| 层序地层格架下烃源岩地球化学研究:以尼日尔Termit盆地为例 |
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| 引用本文： | 李美俊,赖洪飞,毛凤军,刘计国,肖洪,唐友军.层序地层格架下烃源岩地球化学研究:以尼日尔Termit盆地为例[J].地球科学,2018,43(10):3603-3615. |
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| 作者姓名： | 李美俊 赖洪飞 毛凤军 刘计国 肖洪 唐友军 |
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| 作者单位： | 1.油气资源与勘探技术教育部重点实验室, 长江大学资源与环境学院, 湖北武汉 430100 |
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| 基金项目： | 油气资源与探测国家重点实验室自主研究课题PRP/indep-2-1402国家自然科学基金项目4187030080 |
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| 摘 要： | 如何利用有限的烃源岩样品的实验分析数据和地质资料尽可能地提高烃源岩评价和预测的精度，是当今烃源岩地球化学研究亟需解决的问题.采用层序地层学与油气地球化学相结合的方法，研究了非洲尼日尔Termit盆地基于层序地层格架下，上白垩统Yogou组烃源岩空间分布特征及有机质地球化学性质，初步展示了层序地层格架下烃源岩地球化学研究的方法、应用效果及优势.Termit盆地上白垩统Yogou组海相泥页岩是该盆地主要的烃源层，自下而上可划分为YSQ1、YSQ2和YSQ3共3个三级层序.根据层序/体系域发育特征、岩性录井和测井曲线响应特征，识别出外陆棚、内陆棚、三角洲、滨岸相泥岩及煤/炭质泥岩共5种不同沉积类型的烃源岩，不同层序与体系域具有不同的烃源岩纵向叠置关系和横向分布特征.不同类型的烃源岩有机质具有明显不同的地球化学性质:外陆棚和内陆棚泥岩有机质丰度中等-好，有机质生物来源中，低等水生生物贡献高，沉积于偏还原的沉积环境.滨岸和三角洲相泥岩有机质丰度高，具有低等水生生物和高等植物来源的双重贡献，沉积于偏氧化的沉积环境.三级层序或其体系域控制下的沉积相分布和演化导致不同类型烃源岩的发育和横向分布特征，同一沉积相类型的烃源岩具有相似的地球化学性质.与传统的以组、段为单元的烃源岩地球化学研究相比，层序地层格架下的烃源岩评价可以刻画不同层序、不同体系域和沉积相带烃源岩有机质地球化学性质的差异，提高资源评价和油-源对比的精度.
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| 关 键 词： | 烃源岩评价 层序地层格架 地球化学性质 Termit盆地 中西非裂谷系 石油地质 |
| 收稿时间： | 2018-04-02 |
Geochemical Assessment of Source Rock within a Stratigraphic Geochemical Framework: Taking Termit Basin (Niger) as an Example |
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| Abstract: | How to improve the accuracy of source rock evaluation and prediction based on limited source rock samples data and geological data is a key problem that needs to be solved in the study of source rock geochemistry.By using sequence stratigraphy and petroleum organic geochemistry, this paper studies the spatial distribution and geochemical nature of source rocks of Upper Cretaceous Yogou Formation in the Termit Basin, Niger. This case study preliminarily exhibits the method, application and advantages of geochemical sequence stratigraphy. The main source beds in the Termit Basin are the marine mudstones of the Upper Cretaceous Yogou Formation, which can be divided into three third-order sequences, namely, YSQ1, YSQ2 and YSQ3 from the bottom to the top. Five types of source rocks with different sedimentary facies were subdivided on the basis of sequence/systems tracts, lithology and loggings, which include the lower offshore, upper offshore mudstones, delta and shoreface mudstones, coal seams/carbonaceous mudstones. Different sequences and systems tracts have different vertical and areal distribution patterns of these five source rock types. The organic matters from different source rocks have distinctly different geochemical characteristics. Lower and upper offshore mudstones have fair to good hydrocarbon generative potential with more contribution of lower aquatic organisms, depositing in relatively reducing environment. While delta and shoreface mudstones have good to excellent organic carbon abundances with organic matter input of both lower aquatic organisms and terrestrial organic matter, which deposited in oxidizing environment. The occurrence and lateral distribution of different types of source rocks are evidently controlled by the sedimentary facies distribution and evolution within the third-order sequences or systems tracts, and the same type of source rocks has similar geochemical characteristics. Compared with conventional source rock geochemical assessment, geochemical sequence stratigraphy can provide a practical framework to describe the detailed geochemical characteristics of different sequences, systems tracts and depositional facies within a formation or a member, and subsequently improve the accuracy of hydrocarbon resources assessment and oil-source correlation. |
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