折射方法在南沙礼乐盆地西南海域中生界研究中的应用
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摘要
钻探和拖网取样资料都表明南沙海区东北部礼乐滩及附近海域存在大套中生代海相沉积,但其西南侧是否也存在中生界不清楚。新的长排列(偏移距超过6km)多道地震测线C2B经过南沙礼乐滩西南海域(水深1.5~1.7km),反射剖面显示了重要的角度不整合界面,上覆地层呈平行披盖结构,下伏地层则存在明显的挤压变形;长排列炮集记录则显示了清晰的折射波。利用OBSTOOL软件进行了折射波震相的拾取,折射波速度计算结果表明不整合界面上覆层地震速度为2.5~3.0km/s,下伏层地震速度为3.5~5.5km/s,跨不整合界面发生速度突变(其差值约1.0~2.0km/s),表明地层严重缺失。结合南海的构造演化过程、钻探和拖网取样结果,以及与南海北部潮汕坳陷已经确定的中、新生代地层速度的对比,将上覆层划为新生界,下伏层划为中生界。C2B测线东南端下构造层属于中生界褶皱构造,地层速度较低,约3.5km/s,低于潮汕坳陷西南部中生界的地震折射波速度为3.5~4.2km/s,推测为早白垩世边缘海相沉积,可能预示礼乐盆地西南海域较好的中生界油气储集。
Extensive drilling and geological sampling demonstrate that Mesozoic marine deposits occur in the northeast of the Nansha Waters,the southern margin of the South China Sea(SCS).It has been long debated whether the lower structural layer with compressional structures and closely spaced reflections below the strongly eroded unconformity is the Mesozoic or Cenozoic strata in the southwest of Liyue Basin.A new high resolution 2Dseismic survey with long cable was carried out over the regions of the southwest of the Liyue bank in 2013.The water depth is 1.5~1.7km there,and the maximum offset of the survey line is about 6.1km.The multi-channel seismic data shows remarkable information of refraction wave from the erosional unconformity.In this paper,OBSTOOL is used to pick up the refraction wave from the multi-channel seismic data.A major velocity leap(1.0~2.0km/s)is found across the prominent unconformity calculated from the refraction wave of long cable seismic data,which indicates a hiatus and an abrupt lithological change.According to velocity leap and velocity contrast between the Mesozoic and Cenozoic of Chaoshan Depression in the northern margin of the SCS,the compressional structures are interpreted as the marine Mesozoic,while the overlying strata are Cenozoic.The refraction velocity of the Mesozoic in the southeastern part of line C2 Bis about 3.5km/s,generally lower than that of 3.5~4.2km/s in the southeastern part of the Chaoshan Depression,which may imply that the reservoir properties for oil and gas accumulation are better in the southwest of Liyue bank.
Extensive drilling and geological sampling demonstrate that Mesozoic marine deposits occur in the northeast of the Nansha Waters,the southern margin of the South China Sea(SCS).It has been long debated whether the lower structural layer with compressional structures and closely spaced reflections below the strongly eroded unconformity is the Mesozoic or Cenozoic strata in the southwest of Liyue Basin.A new high resolution 2Dseismic survey with long cable was carried out over the regions of the southwest of the Liyue bank in 2013.The water depth is 1.5~1.7km there,and the maximum offset of the survey line is about 6.1km.The multi-channel seismic data shows remarkable information of refraction wave from the erosional unconformity.In this paper,OBSTOOL is used to pick up the refraction wave from the multi-channel seismic data.A major velocity leap(1.0~2.0km/s)is found across the prominent unconformity calculated from the refraction wave of long cable seismic data,which indicates a hiatus and an abrupt lithological change.According to velocity leap and velocity contrast between the Mesozoic and Cenozoic of Chaoshan Depression in the northern margin of the SCS,the compressional structures are interpreted as the marine Mesozoic,while the overlying strata are Cenozoic.The refraction velocity of the Mesozoic in the southeastern part of line C2 Bis about 3.5km/s,generally lower than that of 3.5~4.2km/s in the southeastern part of the Chaoshan Depression,which may imply that the reservoir properties for oil and gas accumulation are better in the southwest of Liyue bank.
引文
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[15]Cullen A.Nature and significance of the west Baram and Tinjar lines,Nw Borneo[J].Marine and Petroleum Geology,2014,51(0):197-209.
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[17]Kudrass H R,Wiedicke M,Cepeck P,et al.Mesozoic and Cainozoic rocks dredged from the South China Sea(Reed Bank area)and Sulu Sea and their significance for plate-tectonic reconstructions[J].Marine and Petrol.Geol.,1986,3:19-30.
