核磁共振技术在致密岩心孔隙量化表征
Application of NMR technology in quantitative characterization of tight core pores
致密岩心孔喉细小、结构复杂的特点使得孔隙量化表征十分困难，传统技术虽有成效，但过程繁琐、干扰因素多。为了实现致密岩心的孔隙量化表征，采用核磁共振技术（nuclear magnetic resonance, NMR），利用T_2弛豫时间和孔隙半径r的正比关系，可测致密岩心的孔隙度、渗透率和孔径分布，利用核磁共振T_2截止值，可区分孔隙中的自由流体和束缚流体。本文从核磁共振表征岩心孔隙的原理出发，分析了核磁共振〖T 2〗谱与岩心孔隙度、渗透率、孔径分布、孔隙内可动流体的关系。根据上述原理进而通过实例，验证了核磁共振技T 2〗截止值和孔径分布测试表明：1号岩心T_2截止值为21.85 ms，2号岩心的T_2截止值为40.11 ms；1号岩心小孔隙分量大，2号岩心孔隙分布较均匀。截止值的计算结果表明地区经验法得出的T_2截止值不完全适用于该区域的致密岩心，有必要建立区域性的截止值变化范围图版。
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核磁共振T_2谱孔径分布致密岩心
高胜天,王诚,马超,黄晓依,刘鑫.核磁共振技术在致密岩心孔隙量化表征[EB/OL].(2024-05-31)[2025-09-21].http://www.paper.edu.cn/releasepaper/content/202405-175.点此复制
The small pore throats and complex structure of tight cores make the quantitative characterization of pores very difficult, and although traditional techniques are effective, there are limitations of cumbersome processes and many disturbing factors. In order to quantitatively characterize the porosity of tight cores, the porosity, permeability and pore size distribution of tight cores can be measured by nuclear magnetic resonance (NMR) using the proportional relationship between T_2 relaxation time and pore radius, and the free fluid and bound fluid in pores can be distinguished by T_2 cut-off value. Based on the principle of core porosity characterization by NMR, the relationship between T_2 and core porosity, permeability, pore size distribution and movable fluid in pore is discussed. Through above principles and examples, the accuracy and applicability of the NMR in the quantitative characterization of porosity and permeability of tight cores are verified. The cut-off values and pore size distribution tests of the experimental cores show that the cut-off value of core 1 is 21.85 ms and that of core 2 is 40.11 ms. Core 1 has a large small pore fraction and core 2 has a more uniform pore distribution. The results show that the cut-off values of T_2 obtained by regional method are not fully applicable, and it is necessary to establish a regional version of the cut-off variation range chart.
nuclear magnetic resonanceT_2 spectrumpore size distributiontight cores
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