塔北轮南地区油气成因与成藏探讨

通过对塔里木轮南地区不同层位、不同部位原油烃类化学组成的剖析 ,认为该区原油至少可分为两种不同的成因类型 ,可能存在多成藏期次 .三叠系、侏罗系原油化学组成与分布均一 ,其与轮南中西部断垒、桑塔木断垒西部奥陶系原油性质极为接近 ,以低分子量正构烷烃占优势 ,重排补身烷与重排甾烷、三环萜烷及Ts不甚发育 ,C2 3 三环萜烷为主峰 ,相对低值C2 7/C2 9甾烷等为特征 (第I类 ) ,奥陶系原油还具有中性氮化合物含量高的特征 ;以两断垒带东部石炭系、奥陶系为代表的原油以高值饱芳比、正构烷烃主峰碳后移、高含量C15 重排倍半萜与重排甾烷、低含量中性氮化合物、C2 0 三环萜烷为主峰、相对高值C2 7/C2 9甾烷、甾烷 /藿烷、Ts/ (Ts+Tm)、三环萜 /五环萜值等为特征 (第Ⅱ类 ) .轮南地区原油类型不同由主系油源不同所致 .烃类与非烃类运移指标反映奥陶系、石炭系原油具有自西而东的运移趋势 ;三叠系原油具有不太明显的由北而南的运移趋势 .烃类指标反映三叠系、侏罗系与同类型奥陶系原油间的运移分馏效应不太明显 ,其可能来自相同的烃源岩但成烃与成藏期不同

Formation and accumulation of oil and gas in Lunnan area, Talimu Basin

The hydrocarbons compositions of the crude oils from the different horizons and different positions of Lunnan area are analyzed, and it is held that in this area, there are the crude oils of two genetic types at least. One is composed of Ordovician oils in the west of Lunnan and Sangtamu structural belts and Ordovician oil and a part of Carboniferous oil near the two structural belts, which are characterized by the predominance of alkanes of low molecular mass, lower content of rearranged drimane and sterane, tricyclic terpanes and Ts (18((H) -trisnorhopane), the maximum peak of C_(23)-tricyclic terpane among tricyclic terpanes, and low ratios of C_(27)-/C_(29)-sterane. The Ordovician oils are also characterized by high content of nitrogenic compounds. Another is Ordovician oils in the east of Lunnan and Sangtamu structural belts, and Carboniferous and Ordovician oils near the two structural belts, which are characterized by higher ratios of saturate/aromatic hydrocarbons, C_(27)/C_(29) steranes, steranes/hopanes, Ts/(Ts+Tm)and tricyclic terpanes/pentcyclic terpanes, high contents of rearranged drimanes and steranes, low content of nitrogenic compounds, and maximum peak of alkane moving afterward. Triassic and Jurassic oils discovered in Lunnan area are classified as the first oil family because of similar sterane and terpane fingerprints. Comprehensive studies show that different source rocks cause the two types of the oils. It is suggested the Triassic and Jurassic oils are likely not formed in the same period as the Ordovician oils with similar genesis for no migration fraction effects are observed based on the parameters of tricyclic terpane/pentcylclic terpanes etc. Obvious migration effects from the west to the east and slight migration effects from the north to the south are observed in Ordovican and Carboniferous oils with similar genesis as well as Triassic oils, which indicates oil migration trend of the area.