Influence of thermal maturity on carbon isotopic composition of individual aromatic hydrocarbons during anhydrous closed-system pyrolysis

- Effect of maturation on δ13C of aromatics at relatively high temperature studied.
- δ13C of substituted aromatics showed enrichment as maturity increased (400-500 °C).
- However, δ13C of unsubstituted aromatics remained unchanged.
- δ13C of unsubstituted aromatics can be used as a tool for oil-source correlation.

Anhydrous closed-system pyrolysis experiments were conducted on the pure alkyl naphthalenes, n-alkanes and three crude oils at the highly to over mature stage in order to investigate compositional and isotopic changes of individual aromatic hydrocarbons during laboratory maturation. On the whole, aromatic hydrocarbons have better thermal stability than n-alkanes. While the carbon isotopic composition of substituted aromatic hydrocarbons exhibits a positive correlation with increasing thermal maturity, there is no significant fractionation in the carbon isotopic composition of unsubstituted aromatic hydrocarbons. This finding suggests that the carbon isotopic distribution of unsubstituted aromatic hydrocarbons can be used as an effective tool for oil-oil and oil-source correlation, especially for highly-over mature fields.