Based on GC-MS analyses of aromatic fractions of oils and source rock extracts, a series of triaromatic steroids (TAS) were detected in Ordovician oils from Tahe Oilfield, Tarim Basin. The results show that the distribution of TAS can be applied to define the oil family and origination. The contents of C2820S and C2820R triaromatic steroids in most of the oil samples are relatively higher than those of C2620S,C2620R+C2720S and C2720R TAS. However the oils from the well T904 in the eastern Tahe Oilfield and well TD2 from the east part of Tarim Basin are characterized by relatively high contents of C 2620S,C2620R+C2720S and C2720R derivatives. The distribution of triaromatic steroids of middle-upper Ordovician marl from the wells LN46 and TZ12 resembles that of the most Ordovician oils from Tahe Oilfield. The distribution of triaromatic steroids of typical Cambrian black shales from wells KN1 and TD2 resembles that of oils from wells 904 and TD2. By using C26/ C2820S versus C27/C2g 20R triaromatic steroids plot, two genetic oil families can be easily classified; oil family derived from Cambrian and middle-upper Ordovician source rocks, which is also supported by bulk carbon isotopic compositions. Finally, a criterion relative to triaromatic steroids was proposed, which can be used to classify oil families. Oils with C26/C2g 20S TAS >0. 30 and C27/C28 20R TAS>0. 75 are thought to be derived from Cambrian source rocks, and oils with C26/C2g 20S TAS< 0. 30 and C27/C28 20R TAS<0. 30 from middle-upper Ordovician source rocks.%根据原油和烃源岩抽提物芳烃馏分的色谱质谱分析结果,对塔里木盆地塔河油田奥陶系原油和烃源岩有机质三芳甾(TAS)分布特征进行研究.结果表明:三芳甾分布差异可以有效地划分奥陶系原油的族群及来源；绝大多数奥陶系原油具有C2820S和C2820R相对于C2620S,C2620R+C2720S和C2720R优势的三芳甾分布特征,而塔河油田东部九区T904和塔东地区TD2井原油具有相反的特征；以LN46、TZ12等井为代表的中上奥陶统泥灰岩具有类似于塔河油田奥陶系原油的三芳甾分布特征,而以KN1、TD2等井为代表的寒武系黑色泥岩具有类似于T904和TD2井原油的三芳甾分布特征；可将塔河油田奥陶系原油划分为来自寒武系烃源岩的原油族群和来自中上奥陶统烃源岩的原油族群两个成因类型；判识寒武系烃源层油气来源的三芳甾地球化学判识标准为C26/C28 20S＞0.30,C27/C28 20R TAS＞0.75；中上奥陶统烃源层油气来源的三芳甾判识标准为C26/C28 20S＜0.30,C27/C28 20R TAS＜0.30.
展开▼