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[19]鄢全树,石学法,王昆山,等.南沙微地块花岗质岩石la-IcpMs锆石U-Pb定年及其地质意义[J].地质学报,2008,82(8):1057-1067.[YAN Quanshu,SHI Xuefa,WANG Kunshan,et al.LA-ICPM S Zircon U-Pb dating of granitic rocks from the Nansha micro—block,South China Sea,and its geological significance[J].Acta Geologica Sinica,2008,82(8):1057-1067.]
[20]邱燕,陈国能,刘方兰,等.南海西南海盆花岗岩的发现及其构造意义[J].地质通报,2008,27(12):2104-2107.[QIU Yan,CHEN Guoneng,LIU Fanglan,et al.Discovery of granite and its tectonic significance in southwestern basin of the SouthChina Sea[J].Geological Bulletin of China,2008,27(12):2104-2107.]
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[23]陆基孟.地震勘探原理[M].北京:中国石油大学出版社,1993:30-38.[LU Jimeng.Principle of Seismic Exploration[M].Beijing:China University of Petroleum Press,1993:30-38.]
[24]Yan P,Wang L,Wang Y.Late Mesozoic compressional folds in Dongsha waters,the northern margin of the South China Sea[J].Tectonophysics,2014,615-616(0):213-223.
[25]吕修亚,阎贫,陈洁,等.折射方法在南海北部潮汕坳陷中生界地层研究中的应用[J].热带海洋学报,2009,28(1):43-47.[LV Xiuya,YAN Pin,CHEN Jie,et al.Application of refraction velocity in studing Mesozoic strata in Chaoshan depression on northern margin of South China Sea[J].JTO,2009,28(1):43-47.]
[26]郝沪军,汪瑞良,张向涛,等.珠江口盆地东部海相中生界识别及分布[J].中国海上油气,2004,16(2):84-88.[HAO Hujun,WANG Ruiliang,ZHANG Xiangtao,et al.Mesozoic marine sediment identificationand distribution in the eastern Pearl River Mouth Basin[J].China Offshore Oil and Gas(Geology),2004,16(2):84-88.]
[27]苏乃容,曾麟,李平鲁.珠江口盆地东部中生代凹陷地质特征[J].中国海上油气(地质),1995,9(4):228-236.[SU Nairong,ZENG Lin,LI Pinglu.Geological features ofMesozoic sags in the eastern part of PearlRiver Mouth Basin[J].China Offshore and Gas(Geology),1995,9(4):228-236.]
[28]Hao H J,Zhang X T,You H Q,et al.Characteristics and hydrocarbon potential of Mesozoic strata in eastern Pearl River Mouth basin,Northern South China Sea[J].Journal of Earth Science,2009,20(1):117-123.
[29]王彦林,阎贫.深地震探测的分辨率分析——以南海北部obs数据为例[J].地球物理学报,2009(9):2282-2290.[WANG Yanlin,YAN Pin.Lateral resolution analysis of deep crustal sounding results:a case study on the data from ocean bottom seismometer in the northern South China Sea[J].ChineseJournalofGeophysics,2009(9):2282-2290.]
[30]郝沪军,施和生,张向涛,等.潮汕坳陷中生界及其石油地质条件——基于lf35-1-1探索井钻探结果的讨论[J].中国海上油气,2009,21(3):151-155.[HAO Hujun,SHI Hesheng,ZHANG Xiangtao,et al.Mesozoic sediments and their petroleum geology conditions in Chaoshan sag:a discussion based on drilling results from the exploratory well LF35-1-1[J].China Offshore Oil Gas(Geology),2009,21(3):151-155.]
[31]Yan P,Wang Y,Liu H.Post-spreading transpressive faults in the South China Sea Basin[J].Tectonophysics,2008,450(1-4):70-78.
[32]Hwang C,Chang E T Y.Seafloor secrets revealed[J].Science,2014,346(6205):32-33.
[33]Yao B C.Tectonic evolution of the South China in Cenozic[J].Mar.Geol.Quat.Geol.,1996,16(2):1-13.
[34]Schluter H U,Hinz K,Block M.Tectono-stratigraphic terranes and detachment faulting of the South China Sea and Sulu Sea[J].Marine Geology,1996,130:39-78.
[2]何家雄,姚永坚,马文宏,等.南海东北部中生代残留盆地油气勘探现状与油气地质问题[J].天然气地球科学,2007(5):635-642.[HE Jiaxiong,YAO YongJian,MA Wenhong,et al.Status of oil&gas exploration and analysis of geological character in mesozoic residual basins,northeastern South China Sea[J].Natural Gas Geoscience,2007(5):635-642.]
