四川盆地海、陆相烃源岩有机质稳定碳同位素组成变化及其地球化学意义
- 1. 浙江大学地球科学学院, 杭州 310027;
- 2. 中国地质大学(武汉), 武汉 430074;
- 3. 中国石油大学(北京)地球科学学院, 北京 102249;
- 4. 中国石化勘探分公司, 成都 610000
基金项目:
国家科技重大专项（2011ZX05005-03-009HZ）；教育部高等学校博士学科点专项科研基金博导类资助课题（20130101110051）
作者简介:
朱扬明,男,1954年出生,教授,博士,油气地球化学,E-mail:zyming@zju.edu.cn
- 收稿日期:
2017-03-07
- 修回日期:
2017-05-03
- 刊出日期:
2017-12-10
摘要: 采用质谱和色谱-同位素质谱技术，测定了500余个干酪根及饱和烃、芳烃组份、正构烷烃的δ13C值，以此揭示了四川盆地海、陆相烃源岩有机碳同位素组成随地质时代的变化特点及其在高成熟阶段的演化特征，并结合其他相关分析资料，应用碳同位素剖析了不同类型海、陆相烃源岩的有机质生源及沉积环境。研究结果表明，该盆地从震旦系灯影组到中三叠统雷口坡组的海相地层中，干酪根的碳同位素组成随层位变新呈逐渐变重的趋势，可能的原因之一是浮游植物的进化作用；而上三叠统须家河组至中侏罗统千佛崖组的陆相有机质碳同位素组成则有反向的年代变化，主要与生源构成和沉积环境性质有关。这些海、陆相烃源岩的有机源难以用干酪根δ13C值进行区分，而可用饱和烃与芳烃组份的δ13C及其CV值来区别。海洋和湖泊不同沉积相带烃源岩的干酪根具有明显不同的δ13C值，结合其他相关资料可识别其有机质来源。煤系地层中煤与泥岩在干酪根碳同位素组成上没有可区分性，而两者有不同的正构烷烃碳同位素分布曲线。从成熟晚期到高-过成熟阶段，海、陆相干酪根的碳同位素均变重1~2‰，煤系泥岩的正构烷烃碳同位素分布曲线由负向线型分布向平直型演变。这些碳同位素的变化特征为油气源对比和烃源识别提供了依据。
Compositional Variations and Geochemical Significances of Stable Carbon Isotope for Organic Matters from Marine and Terrestrial Source Rocks in Sichuan Basin
- 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
Funds:
National Science and Technology Major Project, No. 2011ZX05005-03-009HZ; Specialized Research Fund for the Doctoral Program of Higher Education, No. 20130101110051
- Received Date:
2017-03-07
- Rev Recd Date:
2017-05-03
- Publish Date:
2017-12-10
Abstract: 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.
朱扬明, 李颖, 郝芳, 邹华耀, 郭旭升. 四川盆地海、陆相烃源岩有机质稳定碳同位素组成变化及其地球化学意义[J]. 沉积学报, 2017, 35(6): 1254-1264. doi: 10.14027/j.cnki.cjxb.2017.06.016
ZHU YangMing, LI Ying, HAO Fang, ZOU HuaYao, GUO XuSheng. Compositional Variations and Geochemical Significances of Stable Carbon Isotope for Organic Matters from Marine and Terrestrial Source Rocks in Sichuan Basin[J]. Acta Sedimentologica Sinica, 2017, 35(6): 1254-1264. doi: 10.14027/j.cnki.cjxb.2017.06.016
| Citation: |
ZHU YangMing, LI Ying, HAO Fang, ZOU HuaYao, GUO XuSheng. Compositional Variations and Geochemical Significances of Stable Carbon Isotope for Organic Matters from Marine and Terrestrial Source Rocks in Sichuan Basin[J]. Acta Sedimentologica Sinica, 2017, 35(6): 1254-1264. doi: 10.14027/j.cnki.cjxb.2017.06.016
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