鄂尔多斯盆地靖边油田西部延9原油地球化学特征与油源

为了明确靖边油田西部延9油藏石油的来源，采用原油物性、族组成、饱和烃色谱及色谱-质谱等方法，分析了延9原油地球化学特征，通过对比本区长7烃源岩与湖盆中心志丹地区长7烃源岩地球化学特征，结合区域地质背景研究了延9油藏石油的来源。结果表明，延9原油饱和烃含量均在60%以上，正构烷烃单峰分布，主峰碳主要以C₂₁为主；生物标志物中C₃₀藿烷占优势，其次为C₂₉藿烷，规则甾烷以C₂₉为主，C₂₇和C₂₈含量相似，呈不对称“V”字型分布。延9原油地球化学特征相似，具有统一的物质来源和演化程度，为淡水条件下弱氧化-还原环境形成的成熟原油。油源对比表明，靖边油田本地长7烃源岩与延9原油具有明显的亲缘关系，延长组沉积时期位于湖盆中心的志丹地区长7烃源岩地化特征与延9原油差异明显。延9油藏的形成主要为本地区长7烃源岩成熟后，经叠置砂体及裂缝系统输导，主要经垂向运移至延9储层，再经过短距离侧向运移至圈闭聚集成藏。 

Geochemical characteristics of Yan 9 crude oil and oil-source correlation in western Jingbian Oil Field,Ordos Basin

The geochemical characteristics of the Yan 9 reservoir were analyzed by means of petrophysical properties, hydrocarbon group composition, saturated hydrocarbon chromatography and gas chromatography-mass spectrometry in order to clarify the source of oil in the Yan 9 reservoir in the west of Jingbian Oil Field. The geochemical characteristics of Chang 7 source rocks in the study area and the Zhidan area were compared, and the source of Yan 9 oil was studied in combination with regional geological background. The results showed that the saturated hydrocarbon content of Yan 9 crude oil is above 60%, and the n-alkanes are distributed with a single mode with C₂₁ as the main carbon peak, C₃₀ hopane as the dominant biomarker, followed by C₂₉ hopane. Regular steroids are mainly C₂₉, while C₂₇ and C₂₈ are similar, showing an asymmetric "V" distribution. The Yan 9 crude oil has similar geochemical characteristics and unified material source and evolution degree. It is a mature crude oil derived from a source deposited in a weak oxidation-reduction environment under freshwater conditions. Oil-source correlation showed that the source rocks of the Chang 7 reservoir in the Jingbian Oil Field are related to the Yan 9 crude oil, and the geochemical characteristics of the Chang 7 source rocks in the Zhidan area, which is located in the center of the lacustrine basin, are obviously different from the Yan 9 crude oil. The formation of Yan 9 oil is mainly due to the maturation of Chang 7 source rocks in this area. The oils were transported by superimposed sand bodies and fracture systems, migrated vertically to the Yan 9 reservoir, and then migrated laterally to traps for accumulation.