A Discussion on Petroleum Migration in the Lunnan Oilfield of Xinjiang Based on Nitrogen Compounds
Wang Tieguan Li Sumei Zhang Aiyun Zhang ShuichangUniversity of Petroleum, Beijing, 102200) Geology Survey of Canada, CalgaryChina University of Geosciences, Beijing, 100083 Institute of Petroleum Exploration and Exploitation, Beijing, 100083
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.
【CateGory Index】： P618.13
【CateGory Index】： P618.13