Geochemical characteristics of pore water in shallow sediments from north continental slope of South China Sea and their significance for natural gas hydrate occurrence
Geochemical characteristics of pore water in shallow sediments from north continental slope of South China Sea and their significance for natural gas hydrate occurrence
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DOI：
10.1016/j.proenv.2012.01.381
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
C. Cao;Huaiyan Lei
中科院分区：
文献类型：
--
作者：
C. Cao;Huaiyan Lei
南海北方陆坡是天然气水合物的潜在区和研究重点地区。分析了重力活塞采集的深沪海域、东沙海域和台湾盆地西南部沉积物中主要成分阴阳离子和δ 13 CDIC的孔隙水地球化学参数。结果表明，Cl−浓度在3个站位随深度变化不明显，其值与正常海水相一致; SO 42-浓度在3个站位均表现出明显的自上而下的梯度下降趋势，Ca 2+、Mg 2+、Ca 2 +/Mg 2+与SO 42 −浓度呈相似的下降趋势，但幅度不一致。深沪海域、东沙海域、台湾盆地西南部的SMI分别为11 m、8 m、6 m，沉积物孔隙水的δ 13 CDIC为-10 ‰ ~-27 ‰，与国际上发现天然气水合物的其它地区如布莱克海岭、墨西哥湾等沉积物孔隙水的地球化学特征相似。这些地球化学特征表明，天然气水合物储层释放的甲烷是深部沉积物中的甲烷，甲烷是混合气体，是天然气水合物热解的主要原因。总结了利用浅层沉积物孔隙水地球化学异常特征追踪深层天然气水合物的一系列异常标志和识别方法。
Northern slope of the South China Sea is a potential area of gas hydrates and research focus areas. Analyzed geochemical parameters about pore water of the anions and cations of major components and δ13CDICin the sediments from Shenhu sea area, Dongsha sea area and Southwest Taiwan Basin and collected by gravity piston. The results showed that Cl−concentration were no significant changes with depth at the three stations and their values were consistent with the normal sea water, SO42-concentration showed significant changes in gradient descent from core top to bottom at three stations and Ca2+, Mg2+, Ca2+/Mg2+showed a similar downward trend with SO42−concentration, but the amplitude is inconsistent. The SMI of Shenhu sea area, Dongsha sea area, Southwest Taiwan Basin were separately 11m, 8m, 6m andδ13CDICof pore water in the sediments range from -10 ‰ to -27 ‰, which were similar with geochemistry characteristics of pore water in the sediments at other international regions of being found gas hydrate, such as Blake Ridge and Mexico Gulf. These geochemistry characteristics may suggest that natural gas hydrate reservoir released methane in deep sediments and methane was mixture gas as main causes of pyrolysis. Summary a series anomaly indicators and identification methods that use these geochemical anomalies characteristics about pore water of shallow sediments to trace gas hydrate in deep stratum.