利用多道地震反射数据探测神狐海域渗漏型水合物
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摘要
以海底为基准,将高分辨率多道地震反射数据分离为两个独立部分,并分别对水体和地层成像.水体的成像结果显示了两个明显形如羽状流的异常,与之对应地层的地震反射剖面显示在海底处出现海底下陷、气体溢出口等与甲烷渗漏相关的地形地貌特征,并在海底之下不足100m的深度位置出现一个指示天然气水合物存在的明显的似海底反射.详尽的速度分析发现,似海底反射和溢出口之下沉积地层的声波速度明显下降,并且地震反射特征也与地层含气有关.通过对所有信息综合分析,推测这些地球物理异常和特殊地形地貌特征(如羽状流、声波速度反转、溢出口、海底下陷、浅部BSR等)很可能是甲烷气体沿运移通道进入近海底沉积物中形成天然气水合物或溢出至海水中所致.研究结果表明,多道高分辨率地震反射数据具有探测渗漏型天然气水合物的能力.
Taking the seafloor as datum, the high resolution seismic reflecting data acquired in Shenhu area are divided into two parts for the imaging of water column and strata respectively. Two apparent echoes shaped like plume show in the water column and the particular geomorphology such as vents and depressions of seafloor suggests the existence of the gas seepage occurred opposite them on the seismic reflecting section. Moreover, a classical bottom simulating reflector which indicates the presence of gas hydrates appears at the depth less than 100 m. The detailed velocity field reveals that acoustic velocity of sediments decreases beneath both the seep sites and bottom simulating reflector and the seismic reflecting characteristics seem to be related to the gas-bearing of strata. It can be concluded that geophysical anomalies (plumes, acoustic velocity reverse, BSR (bottom simulating reflector)) and the expressions of particular geomorphology of seabed (vents and depressions or craters) should have been resulted from the migration of free gas into the sediments of subsurface and then the formation of gas hydrates or the direct seepage into the seawater. This study indicates that high resolution multi-channel seismic reflecting data has great potential for characterizing the anomalies and then detecting the seepage gas hydrates reservoir.
Taking the seafloor as datum, the high resolution seismic reflecting data acquired in Shenhu area are divided into two parts for the imaging of water column and strata respectively. Two apparent echoes shaped like plume show in the water column and the particular geomorphology such as vents and depressions of seafloor suggests the existence of the gas seepage occurred opposite them on the seismic reflecting section. Moreover, a classical bottom simulating reflector which indicates the presence of gas hydrates appears at the depth less than 100 m. The detailed velocity field reveals that acoustic velocity of sediments decreases beneath both the seep sites and bottom simulating reflector and the seismic reflecting characteristics seem to be related to the gas-bearing of strata. It can be concluded that geophysical anomalies (plumes, acoustic velocity reverse, BSR (bottom simulating reflector)) and the expressions of particular geomorphology of seabed (vents and depressions or craters) should have been resulted from the migration of free gas into the sediments of subsurface and then the formation of gas hydrates or the direct seepage into the seawater. This study indicates that high resolution multi-channel seismic reflecting data has great potential for characterizing the anomalies and then detecting the seepage gas hydrates reservoir.
引文
Anderson,A.L.,Bryant,W.R.,1990.Gassy sediment oc-currence and properties—northern Gulf of Mexico.Geo-Marine Letters,10(4):209-220.doi:10.1007/BF02431067
Biescas,B.,Sallarès,V.,Pelegrí,J.L.,et al.,2008.Imagingmeddy finestructure using multichannel seismic reflec-tion data.Geophysical Research Letters,35:L11609.doi:10.1029/2008GL033971
Chen,L.,Song,H.B.,2005.Geophysical features and identi-fication of natural gas seepage in marine environment.Progress in Geophysics,20(4):1067-1073(in Chinesewith English abstract).
