Compositional Variations and Geochemical Significances of Stable Carbon Isotope for Organic Matters from Marine and Terrestrial Source Rocks in Sichuan Basin
ZHU YangMing1, LI Ying1, HAO Fang2, ZOU HuaYao3, GUO XuSheng4
1. School of Earth Sciences, Zhejiang University, Hangzhou 310027, China;
2. China University of Geosciences, Wuhan 430074, China;
3. College of Earth Sciences, China University of Petroleum, Beijing 102249, China;
4. Southern Exploration Company, SINOPEC, Chengdu 610000, China
Over 500 kerogens as well selected saturate and aromatic fractions and n-alkanes from various age source rocks in the Sichuan basin were analyzed using MS and GC-ir-MS for δ13C ratios, to characterize the age-trend in organic carbon isotopic composition in marine and terrestrial sediments and their thermal evolution during over-mature stage. Moreover, different kind of marine and terrestrial source rocks with respect to their biological organic sources were distinguished using carbon isotopes in combination with other analytical data. The results indicate the kerogens from marine sediments in Sinian Dengying to middle Triassic Leikoupo Formations in this basin show a trend toward isotopically heavy values with decreasing age, possibly due to biological evolution. Whereas, a reversal isotopic-age trend for the terrigenous organic carbon is observed in upper Triassic Xujiahe to middle Jurassic Qingfoyan Formations and is considered to be dependent of biological source and sedimentary environment. The organic inputs of marine and terrestrial source rocks cannot be differentiated using the carbon isotopic ratios of kerogen, however, it can be distinguished by δ13C values of saturated and aromatic fractions and CV values. The marine and lacustrine source rocks with different facies are of obviously varying δ13C values of kerogens, thus the isotopic ratio, combined with additional relate-source data, can be acted as an indicator for their organic source. Coal and mudstone in coal-bearing strata is not distinguishable for their kerogen carbon isotopes, but has different profiles of n-alkane isotopes with more negative values in mudstone related to coal. The marine (type-Ⅱ)and terrigenous (type-Ⅲ) kerogens both continuously become isotopically enriched in 13C by 1‰~2‰ with maturation during high-over maturity. The negatively sloping curve of carbon isotope for individual n-alkanes from coaly source rock at mature stage is transferred into a flat one at high maturity. These variations in carbon isotope compositions are helpful for oil & gas-rock correlation and hydrocarbon source identification.
胡见义,黄第藩. 中国陆相石油地质理论基础[M]. 北京:石油工业出版社,1991:189.[Hu Jianyi, Huang Difan. The bases of nonmarine petroleum geology in China[M]. Beijing:Petroleum Industry Press, 1991:189.]
[2]
梁狄刚,郭彤楼,陈建平,等. 中国南方海相生烃成藏研究的若干新进展(二):南方四套区域性海相烃源岩的地球化学特征[J]. 海相油气地质,2009,14(1):1-15.[Liang Digang, Guo Tonglou, Chen Jianping, et al. Some progresses on studies of hydrocarbon generation and accumulation in marine sedimentary regions, southern China (part 2):Geochemical characteristics of four suits of regional marine source rocks, South China[J]. Marine Oil and Gas Geology, 2009, 14(1):1-15.]
[3]
Peters K E, Walters C C, Moldowan J M. The biomarker guide:I. biomarkers and isotopes in the environment and human history[M]. 2nd Ed. Cambridge:Cambridge University Press, 2005:136-156.
[4]
Sackett W M. Determination of kerogen maturity by the pyrolysis-carbon isotope method[J]. Organic Geochemistry, 1984, 6:359-363.
[5]
Galimov E M. Isotope organic geochemistry[J]. Organic Geochemistry, 2006, 37(10):1200-1262.
[6]
Sofer Z. Stable carbon isotope compositions of crude oils:application to source depositional environments and petroleum alteration[J]. AAPG Bulletin, 1984, 68(1):31-49.
[7]
朱扬明,顾圣啸,李颖,等. 四川盆地龙潭组高热演化烃源岩有机质生源及沉积环境探讨[J]. 地球化学,2012,41(1):35-44.[Zhu Yangming, Gu Shengxiao, Li Ying, et al. Biological organic source and depositional environment of over-mature source rocks of Longtan Formation in Sichuan Basin[J]. Geochemica, 2012, 41(1):35-44.]
