GEOCHEMICAL CHARACTERISTICS OF AROMATIC HYDROCARBONS OF CRUDE OILS FROM ORDOVICIAN RESERVOIR IN THE TAHE OILFIELD

Aromatic hydrocarbons as the important components of crude oils are widely used in estimating depositional environment of source rooks and maturity of oil.The maturity and migration information of Ordovician oil in the main area of Tahe Oilfield can not be exactly inferred by the normal biomarker parameters of saturated hydrocarbon because of strong biodegradation,but it can be indicated by the aromatic hydrocarbon because of its good restrain to biodegradation.The GC-MS analyses of aromatic hydrocarbon indicates the Ordovician oils have rich naphthalene,phenanthrene and dibenzothiophene,but poor dibenzofuran and diphenyl,which demonstrated that all Ordovician oils come from the same source rocks.The environment of parent material is reduction-strong reduction.The maturation degree of Ordovician oil increases from west to east,from north to south,which is proved by alkylnaphthalene index,DBT and triaromatic steroid.As a result,Manjiaer Depression in the southeast of Shaya uplift belt is regarded as the main hydrocarbon kitchen of Ordovician gas and oil.