在天然气水合物资源的评估与开采中，需要确定水合物在不同土层孔隙中的平衡条件，传统上该条件被表示为压力-温度空间中的一条曲线。然而研究表明，土体中天然气水合物的平衡条件除了温度、压力以及孔隙溶液浓度外，还与孔隙大小分布、水合物含量等因素有关。本项目围绕天然气水合物在土体中的相平衡条件展开研究，并就中心研究内容辅助性的研究了土体中水合物的赋存形态、形成与分解的微细观过程、水合数等问题，重点开展了土体中水合物形成与分解过程中的核磁共振探测以及孔隙介质中天然气水合物相平衡模型的建立和模拟，突破了孔隙介质中水合物生成与分解微细观过程探测中的技术瓶颈和传统孔隙介质中水合物相平衡模型中只能考虑单一孔径的局限，在深刻揭示多孔介质中水合物生成与分解的微细观过程基础上，建立能够描述任意土体中与任意含盐量条件下水合物的相平衡模型并对其进行实验验证，为天然气水合物资源的评估与开采提供理论与技术支持。

In the evaluation and recovery of natural gas hydrate as an energy resource, it is necessary to determine the equilibrium conditions of natural gas hydrate in pores of different sediments, which is represented as a curve on the P-T plane traditionally. However, research showed that in addition to temperature, pressure and pore water salinity, natural gas hydrate equilibrium conditions also include pore-size distribution, hydrate saturation and so on. Oriented to phase equilibrium conditions of hydrate in sediments, auxiliary work such as distribution of hydrate in sediments, micro-level process during hydrate formation and dissociation, hydrate number and other issues would be carried out. The research is proposed to investigate the NMR micro-level probing during hydrate formation and dissociation in sediments which is crucial in studying the micro-level process during hydrate formation and dissociation in sediments. Based on experimental study, we developed a phase equilibrium model for gas hydrates considering pore-size distribution and pore water salinity of sediments and related numerical analysis was carried out. This research will provide vital theoretical and technical support for mitigating production-related hazards such as borehole, local regional slope stability and optimizing the recovery procedures for extracting methane from hydrate bearing sediments.