南海东北部陆坡水合物钻探区BSR推导流体运移速率研究
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摘要
2013年广州海洋地质调查局在我国南海东北部陆坡海域实施天然气水合物钻探,获取了多种类型的高纯度水合物实物样品,进一步表明了南海存在丰富的天然气水合物资源前景。在此钻探之前,通过多年的地球物理、地球化学以及地质综合调查工作,积累了大量与天然气水合物赋存相关的各种地质数据。本文利用1D流体运移模型,结合热流站位的温压场数据以及多道地震数据所反映的BSR信息,计算了各个有效热流站位的流体运移速率,并结合钻探区的地质构造背景和钻探井位天然气水合物层位的分布情况,分析了流体运移速率分布特征,初步阐释了流体运移速率、构造背景以及与天然气水合物形成的相互关系。计算结果表明,钻探区流体运移速率数据分布区间为-25~+38cm/a,反映了钻探区构造背景相对复杂。流体运移速率分布具有规律性,主要受到断层和气烟囱的类别控制,可分为两大类。第一类为位于钻探区北部高地的继承性断层,断面直立陡倾并部分切穿海底,伴有大型气烟囱顶部或数量众多的侧翼小型活动正断层,为深部大规模流体运移提供了充足通道。受此类地质条件控制的流体运移速率表现为幅值波动较大,天然气水合物多发育在海底浅层,且呈现多层分布。第二类为位于钻探区西南部以及东部较大水深的滑动断层以及小型气烟囱,断层主体表现断层面清晰,断面较缓,刺穿尺度较短,气烟囱发育也比较晚,一定程度上限制了来自深部流体运移的规模。受此类地质条件控制的流体运移速率表现较为缓和,流体运移速率波动范围小,天然气水合物多发育在海底深层。
In 2013,Guangzhou Marine Geological Survey conducted a drilling expedition on the continental margin along the northeastern slope of the South China Sea,successfully recovering core samples containing gas hydrate in various types,which further confirmed the existence of a huge resource prospects of gas hydrate in the South China Sea.Prior to the expedition and following several years of geophysical,geochemical and comprehensive geological investigations,we obtained reliable data which provide abundant evidence for the occurrence of gas hydrate around the drilling area.In this paper,by employing a simple 1Dvertical fluid flow model with the BSR interpretation of multichannel seismic data and heat flow measurements,we calculated fluid migration rates in valid heat flow sites,then analyzed the characteristics of rates distribution through a combination of knowledge of geological background and occurrence depth of gas hydrate-bearing layers,attentively delineating the relationship among fluid migration rates,tectonic background and gas hydrate occurrence in the drilling area.The initial results show that 1D vertical fluid rates are between-25and38cm/yr,indicating complex geological background in the drilling area.The distribution of fluid migration rates has two distinct patterns,apparently being controlled by the faults and diapirs in two particular categories.The first one is concentrated within the northern highland of the drilling area in relation to inherited steep faults,apart of which,in particular,often evolve upward to the seafloor.In addition,several domes of large diapirs develop underneath and a number of active mini faults grow in the flanks,providing feeding channels for fluid migration from deeper sediment.Thus,the rates of this category manifest a pattern of dramatic variations,and gas hydrates occur in shallow multi-layers of sediments.The second one is distributed in the southwestern and eastern lowland of the drilling area.Besides a few of small young diapirs developing underneath,some low-angle glide faults with clear fractured surface formed in relatively short length,thus presumably constraining the ability of fluid migration from deeper sediment.As a result,the rates of this category manifest mild variations,and gas hydrates occur in relatively deep sediments.
