Open AccessPyrolytic Evidence for Unsubstituted Aromatics as Potential Oil–Oil/Source Correlation Indicators
Author(s) -
Yongxin Chen,
Xilong Zhang,
Yingqin Wu,
Yongqiu Xia,
Shengyin Zhang
Publication year - 2022
Publication title -
acs omega
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.779
H-Index - 40
ISSN - 2470-1343
DOI - 10.1021/acsomega.2c01908
Subject(s) - asphaltene , source rock , pyrolysis , maturity (psychological) , carbon fibers , chemistry , isotopes of carbon , phenanthrene , pyrolytic carbon , composition (language) , carbon number , vitrinite , mineralogy , environmental chemistry , organic chemistry , geology , total organic carbon , coal , paleontology , materials science , structural basin , composite number , composite material , psychology , developmental psychology , linguistics , philosophy , alkyl
Most oil source correlation indicators are invalid because of the high maturity of the deep marine strata. Thus, a suitable indicator with high thermal stability requires to be established. In this study, to understand the effect of thermal maturation on the carbon isotopic composition of unsubstituted aromatics, we performed a number of anhydrous thermal simulation experiments involving two typical Chinese shales (lacustrine and marine shales), their corresponding expelled oils, three crude oils, and their associated oil fractions, that is, saturates, aromatics, resins, and asphaltenes (SARA). The generated unsubstituted aromatics were examined in terms of molecular distributions and carbon isotopic composition. The results show that unsubstituted aromatics in different types of samples demonstrated similar variation characteristics. Phenanthrene can be formed continuously in 0.45%/0.55-2.30% R o (equivalent vitrinite reflectance), especially in the high-over maturity stage. However, their carbon isotope composition shows minor variations. The unsubstituted aromatic carbon isotopic information in source rocks can be preserved during the whole pyrolysis process. Their carbon isotopic values in source rocks and their corresponding expelled oils are extremely similar. Furthermore, no evident difference exists in the carbon isotopes of unsubstituted aromatics formed by crude oil and associated oil fractions. These results indicate that these types of parameters are suitable for oil-oil/source correlation in deep marine strata with high-over maturity.