张景坤, 周基贤, 王海静, 米巨磊, 寇晨辉, 王岩, 周妮, 曹剑. 准噶尔盆地西北缘超剥带轻质油的发现及意义[J]. 地质通报, 2017, 36(4): 493-502.
    引用本文: 张景坤, 周基贤, 王海静, 米巨磊, 寇晨辉, 王岩, 周妮, 曹剑. 准噶尔盆地西北缘超剥带轻质油的发现及意义[J]. 地质通报, 2017, 36(4): 493-502.
    ZHANG Jingkun, ZHOU Jixian, WANG Haijing, MI Julei, KOU Chenhui, WANG Yan, ZHOU Ni, CAO Jian. The discovery of light oil in the overlap-erosion zones of the northwestern Junggar Basin and its significance[J]. Geological Bulletin of China, 2017, 36(4): 493-502.
    Citation: ZHANG Jingkun, ZHOU Jixian, WANG Haijing, MI Julei, KOU Chenhui, WANG Yan, ZHOU Ni, CAO Jian. The discovery of light oil in the overlap-erosion zones of the northwestern Junggar Basin and its significance[J]. Geological Bulletin of China, 2017, 36(4): 493-502.

    准噶尔盆地西北缘超剥带轻质油的发现及意义

    The discovery of light oil in the overlap-erosion zones of the northwestern Junggar Basin and its significance

    • 摘要: 含油气盆地超剥带的勘探以重质油-油砂为主。在准噶尔盆地西北缘超剥带的中生代油砂中发现了轻质油,报道了其基本特征与成藏模式,并探讨了勘探意义。结果表明,轻质油呈黄绿色荧光,与呈黄褐色荧光的重质油共生。油砂连续抽提发现,重质油充注在前(颗粒吸附烃/包裹体烃),轻质油充注在后(孔隙游离烃),油源均来自研究区玛湖凹陷下二叠统风城组,典型生标特征为Pr/Ph值小于1,伽马腊烷/C30藿烷为0.43~0.82,C20、C21、C23三环萜烷呈上升型分布。油砂无机地球化学研究发现,2期原油充注明显,形成了2期方解石胶结物,早期MnO和FeO含量在1%~1.5%之间,晚期大于1.5%。白垩纪前,风城组生源成熟油在充注过程中遭受降解,形成重质油-油砂;白垩纪至今,风城组生源高熟轻质油沿横断裂直接运移至超剥带,在断裂“纵横交叉”之处最富集。据此认为,研究区横断裂沿线是这类轻质原油勘探值得考虑的领域。超剥带的勘探可能不仅局限于传统认为的重质油-油砂,若存在有利的成藏条件,亦有可能形成轻质油气的聚集。

       

      Abstract: The heavy oil and oil sand constitute the primary target of exploration in the overlap-erosion zones of petroliferous basins. Here the authors present the first discovery of light oil in Mesozoic oil sands in the overlap-erosion zones of the northwestern Jung-gar Basin, report the basic characteristics and accumulation model of the light oil and investigate their implications for exploration. The results show that the light oil fluoresces yellowish green light and coexists with heavy oil with dark fluorescence. Reservoir sequential extraction of oil sands shows that the heavy oil (grain adsorbed and/or inclusion oils) charged reservoir before the light oil (pore free oils) and the oil sources were both from the Lower Permian Fengcheng Formation in the Mahu sag. Representative bio-marker evidence includes Pr/Ph < 1, gammacerane/C30 hopance=0.43~0.82 and tricyclic terpanes C20 < C21 < C23. Inorganic geochemi-cal studies support this two-stage oil charging events. The MnO and FeO values of diagenetic calcites are 1%~1.5% and >1.5%, respectively. Before the Cretaceous, the Fengcheng-sourced mature oil charged to the overlap-erosion zones of the study area and was biodegraded, and formed oil sand. Since the Cretaceous, the Fengcheng-sourced highly-mature and light oil has migrated from the Mahu sag to the overlap-erosion zones of the study area along transverse faults. As a result, the light oil accumulated mostly in the cross points of reverse and transverse faults. Accordingly, the zones along transverse faults are potential for light-oil exploration. The exploration in overlap-erosion zones of petroliferous basins might not be merely confined to heavy oil and oil sand. Light oil and gas could accumulate if favorable reservoir forming conditions exist.

       

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