伶仃洋海底浅层气的基本特征
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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。
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 CO_2 and CH_(4).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 900km~2,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 CH_(4) 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.
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 CO_2 and CH_(4).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 900km~2,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 CH_(4) 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.
引文
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7 García-GarcaíAna,O range D L,Maher N Met al.Geophysicalevidence for gas geohazards off Iskenderun Bay,SE Turkey.Marine&Petroleum Geology,2004,21(10):1255~1264
8寇养琦,杜德莉.南海北部陆架第四纪古河道沉积特征.地质学报,1994,68(3):268~276Kou Yangq i,Du D eli.Sed im entary features of shallow ancient riverchannels on the northern shelf of the South Ch ina Sea.ActaGeologica Sinica,1994,68(3):268~276
9钟建强,詹文欢,古森昌等.珠江三角洲区域稳定性的地质环境分析.海洋地质与第四纪地质,1996,16(2):34~41Zhong Jianq iang,Zhan W enhuan,Gu Senchanget a.l Geologicalenvironm ent analyses of regional stab ilities in the Zhu jiang R iverdelta.Marine Geology&Quaternary Geology,1996,16(2):34~41
10陈耀泰.珠江口沉积分区.中山大学学报(自然科学版),1995,34(3):109~114Chen Yaotai.Sedimentation divisions of Pearl R iver mouth.ActaScientiarum Naturalium Universitatis Sunyatseni,1995,34(3):109~114
11冯文科,鲍才旺,陈俊仁等.南海北部海底地貌初步研究.海洋学报,1982,4(4):462~471FengW enke,Bao Caiwang,Chen Junrenet a.l Prelimnary study onsubmarine relief of the northern South Ch ina Sea.Acta O ceanologicaSinica,1982,4(4):462~471
12黄镇国,张伟强,蔡福祥.珠江水下三角洲.地理学报,1995,50(3):206~213Huang Zhenguo,Zhang W eiq iang,Cai Fuxiang.The subm ergedZhu jiang delta.Acta Geographica Sinica,1995,50(3):206~213
13鲍才旺.珠江口陆架区埋藏古河道与古三角洲.海洋地质与第四纪地质,1995,15(2):25~34Bao Caiwang.Buried ancient channels and deltas in the Zhu jiangR iver mouth shelf area.Marine Geology&Quaternary Geology,1995,15(2):25~34
2陈少平,孙家振,沈传波等.杭州湾地区浅层气成藏条件分析.海洋地质与第四纪地质,2004,24(2):85~88Chen Shaop ing,Sun Jiazhen,Shen Chuanboet a.l Reservoirformation cond ition of shallow gas in the area of the Hangzhou Bay.Marine Geology&Quaternary Geology,2004,24(2):85~88
3冯志强,冯文科,薛万俊等.南海北部地质灾害及海底工程地质条件评价.南京:河海大学出版社,1996.82~115Feng Zh iq iang,Feng W enke,Xue W an junet a.l Evaluation ofMarine Geologic Hazards and Engineering Geological Cond itions inthe Northern South Ch ina Sea.Nan jing:Hohai Un iversity Press,1996.82~115
4夏真,林进清,郑志昌.海岸带海洋地质环境综合调查方法.地质通报,2005,24(6):570~575X ia Zhen,L in Jinq ing,Zheng Zh ichang.Integrated investigationm ethods for the marine geo-environm ent in coastal zone.GeologicalBulletin ofChina,2005,24(6):570~575
5 Lee G H,K im D C,K im H Jet al.Shallow gas in the central partof the Korea Strait shelf mud off the southeastern coast of Korea.Continental ShelfResearch,2005,25(16):2036~2052
6 K im Dae C,Lee Gwang H,Seo Young Ket al.D istribution andacoustic characteristics of shallow gas in the Korea strait shelf mudoff SE Korea.Marine Georesources and Geotechnology,2004,22(1~2):21~31
7 García-GarcaíAna,O range D L,Maher N Met al.Geophysicalevidence for gas geohazards off Iskenderun Bay,SE Turkey.Marine&Petroleum Geology,2004,21(10):1255~1264
8寇养琦,杜德莉.南海北部陆架第四纪古河道沉积特征.地质学报,1994,68(3):268~276Kou Yangq i,Du D eli.Sed im entary features of shallow ancient riverchannels on the northern shelf of the South Ch ina Sea.ActaGeologica Sinica,1994,68(3):268~276
9钟建强,詹文欢,古森昌等.珠江三角洲区域稳定性的地质环境分析.海洋地质与第四纪地质,1996,16(2):34~41Zhong Jianq iang,Zhan W enhuan,Gu Senchanget a.l Geologicalenvironm ent analyses of regional stab ilities in the Zhu jiang R iverdelta.Marine Geology&Quaternary Geology,1996,16(2):34~41
10陈耀泰.珠江口沉积分区.中山大学学报(自然科学版),1995,34(3):109~114Chen Yaotai.Sedimentation divisions of Pearl R iver mouth.ActaScientiarum Naturalium Universitatis Sunyatseni,1995,34(3):109~114
11冯文科,鲍才旺,陈俊仁等.南海北部海底地貌初步研究.海洋学报,1982,4(4):462~471FengW enke,Bao Caiwang,Chen Junrenet a.l Prelimnary study onsubmarine relief of the northern South Ch ina Sea.Acta O ceanologicaSinica,1982,4(4):462~471
12黄镇国,张伟强,蔡福祥.珠江水下三角洲.地理学报,1995,50(3):206~213Huang Zhenguo,Zhang W eiq iang,Cai Fuxiang.The subm ergedZhu jiang delta.Acta Geographica Sinica,1995,50(3):206~213
13鲍才旺.珠江口陆架区埋藏古河道与古三角洲.海洋地质与第四纪地质,1995,15(2):25~34Bao Caiwang.Buried ancient channels and deltas in the Zhu jiangR iver mouth shelf area.Marine Geology&Quaternary Geology,1995,15(2):25~34
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