低渗透储层压裂液伤害核磁共振评价方法

NMR evaluation of reservoir dammage caused by fracturing liquid on low permeable reservoir

压裂是有效开发特低渗透储层的重要措施,研究压裂液与储层配伍性是压裂作业的基础与关键。为此,以低渗透储层岩心为研究对象,以核磁共振技术为主要研究手段,对压裂液浸入岩心前后及KC l溶液反排后进行核磁共振测试,对测试结果进行指数拟合和积分运算,得到相应的核磁共振特征参数和流体分布状态变化特征。结果表明,岩心T2均值和束缚水饱和度的变化能够很好地描述压裂液对低渗透储层的伤害类型和伤害程度;醇基胍胶压裂液对所研究岩心的伤害主要是由大分子物质的吸附和滞留引起的,而压裂液滤液的浸入对岩心束缚水的影响很小,平均增幅为1.69%;经KC l溶液反排后,岩心束缚水饱和度基本上恢复到初始值。

Fracturing is a key method to develop ultra-low permeable oil (gas) reservoir, and the research of compatibility between fracturing fluid and reservoir rock is fundamental and critical to fracturing project. Therefore, taking the ultra-low permeable core as the research object, and based on the NMR (nuclear magnetic resonance) technique, we take the NMR test on the core before and after the fracture fluid immersion, as well as the core after the brine water reverse driving, and then implement the exponential fitting and integral operation on the test results, subsequently, we can get the relevant NMR characteristic parameters and fluid distribution variation. The research indicates that, the T2 cutoff value and the variation of the bound water saturation can depict perfectly the degree and the type of damaged by the fracturing liquid. The result also indicates that the dominant formation damage factor of the study area fractured by the alcohol guar fracturing fluid is the adsorption and detention of macromolecular fluid, while the filter liquor of fracturing fluid has slight effect on irreducible water, only increased by 1.69% averagely; the saturation of the bound water is basically retrieved to the original state after the reverse driving by the brine water.