东海盆地西湖凹陷平北斜坡带平湖组煤系原油地球化学特征与油-源精细对比

Geochemical characteristics of crude oil from coal measure source rocks and fine oil-source correlation in the Pinghu Formation in Pingbei slope belt， Xihu Sag， East China Sea Shelf Basin

李天军 黄志龙 郭小波 赵静 蒋一鸣 谭思哲

Tianjun Li Zhilong Huang Xiaobo Guo Jing Zhao Yiming Jiang Sizhe Tan

东海盆地西湖凹陷平北斜坡带平湖组煤系原油性质及分布规律复杂，烃源岩纵、横向沉积环境及生物来源非均质性强，具有斜坡带和西次凹多源供烃特征。将地质与地球化学相结合，进行了原油类型划分与油-源精细对比，梳理了原油分布与生烃次洼的关系。结果表明：平北地区原油以凝析油为主，含少量轻质油和正常原油，根据生物标志化合物特征，可划分为3种类型。Ⅰ类原油主要分布在孔雀亭地区，主要来源于陆源高等植物的裸子植物松柏目树脂，与本地平湖组中段下亚段（平中下亚段）-平湖组下段（平下段）烃源岩具有明显亲缘关系。Ⅱ类原油主要分布在武云亭地区的平上段及平中上亚段和NB8洼陷，具有陆源裸子植物和蕨类植物双重贡献，且蕨类植物贡献更大，与平上段、平中上亚段烃源岩有明显亲缘关系，并有成熟度较高的低带-西次凹海源有机质的贡献。Ⅱ类原油主要分布在武云亭及宝云亭—团结亭地区，陆源裸子植物松柏目树脂贡献更大，与平中下亚段和平下段烃源岩具有明显亲缘关系。研究成果对深化平北斜坡带油源的新认识和油气藏预测及勘探部署有较大指导作用。

The properties and distribution of crude oil from the coal measure source rocks are complex in Pingbei slope belt of Xihu Sag， East China Sea Shelf Basin. In addition， the sedimentary environment and organic matter origin of coal measure source rocks are highly variable in both vertical and horizontal views. The oil reservoirs in this area are characterized by hydrocarbon supply from multiple sources including western subsag and the slope zone. A combination of geological and geochemical analyses is applied to study crude oil types and fine oil-source correlation. Finally， the relationship between crude oil distribution and hydrocarbon-generating subsag is clarified. The results show that the crude oil in Pingbei area is mainly condensate oil， accompanied by a small amount of light and normal crude oil， and it can be grouped into three types （i.e. TypeⅠ，Ⅱ andⅡ） based on biomarker compound features. TypeⅠcrude oil mainly sourced from coniferales resinites of gymnosperms of terrestrial higher plants， is mainly distributed in Kongqueting area， and is obviously related to the source rocks in the lower member and lower submember of middle member of Pinghu Formation in the western subsag. TypeⅡ crude oil mainly occurs in the upper member and upper submember of middle member of Pinghu Formation in Wuyunting area and the NB8 subsag. It is speculated that both terrestrial gymnosperms and ferns， together with high-maturity marine organic matters from lower slope belt and western sabsag， have made contributions to the generation of TypeⅡ crude oil， with the contribution of ferns even greater， and this type of crude oil is obviously related to the source rocks in the upper member and upper submember of middle member of Pinghu Formation. In addition， TypeⅡ crude oil is mainly distributed in Wuyunting area and Baoyunting-Tuanjieting area， with greater contributions made by coniferales resinites of terrestrial gymnosperms； and it is obviously related to the source rocks in the lower member and lower submember of middle member of Pinghu Formation. The research results are of guiding value to the new understanding of oil source， reservoir prediction and hydrocarbon exploration in Pingbei slope belt.

10.11743/ogg20220215