[8]
黄籍中. 中上扬子区海相沉积烃源研究(之二)[J]. 天然气勘探与开发,2000,23(1):9-27.[Huang Jizhong. Study on hydrocarbon source of marine sediments in Middle-Upper Yangtze platform (part 2)[J]. Natural Gas Exploration and Development, 2000, 23(1):9-27.]
[9]
黄籍中,冉隆辉. 四川盆地震旦系灯影灰岩黑色沥青与油气勘探[J],石油学报,1989,10(1):27-36.[Huang Jizhong, Ran Longhui. Bitumen and oil-gas exploration in Sinian "Denying limestone" in Sichuan Basin[J]. Acta Petrolei Sinica, 10(1):27-36.]
[10]
王顺玉,戴鸿鸣,王海清,等. 大巴山、米仓山南缘烃源岩特征研究[J]. 天然气地球科学,2000,11(4/5):4-16.[Wang Shunyu, Dai Hongming, Wang Haiqing, et al. Source rock feature of the south of the Dabashan and Mi-cangshan area[J]. Natural Gas Geoscience, 2000, 11(4/5):4-16.]
[11]
童崇光. 四川盆地油气地质研究[J]. 西安地质学院学报,1990,12(3):9-17.[Tong Chongguang. New progress of the oil-gas geology research in the Sichuan Basin[J]. Journal of Xi'an College of Geology, 1990, 12(3):9-17.]
[12]
四川油气区石油地质志编写组. 中国石油地质志(卷十)四川油气区[M]. 北京:石油工业出版社,1989:299.[Editorial Group of Sichuan Oil and Gas Field. Petroleum geology of China (Vol. 10) Sichuan oil and gas field[M]. Beijing:Petroleum Industry Press, 1989:299.]
[13]
黄籍中,陈盛吉,宋家荣,等. 四川盆地烃源体系与大中型气田形成[J]. 中国科学D辑:地球科学,1996,26(6):504-510.[Huang Jizhou, Chen Shengji, Song Jiarong, et al. Hydrocarbon source systems and formation of gas fields in Sichuan Basin[J]. Science in China Series D:Earth Sciences, 1997, 40(1):32-42.]
[14]
黄仁春. 川东北元坝地区雷口坡组天然气来源与成藏分析[J]. 现代地质,2014,28(2):412-418.[Huang Renchun. Source and accumulation of natural gas in Leikoupo Formation, Yuanba area, eastern-northern Sichuan Basin[J]. Geoscience, 2014, 28(2):412-418.]
[15]
陈盛吉,万茂霞,杜敏,等. 川中地区侏罗系油气源对比及烃源条件研究[J]. 天然气勘探与开发,2005,28(2):11-14.[Chen Shengji, Wan Maoxia, Du Min, et al. Jurassic oil-gas source correlation and hydrocarbon source condition in central Sichuan region[J]. Natural Gas Exploration & Development, 2005, 28(2):11-14.]
[16]
Welte D H, Kalkreuth W. Age-trend in carbon isotopic composition in Paleozoic sediments[J]. Naturwissenschaften, 1975, 62(10):482-483.
[17]
Galimov E M. 13C/12C in kerogen[M]//Durand B. Kerogen-Insoluble Organic Matter from Sedimentary Rocks. Paris:Editions Technip, 1980:271-299.
[18]
Lewan M D. Stable carbon isotopes of amorphous kerogens from Phanerozoic sedimentary rocks[J]. Geochimica et Cosmochimica Acta, 1986, 50(8):1583-1591.
[19]
张大江,王大锐,章聆. 我国不同地质时期沉积有机质中稳定碳同位素组成特征及其意义[J]. 科学通报,1991,36(4):302-305.[Zhang Dajiang, Wang Darui, Zhang Ling. Characteristics of stable isotopic composition of sedimentary organic matter in different geological ages, China[J]. Chinese Science Bulletin, 1991, 36(4):302-305.]
[20]
Kump L R, Arthur M A. Interpreting carbon-isotope excursions:carbonates and organic matter[J]. Chemical Geology, 1999, 161(1/2/3):181-198.
