低渗透储层T2截止值实验研究及其测井应用

由于一个地区甚至一口井很难有一个统一的截止值，无法用单一的截止值方法区分束缚水和自由流体，因而用核磁共振测井来解释束缚水饱和度存在着实用上的困难。为此，借鉴已发表的实验方法对塔中地区低渗透储层岩心进行了核磁共振实验。在进行实验结果分析时充分考虑到岩石孔隙结构的变化，发现T2截止值与孔隙结构综合指数(∫k/φ)密切相关，故提出了一种应用于测井解释的变T2截止值方法。在实际测井解释中，采用变T2截止值求得的束缚水饱和度与压汞实验数据较吻合。

T2 cutoff value in low-permeability reservoirs and its application

Nuclear magnetic resonance (NMR) logging data cannot be used directly to infer irreducible water saturation because relaxation time T_2 varies with wells,leading to difficulty in distinguishing irreducible water from free fluid by a unified T_2 value.NMR experiments were designed according to existing publications, and were carried out on low permeability cores from the center of Tarim basin. It was found that the T_2 value was closely related to the composite index of pore structure.A method that uses variable T_2 values in the interpretation of logging data was developed. Practice showed that the irreducible water saturations calculated by the method were in good agreement with mercury penetration experiment data.