| 水合物生成导致沉积物孔隙结构和渗透率变化的低场核磁共振观测 |
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| 引用本文： | 张永超, 刘昌岭, 刘乐乐, 陈鹏飞, 张准, 孟庆国. 水合物生成导致沉积物孔隙结构和渗透率变化的低场核磁共振观测[J]. 海洋地质与第四纪地质, 2021, 41(3): 193-202. doi: 10.16562/j.cnki.0256-1492.2021031501 |
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| 作者姓名： | 张永超 刘昌岭 刘乐乐 陈鹏飞 张准 孟庆国 |
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| 作者单位： | 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，青岛 266071;; 2.青岛海洋科学与技术国家实验室海洋矿产资源评价与探测技术功能实验室，青岛 266071;; 3.中国地质大学（武汉）工程学院，武汉 430074 |
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| 基金项目： | 国家自然科学基金;南海含有孔虫沉积物双重孔隙特征对水合物分解过程中渗透率演化的影响机理;水合物降压开采粉砂质储层孔隙结构演化及渗透性响应机理研究;国家重点研发计划 |
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| 摘 要： | 含水合物储层的宏观物性表现是由储层沉积物的微观孔隙特征所控制的。理解沉积物在水合物生成过程中微观孔隙结构特征变化对于其物性特征的预测和分析有重要意义。本文利用低场核磁共振（LFNMR）技术监测了不同砂样中氙气水合物的生成过程，利用横向弛豫时间（T2）谱对生成过程中的微观孔隙结构及水相渗透率演化规律进行了分析。研究表明，水合物优先生成于沉积物较大孔隙中，在半径较小的孔隙中水合物很难生成；生成前期水合物的生长速率较快，后期逐渐减缓；水合物的生成导致沉积物孔隙尺寸和分布的变化，表现为随着水合物的生成，沉积物水相孔隙空间的最大孔隙半径和平均孔隙半径逐渐减小，孔隙空间的分形系数逐渐增大；沉积物水相渗透率随水合物生成过程中水合物饱和度的增加，先迅速减小后缓慢减小；具有不同孔隙结构特征的样品水相渗透率变化规律存在差异；相较于SDR模型和Kozeny-Carman模型，分形方法能够更好地体现孔隙结构变化对渗透率的影响。
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| 关 键 词： | 水合物 低场核磁共振 生成过程 孔隙结构 渗透率 物性分析 |
| 收稿时间： | 2021-03-15 |
| 修稿时间： | 2021-03-29 |
Sediment pore-structure and permeability variation induced by hydrate formation: Evidence from low field nuclear magnetic resonance observation |
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| ZHANG Yongchao, LIU Changling, LIU Lele, CHEN Pengfei, ZHANG Zhun, MENG Qingguo. Sediment pore-structure and permeability variation induced by hydrate formation: Evidence from low field nuclear magnetic resonance observation[J]. Marine Geology & Quaternary Geology, 2021, 41(3): 193-202. doi: 10.16562/j.cnki.0256-1492.2021031501 |
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| Authors: | ZHANG Yongchao LIU Changling LIU Lele CHEN Pengfei ZHANG Zhun MENG Qingguo |
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| Affiliation: | 1.The Key Laboratory of Gas Hydrate, Ministry of Natural Resources, Qingdao Institute of Marine Geology, Qingdao 266071, China;; 2.Laboratory for Marine Mineral Resources, Pilot National Laboratory for Marine Science and Technology, Qingdao 266071, China;; 3.Faculty of Engineering, China University of Geosciences, Wuhan 430074, China |
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| Abstract: | The macro-scale physical properties of hydrate-bearing sediments is in fact controlled by their micro-scale pore-structures. Understanding the changes in pore-structure characteristics of the sediments during the process of hydrate formation is essential to the analyzing and predicting of the sediment properties. In this paper, the formation processes of Xenon hydrate in different sandy samples are measured with the low-field nuclear magnetic resonance (LFNMR) method. The obtained transverse relaxation time (T2) spectra are interpreted for study of the changes in pore-structure and physical properties of the sediments during the hydrate formation. The results show that Xenon hydrates preferentially form in larger pores and only little amount of hydrates formed in smaller pores; the forming rate of hydrate is higher at the early stage of formation but decrease slowly at the later stage; the hydrate formation process also leads to the changes in pore size and pore-size distribution patterns, for examples, the maximum radius and mean radius of the water-phase pores decrease with increasing hydrate saturation, while the fractal dimension of the effective water-phase pores increases with the increasing hydrate saturation; the water-phase permeability decreases rapidly in the early stage of hydrate formation, but slowly decrease since then; the changes of water-phase permeability during hydrate formation are affected by the pore-structures of the sediment; compared to the SDR model and the Kozeny-Carman model, the fractal model of permeability performs better in showing the influences of pore-structure characteristics on the changes of water-phase permeability during the hydrate formation. |
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| Keywords: | hydrate low-field nuclear magnetic resonance formation process pore structure permeability physical property analysis |
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