应用含氮化合物探讨新疆轮南油田油气运移

A Discussion on Petroleum Migration in the Lunnan Oilfield of Xinjiang Based on Nitrogen Compounds

新疆轮南地区原油中含有丰富的吡咯类含氮化合物,不同层系或相同层系原油中吡咯类化合物总体分布型式相似,但绝对丰度与相对分布差异明显,显示显著的油气运移分馏效应。分析结果表明,奥陶系原油与三叠系、侏罗系原油具不同成藏期次与油气运移方向,奥陶系、石炭系原油运移方向为自西而东,主要注入点在轮南、桑塔木断垒带的西南侧;三叠系、侏罗系原油主要通过断层运移、聚集成藏,在后期构造演化过程中发生侧向分配调整。吡咯类化合物指示的油气运移信息反映了轮南地区地层的发育与构造演化史。

Non-hydrocarbon technique has attracted more and more attention in petroleum exploration and exploitation. It has been proved that pyrrolic nitrogen compounds, a kind of non-hydrocarbon fraction, could be used as effective ' tracers' in oil migration and as parameters in evaluating the quantity of migrated oil. These compounds are generally of polarity, and so will take part in the interaction of the oil-water-rock system, which is the reason why the compounds have an obvious migration fractionation effect.There are abundant pyrrolic nitrogen compounds in oils of the Lunnan area, and there are obvious differences in the absolute abundance and relative distribution of the compounds among oils of the same formation or different formations, showing significant oil-migration fractionation effects, the results indicate that: (1) Tertiary and Jurassic oils have possibly migrated for a longer distance than Ordovician and Carboniferous oils. This is shown by the following facts-, a) The average abundance of pyrrolic nitrogen compound f ractionation of Ordovician oil is 37. 65×10-6, generally higher than that of Tertiary and Jurassic oils (average value 13. 6×10-6) and Carboniferous oils (average value 10. 21×10-6); b) Tertiary and Jurassic oils are rich in highly alkyl-substituted carbazoles and benzocarbazoles relative to Ordovician and Carboniferous oils; c) Tertiary and Jurassic oils are rich in isomers in which nitrogen atoms are marked relative to Ordovician and Carboniferous oils. (2) According to the f ractionation of pyrrolic compounds, the position of the main changing point of Ordovician and Carboniferous oils is dominant in the southwest of the Lunnan and Sandamo faults, and the direction of oil migration is from west to east. Therefore, the source rock is inferred to be the lower indigenous strata in the Manjaer sag. (3) Similarly, it is suggested that the main charging point of Tertiary and Jurassic oils be at the higher location of the Lunnan fault. Oils accumulated in Tertiary and Jurassic formations have probably been regulated by tectonization lately. The oils are likely to migrate from northwest to southeast during the redistribution. (4) The results also show that part of the Carboniferous oil may be generated by the Carboniferous source rocks of the same horizon or nearby.