Oil-Source Correlations And Oil Migration Of Triassic-Jurassic In Eastern Fukang Depression

The eastern Fukang Depression of Junggar Basin is characterized by diversified hydrocarbon properties and extremely complex oil-source relations.So that large disputes in hydrocarbon sources have existed for a long term.Oil-source correlations analyses were systematically carried out based on the carbon isotopes and biomarker characteristics.On the basis of clarifying the main reservoir sources of crude oil,oil migration direction were clarified by Nitrogenous Compounds.Four groups of source rocks including Jurassic source rock,Triassic source rock,Permian source rock and Carboniferous source rock exist in the study area.The Jurassic source rock is characterized by high Pr/Ph,low carotene and low gammacerane,and could be divided into mudstone and coal.The Triassic source rock is characterized by medium Pr/Ph,low or none diasterane and sterane,and high Ts/Tm.The Permian source rock is characterized by medium Pr/Ph,high gammacerane and high carotene.The Carboniferous source rock could be divided into two types,while the tuffite on Bashan Formation of Carboniferous is characterized by low Pr/Ph and high gammacerane,and the dark mudstone on Bashan Formation of Carboniferous is characterized by high Pr/Ph and low gammacerane.The crude oil of Triassic to Jurassic in the study area can be divided into four categories.The first type of crude oil was featured by light carbon isotopes,low – medium Pr/Ph ratio,high carotene and high gammacerane.The second type of crude oi was possessed with light carbon isotopes also,medium Pr/Ph ratio,high Ts/Tm ratio and low gammacerane.The third type of crude oil was characterized by heavy carbon isotopes,high Pr/Ph ratio,tiny gammacerane and little carotene.The characteristics of carbon isotopes and biomarkers of the fourth type of crude oil was among the first three types.By means of the comparison of biomarker characteristics and carbon isotope between crude oil and source rock,this paper considered that the first type of crude oil was similar with source rock on Pingdiquan Formation of Permian in terms of features,it was generated by source rock of Permian;The second type of crude oil had a good affinity with source rock of Triassic;The characteristics of the third type of crude oil was similar with Jurassic argillaceous source rock,it came from Jurassic argillaceous source rock;There were similarities and differences between the forth type of crude oil and Permian Triassic and Jurassic mudstones.it was mixed generated by three types of source rocks.By nitrogen transport index,the study of part reservoirs in research area came to the conclusion that the main filling direction of north reservoirs in Cainan oil field was from southwest Fukang Depression to Cainan oil field.The oil entered Cainan oil field east block through the southwest and south boundary of Cainan oil field.Then it kept on filling migrating and accumulating to north and northeast direction.The oil arrived at Cai 8 well area at last.