束缚水饱和度是油气储层计算储量、分析产出流体类型的关键参数。火山岩储层具有岩性多样、孔隙结构复杂、非均质性强等特点，必须通过对全直径岩心进行分析，才能获得比较准确的束缚水饱和度。常规方法分析全直径岩心束缚水饱和度，存在测试周期长、样本难以获取以及可能产生黏性指进等问题。采用核磁共振技术结合离心实验技术，用小岩心测量得到的可动流体T2截止值标定全直径岩心T2谱，进而得到全直径岩心束缚水饱和度的实验新方法，解决了常规方法测试存在的问题。对比核磁共振方法与驱替实验所得全直径岩心束缚水饱和度，结果表明，对均质性较好、不含裂缝或微裂缝的火山岩岩心，核磁共振方法与驱替实验测量得到的结果吻合较好；对含有裂缝或微裂缝的火山岩岩心，核磁共振方法由于避免了指进现象，测得的束缚水饱和度不受裂缝、微裂缝的影响。
Irreducible water saturation is one of the fundamental parameters for characterizing reservoir formations, and the key factor for determining reserve calculation and fluid type identification. CT analysis on 125 whole cores shows that volcanic rocks have the complex porous structure and possess strong heterogeneity. As a result, accurate Swi can be only measured on whole cores. A new testing method for whole cores is proposed by combining Nuclear Magnetic Resonance(NMR) with centrifugal tests. Using T2 spectrum of whole core demarcated by a T2 cutoff, this new method measures irreducible water saturation. The T2 cutoff is measured on 25mm or 38mm diameter core samples which drilled from the whole core. Experiments on 52 volcanic rocks show that although the measured T2 cutoff values vary greatly among different volcanic rock types, but there is little difference between the values in the same group of volcanic rocks sub-classified by lithology. And NMR method can provide reliable measurements when it is applied to Sw measurement of volcanic rocks if the T2 cutoff is measured on cores from the same group sub-classified by lithology. The new method overcomes the problems involving size and shape restricts, long test cycles, and viscous fingering defects of conventional methods. Comparing with conventional method, the results of the new method well coincide with the experimental results on homogeneous rocks, and are more accurate with fractured samples.
