致密砂岩气藏润湿性对液相圈闭损害的影响

致密砂岩储层易因外来工作液入侵造成严重的液相圈闭损害,岩石表面润湿性对于液相圈闭损害程度具有重要影响。使用氟碳表面活性剂Zonyl8740处理岩心,降低岩心表面能,制得不同润湿程度的岩心。通过岩心驱替和毛管自发渗吸实验分别研究了气湿岩心和液湿岩心的束缚水饱和度、自吸油水动态;建立初始含水饱和度岩心流动实验,对比了钻井液加入气湿反转剂前后液相圈闭损害率。实验表明,致密砂岩表面由液湿反转为优先气湿可大幅度减弱毛管自吸效应、降低自吸液量和最终滞留饱和度。气湿反转剂可有效减少钻井液对储层液相圈闭损害。对预防致密砂岩储层液相圈闭损害具有一定指导意义。

Effect of tight sandstone gas reservoir wettability on liquid traps damage

In tight sandstone reservoirs, the liquid traps may be readily damaged by invasion of external work fluid. The wettabiity of rock surface has a significant impact on the damage degree to liquid traps. The fluorocarbon surfactant Zonyl8740 was used to treat the cores, reduce the surface energy of the cores and obtain cores with different wetting degree. Through experiment on core displacement and capillary spontaneous imbibition, the irreducible water saturation and spontaneous imbibition oil/water dynamic of gas wet cores and liquid wet cores were studied respectively. The core flow test with initial water saturation was built, and the damage degrees to liquid trap were compared, before and after gas-wet reversing agent was added to the drilling fluid. Experiments show that inversion of liquid wetting on tight sandstone surface to preferential gas wetting can significantly weaken the spontaneous imbibition effective of capillary, and reduce the spontaneous imbibition amount and the final retained saturation. Gas wet reverse agent can effectively reduce the damage to liquid traps by drilling fluid and has a guiding significance to preventing damage to liquid traps in tight sandstone reservoirs.