In 2013,Guangzhou Marine Geological Survey conducted a drilling expedition on the continental margin along the northeastern slope of the South China Sea,successfully recovering core samples containing gas hydrate in various types,which further confirmed the existence of a huge resource prospects of gas hydrate in the South China Sea.Prior to the expedition and following several years of geophysical,geochemical and comprehensive geological investigations,we obtained reliable data which provide abundant evidence for the occurrence of gas hydrate around the drilling area.In this paper,by employing a simple 1Dvertical fluid flow model with the BSR interpretation of multichannel seismic data and heat flow measurements,we calculated fluid migration rates in valid heat flow sites,then analyzed the characteristics of rates distribution through a combination of knowledge of geological background and occurrence depth of gas hydrate-bearing layers,attentively delineating the relationship among fluid migration rates,tectonic background and gas hydrate occurrence in the drilling area.The initial results show that 1D vertical fluid rates are between-25and38cm/yr,indicating complex geological background in the drilling area.The distribution of fluid migration rates has two distinct patterns,apparently being controlled by the faults and diapirs in two particular categories.The first one is concentrated within the northern highland of the drilling area in relation to inherited steep faults,apart of which,in particular,often evolve upward to the seafloor.In addition,several domes of large diapirs develop underneath and a number of active mini faults grow in the flanks,providing feeding channels for fluid migration from deeper sediment.Thus,the rates of this category manifest a pattern of dramatic variations,and gas hydrates occur in shallow multi-layers of sediments.The second one is distributed in the southwestern and eastern lowland of the drilling area.Besides a few of small young diapirs developing underneath,some low-angle glide faults with clear fractured surface formed in relatively short length,thus presumably constraining the ability of fluid migration from deeper sediment.As a result,the rates of this category manifest mild variations,and gas hydrates occur in relatively deep sediments.
引文
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[39]王淑红,宋海斌,颜文.外界条件变化对天然气水合物相平衡曲线及稳定带厚度的影响[J].地球物理进展,2005,20(3):761-768.
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[3]EWING J I,HOLLISTER C H.Regional aspects of deep sea drilling in the western North Atlantic[R].Initial Reports,Deep Sea Drilling Projects 11.Washington:U.S.Government Printing Office,1972:951-973.
[4]MILKOV A V,CLAYPOOL G E,LEE Y J,et al.In situ methane concentrations at Hydrate Ridge Offshore Oregon:new constraints on the global gas hydrate inventory from an active margin[J].Geology,2003,31:833-836.
[5]MAKOGON Y F,HOLDITCH S A,MAKOGON T Y.Natural gas hydrates:apotential energy source for the 21st Century[J].Journal of Petroleum Science and Engineering,2007,56:14-31.
[6]张洪涛,张海啟,祝有海.中国天然气水合物调查研究现状及其进展[J].中国地质,2007,34(6):953-961.
[7]MATSUMOTO R,RYU B J,LEE S R,et al.Occurrence and exploration of gas hydrate in the marginal sea and continental margin of the Asia and Oceania region[J].Marine and Petroleum Geology,2011,28:1751-1767.
[8]张光学,梁金强,陆敬安,等.南海东北部陆坡天然气水合物藏特征[J].天然气工业,2014,34(11):1-10.
[9]梁金强,王宏斌,苏新,等.南海北部陆坡天然气水合物成藏条件及其控制因素[J].天然气工业,2014,34(7):128-135.
[10]沙志彬,王宏斌,杨木壮,等.天然气水合物成矿带的识别技术研究[J].现代地质,2008,22(3):438-446.
[11]ZUHLSDORFF L,SPIESS V,HUBSCHER C,et al.Implications for focused fluid transport at the northern Cascadia accretionary prism from a correlation between BSR occurrence and near sea floor reflectivity anomalies imaged in a multi-frequency seismic data set[J].International Journal of Earth Sciences,2000,88(4):655-667.
[12]栾锡武,翟世奎,干晓群.冲绳海槽中部热液活动区构造地球物理特征分析[J].沉积学报,2001,19(1):43-47.
[13]STALLMAN R W.Notes on the use of temperature data for computing ground water velocity.Society Hydrotechnique of France[C]∥The 6th assembly on hydraulics report.Nancy,France:Society Hydrotechnique of France,1960,3:1-7.
[14]BREDOEHOEFT J D,PAPADOPULOS I S.Rates of vertical ground water movement estimated from the earth thermal profile[J].Water Resource Research,1965,1(2):325-328.
[15]GREVEMEYER I,KOPF A J,FEKETE N,et al.Fluid flow through active mud dome Mound Culebra offshore Nicoya Peninsula,Costa Rica:evidence from heat flow surveying[J].Marine Geology,2004,207:145-147.
[16]CHEN L W,CHI W C,LIU C S,et al.Deriving regional vertical fluid migration rates offshore southwestern Taiwan using bottom simulating reflectors[J].Marine Geophysical Research,2012,33(4):379-388.
[17]BRIAIS A,PATRIAT P,TAPPOMMIER P.Updated interpretation of magnetic anomalies and seafloor spreading stages in the South China Sea:implications for the tertiary tectonics of Southeast Asia[J].Journal of Geophysical Research,1993,98:6299-6328.
