Geochemical characteristics and source of crude oil of Cretaceous Tongbomiao Formation in Urxun Depression,Hailar Basin
The Cretaceous Tongbomiao Formation in Urxun Depression of the Hailar Basin has achieved explora-tion breakthroughs,it is a new layer with great potential for resources.On the basis of dividing the Tongbomiao Formation into three layers,the abundance,type,and maturity of the source rocks in each small layer of the trough in the study area were evaluated trough analysis and laboratory data such as TOC,pyrolysis,Ro,group composition,chromatography,color quality,and carbon isotopes.The geochemical characteristics of the crude oil in the Tongbomiao Formation were analyzed in depth,and the source of the crude oil was quantitatively calcu-lated,and the favorable exploration direction was predicted.The results show that:(1)The overall development of the Tongbomiao Formation in Urxun Depression is a medium source rock with a TOC mean of about 1％,mainly of type Ⅰ-Ⅱ2.The mudstone of the Tongbomiao Formation(t2)is source rock of type Ⅰ,and the R in the trough is 0.6％-1.5％,which is in the mature stage.(2)The crude oil of the Tongbomiao Formation in the research area can be divided into three categories.The crude oil of the third section of the Tongbomiao Formation(t3)in north Urxun,the crude oil of the third section of the Tongbomiao Formation(t3)in south Urxun,and the crude oil of the second section of the Tongbomiao Formation(t2)in south Urxun.T3 crude oil of North Urxun has high saturation hydrocarbons content,high ratio of Pr to Ph,heavy carbon isotopes of saturated hydrocarbons and aro-matic hydrocarbons,and high content of C27 rearranged steranes and tricyclic terpenes.T3 crude oil of South Urxun has high saturation hydrocarbons content,light carbon isotopes of saturated hydrocarbons and aromatic hydrocar-bons,and moderate content of C27 rearranged steranes and tricyclic terpenes.T2 crude oil of South Urxun has low saturated hydrocarbon content,high OEP value,light carbon isotopes of saturated hydrocarbons and aromatic hydrocarbons,and low content of C27 rearranged steranes and tricyclic terpenes.(3)All three types of crude oil in the Tongbomiao Formation are binary mixtures of the mudstone of first section of the Nantun Formation(n1)and the mudstone of the Tongbomiao Formation.The first type of crude oil is closer to the source rock of n1 in north Urxun,and the mixed source ratio calculation shows that its contribution from the mudstone of n1 in north Urxun is 62.9％.The second type of crude oil is closer to the source rock of n1 in south Urxun,and the mixed source ratio calculation shows that its contribution from the mudstone of n1 in south Urxun is 59.5％.The third type of crude oil is closer to the source rock of t2 in south Urxun,and the mixed source ratio calculation shows that its contribution from the mudstone of t2 in south Urxun is 75.4％.(4)The dark mudstone with a depth of over 200 m is developed in the north Urxun and south Urxun troughs,which can be used for exploration of oil reservoirs of t3 with mainly external hydrocarbons supply and oil reservoirs of t2,respectively.The north Urxun trough and east Urxun slope zone can be regarded as favorable areas for further exploration of the Tongbomiao Formation in Urxun Depression.
evaluation of source rocksoil and source correlationcontribution ratiocarbon isotopegeochemical characteristicsTongbomiao FormationCretaceousUrxun DepressionHailar Basin
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维普
