饱和度急剧增加,随着自吸时间的增加,岩心含水饱和度增加幅度越来越小,自吸16h后岩心吸入水量已基本保持不变;应用核磁共振技术研究了吸入水量与孔隙结构的关系,发现孔隙结构越复杂,岩心吸水量越大;通过反排实验发现,岩心含水饱和度以及水锁伤害率随反排孔隙体积(PV)数的增加而减小并趋于平缓,反排25PV后水锁伤害基本得到解除;针对目前水锁伤害评价存在的不足,结合储层中水锁伤害的产生和解除,提出一种改进的水锁伤害评价方法——动态水锁评价方法.

Water locking happens widely in volcanic gas reservoirs. and will seriouly affect the reservoir development. Based on the lab experiments combined with the NMR technology, the damage degree and the damage mechanism under the spontaneous imbibition condition are studied, and the water lock removal process in volcanic gas reservoirs is simulated by the gas flood experiment. It is shown that the water saturation due to the spontaneous imbibition is not linear with respect to the imbibition time, the saturation in the cores is increased dramatically in the first 2h from the time when the imbibition begins, after 16 hours the spontaneous imbibitions are stopped and the saturation remains almost unchanged. Applying the NMR technology to the relation between the water absorption and the pore structure, it is found that the more complex the pore structure, the larger the amount of the water imbibitions will be. The gas is used to draw the water from the cores, and it is discovered that with the increase of the pore volume, the water saturation and the damage rate due to the water locking decrease and they tend to be in moderate levels, the water lock damage is basically avoided after 25 pore volumes are driven by gas. To overcome the drawbacks of the evaluation methodology in water blocking, an improved method, the dynamic evaluation method in water blocking, is proposed.