Crutchley,G.J.,Pecher,I.A.,Gorman,A.R.,et al.,2010.Seismic imaging of gas conduits beneath seafloor seepsites in a shallow marine gas hydrate province,Hikurangi Margin,New Zealand.MarineGeology,272(1-4):114-126.doi:10.1016/j.margeo.2009.03.007
Cook,A.E.,Goldberg,D.,Kleinberg,R.L.,2008.Fracture-controlled gas hydrate systems in the northern Gulf ofMexico.Marine and Petroleum Geology,25(9):932-941.doi:10.1016/j.marpetgeo.2008.01.013
Domenico,S.N.,1977.Elastic properties of unconsolidatedporous sand reservoirs.Geophysics,42(7):1339-1368.doi:10.1190/1.1440797
Dong,C.Z.,Song,H.B.,Bai,Y.,et al.,2010.The latest de-velopment of seismic oceanography.Progress in Geo-physics,25(1):109-123(in Chinese with English ab-stract).
Faure,K.,Greinert,J.,Pecher,L.A.,et al.,2006.Methaneseepage and its relation to slumping and gas hydrate atthe Hikurangi margin,New Zealand.NZJ.Geol.Geo-phys.,49(4):503-516.doi:10.1080/00288306.2006.9515184
Gay,A.,Lopez,M.,Berndt,C.,et al.,2007.Geological con-trols on focused fluid flow associated with seafloorseeps in the Lower Congo basin.Marine Geology,244(1-4):68-92.doi:10.1016/j.margeo.2007.06.003
Gong,Z.S.,Li,S.T.,Wang,J.Y.,et al.,2004.Dynamic Re-search of oil and gas accumulation in northern marginalbasin of South China Sea.Science Press,Beijing,339(inChinese).
Holbrook,W.S.,Páramo,P.,Pearse,S.,et al.,2003.Ther-mohaline fine structure in an oceanographic front fromseismic reflection profiling.Science,301(5634):821-824.doi:10.1126/science.1085116
Hovland,M.,Svensen,H.,2006.Submarine pingoes:indica-tors of shallow gas hydrates in a pockmark at Nyegga,Norwegian Sea.Marine Geology,228(1-4):15-23.doi:10.1016/j.margeo.2005.12.005
Kuang,Z.G.,Guo,Y.Q.,2011.The sedimentary facies andgas hydrate accumulation model since Neogene of Shen-hu Sea area,Northern South China Sea.Earth Science—Journal of China University of Geosciences,36(5):914-920(in Chinese with English abstract).
Lammers,S.,Suess,E.,Hovland,M.,1995.A large meth-ane plume east of Bear Island(Barents Sea):implica-tions for the marine methane cycle.Geol.Rundsch.,84(1):59-66.doi:10.1007/BF00192242
Lewis,K.B.,Marshall,B.A.,1996.Seep faunas and otherindicators of methane-rich dewatering on New Zealandconvergent margins.NZJ.Geol.Geophys.,39(2):181-200.doi:10.1080/00288306.1996.9514704
Priest,J.A.,Best,A.I.,Clayton,C.R.I.,2006.Attenuationof seismic waves in methane gas hydrate-bearing sand.Geophys.J.Int.,164(1):149-159.doi:10.1111/j.1365-246X.2005.02831.x
Sassen,R.,Losh,S.L.,CathlesⅢ,L.,et al.,2001.Massivevein-filling gas hydrate:relation to ongoing gas migra-tion from the deep subsurface in the Gulf of Mexico.Marine and Petroleum Geology,18(5):551-560.doi:10.1016/S0264-8172(01)00014-9
Satyavani,N.,Thakur,N.K.,Aravind Kumar,N.,et al.,2005.Migration of methane at the diapiric structure ofthe western continental margin of India—insights fromseismic data.Marine Geology,219(1):19-25.doi:10.1016/j.margeo.2005.04.008
Schroot,B.M.,Klaver,G.T.,Schüttenhelm,R.T.E.,2005.Surface and subsurface expressions of gas seepage tothe seabed—examples from the Southern North Sea.Marine and Petroleum Geology,22(4):499-515.doi:10.1016/j.marpetgeo.2004.08.007
Sloan,E.D.,1998.Clathrate hydrates of natural gases.Mar-cel Dekker,Inc,New York,705.
Song,H.B.,Dong,C.Z.,Chen,L.,et al.,2008.Reflectionseismic methods for studying physical oceanography:in-troduction of oceanography.Progress in Geophysics,23(4):1156-1164(in Chinese with English abstract).
