南海琼东南盆地气态烃地球化学特征及天然气水合物资源远景预测

Geochemical Characteristics of Gaseous Hydrocarbons and Hydrate Resource Prediction in the Qiong-dongnan Basin of the South China Sea

天然气水合物研究覆盖了地球物理学、地球化学和地质学等多门学科,其中勘查地球化学方法可以从海底介质中直接获得与天然气水合物有关的地球化学信息,圈定水合物异常区域。近些年来大量的研究工作和陆续发现的地球物理和地球化学证据显示,南海北部海域是我国勘查天然气水合物最有潜力的区域之一。依据广州海洋地质调查局2005年第4航次获得的南海琼东南盆地沉积物酸解烃测试结果和高异常段位同位素分析数据,探讨了琼东南盆地气态烃地球化学分布特征和异常成因。结合西沙海槽已有的勘探资料和水合物成藏地质条件,分析南海北部西沙海槽—琼东南地区与天然气水合物有关的地球化学异常特征,并对水合物成藏远景进行了预测。研究成果为南海北部天然气水合物勘探提供地球化学证据。

Researches on gas hydrates are based upon geophysics, geochemistry and geology, and so on. By geochemical prospecting approach, as one of these researches, we could obtain some geochemical marker of gas hydrate from sediment undersea, and then establish the anomaly area of gas hydrate. Recently many geophysical and geochemical evidences have been discovered, which indicate that the northeast of the South China Sea is one of the most prospective gas hydrate bearing areas in China. In 2005, 93 sites at the geochemical work area for gas hydrate in Qiong-dongnan Basin of the South China Sea have been detected on-site. According to the acidolysis hydrocarbon test of the sediment from this detection and the isotopic analysis, the distribution of gaseous hydrocarbon anomaly and its causes have been studied in this paper. The prospect of gas hydrate in this work area has been estimated here on the ground of the geological condition for gas hydrate accumulation and the detective study over the Xisha Trough. The results will show an outstanding geochemical marker for gas hydrate prospecting in this work area.