Indicative function of aromatic hydrocarbon in crude oil on depositional environment

Abstract：In order to study the indicative function of aromatic hydrocarbon in crude oil on the depositional environment,31 crude oil samples from Tazhong marine crude oil,Qaidam salt-lake facies crude oil,Jizhong Sag freshwater-lake facies crude oil and Turpan coal-derived oil basins were chosen for analysis by GC-MS.The results show that the abundances of cadalene and retene in aromatic diterpenoids indicateed the input degree of higher plants for the marine and salt-lake facies crude oils,a lower than 0.24% mass fraction of cadalene in naphthaline series and a lower than 1.21% mass fraction of retene in phenanthrene series.However,these two values are in the range of 0.12%-8.65% and 0.71%-20.03% in the freshwater-lake facies and coal-derived oils,respectively.Dibenzothiophene and dibenzofuran may be derived from the same precursor compound,but fluorenes have different genesis,and the value of dibenzothiophene/dibenzofuran ratio can reflect redox condition,whch is generally higher than 0.7 in the marine and salt-lake facies crude oils,0.48 in the freshwater-lake facies crude oil and lower than 0.14 in the coal-derived oil.The ratio of dibenzothiophene/phenanthrene is the most effective parameter to distinguish between marine（0.25） and terrestrial（0.2） crude oils.The salt-lake facies crude oil is characterized by high abundance of triaromatic steroid（triaromatic steroid series/aromatic hydrocarbon ratio 12%） and C26/C28（20S） triaromatic steroid ratio（0.45）.The coal-derived oil contains whole benzohopane series typically.