[18]CLIFT P D,LIN J,BARCKHAUSEN U.Evidence of low flexural rigidity and low viscosity lower continental crust during continental break-up in the South China Sea[J].Marine and Petroleum Geology,2002,19:951-970.
[19]刘昭蜀,赵焕庭.南海地质[M].北京:科学出版社,2002:14-16.
[20]HE L J,WANG K L,XIONG L P,et al.Heat flow and thermal history of the South China Sea[J].Physics of the Earth and Planetary Interiors,2001,126:211-220.
[21]黄慈流,钟建强.南海东北部及其邻近新生代构造事件[J].热带海洋,1994,13(1):55-62.
[22]姚伯初,万玲,吴能友.大南海地区新生代板块构造活动[J].中国地质,2004,31(2):113-122.
[23]MCDONNELL S L,MAX M D,CHERKIS N Z,et al.Tectomo-sedimentary controls on the likelihood of gas hydrate occurrence near Taiwan[J].Marine and Petroleum Geology,2000,17(8):929-936.
[24]姚伯初,杨木壮.南海晚新生代构造运动与天然气水合物资源[J].海洋地质与第四纪地质,2008,28(4):93-100.
[25]FUH S C,CHERN C C,LIANG S C,et al.The biogenic gas potential of the submarine canyon systems of Plio-Peistocene Foreland Basin,Southwestern Taiwan[J].Marine and Petroleum Geology,2009,26(7):1087-1099.
[26]黄永样,SUESS E,吴能友,等.南海北部陆坡甲烷和天然气水合物地质:中德合作OS-177航次成果专报[M].北京:地质出版社,2008:48-51.
[27]陆红锋,刘坚,陈芳,等.南海台西南区碳酸盐岩矿物学和稳定同位素组成特征:天然气水合物存在的主要证据之一[J].地学前缘,2005,12(3):268-276.
[28]HAN X Q,SUESS E,HUANG Y Y,et al.Jiulong methane reef:microbial mediation of seep carbonates in the South China Sea[J].Marine Geology,2008,249:243-256.
[29]沙志彬,王宏斌,张光学,等.底辟构造与天然气水合物的成矿关系[J].地学前缘,2005,12(3):283-288.
[30]徐行,施小斌,罗贤虎,等.南海西沙海槽地区的海底热流测量[J].海洋地质与第四纪地质,2006,26(4):51-58.
[31]KALACHAND S,RAJESH V,SATYAVANI N,et al.Gas hydrate stability thickness map along the Indian continental margin[J].Marine and Petroleum Geology,2011,28(10):1779-1786.
[32]GOTO M,MIZOGUCHI T,KIMURA R,et al.Variations in the thermal conductivities of surface sediments in the Nankai subduction zone off Tokai,central Japan[J].Marine Geophysical Research,2012,33(3):269-283.
[33]陆敬安,杨胜雄,吴能友,等.南海神狐海域天然气水合物地球物理测井评价[J].现代地质,2008,22(3):447-451.
[34]梁劲,王明君,王宏斌,等.南海神狐海域天然气水合物声波测井速度与饱和度关系分析[J].现代地质,2009,23(2):217-223.
[35]王祝文,李舟波,刘菁华.天然气水合物的测井识别和评价[J].海洋地质和第四纪地质2003,23(2):97-102.
[36]SLOAN E D.Clathrate hydrates of natural gases[M].New York:Marcel Dekker,1998:52-67.
[37]DICKENS G R,QUINBY-HUNT M S.Methane hydrate stability in seawater[J].Geophysical Research Letters,1994,21(19):2115-2118.
[38]金春爽,汪集旸,张光学.南海天然气水合物稳定带的影响因素[J].矿床地质,2005,24(4):388-397.
[39]王淑红,宋海斌,颜文.外界条件变化对天然气水合物相平衡曲线及稳定带厚度的影响[J].地球物理进展,2005,20(3):761-768.
[40]YAMANO R D,UYEDA S,AOKI Y,et al.Estimates of heat flow derived from gas hydrates[J].Geology,1982,10(7):339-343.
[41]HYNDMAN R D,FOUCHER J P,YAMANO M,et al.Deep sea bottom simulating reflectros calibration of the base of the hydrate stability field as used for heat flow estimates[J].Earth and Planetary Science Letters,1992,109(3/4):289-301.
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