Characteristics of aromatic hydrocarbons and its stable carbon isotope compositions in crude oils

Aromatic hydrocarbons contain plenty of geochemistry information as ubiquitous constituents of crude oils.Characteristics of aromatic hydrocarbons and its stable carbon isotope compositions are usually used to assess the source and thermal maturity.In order to find out the aromatics geochemical index and the stable carbon isotope compositions which are suitable for oil samples identification.The composition of aromatics and their stable carbon isotope composition in different areas were studied.In this paper, relative contents, characteristic ratios and stable carbon isotope compositions of aromatic hydrocarbons in crude oils were determined from different areas.In terms of aromatic hydrocarbons relative contents, seven kinds of crude oils have shown their own features.From the characteristics of the ratios of aromatic hydrocarbon in crude oil, the maturity parameters (MNR、TNR1、TNR2、MPR、MPI1、MPDF1 and MPDF2) reflected high maturity of all the crude oil, other parameters, such as DNR1、DNR2 and TNR4, revealed the organic source and biodegradation of crude oil and other information.From the one-way analysis of variance (ANOVA) results of aromatics feature ratios, it was found that the differences between DNR1, DNR2 and TNR4 in different crude oils were more obvious than those of MNR and MPI1. From the compositions of stable carbon isotope of aromatic hydrocarbons in crude oils, crude oils between the various regions have the differences which the Brazil crude oil enriched ¹³C while of Oman crude oil and Venezuelan crude oil showed depleted ¹³C.Plots of aromatic hydrocarbon ratios versus δ¹³C values of dimethylnaphthalene and phenanthrene were constructed to discriminate crude oils from different areas.The results demonstrate that this method can distinguish different kinds of crude oisl more effectively.Finally, principal component analysis (PCA) were applied to the compositions of stable carbon isotope of aromatic hydrocarbons data sets in order to evaluate their different features.Indeed, there are diverse stable carbon isotope compositions characteristics and clear distinction among these crude oils.the use of aromatics stable carbon isotopic compositions of diverse oils can be applied on the identification of oil samples source.