赋存环境对含甲烷水合物沉积物力学特性的影响  

The effect of occurrence environments on the mechanical behavior of methane hydrate-bearing sediments

作　　者：冯帅 陈盼[1,2] 周家作 韦昌富 FENG Shuai;CHEN Pan;ZHOU Jia-zuo;WEI Chang-fu(State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,Hubei 430071,China;University of Chinese Academy of Sciences,Beijing 100049,China;College of Marine Science and Technology,China University of Geosciences,Wuhan,Hubei 430074,China)

机构地区：[1]中国科学院武汉岩土力学研究所,岩土力学与工程国家重点实验室,湖北武汉430071 [2]中国科学院大学,北京100049 [3]中国地质大学海洋学院,湖北武汉430074

出　　处：《岩土力学》2024年第7期1987-1999,共13页Rock and Soil Mechanics

基　　金：国家自然科学基金项目(No.51939011);中国科学院青年创新促进会(No.2020326);中国科学院武汉岩土力学研究所创新探索项目。

摘　　要：海域水合物沉积物储层的强度与刚度特性对水合物的安全高效钻采有重要意义。为研究赋存环境变化对泥质水合物沉积物抗剪强度特性的影响,基于改进的水合物三轴剪切仪开展了一系列饱水与饱气及地应力条件变化下甲烷水合物沉积物的排水剪切试验。试验结果表明,赋存环境变化对泥质水合物的抗剪强度与刚度产生显著影响。饱水条件下相同水合物饱和度沉积物抗剪强度显著降低,抗剪强度最大降低率达52.0%。赋存环境变化对内摩擦角影响有限,对黏聚力影响显著。与饱气条件下的结果相比,饱水条件下有效黏聚力最大降低率达68.1%,进一步确定了有效黏聚力随水合物饱和度演化的指数方程。水饱和下水合物沉积物的变形模量显著降低,变形模量E_(50)的最大降低比达72.7%;水饱和条件下,变形模量随水合物饱和度的增大呈线性增长。基于气饱和与水饱和条件下水合物沉积物骨架的受力分析,初步揭示了两种赋存环境下水合物沉积物力学特性的演化机制。研究成果可为天然气水合物赋存机制揭示及储层稳定性评价提供基础数据与方法支持。The shear strength and stiffness characteristics of methane hydrate sediments in seabed reservoirs are crucial for the safe and efficient exploration and exploitation of hydrates.To investigate the impact of changes in occurrence environments on the shear strength characteristics of muddy hydrate-bearing sediments,a series of drained shear tests have been conducted on methane hydrate-bearing muddy silt sediments under varying conditions of saturation(water-saturated and gas-saturated)and confining pressure based on the improved triaxial shear tester for hydrate-bearing sediments.The experimental results show that changes in the occurrence environment in sediments have significant effects on the shear strength and stiffness characteristics of hydrate-bearing muddy silt sediments.Compared to gas-saturated sediments,the shear strength of hydrate-bearing sediments with the same hydrate saturation greatly reduces under water-saturated condition,with a maximum reduction ratio of 52.0%.Although the effect of occurrence environmental changes on the internal friction angle of sediment is limited,the effect on the cohesion of sediment is significant.Compared to the results from gas-saturated sediments,the reduction ratio of the effective cohesion for the water-saturated hydrate-bearing sediments can reach 68.1%.Furthermore,the exponential equation is developed for describing the relation between the effective cohesion and hydrate saturation.Under water-saturated conditions,the deformation modulus of hydrate-bearing sediments decreases significantly,with a maximum reduction ratio of 72.7%for E_(50).Additionally,the deformation modulus increases linearly with hydrate saturation under water-saturated conditions.Lastly,based on the stress analysis of the skeleton of hydrate-bearing sediments under gas-saturated and water-saturated conditions,the evolution mechanism of the mechanical properties of hydrate-bearing sediments under these two different occurrence environments is preliminarily revealed.The observations can offer fun

关 键 词：甲烷水合物 泥质粉砂 水饱和 抗剪强度 变形模量 

分 类 号：TU441[建筑科学—岩土工程]