Geochemical characteristics of aromatic hydrocarbon in crude oil and source rocks from Nai 1 block of Naiman depression,Kailu Basin

According to GC-MS analysis on 3 crude oil samples and 4 source rock samples from Nai 1 block,Naiman depression,characteristics of aromatic hydrocarbon of oil and source rock,sedimentary conditions and oil-source correlation,origin of oil were investigated as follows,there exists fundamental difference of geochemistry characteristics of aromatic hydrocarbon between Shahai formation source rocks and Lower Jiufotang formation source rocks.Source rocks from Shahai Formation are characterized by high abundance of naphthalene and phenanthrene,low abundance of aromatic sterane,relatively high abundance of 1,2,5-TMN and 1,2,5,6-TeMN,lower SF/OF,which can be inferred that source rocks from Shahai formation are mainly developed in limnetic and meta-oxidizing environment.Besides,some terrestrial organic matter may exist in native mater sedimentary.In contrast,source rocks and oils from the Lower Jiufotang Formation are characterized by high abundance of retene and pimanthrene,high SF/OF,a certain content of perylene,suggesting the diversity of source rocks and oil native materials,which were mainly developed in saltier and string reducing lacustrine environment.Aromatic parameters based on F1 and F2,methyl-DBT index,C2820S/(20S+20R)-Triaromatic steroid maturity parameters,Polycyclic aromatic hydrocarbons maturity parameters and Methylated-2-methyltrimethyltride-cylchromans(MTTC) indicate that source rocks and crude oil samples are mainly developed in low-middle mature thermal evolution stage.In addition,it can be inferred by the aromatic hydrocarbon characteristics,maturity parameters and comprehensive analysis of sedimentary environment that crude oil in Nai 1 block,Naiman depression,was mainly origined from Lower Cretaceous source rocks in Lower Jiufotang Formation.