泥质粉砂沉积物—天然气水合物混合体系的力学特性  

Mechanical properties of the mixed system of clayey-silt sediments and natural gas hydrates

作　　者：李彦龙[1,2,3] 刘昌岭 廖华林[4] 董林 卜庆涛[1,2] 刘志超 LI Yanlong;LIU Changling;LIAO Hualin;DONG Lin;BU Qingtao;LIU Zhichao(Key Laboratory of Gas Hydrate,Ministry of Natural Resources//Qingdao Institute of Marine Geology,China Geological Survey,Qingdao,Shandong 266071,China;Laboratory for Marine Mineral Resources,Pilot National Laboratory for Marine Science and Technology-Qingdao,Qingdao,Shandong 266071,China;Faculty of Engineering,China University of Geosciences-Wuhan,Wuhan,Hubei 430074,China;School of Petroleum Engineering,China University of Petroleum-East China,Qingdao,Shandong 266580,China)

机构地区：[1]自然资源部天然气水合物重点实验室·中国地质调查局青岛海洋地质研究所 [2]青岛海洋科学与技术试点国家实验室海洋矿产资源评价与探测技术功能实验室 [3]中国地质大学(武汉)工程学院 [4]中国石油大学(华东)石油工程学院

出　　处：《天然气工业》2020年第8期159-168,共10页Natural Gas Industry

基　　金：国家自然科学基金项目“南海神狐海域水合物储层静力触探响应特征及其主控因素研究”(编号:41976074);山东省泰山学者特聘专家项目(编号:ts201712079)。

摘　　要：天然气水合物开采过程中,厘清储层力学参数的演化特征是进行工程地质风险评估的基础,但目前针对中国南海含天然气水合物泥质粉砂储层力学性质评价与测试相关研究的报道却鲜见。为此,以南海北部神弧海域W18/19矿体天然气水合物顶界沉积物为研究对象,用四氢呋喃(THF)水合物代替天然气水合物,以此来探讨泥质粉砂沉积物-天然气水合物混合体系的力学参数演化特征。研究结果表明:①在低质量丰度条件(小于等于16.7%)下泥质粉砂沉积物-天然气水合物混合体系呈现应变硬化破坏特征,抗剪强度、切线模量、内聚力随着水合物含量的增大而增大;②纯天然气水合物的应力-应变曲线表现出明显的脆性破坏特征,与低丰度条件下的泥质粉砂沉积物-天然气水合物混合体系破坏特征截然不同。进而提出了采用丰度(质量丰度或体积丰度)代替原有的砂质沉积物中饱和度概念来表征天然气水合物含量的建议,在考虑天然气水合物合成结束后泥质粉砂沉积物含水率影响的基础上,将泥质粉砂型天然气水合物-沉积物混合体系划分为纯沉积物、含天然气水合物沉积物、含沉积物天然气水合物和纯天然气水合物4种基本类型,以克服目前针对含天然气水合物泥质粉砂储层力学性质研究中所存在的不足。Mechanical properties of hydrate-bearing sediments are crucial to evaluating hydrate production related geohazards.However,the mechanical parameters of the hydrate reservoirs in the Shenhu area of the South China Sea are rarely reported by previous researchers.In this paper,the sediments from the top layer of the hydrate reservoirs in the Shenhu area are taken as samples to analyze the triaxial shearing behaviors of clayey-silt sediments containing tetrahydrofuran(THF)hydrates.The results indicate that the stress-strain curves of THF hydrate-bearing clayey-silt sediments show strain-hardening failure characteristics under a relatively low hydrate mass fraction(≤16.7%).Triaxial shearing strength,tangent modulus,and cohesion force increase with the increase of hydrate mass fraction.However,prime results from pure THF hydrates reveal a brittle failure mode,which is totally different from that when hydrate mass fraction is more than 16.7%.Therefore,hydrate fraction(either mass fraction or volume fraction),rather than hydrate saturation,is strongly recommended to characterize the content of hydrate within clayey-silt sediments.The hydrate-sediment system is suggested to be divided into pure sediment,hydrate-bearing sediment(HBS),sediment-bearing hydrate(SBH),and pure hydrate,for which a universally applicable mechanical property evaluation method is thus established.

关 键 词：天然气水合物 力学性质 泥质粉砂储集层 南海北部神狐海域 四氢呋喃 质量丰度 三轴实验 

分 类 号：P618.13[天文地球—矿床学]