海洋天然气水合物发育顶界模拟——沉积物毛细管作用影响  

Modeling of Sedimentary Pore Capillary Effect on the Top Occurrence of Marine Gas Hydrates

作　　者：曹运诚 周海玲 郑子涵 陈多福[1] CAO YunCheng;ZHOU HaiLing;ZHENG ZiHan;CHEN DuoFu(College of Oceanography and Ecological Science,Shanghai Ocean University,Shanghai 201306,China)

机构地区：[1]上海海洋大学海洋科学与生态环境学院,上海201306

出　　处：《沉积学报》2024年第4期1229-1238,共10页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41730528,41776050);国家重点研发计划(2018YFC0310001)。

摘　　要：【目的】海洋沉积物孔隙内部的毛细管作用可以升高水合物—水二相甲烷的溶解度,影响天然气水合物的分布。确定毛细管作用对水合物发育顶界的影响,可以为水合物的成藏演化研究及水合物勘察提供理论支撑。【方法】考虑毛细管作用,根据甲烷的质量守恒,建立了基于海底沉积物孔隙水硫酸根浓度计算水合物发育顶界深度的模型,利用数值模拟方法研究布莱克海台ODP994站位沉积物孔隙毛细管作用影响下的甲烷浓度分布和水合物发育顶界。【结果与结论】模拟计算显示考虑实际孔径计算的ODP994站位水合物发育顶界为194 m,与实际的水合物发育顶界深度一致。毛细管作用可以增大水合物—水二相甲烷溶解度,使生成水合物所需甲烷浓度升高。毛细管作用升高流体溶解的甲烷浓度,有利于甲烷运移到更浅的深度,可以使水合物发育顶界更浅。水合物顶界附近的局部的最大孔径沉积层具有更小的水合物-水二相甲烷溶解度,是水合物发育顶界优先发育位置。因此,确定水合物稳定带内的沉积物孔隙特征,是评估天然气水合物顶界的重要基础。[Objective]Capillary effects increase the solubility of methane in fluids in equilibrium with hydrate,which affects the gas-hydrate distribution.Revealing the influence of capillary effects on the distribution of hydrates can provide theoretical support for the study of hydrate accumulation and hydrate exploration.[Methods]A numeri⁃cal model was developed to investigate and predict the influence of capillary effects on the top occurrence of gas hydrate,and applied at site ODP994.[Results and Conclusions]The predicted top occurrence was calculated to be about 194 m,consistent with the depth determined from chloride anomalies.The top occurrence of gas hydrate tends to be located at depths where the pore radius is locally larger compared to adjacent layers.The methane concentration in hydrate zone could be increased by capillary effects by increasing solubility of methane in fluids in equilibrium with hydrate.And dissolved methane would be more readily transported upward from hydrate zone,resulting in a shallower top hydrate occurrence.Therefore,capillary effects in gas hydrate stability zones plays a important role in determining the upper boundary of gas hydrates.

关 键 词：毛细管作用 硫酸根甲烷界面 甲烷通量 水合物发育顶界 数值模拟 

分 类 号：P618.13[天文地球—矿床学]