【摘要】 浅层气主要分布于河口和陆架海区的浅沉积层中,是一种会诱发地质灾害的隐患,珠江口伶仃洋海域也发现了浅层气。由于伶仃洋沿岸经济发达,海底管线、跨海大桥及港口码头堤坝等近岸海底工程构筑极多,海底浅层气威胁到海洋工程的安全。2003~2005年,广州海洋地质调查局使用浅层剖面测量系统、单道地震系统、旁侧声纳扫描系统、海洋环境多参量测量系统和钻探设备,对珠江口伶仃洋的海底浅层气进行了综合调查。文章借助于调查资料和样品测试结果,并通过反演,确定物探剖面显示的反射模糊区即为含浅层气区。伶仃洋海底浅层气主要成分为CO2和CH4两种气体,地层含气量较低,无大量溢出现象,但在海洋工程建设中应引起重视。更多还原

【Abstract】 hallow gas mostly distributes in the areas of estuary and continental shelf and is a kind of potential geo-hazards because it can influence the physical-mechanical property of the sediments.It is also detected in the Pearl River estuary,a well developed area with a wealth of engineering underwater constructions,such as pipe lines,bridges,and cables,which might be threatened by shallow gas.Guangzhou Marine Geological Survey（GMGS） carried out a comprehensive project of marine geo-environment & geo-hazards investigation in the Pearl River estuary between 2003 and 2005,and shallow gas of Lingdingyang Firth was investigated by Sub-Bottom Profiler system（SBP）,Single-Channel Seismic system（SCS）,Side Scan Sonar system（SSS）,Underwater Undulation Towed Vehicle system（U-TOW）,and Drilling Core.Based on these data and results of soil sample test,we suggest that the blurry reflected areas by inversing represent the areas with shallow gas.Shallow gas in Lingdingyang Firth locates between 8.2m and 12.3m under seafloor and includes CO₂ and CH₄.The SBP and SCS data,lithology,as well as soil sample testing have shown that the geotechnical properties of the gas strata are different from other areas.The natural moisture content,natural void ratio,and compression coefficient of the gas strata are larger than other areas,but the natural density is smaller,which means that the strata are swelled by shallow gas with their framework destroyed.The total area of shallow gas is quite large,about 900km²,distributing in several places.As the density of shallow gas is low and no escaping has been detected which was inferred by no pockmarks indicated by SSS and no CH₄ detected by U-TOW,exploitation is not likely to present.However,soil mass deformation which might be caused by future gas escapes should be considered for marine engineering.更多还原