上扬子地区下寒武统筇竹寺组页岩沉积环境
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摘要
上扬子地区下寒武统页岩展现出了良好的页岩气勘探前景,是油气资源的重要战略接替领域。通过露头观测、岩心描述、薄片观察、扫描电镜分析以及主微量元素地球化学分析,对该套页岩沉积环境进行了综合研究。根据矿物学、岩石组构及沉积构造的不同,在筇竹寺组识别出5大类12小类岩相类型,进一步总结了浅水陆棚、深水陆棚、斜坡-盆地沉积体系中发育的6类典型的沉积序列,建立了相应的沉积模式。浅水陆棚沉积处于氧化、相对低的古海洋生产力条件下,发育磷质-云质-泥质沉积序列和砂质-泥质-灰质沉积序列,有机质含量普遍偏低。深水陆棚以及斜坡-盆地沉积处于贫氧-缺氧、高海洋生产力的条件下,发育富含有机质的泥质-磷质-云质沉积序列、硅质-泥质沉积序列和泥质沉积序列。在四川盆地资阳-长宁一线陆内裂陷槽内部以及四川盆地之外东南部黔中、黔北及鄂西-渝东等大部分深水陆棚沉积区是富有机质页岩发育的有利区域。此外,热液活动为黔西北地区下寒武统牛蹄塘组黑色页岩提供了必要的物质基础和保存条件,有利于形成富有机质的页岩。
The lower Cambrian shale shows a bright potential for shale gas exploration and is an important strategic successor play for oil and gas exploration in the Upper Yangtze region.The sedimentary environment of the Qiongzhusi Formation shale was comprehensively studied through outcrop observation,core description,thin section observation,SEM analysis,and geochemical analysis of major and trace elements.According to mineralogy,rock fabrics and sedimentary structures,five major-and 12 sub-lithofacies types were identified in the Qiongzhusi Formation shale,six typical sedimentary sequences developed in shallow-water shelf,deep-water shelf,and slope-basin sedimentary systems were summarized,and the corresponding sedimentary models were established.Under the paleoceanographic conditions of oxidation and relatively low productivity,phosphorus-dolomitic-argillaceous sedimentary sequences and sandy-argillaceous-calcareous sedimentary sequences were developed in shallow shelf facies with low TOC.In contrast,organic-rich argillaceous-phosphorus-dolomitic,siliceous-argillaceous,and argillaceous sedimentary sequences were developed in deep shelf and slope-basin facies with sediments deposited in oxygen-poor,anoxic oceans with relatively high productivity.The majority of sedimentary zones in deep shelf facies is favorable for the development of organic-rich shales in the interior of intracratonic rift along Ziyang-Changning trend within Sichuan Basin,central and northern Guizhou and western Hubei-Eastern Chongqing areas in southeastern Sichuan Basin.In addition,hydrothermal activities provide necessary materials and preservation conditions for the black shales of the Lower Cambrian Niutitang Formation in northwestern Guizhou,which in turn may generate organic-rich shales.
The lower Cambrian shale shows a bright potential for shale gas exploration and is an important strategic successor play for oil and gas exploration in the Upper Yangtze region.The sedimentary environment of the Qiongzhusi Formation shale was comprehensively studied through outcrop observation,core description,thin section observation,SEM analysis,and geochemical analysis of major and trace elements.According to mineralogy,rock fabrics and sedimentary structures,five major-and 12 sub-lithofacies types were identified in the Qiongzhusi Formation shale,six typical sedimentary sequences developed in shallow-water shelf,deep-water shelf,and slope-basin sedimentary systems were summarized,and the corresponding sedimentary models were established.Under the paleoceanographic conditions of oxidation and relatively low productivity,phosphorus-dolomitic-argillaceous sedimentary sequences and sandy-argillaceous-calcareous sedimentary sequences were developed in shallow shelf facies with low TOC.In contrast,organic-rich argillaceous-phosphorus-dolomitic,siliceous-argillaceous,and argillaceous sedimentary sequences were developed in deep shelf and slope-basin facies with sediments deposited in oxygen-poor,anoxic oceans with relatively high productivity.The majority of sedimentary zones in deep shelf facies is favorable for the development of organic-rich shales in the interior of intracratonic rift along Ziyang-Changning trend within Sichuan Basin,central and northern Guizhou and western Hubei-Eastern Chongqing areas in southeastern Sichuan Basin.In addition,hydrothermal activities provide necessary materials and preservation conditions for the black shales of the Lower Cambrian Niutitang Formation in northwestern Guizhou,which in turn may generate organic-rich shales.
