盐度影响下松散沉积物中甲烷水合物生成特征研究  

Effect of salinity on the formation of methane hydrate in unconsolidated sediments

作　　者：纪云开 王佳贤 邱晓倩 孟庆国[1,2] 张永超 胡高伟 蔡峰[1,2] 刘昌岭 JI Yunkai;WANG Jiaxian;QIU Xiaoqian;MENG Qingguo;ZHANG Yongchao;HU Gaowei;CAI Feng;LIU Changling(Key Laboratory of Gas Hydrate of Ministry of Natural Resources,Qingdao Institute of Marine Geology,Qingdao 266237,China;Laboratory for Marine Mineral Resources,Qingdao Marine Science and Technology Center,Qingdao 266237,China;Faculty of Engineering,China University of Geosciences(Wuhan),Wuhan 430074,China;School of Ocean Sciences,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]青岛海洋地质研究所自然资源部天然气水合物重点实验室,青岛266237 [2]青岛海洋科技中心海洋矿产资源评价与探测技术功能实验室,青岛266237 [3]中国地质大学(武汉)工程学院,武汉430074 [4]中国地质大学(北京)海洋学院,北京100083

出　　处：《海洋地质与第四纪地质》2024年第6期71-81,共11页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金“南海北部高富集天然气水合物储层特征与成藏控制机理研究”(U2244224),“南海神狐海域水合物储层气-水-水合物三相共存微观机理研究”(42206233),“海洋沉积物中水合物生成过程的孔隙水转化规律及其控制机理研究”(42176212);泰山学者工程项目(tsqn202312280)。

摘　　要：深入认识含盐水松散沉积物体系中甲烷水合物生成特征,对精准评价海域天然气水合物资源量有重要意义。本研究利用低场核磁共振原位探测技术研究了盐度对松散砂样中甲烷水合物生成特征的影响。结果表明,松散砂样体系下不同大小孔隙中水合物生成诱导时间存在差异;甲烷水合物更易在小孔隙中生成。随着孔隙水盐度增大,水合物生成诱导时间呈现指数增长。在最初20 min内,随着孔隙水盐度的增大,水合物生成速率先升后降,在盐度为3.0 wt%条件下生成速率最大。在松散砂样体系下的不同位置处,甲烷水合物生成诱导时间的差异性以及孔隙水通过水合物膜的方式转变会引起水合物生成过程中生成速率的变化。沉积物表面影响和水合物的阻隔作用使砂样中部分孔隙水不能转化为水合物,而孔隙水盐度的增加促使这种作用增强,孔隙水最终转化率降低,水合物饱和度减小。In-depth understanding of the characteristics of methane hydrate formation in unconsolidated sediments containing saline solution is of great significance for the accurate evaluation of hydrate resources in marine sediments.In this study,the effect of salinity on the formation characteristics of methane hydrate in unconsolidated sand samples was studied using the low-field nuclear magnetic resonance in-situ detection technology.Results show that there were differences in the induction time of hydrate formation in pores of different sizes in the unconsolidated sands;methane hydrate was more likely to form in small pores.As the salinity of pore water increased,the induction time of hydrate formation increased exponentially.In the first 20 minutes,the hydrate formation rate first increased and then decreased,and the formation rate was the highest under the salinity of 3.0 wt%.At different locations of the unconsolidated sediments,the difference in the induction time of methane hydrate formation and the mode change of water through the hydrate film caused changes in the hydrate formation rate.The large potential energy on sediment surface and the barrier effect caused by the presence of hydrates prevented some pore water in the samples from being converted into hydrates.The increase in the initial salinity of pore water could enhance the barrier effect,decrease the final conversion rate of pore water,and reduce the hydrate saturation.

关 键 词：水合物生成 松散沉积物 低场核磁共振 盐度 

分 类 号：P774.4[天文地球—海洋科学]