西南石油大学学报(自然科学版) ›› 2018, Vol. 40 ›› Issue (3): 63-75.DOI: 10.11885/j.issn.1674-5086.2017.12.01.01

• 地质勘探 • 上一篇    下一篇

琼东南盆地甲烷微渗漏活动地球化学示踪研究

冯俊熙1,2, 杨胜雄2, 孙晓明1, 梁金强1,2   

  1. 1. 中山大学海洋科学学院, 广东 广州 510006;
    2. 国土资源部海底矿产资源重点实验室·广州海洋地质调查局, 广东 广州 510075
  • 收稿日期:2017-12-01 出版日期:2018-06-01 发布日期:2018-06-01
  • 通讯作者: 杨胜雄,E-mail:yangshengxiong@hydz.cn
  • 作者简介:冯俊熙,1988年生,男,汉族,广东广州人,在站博士后,主要从事海底冷泉与天然气水合物地质研究工作。E-mail:910113049@qq.com;杨胜雄,1964年生,男,汉族,广东揭西人,教授级高级工程师,博士,主要从事海洋地质调查与研究工作。E-mail:yangshengxiong@hydz.cn;孙晓明,1963年生,男,汉族,江苏如皋人,教授,博士,主要从事海洋矿产地质研究工作。E-mail:eessxm@mail.sysu.edu.cn;梁金强,1967年生,男,汉族,广东茂名人,教授级高级工程师,主要从事海洋天然气水合物调查与研究工作。E-mail:ljinqiang@21.cn.com
  • 基金资助:
    中国博士后科学基金面上项目(2017M622654);国土资源部海底矿产资源重点实验室开放基金(KLMMR-2017-A-08);国家水合物专项(GZH201500302)

Geochemical Tracers for Methane Microleakage Activity in the Qiongdongnan Basin

FENG Junxi1,2, YANG Shengxiong2, SUN Xiaoming1, LIANG Jinqiang1,2   

  1. 1. School of Marine Sciences, Sun Yat-sen University, Guangzhou, Guangdong 510006, China;
    2. MLR Key Laboratory of Marine Mineral Resources, Guangzhou Marine Geological Survey, Guangzhou, Guangdong 510075, China
  • Received:2017-12-01 Online:2018-06-01 Published:2018-06-01

摘要: 为了深入认识南海北部琼东南盆地的甲烷微渗漏活动,通过测试位于该盆地某似海底放射(BSR)发育区内柱状样HQ-6PC和HQ-38PC的孔隙水阴阳离子浓度及δ13CDIC等指标,对甲烷微渗漏活动特征进行了研究。结果显示,在柱状样HQ-6P和HQ-38PC的5.2 m以上部分,硫酸盐消耗由有机质硫酸盐还原作用(OSR)和甲烷缺氧氧化作用(AOM)共同主导,而在柱状样HQ-38PC的5.2 m以下部分主要受AOM的影响。柱状样HQ-38PC的硫酸根甲烷转换界面(SMTZ)埋深为9.9 m,甲烷向上扩散的通量约为32 mmol·m-2·a-1。两个柱状样孔隙水的Mg/Ca和Sr/Ca质量比随深度的变化指示其中形成的自生碳酸盐矿物主要为高镁方解石。HQ-6PC的Cl-浓度在3.5 m以下明显降低,可能有天然气水合物分解时排放的低盐度流体加入,而HQ-38PC在4.0~5.5 m处存在较高的盐度异常,暗示其中可能混入了来自水合物形成时排放的高盐度流体。因此,两个站位浅表层发育显著的甲烷微渗漏活动,其下方可能发育水合物。

关键词: 甲烷微渗漏, 孔隙水, 地球化学, 天然气水合物, 琼东南盆地

Abstract: To understand methane microleakage activity in the Qiongdongnan Basin of the northern South China Sea, the concentrations of pore water anions and cations, δ13CDIC, and other indices of the core samples HQ-6PC and HQ-38PC were measured using bottom stimulating reflectors (BSR) in the development zone to study the characteristics of methane microleakage. The results showed that sulfate consumption was dominated by organic sulfate reduction (OSR) and anaerobic oxidation of methane (AOM) in the HQ-6PC and HQ-38PC core samples above 5.2 m, whereas the effects of AOM were predominant in the HQ-38PC core sample below 5.2 m. The sulfate-methane transition zone (SMTZ) of the HQ-38PC core sample had a depth of 9.9 m and an upward methane flux of 32 mmol·m-2·a-1. The change in Mg/Ca and Sr/Ca depth in the pore water of the two core samples indicated that the authigenic carbonate minerals formed within were primarily high-magnesium calcites. The Cl- concentration of HQ-6PC was significantly decreased below 3.5 m. Inclusions of low-salinity fluid released from hydrate decomposition are likely present. There is a relatively large salinity anomaly in HQ-38PC between 4.0~5.5 m, suggesting that there might be mixing with high-salinity fluid released during hydrate formation. Thus, there is significant methane microleakage activity in the shallow surface of the two stations and possible hydrate development underneath.

Key words: methane microleakage, pore water, geochemistry, natural gas hydrates, Qiongdongnan Basin

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