[21]
梁狄刚,郭彤楼,陈建平,等. 中国南方海相生烃成藏研究的若干新进展(一):南方四套区域性海相烃源岩分布[J]. 海相油气地质,2008,13(2):1-16.[Liang Digang, Guo Tonglou, Chen Jianping, et al. Some progresses on studies of hydrocarbon generation and accumulation in marine sedimentary regions, southern China (part 1):Distribution of four suits of regional marine source rocks[J]. Marine Origin Petroleum Geology, 2008, 13(2):1-16.]
[22]
梁狄刚,郭彤楼,边立曾,等. 中国南方海相生烃成藏研究的若干新进展(三):南方四套区域性海相烃源岩的沉积相及发育的控制因素[J]. 海相油气地质,2009,14(2):1-19.[Liang Digang, Guo Tonglou, Bian Lizeng, et al. Some progresses on studies of hydrocarbon generation and accumulation in marine sedimentary regions, southern China (part 3):Controlling factors on the sedimentary facies and development of Paleozoic marine source rocks[J]. Marine Oil and Gas Geology, 2009, 14(2):1-19.]
[23]
孙玉梅,李友川,黄正吉. 部分近海湖相烃源岩有机质异常碳同位素组成[J]. 石油勘探与开发,2009,36(5):609-616.[Sun Yumei, Li Youchuan, Huang Zhengji. Abnormal carbon isotopic compositions in organic matter of lacustrine source rocks close to sea[J]. Petroleum Exploration and Development, 2009, 36(5):609-616.]
[24]
Freeman K H, Hayes J M, Trendel J M, et al. Evidence from carbon isotope measurements for diverse origins of sedimentary hydrocarbons[J]. 1990, Nature, 343(6255):254-256.
[25]
Harris N B, Freeman K H, Pancost R D, et al. The character and origin of lacustrine source rocks in the Lower Cretaceous synrift section, Congo Basin, west Africa[J]. AAPG Bulletin, 2004, 88(8):1163-1184.
[26]
Chikaraishi Y, Naraoka H. δ13C and δD relationships among three n-alkyl compound classes (n-alkanoic acid, n-alkane and n-alkanol) of terrestrial higher plants[J]. Organic Geochemistry, 2007, 38(2):198-215.
[27]
Buchardt B, Clausen J, Thomsen E. Carbon isotope composition of Lower Palaeozoic kerogen:effects of maturation[J]. Organic Geochemistry, 1986, 10(1/2/3):127-134.
[28]
苏艾国. 干酪根碳同位素在成熟和风化过程中变化规律初探[J]. 矿物岩石地球化学通报,1999,18(2):79-84.[Su Aiguo. Discussion on variation of carbon isotope of kerogen during thermal maturation and weathering[J]. Bulletin of Mineralogy, Petrology and Geochemistry, 1999, 18(2):79-84.]
[29]
熊永强,张海祖,耿安松. 热演化过程中干酪根碳同位素组成的变化[J]. 石油实验地质,2004,26(5):484-487.[Xiong Yongqing, Zhang Haizu, Geng Ansong. Variation of carbon isotopic composition of kerogen during thermal evolution[J]. Petroleum Geology and Experiment, 2004, 26(5):484-487.]
[30]
Clayton C J, Bjorøy M. Effect of maturity on 13C/12C ratios of individual compounds in North Sea oils[J]. Organic Geochemistry, 1994, 21(6/7):737-750.
[31]
Murray A P, Summons R E, Boreham C J, et al. Biomarker and n-alkane isotope profiles for Tertiary oils:relationship to source rock depositional setting[J]. Organic Geochemistry, 1994, 22(3/4/5):521-542.
[32]
Schouten S, Hartgers W A, Lòpez J F, et al. A molecular isotopic study of 13C-enriched organic matter in evaporitic deposits:recognition of CO2-limited ecosystems[J]. Organic Geochemistry, 2001, 32(2):277-286.
[33]
Badewien T, Vogts A, Rullkötter J. n-Alkane distribution and carbon stable isotope composition in leaf waxes of C3 and C4 plants from Angola[J]. Organic Geochemistry, 2015, 89-90:71-79.
[34]
Tu T T N, Derenne S, Largeau C, et al. Diagenesis effects on specific carbon isotope composition of plant n-alkanes[J]. Organic Geochemistry, 2004, 35(3):317-329.
[35]
Marais D J D, Donchin J H, Nehring N L, et al. Molecular carbon isotopic evidence for the origin of geothermal hydrocarbons[J]. Nature, 1981, 292(5826):826-828.