引文
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[2] 金之钧,胡宗全,高波,等.川东南地区五峰组—龙马溪组页岩气富集与高产控制因素[J].地学前缘,2016,23(1):1-10.Jin Zhijun,Hu Zongquan,Gao Bo,et al.Controlling factors on the enrichment and high productivity of shale gas in the Wufeng-Longmaxi Formations,southeastern Sichuan Basin[J].Earth Science Frontiers,2016,23(1):1-10.
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[5] 董大忠,程克明,王玉满,等.中国上扬子区下古生界页岩气形成条件及特征[J].石油与天然气地质,2010,31(3):288-301.Dong Dazhong,Cheng Keming,Wang Yuman,et al.Forming conditions and characteristics of shale gas in the Lower Paleozoic of the Upper Yangtze region,China[J].Oil & Gas Geology,2010,31(3):288-301.
[6] 赵建华,金之钧,金振奎,等.四川盆地五峰组—龙马溪组页岩岩相类型与沉积环境[J].石油学报,2016 (5):572-586.Zhao Jianhua,Jin Zhijun,Jin Zhenkui,et al.Lithofacies and sedimentary environment of shale in Wufeng-Longmaxi Formation,Sichuan Basin[J].Acta Petrolei Sinica,2016,37:572-586.
[7] 刘忠宝,高波,张钰莹,等.上扬子地区下寒武统页岩沉积相类型及分布特征[J].石油勘探与开发,2017,44(1):21-31.Liu Zhongbao,Gao Bo,Zhang Yuying,et al.Types and distribution of the shale sedimentary facies of the Lower Cambrian in Upper Yangtze area,South China[J].Petroleum Exploration and Development,2017,44(1):21-31.
[8] 王阳,陈洁,胡琳,等.沉积环境对页岩气储层的控制作用[J].煤炭学报,2013,38(5):845-850.Wang Yang,Chen Jie,Hu Lin,et al.Sedimentary environment control on shale gas reservoir:A case study of Lower Cambrian Qiongzhusi Formation in the Middle Lower Yangtze area [J].Journal of China Coal Society,2013,38(5):845-850.
[9] Wang Shufang,Zou Caineng,Dong Dazhong,et al.Multiple controls on the paleoenvironment of the Early Cambrian marine black shales in the Sichuan Basin,SW China:Geochemical and organic carbon isotopic evidence[J].Marine and Petroleum Geology,2015,66:660-672.
[10] 贾智彬,侯读杰,孙德强,等.贵州地区下寒武统牛蹄塘组烃源岩热水沉积成因鉴别与强度评价[J].石油以天然气地质,2016,39(3):429-437.Jia Zhibin,Hou Dujie,Sun Deqiang,et al.Genesis and intensity of hydrothermal sedimentation in hydrocarbon source rocks in the Lower Cambrian Niutitang Formation,Guizhou area[J].Oil & Gas Geology,2016,39(3):429-437.
[11] Zhang Yuying,He Zhiliang,Jiang Shu,et al.Marine redox stratification during the early Cambrian(ca.529-509 Ma)and its control on the development of organic～rich shales in Y angtze Platform[J].Geochemistry,Geophysics,Geosystems,2017,18(6):2354-2369.
[12] 牟传龙,梁薇,周恳恳,等.中上扬子地区早寒武世 (纽芬兰世—第二世)岩相古地理[J].沉积与特提斯地质,2012,32(3):41-53.Mou Chuanlong,Liang wei,Zhou Kenken,et al.Sedimentary facies and palaeogeography of the middle-upper Yangtze area [J].Sedimentary Geology and Tethyan Geology,2012,32(3):41-53.
[13] 黄金亮,邹才能,李建忠,等.川南下寒武统筇竹寺组页岩气形成条件及资源潜力[J].石油勘探与开发,2012,39(1):69-75.Huang Jinliang,Zou Caineng,LiJianzhong,et al.Shale gas generation and potential of the Lower Cambrian Qiongzhusi formation in Southern Sichuan Basin of China[J].Petroleum Exploration and Development,2012,39(1):69-75.
