鄂尔多斯盆地陇东地区延长组低渗透油藏成藏期次研究

主要对陇东地区延长组流体包裹体特征进行了研究,结合烃源岩生烃史、原油成熟度，综合分析研究区的成藏期次。流体包裹体镜下观察与荧光特征显示陇东地区延长组存在两期油气包裹体：第一期油气包裹体在单偏光下呈灰褐色或深褐色的液烃包裹体,丰度较低,盐水包裹体均一温度主峰为75~95 ℃；第二期油气包裹体以气液烃包裹体为主,液烃表现为无色或淡黄色的单偏光特征与浅黄色至蓝绿色的荧光特征,丰度较高,盐水包裹体均一温度主峰为75~95 ℃与100~120 ℃。结合烃源岩生烃史与原油成熟度认为,陇东地区延长组存在三期成藏：距今约为140~130 Ma的早期低熟油小规模充注时期；发生于120~100 Ma,与烃源岩生烃高峰期相对应的中期成熟度大规模成藏期；距今约为100~40 Ma的晚白垩世构造抬升调整成藏时期。

A study of the accumulation periods of low permeability reservoir of Yanchang Formation in Longdong Area, Ordos Basin

The hydrocarbon accumulation time of Yanchang Formation in Longdong Area is determined according to the characteristics of fluid inclusion,combined with the hydrocarbon generation history of source rock and oil maturity.The characteristics of fluid inclusion under microscope and UV fluorescence suggest that there are two periods of hydrocarbon inclusion.The first stage of hydrocarbon inclusion is dust or dark brown liquid hydrocarbon inclusion under polarized light microscope,its abundance is low,and the homogenization temperature of accompanied saline inclusions is 75—95℃.The second stage of hydrocarbon inclusion is mainly gas and liquid hydrocarbon inclusion,the liquid is colorless or light yellow under polarized light microscope and light yellow to bluish green under fluorescence microscope,its abundance is high,and the main peaks of homogenization temperature of accompanied saline inclusions are 75—95℃ and 100—120℃.Three periods of hydrocarbon accumulation are showed: the early period of low mature oil charging in a small scale at 140—130 Ma,the middle period of mature oil accumulating in a large scale at 120—100 Ma corresponding to the peak of hydrocarbon generation,and the late period of adjusting accumulation at 100—40 Ma.