南海北部天然气水合物赋存区沉积物渗透性敏感规律试验研究  

Experimental study on the sensitivity of hydraulic permeability of fine-grained sediments sampled from a gas hydrate distribution area in the northern South China Sea

作　　者：宋德坤 刘乐乐 王栋[1] SONG Dekun;LIU Lele;WANG Dong(Shandong Engineering Research Center of Marine Exploration and Conservation,Ocean University of China,Qingdao 266100,China;MNR Key Laboratory of Gas Hydrate,Qingdao Institute of Marine Geology,China Geological Survey,Qingdao 266237,China)

机构地区：[1]中国海洋大学海底建设与保护山东省工程研究中心,山东青岛266100 [2]中国地质调查局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,山东青岛266237

出　　处：《地学前缘》2024年第6期405-414,共10页Earth Science Frontiers

基　　金：山东省自然科学基金优秀青年基金项目(ZR2022YQ54);山东省泰山学者工程青年专家项目(tsqn202306297)。

摘　　要：天然气水合物主要分布于含有黏土矿物的海洋细颗粒沉积物中。我国南海北部海域沉积物中含有大量的伊利石,揭示其渗透性在降压开采过程中的变化规律对于合理调控水气产出过程非常重要。本文采用取自南海北部水合物试采目标海域的沉积物重塑土样,在不同的孔隙液盐度条件下,进行了界限含水率测定试验、渗流固结试验和稳态渗流试验,获得了土样液限含水率、塑限含水率、塑性指数、渗透系数和渗透率数据,分析了南海沉积物渗透性的应力敏感性和化学敏感性规律。结果表明:南海沉积物的界限含水率指标均随着孔隙液盐度的增加而降低;南海沉积物的渗透性随着孔隙液盐度的增加而增强,随着应力的增加而减弱,并且应力敏感性程度随着孔隙液盐度的增加而变大,化学敏感性程度随着应力的增加而变小;采用归一化孔隙比获得的渗透系数拟合关系不受孔隙液盐度的影响,便于工程应用。Natural gas hydrates are mainly distributed in fine-grained marine sediments containing clay minerals.For instance,the sediments in the northern region of the South China Sea contain a large amount of illite.Understanding the changes in permeability during the depressurization extraction process is crucial for effectively regulating the production of gas from hydrates.This study utilized remolded soil samples taken from the target hydrate test-production area in the northern South China Sea and conducted limit water content tests,drained consolidation tests,and steady-state seepage tests under different pore fluid concentration conditions.Data on the liquid limit,plastic limit,plasticity index,permeability coefficient,and permeability were obtained.The stress sensitivity and chemical sensitivity of the permeability of South China Sea sediments were analyzed.The results indicated that the limit water content parameters of the South China Sea sediments decreased as the pore fluid concentration increased.The permeability of the sediments increased with the pore fluid concentration,while it decreased with increasing stress.Moreover,the degree of stress sensitivity increased as the pore fluid concentration rose,whereas the degree of chemical sensitivity diminished with increasing stress.The fitting relationship of the permeability coefficient obtained using the normalized void ratio was found to be unaffected by pore fluid concentration,making it convenient for engineering applications.

关 键 词：渗透率 渗透系数 界限含水率 敏感性指标 降压开采 

分 类 号：P744.4[天文地球—海洋科学] O357.3[理学—流体力学] P618.130.21[理学—力学]