基于包裹体信息分析准噶尔盆地柴窝堡凹陷芦草沟组储层油源及成藏期次

Inclusion Data Analysis for the Determination of Oil Source and Accumulation Stages in Lucaogou Formation in the Chaiwopu Sag,Junggar Basin

柴窝堡凹陷芦草沟组原油的研究工作取得了重要进展,但由于构造沉积演化十分复杂,目前油源方面的认识仍不清楚,成藏时间尚不明确。利用改进的石油包裹体烃组分分析方法和包裹体定年技术讨论了研究区芦草沟组原油的来源和成藏期次。结果表明,研究区芦草沟组储层第一期充注原油正构烷烃主峰碳数低,C_(21)三环萜烷和C_(27)甾烷相对丰度较高,显示蓝色荧光,为北部半深湖-深湖相芦草沟组烃源岩生成的高成熟原油,于早白垩世在达1井区聚集成藏;第二期充注原油正构烷烃主峰碳数高,C_(20)三环萜烷或C_(23)三环萜烷、C_(29)甾烷相对丰度较高,显示黄绿色、黄色荧光,为研究区滨浅湖相芦草沟组烃源岩生成的较低成熟度原油,于晚白垩世末期-古新世早期在达1井区聚集成藏。

Hydrocarbon accumulation in the Chaiwopu Sag has been well documented,however the tectonic and sedimentary evolution in the Chaiwopu Sag is complex,and the source of oil and the timing of hydrocarbon ac-cumulation are still controversial.Here,the hydrocarbon source and accumulation of the Lucaogou Formation is discussed through an improved molecular composition of inclusion method,and the fluid inclusions in the Chai-wopu Sag(Junggar Basin).Distribution characteristics of the n-alkanes are dominated by low carbon numbers,and the relative abundance of C_(21)-tricyclic terpane and C_(27)-steranes are higher in the early-charging oil,showing blue fluorescence.The first stage(Early Cretaceous)oil came mainly from the Lucaogou Formation(semi-)deep lacustrine-facies source rocks in the north.Meanwhile,distribution characteristics of the n-alkanes are dominated by high carbon numbers,and the relative abundance of C_(20)-tricyclic terpane or C_(23)-tricyclic terpane and C_(29)-steranes are higher in the second-charging oil,showing yellow-green or yellow fluorescence.The second stage lasted from the end Late Cretaceous to the Early Paleocene,and the oil came mainly from the local Lucao-gou Formation shore-shallow lacustrine-facies source rocks.