[14] 刘忠宝,杜伟,高波,等.层序格架中富有机质页岩发育模式及差异分布:以上扬子下寒武统为例[J].吉林大学学报(地球科学版),2018,48(1):1-14.Liu Zhongbao,Du Wei,Gao Bo,et al.Sedimentary model and distribution of organic-rich shale in the sequence stratigraphic framework:A case study of Lower Cambrian in Upper Yangtze region[J].Journal of Jilin University(Earth Science Edition),2018,48(1):1-14.
[15] 黄福喜,陈洪德,侯明才,等.中上扬子克拉通加里东期(寒武-志留纪)沉积层序充填过程与演化模式[J].岩石学报,2011,27(8):2299-2317.Huang Fuxi,Chen Hongde,Hou Mingcai,et al.Filling process and evolutionary model of sedimentary sequence of Middle-Upper Yangtze craton in Caledonian(Cambrian-Silurian)[J].Acta Petrologica Sinica,2011,27(8):2299-2317.
[16] 魏国齐,杨威,杜金虎,等.四川盆地高石梯—磨溪古隆起构造特征及对特大型气田形成的控制作[J].石油勘探与开发,2015,42(3):257-265.Wei Guoqi,Yang Wei,Du Jinhu,et al.Tectonic features of Gaoshiti-Moxi paleo-uplift and its controls on theformation of a giant gas field,Sichuan Basin,SW China[J].Petroleum Exploration and Development,2015,42(3):257-265.
[17] 刘树根,王一刚,孙玮,等.拉张槽对四川盆地海相油气分布的控制作用[J].成都理工大学学报(自然科学版),2016,43(1):1-23.Liu Shugen,Wang Yigang,Sun Wei,et al.Control of intracratonic sags on the hydrocarbon accumulations in the marine strata across the Sichuan Basin,China[J].Journal of Chengdu University of Technology(Science & Technology Edition),2016,43(1):1-23.
[18] 梁国宝.上扬子地块盆—山结构及铅锌成矿规律研究[D].武汉:中国地质大学(武汉),2015.Liang Baoguo.Study on the basion-mountain construction and the Lead-Zinc metallogenic regularity of the Upper Yangtze block[D].Wuhan:China University of Geosciences(Wuhan),2015.
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[20] 陈其英,郭师曾.中国东部震旦纪和寒武纪磷块岩的结构成因类型及其沉积相和环境[J].地质科学,1985,3:224-235.Chen Qiying,GuoShizeng.Texture-genetic types,facies characteristics and formation environment of phosphorites of Sinain and Cambrian in eastern China[J].Chinese Journal of Geology,1985,3:224-235.
[21] Wang Jianguo,Chen Daizhao,Wang Dan,et al.Petrology and geochemistry of chert on the marginal zone of Yangtze Platform,western Hunan,South China,during the Ediacaran～Cambrian transition[J].Sedimentology,2012,59(3):809-829.
[22] Jones B,Manning D A C.Comparison of geochemical indices used for the interpretation of palaeoredox conditions in ancient mudstones[J].Chemical Geology,1994,111:111-129.
[23] Wignall P B,Twitchett R J.Oceanic anoxia and the end Permian mass extinction [J].Science 1996,272:1155-1158.
[24] Rimmer S M.Geochemical paleoredox indicators in Devonian-Mississippian black shales,central Appalachian Basin(U.S.A.)[J].Chemical Geology,2004,206:373-391.
[25] 陈代钊,汪建国,严德天,等.扬子地区古生代主要烃源岩有机质富集的环境动力学机制与差异[J].地质科学,2011,46(1):5-26.Chen Daizhao,Wang Jianguo,Yan Detian,et al.Environmental dynamics of organic accumulation for the principal paleozoic source rocks on Yangtze block[J].Chinese Journal of Geology,2011,46(1):5-26.
[26] Jin Chengsheng,Li Chao,Algeo T J,et al.A highly redox-heterogeneo-us ocean in South China during the early Cambrian(～529～514 Ma):Implications for biota-environment co-evolution[J].Earth and Planetary Science Letters,2016,441:38-51.
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