[3]张莉,沙志彬,王立飞.南沙海域礼乐盆地中生界油气资源潜力[J].海洋地质与第四纪地质,2007,27(4):97-102.[ZHANG Li,SHA Zhibin,WANG Lifei.Hydrocarbon resources potentialof mesozoic in liyue Basin,northeastern Nansha Sea areas[J].Marine Geology and Quaternary Geology,2007,27(4):97-102.]
[4]刘宝明,刘海龄.南海及邻区中生界——新的油气勘探领域[J].海洋地质与第四纪地质,2011,31(2):105-109.[LIU Baoming,LIU Hailing.The mesozoic in the South China Sea and adjacent areas:new targets for hydrocarbon exploration[J].Marine Geology and Quaternary Geology,2011,31(2):105-109.]
[5]阎贫,王彦林.南沙礼乐盆地Sampaguita气田发现的启示[J].海洋开发与管理,2013,(S1):64-67.[YAN Pin,WANG Yanlin.Enlightenment from discovering of Sampaguita gas field in Liyue Basin[J].Ocean Development and Management,2013,(S1):64-67.]
[6]孙龙涛,孙珍,周蒂,等.南沙海区礼乐盆地沉积地层与构造特征分析[J].大地构造与成矿学,2008,32(2):151-158.[SUN Longtao,SUN Zhen,ZHOU Di,et al.Stratigraphic and structural characteristics of line basin in Nansha area[J].Geotectonica et Metallogenia,2008,32(2):151-158.]
[7]Yan P,Liu H L.Tectonic-stratigraphic division and blind fold structures in Nansha waters,South China Sea[J].Asian Earth Sci,2004,24:337-348.
[8]王彦林,阎贫,郑红波,等.南沙群岛海区北部中生界地震特征分析[J].热带海洋学报,2012,31(4):83-89.[WANG Yanlin,YAN Pin,ZHENG Hongbo,et al.Stratigraphic and structural characteristics of the northern margin of Nansha islands waters in the South China Sea[J].Journal of Tropical Oceanography,2012,31(4):83-89.]
[9]Yao Y,Liu H,Yang C,et al.Characteristics and evolution of Cenozoic sediments in the Liyue basin,Se South China Sea[J].Journal of Asian Earth Sciences,2012,60(0):114-129.
[10]Ding W,Franke D,Li J,et al.Seismic stratigraphy and tectonic structure from a composite multi-channel seismic profile across the entire dangerous grounds,South China Sea[J].Tectonophysics,2013,582(0):162-176.
[11]Taylor B,Hayes D E.The tectonic evolution of the South China Sea basin[C]//Hayes D E,Ed.The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands,Geophysical Monograph.Washington DC:AGU,1980:89-104.
[12]Holloway N H.North Palawan block,Philippines-its relation to Asian mainland and role in evolution of South China Sea[J].AAPG Bull,1982,66(9):1355-1383.
[13]Taylor B,Hayes D E.Origin and history of the South China Sea basin[C]//Hayes D E,Ed.The Tectonic and Geologic Evolution of Southeast Asian Seas and Islands,Geophysical Monograph.Washington DC:American Geophysical Union,1983:23-56.
[14]Madon M,Kim C L,Wong R.The structure and stratigraphy of deepwater Sarawak,Malaysia:implications for tectonic evolution[J].Journal of Asian Earth Sciences,2013,76(0):312-333.
[15]Cullen A.Nature and significance of the west Baram and Tinjar lines,Nw Borneo[J].Marine and Petroleum Geology,2014,51(0):197-209.
[16]Steuer S,Franke D,Meresse F,et al.Oligocene-Miocene carbonates and their role for constraining the rifting and collision history of the dangerous grounds,South China Sea[J].Marine and Petroleum Geology,2014,58,Part B(0):644-657.
[17]Kudrass H R,Wiedicke M,Cepeck P,et al.Mesozoic and Cainozoic rocks dredged from the South China Sea(Reed Bank area)and Sulu Sea and their significance for plate-tectonic reconstructions[J].Marine and Petrol.Geol.,1986,3:19-30.
[18]Sales A O,Jacobsen E C,Morado A A J,et al.The petroleum potential of deep-water northwest Palawan Block Gsec-66[J].Asian Earth Sci.,1997,15(2-3):217-240.
[19]鄢全树,石学法,王昆山,等.南沙微地块花岗质岩石la-IcpMs锆石U-Pb定年及其地质意义[J].地质学报,2008,82(8):1057-1067.[YAN Quanshu,SHI Xuefa,WANG Kunshan,et al.LA-ICPM S Zircon U-Pb dating of granitic rocks from the Nansha micro—block,South China Sea,and its geological significance[J].Acta Geologica Sinica,2008,82(8):1057-1067.]