Suess,E.,Torres,M.E.,Bohrmann,G.,et al.,1999.Gashydrate destabilization:enhanced dewatering,benthicmaterial turnover and large methane plumes at the Cas-cadia convergent margin.Earth and Planetary ScienceLetters,170(1-2):1-15.doi:10.1016/S0012-821X(99)00092-8
Wood,W.T.,Hart,P.E.,Hutchinson,D.R.,et al.,2008.Gas and gas hydrate distribution around seafloor seepsin Mississippi Canyon,northern Gulf of Mexico,usingmulti-resolution seismic imagery.Marine and Petrole-um Geology,25(9):952-959.doi:10.1016/j.marpet-geo.2008.01.015
Wu,N.Y.,Yang,S.X.,Wang,H.B.,et al.,2009.Gas-bear-ing fluid influx sub-system for gas hydrate geologicalsystem in Shenhu area,northern South China Sea.Chi-nese Journal of Geophysics,52(6):1641-1650(inChinese with English abstract).
Wu,N.Y.,Zhang,H.Q.,Yang,S.X.,et al.,2007.Prelimi-nary discussion on natural gas hydrate(NGH)reservoirsystem of Shenhu area,north slope of South China Sea.Natural gas industry,27(9):1-6(in Chinese withEnglish abstract).
Wu,S.G.,Dong,D.D.,Yang,S.X.,et al.,2009.Geneticmodel of the hydrate system in the fine grain sedimentsin the northern continental slope of South China Sea.Chinese Journal of Geophysics,52(7):1849-1857(inChinese with English abstract).
Xu,H.N.,Yang,S.X.,Zheng,X.D.,et al.,2010.Seismicidentification of gas hydrate and its distribution inShenhu area,South China Sea.Chinese Journal of Geo-physics,53(7):1691-1698(in Chinese with Englishabstract).
Yin,X.J.,Zhou,H.Y.,Yang,Q.H.,et al.,2008.The evi-dence for the existence of methane seepages in thenorthern South China Sea:abnormal high methane con-centration in bottom waters.Acta Oceanologica Sinica,30(6):69-75(in Chinese with English abstract).
陈林,宋海斌,2005.海底天然气渗漏的地球物理特征及识别方法.地球物理学进展,20(4):1067-1073.
董崇志,宋海斌,拜阳,等,2010.地震海洋学研究进展.地球物理学进展,25(1):109-123.
龚再升,李思田,汪集旸,等,2004.南海北部大陆边缘盆地油气成藏动力学研究.北京:科学出版社,339.
匡增桂,郭依群,2011.南海北部神狐海域新近系以来沉积相及水合物成藏模式.地球科学——中国地质大学学报,36(5):914-920.
宋海斌,董崇志,陈林,等,2008.用反射地震方法研究物理海洋-地震海洋学简介.地球物理学进展,23(4):1156-1164.
吴能友,杨胜雄,王宏斌,等,2009.南海北部陆坡神狐海域天然气水合物成藏的流体运移体系.地球物理学报,52(6):1641-1650.
吴能友,张海啟,杨胜雄,等,2007.南海神狐海域天然气水合物成藏系统初探.天然气工业,27(9):1-6.
吴时国,董冬冬,杨胜雄,等,2009.南海北部陆坡细粒沉积物天然气水合物系统的形成模式初探.地球物理学报,52(7):1849-1857.
徐华宁,杨胜雄,郑晓东,等,2010.南中国海神狐海域天然气水合物地震识别及分布特征.地球物理学报,53(7):1691-1698.
尹希杰,周怀阳,杨群慧,等,2008.南海北部甲烷渗漏活动存在的证据:近底层海水甲烷高浓度异常.海洋学报,30(6):69-75.
Biescas,B.,Sallarès,V.,Pelegrí,J.L.,et al.,2008.Imagingmeddy finestructure using multichannel seismic reflec-tion data.Geophysical Research Letters,35:L11609.doi:10.1029/2008GL033971
Chen,L.,Song,H.B.,2005.Geophysical features and identi-fication of natural gas seepage in marine environment.Progress in Geophysics,20(4):1067-1073(in Chinesewith English abstract).
