二氧化碳地质封存(CGS)是减少温室气体排放和缓解气候变化最有前景的技术之一，以水合物形式将CO₂封存在废弃的天然气水合物储层中，能够在CGS中发挥关键性作用。基于青海木里地区煤系天然气水合物储层的基本物性特征，研制水合物储层人造岩心，分析岩心密度、孔隙率及渗透率随石英砂粒径的变化特征。通过低场核磁共振技术研究岩心中CO₂水合物饱和度演化特征，阐明水合物生成期间岩心孔隙结构特性。结果表明：随石英砂粒径减小，岩心孔隙率与渗透率呈先上升后下降变化特征；岩心孔径主体分布在0.004~0.050 μm，主要为小孔与微孔孔隙。CO₂水合物核磁饱和度变化可划分为4个阶段：初始期、诱导期、合成期及稳定期，合成期内核磁信号强度降低，岩心中水合物饱和度快速增大。水合物生成期间，岩心孔隙体积比例曲线逐渐由两边向中间靠拢，孔隙分布范围逐渐减小，岩心中超大孔孔隙随水合物生成逐渐消失，微孔孔隙对水合物的生成起决定作用。岩心孔隙率越大，水合物生成效率及饱和度相对较高。研究成果为掌握天然气水合物储层中CO₂封存机理与封存效率提供科学基础。

Carbon Dioxide Geological Storage (CGS) is a promising technology for reducing the greenhouse gas emissions and mitigating the climate change. The hydrate-based CO₂ storage in the abandoned gas hydrate reservoir can play a key role in CGS. In this paper, artificial cores of hydrate reservoir were prepared based on the basic physical properties of coal measure gas hydrate reservoir in Muli Coalfield, and the variations in density, porosity and permeability of the core with particle diameter of quartz sand were analyzed. The variations in CO₂ hydrate saturation in core were analyzed based on the low-field Nuclear Magnetic Resonance (NMR) technology, and the pore characteristics of artificial core during the generation of hydrates were also elaborated. The results show that the porosity and permeability of cores are firstly increased and then decreased with the decreased particle diameter of quartz sand. The core pores are mainly in the diameter between 0.004-0.050 μm, composed of small holes and micropores. The variations in CO₂ hydrate saturation can be divided into four stages: initial phase, induction phase, generation phase and stable phase. The nuclear magnetic signal intensity is decreased in the generation phase, and thus the saturation of hydrate in core increases rapidly. During the generation of hydrate, the curve of core pore volume proportion gradually moves from both sides to the center, and the pore distribution range is gradually decreased. The ultra-large pores gradually disappear with the hydrate formation, and the micropores play a decisive role in the formation of hydrate. Generally, the larger the core porosity is, the higher the hydrate generation efficiency and saturation. The research results provide a scientific basis for mastering the CO₂ storage mechanism and efficiency in gas hydrate reservoir.