GEOCHEMICAL CHARACTERISTICS OF CRUDE OIL FROM YANCHANG AND YAN’AN FORMATIONS IN PENGYANG AREA OF ORDOS BASIN AND THEIR IMPLICATIONS FOR OIL-SOURCE
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摘要:
鄂尔多斯盆地彭阳地区的中生界延长组、延安组油源还存在一定的不确定性,应用分子地球化学的手段和方法,对彭阳地区延长组、延安组的原油及长7烃源岩样品和盆地内部长7优质烃源岩样品开展生物标识化合物地球化学定量分析,并进行油源对比研究。结果表明:鄂尔多斯盆地天环坳陷彭阳地区延长组、延安组原油形成于淡水、微咸水且还原性较强的环境;生物标志化合物地球化学特征相似,属于同一成因类型,具有相同的油源;原油母质类型为低等水生生物和陆生高等植物构成的混合型母质,原油已经成熟。彭阳地区原油在成熟度、母源性质和沉积环境方面与盆地内部长7优质烃源岩具有相似的特征,二者具有较好的亲缘关系,彭阳地区原油不是本地长7泥岩产物,主要来自盆地内部长7优质烃源岩。
Abstract:Abstract: Researches have been devoted to the uncertainties of sources of oil from the Yan’an and Yanchang Formations in the Pengyang area of the Ordos Basin. Using the methods of GC-MS, biomarkers are analyzed, upon which correlation of oil-sources is made for the crude oil samples from the Yanchang and Yan’an Formations with those from the Chang-7 high quality source rock in both the Pengyang area and the area within the basin. Results show that the crude oils produced from the Yanchang Formation and Yan’an Formation of the Pengyang area came from the west Tianhuan Depression and was formed under a deoxidized lake environment of freshwater and mildly brackish water. Biomarker characteristics suggest that the crude oils of Yanchang Formation and Yan’an Formation come from the same oil source, of which the parent materials are mainly from aquatic organisms and higher plant, and the crude oil is mature. Facts show that the maturity, parent materials and sedimentary environment of crude oil from the Pengyang area are similar with the Chang-7 source rock formed within the basin center. It is thus concluded that the crude oil is coming from the Chang-7 mudstone in the basin center, but not the local Chang-7 deposits in the Pengyang area.
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Key words:
- Ordos Basin /
- SAGDdevelopment /
- reservequality /
- keyparameters
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表 1 原油、烃源岩饱和烃色谱参数
Table 1. Chromatogram parameters of saturated hydrocarbons of crude oil and source rock
样品
位置样品 井号 层位 正构烷烃 类异戊二烯烷烃 主峰碳 OEP CPI (C21+C22)
/(C28+C29)∑C21-/
∑C22+Pr/
PhPr/
nC17Ph/
nC18彭阳地区 原油 演27 延8 C21 1.06 1.08 1.2 0.44 1.12 0.52 0.41 演43 延9 C21 1.06 1.1 1.68 0.64 1.01 0.58 0.44 演39 长3 C21 1.05 1.09 1.65 0.75 1.1 0.42 0.32 镇86 长3 C21 1.1 1.13 1.56 0.61 1.03 0.6 0.42 演33 长3 C21 1.04 1.09 1.68 0.68 1.05 0.36 0.28 演34 长7 C21 1.07 1.11 1.7 0.62 0.84 0.47 0.4 演54 长7 C21 1.07 1.11 1.73 1.01 1.18 0.39 0.33 镇86 长7 C21 1.04 1.1 2.28 0.79 1.01 0.46 0.34 演42 长8 C21 1.07 1.09 1.65 0.78 1.05 0.39 0.33 演45 长8 C21 1.06 1.09 1.92 0.66 0.94 0.47 0.36 烃源岩 演43 长7 C25 0.93 1.24 1.41 0.4 3.82 3.17 0.54 演43 长7 C25 0.91 1.21 1.45 0.48 3.72 3.23 0.58 盆地内部 镇120 长7 C17 2.91 1.08 1.3 2.2 1.16 0.37 0.33 镇146 长7 C17 2.83 1.06 1.37 2.49 1.21 0.43 0.37 镇120 长7 C16 2.08 1.1 1.08 2.09 1.09 0.31 0.34 表 2 甾萜类化合物地化参数
Table 2. Geochemical parameters of steride and terpenoid
井号 层位 样品 甾烷参数 萜烷参数 1 2 3 4 5 6 7 8 9 10 11 12 13 14 演27 延8 原油 0.07 0.45 0.62 36.1 30.4 33.5 0.11 0.37 0.08 0.06 0.07 0.56 0.61 1.22 演34 长7 原油 0.08 0.42 0.63 30.6 33.4 36.0 0.11 0.31 0.13 0.06 0.07 0.57 0.60 1.76 演39 长3 原油 0.07 0.42 0.68 34.5 31.9 33.6 0.15 0.34 0.12 0.06 0.06 0.56 0.59 1.40 演42 长8 原油 0.07 0.44 0.65 37.0 29.9 33.1 0.13 0.32 0.11 0.06 0.07 0.58 0.61 1.33 镇120 长7 烃源岩 0.05 0.42 0.63 31.0 34.0 35.0 0.17 0.26 0.13 0.06 0.07 0.56 0.59 0.10 注:1—重排甾烷/规则甾烷;2—αααC29甾烷20S/ (20S+20R);3—C29甾烷αββ/(ααα+αββ);4—C27%Rααα;5—C28%Rααα;6—C29%Rααα;7—三环萜/藿烷;8—升藿烷指数C35(22S+22R)/C32(22S+22R);9—C30重排藿烷/C30藿烷;10—伽马蜡烷/C30(藿烷+莫烷);11—伽马蜡烷/C 30藿烷;12—αααC31藿烷22S/(22S+22R);13—αααC32藿烷22S/(22S+22R);14—Ts/Tm -
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