Crutchley,G.J.,Pecher,I.A.,Gorman,A.R.,et al.,2010.Seismic imaging of gas conduits beneath seafloor seepsites in a shallow marine gas hydrate province,Hikurangi Margin,New Zealand.MarineGeology,272(1-4):114-126.doi:10.1016/j.margeo.2009.03.007
Cook,A.E.,Goldberg,D.,Kleinberg,R.L.,2008.Fracture-controlled gas hydrate systems in the northern Gulf ofMexico.Marine and Petroleum Geology,25(9):932-941.doi:10.1016/j.marpetgeo.2008.01.013
Domenico,S.N.,1977.Elastic properties of unconsolidatedporous sand reservoirs.Geophysics,42(7):1339-1368.doi:10.1190/1.1440797
Dong,C.Z.,Song,H.B.,Bai,Y.,et al.,2010.The latest de-velopment of seismic oceanography.Progress in Geo-physics,25(1):109-123(in Chinese with English ab-stract).
Faure,K.,Greinert,J.,Pecher,L.A.,et al.,2006.Methaneseepage and its relation to slumping and gas hydrate atthe Hikurangi margin,New Zealand.NZJ.Geol.Geo-phys.,49(4):503-516.doi:10.1080/00288306.2006.9515184
Gay,A.,Lopez,M.,Berndt,C.,et al.,2007.Geological con-trols on focused fluid flow associated with seafloorseeps in the Lower Congo basin.Marine Geology,244(1-4):68-92.doi:10.1016/j.margeo.2007.06.003
Gong,Z.S.,Li,S.T.,Wang,J.Y.,et al.,2004.Dynamic Re-search of oil and gas accumulation in northern marginalbasin of South China Sea.Science Press,Beijing,339(inChinese).
Holbrook,W.S.,Páramo,P.,Pearse,S.,et al.,2003.Ther-mohaline fine structure in an oceanographic front fromseismic reflection profiling.Science,301(5634):821-824.doi:10.1126/science.1085116
Hovland,M.,Svensen,H.,2006.Submarine pingoes:indica-tors of shallow gas hydrates in a pockmark at Nyegga,Norwegian Sea.Marine Geology,228(1-4):15-23.doi:10.1016/j.margeo.2005.12.005
Kuang,Z.G.,Guo,Y.Q.,2011.The sedimentary facies andgas hydrate accumulation model since Neogene of Shen-hu Sea area,Northern South China Sea.Earth Science—Journal of China University of Geosciences,36(5):914-920(in Chinese with English abstract).
Lammers,S.,Suess,E.,Hovland,M.,1995.A large meth-ane plume east of Bear Island(Barents Sea):implica-tions for the marine methane cycle.Geol.Rundsch.,84(1):59-66.doi:10.1007/BF00192242
Lewis,K.B.,Marshall,B.A.,1996.Seep faunas and otherindicators of methane-rich dewatering on New Zealandconvergent margins.NZJ.Geol.Geophys.,39(2):181-200.doi:10.1080/00288306.1996.9514704
Priest,J.A.,Best,A.I.,Clayton,C.R.I.,2006.Attenuationof seismic waves in methane gas hydrate-bearing sand.Geophys.J.Int.,164(1):149-159.doi:10.1111/j.1365-246X.2005.02831.x
Sassen,R.,Losh,S.L.,CathlesⅢ,L.,et al.,2001.Massivevein-filling gas hydrate:relation to ongoing gas migra-tion from the deep subsurface in the Gulf of Mexico.Marine and Petroleum Geology,18(5):551-560.doi:10.1016/S0264-8172(01)00014-9
Satyavani,N.,Thakur,N.K.,Aravind Kumar,N.,et al.,2005.Migration of methane at the diapiric structure ofthe western continental margin of India—insights fromseismic data.Marine Geology,219(1):19-25.doi:10.1016/j.margeo.2005.04.008
Schroot,B.M.,Klaver,G.T.,Schüttenhelm,R.T.E.,2005.Surface and subsurface expressions of gas seepage tothe seabed—examples from the Southern North Sea.Marine and Petroleum Geology,22(4):499-515.doi:10.1016/j.marpetgeo.2004.08.007
Sloan,E.D.,1998.Clathrate hydrates of natural gases.Mar-cel Dekker,Inc,New York,705.