[20]邱燕,陈国能,刘方兰,等.南海西南海盆花岗岩的发现及其构造意义[J].地质通报,2008,27(12):2104-2107.[QIU Yan,CHEN Guoneng,LIU Fanglan,et al.Discovery of granite and its tectonic significance in southwestern basin of the SouthChina Sea[J].Geological Bulletin of China,2008,27(12):2104-2107.]
[21]邵磊,尤洪庆,郝沪军,等.南海东北部中生界岩石学特征及沉积环境[J].地质评论,2007,53(2):164-169.[SHAO Lei,YOU Hongqing,HAO Hujun,et al.Petrology and sedimentary environmentsof Mesozoic strata in the Northeastern South China Sea[J].Geol.Rev.,2007,53(2):164-169.]
[22]刘洋波,于宏.国家海洋局第二海洋研究所南海二维测线地震资料处理报告[R].中海油能源发展股份有限公司特普地球物理分公司,2009.[LIU Yangbo,YU Hong.Processing report of two-dimensional seismic survey line in the South China Sea,from the second Institute of Oceanography SOA[R].Computer Processing Center,China National Offshore Oil Corporation,2009.]
[23]陆基孟.地震勘探原理[M].北京:中国石油大学出版社,1993:30-38.[LU Jimeng.Principle of Seismic Exploration[M].Beijing:China University of Petroleum Press,1993:30-38.]
[24]Yan P,Wang L,Wang Y.Late Mesozoic compressional folds in Dongsha waters,the northern margin of the South China Sea[J].Tectonophysics,2014,615-616(0):213-223.
[25]吕修亚,阎贫,陈洁,等.折射方法在南海北部潮汕坳陷中生界地层研究中的应用[J].热带海洋学报,2009,28(1):43-47.[LV Xiuya,YAN Pin,CHEN Jie,et al.Application of refraction velocity in studing Mesozoic strata in Chaoshan depression on northern margin of South China Sea[J].JTO,2009,28(1):43-47.]
[26]郝沪军,汪瑞良,张向涛,等.珠江口盆地东部海相中生界识别及分布[J].中国海上油气,2004,16(2):84-88.[HAO Hujun,WANG Ruiliang,ZHANG Xiangtao,et al.Mesozoic marine sediment identificationand distribution in the eastern Pearl River Mouth Basin[J].China Offshore Oil and Gas(Geology),2004,16(2):84-88.]
[27]苏乃容,曾麟,李平鲁.珠江口盆地东部中生代凹陷地质特征[J].中国海上油气(地质),1995,9(4):228-236.[SU Nairong,ZENG Lin,LI Pinglu.Geological features ofMesozoic sags in the eastern part of PearlRiver Mouth Basin[J].China Offshore and Gas(Geology),1995,9(4):228-236.]
[28]Hao H J,Zhang X T,You H Q,et al.Characteristics and hydrocarbon potential of Mesozoic strata in eastern Pearl River Mouth basin,Northern South China Sea[J].Journal of Earth Science,2009,20(1):117-123.
[29]王彦林,阎贫.深地震探测的分辨率分析——以南海北部obs数据为例[J].地球物理学报,2009(9):2282-2290.[WANG Yanlin,YAN Pin.Lateral resolution analysis of deep crustal sounding results:a case study on the data from ocean bottom seismometer in the northern South China Sea[J].ChineseJournalofGeophysics,2009(9):2282-2290.]
[30]郝沪军,施和生,张向涛,等.潮汕坳陷中生界及其石油地质条件——基于lf35-1-1探索井钻探结果的讨论[J].中国海上油气,2009,21(3):151-155.[HAO Hujun,SHI Hesheng,ZHANG Xiangtao,et al.Mesozoic sediments and their petroleum geology conditions in Chaoshan sag:a discussion based on drilling results from the exploratory well LF35-1-1[J].China Offshore Oil Gas(Geology),2009,21(3):151-155.]
[31]Yan P,Wang Y,Liu H.Post-spreading transpressive faults in the South China Sea Basin[J].Tectonophysics,2008,450(1-4):70-78.
[32]Hwang C,Chang E T Y.Seafloor secrets revealed[J].Science,2014,346(6205):32-33.
[33]Yao B C.Tectonic evolution of the South China in Cenozic[J].Mar.Geol.Quat.Geol.,1996,16(2):1-13.
[34]Schluter H U,Hinz K,Block M.Tectono-stratigraphic terranes and detachment faulting of the South China Sea and Sulu Sea[J].Marine Geology,1996,130:39-78.