Song,H.B.,Dong,C.Z.,Chen,L.,et al.,2008.Reflectionseismic methods for studying physical oceanography:in-troduction of oceanography.Progress in Geophysics,23(4):1156-1164(in Chinese with English abstract).
Suess,E.,Torres,M.E.,Bohrmann,G.,et al.,1999.Gashydrate destabilization:enhanced dewatering,benthicmaterial turnover and large methane plumes at the Cas-cadia convergent margin.Earth and Planetary ScienceLetters,170(1-2):1-15.doi:10.1016/S0012-821X(99)00092-8
Wood,W.T.,Hart,P.E.,Hutchinson,D.R.,et al.,2008.Gas and gas hydrate distribution around seafloor seepsin Mississippi Canyon,northern Gulf of Mexico,usingmulti-resolution seismic imagery.Marine and Petrole-um Geology,25(9):952-959.doi:10.1016/j.marpet-geo.2008.01.015
Wu,N.Y.,Yang,S.X.,Wang,H.B.,et al.,2009.Gas-bear-ing fluid influx sub-system for gas hydrate geologicalsystem in Shenhu area,northern South China Sea.Chi-nese Journal of Geophysics,52(6):1641-1650(inChinese with English abstract).
Wu,N.Y.,Zhang,H.Q.,Yang,S.X.,et al.,2007.Prelimi-nary discussion on natural gas hydrate(NGH)reservoirsystem of Shenhu area,north slope of South China Sea.Natural gas industry,27(9):1-6(in Chinese withEnglish abstract).
Wu,S.G.,Dong,D.D.,Yang,S.X.,et al.,2009.Geneticmodel of the hydrate system in the fine grain sedimentsin the northern continental slope of South China Sea.Chinese Journal of Geophysics,52(7):1849-1857(inChinese with English abstract).
Xu,H.N.,Yang,S.X.,Zheng,X.D.,et al.,2010.Seismicidentification of gas hydrate and its distribution inShenhu area,South China Sea.Chinese Journal of Geo-physics,53(7):1691-1698(in Chinese with Englishabstract).
Yin,X.J.,Zhou,H.Y.,Yang,Q.H.,et al.,2008.The evi-dence for the existence of methane seepages in thenorthern South China Sea:abnormal high methane con-centration in bottom waters.Acta Oceanologica Sinica,30(6):69-75(in Chinese with English abstract).
陈林,宋海斌,2005.海底天然气渗漏的地球物理特征及识别方法.地球物理学进展,20(4):1067-1073.
董崇志,宋海斌,拜阳,等,2010.地震海洋学研究进展.地球物理学进展,25(1):109-123.
龚再升,李思田,汪集旸,等,2004.南海北部大陆边缘盆地油气成藏动力学研究.北京:科学出版社,339.
匡增桂,郭依群,2011.南海北部神狐海域新近系以来沉积相及水合物成藏模式.地球科学——中国地质大学学报,36(5):914-920.
宋海斌,董崇志,陈林,等,2008.用反射地震方法研究物理海洋-地震海洋学简介.地球物理学进展,23(4):1156-1164.
吴能友,杨胜雄,王宏斌,等,2009.南海北部陆坡神狐海域天然气水合物成藏的流体运移体系.地球物理学报,52(6):1641-1650.
吴能友,张海啟,杨胜雄,等,2007.南海神狐海域天然气水合物成藏系统初探.天然气工业,27(9):1-6.
吴时国,董冬冬,杨胜雄,等,2009.南海北部陆坡细粒沉积物天然气水合物系统的形成模式初探.地球物理学报,52(7):1849-1857.
徐华宁,杨胜雄,郑晓东,等,2010.南中国海神狐海域天然气水合物地震识别及分布特征.地球物理学报,53(7):1691-1698.
尹希杰,周怀阳,杨群慧,等,2008.南海北部甲烷渗漏活动存在的证据:近底层海水甲烷高浓度异常.海洋学报,30(6):69-75.
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