A Comparison of the Geochemical and Stable Carbon Isotopic Characteristics of Extracts Obtained from Source Rocks Using Different Solvents

The choice of the solvent to use in the Soxhlet extraction process dramatically affects the extraction yield. In this work, ten hydrocarbon source rocks were extracted using different solvents, and the chemical compositions of their products were analyzed to assess the extraction efficiency and the differences between fractions. The results indicated that using a mixed dichloromethane (DCM) and methanol (MeOH) reagent instead of the traditional chloroform (TCM) reagent can improve extraction efficiency for all rock types except for coal. The improvement in extraction efficiency was attributed to the contributions of non-hydrocarbon compounds (NOSs). A comparative study of the biomarkers of the fractions extracted using different reagents showed no significant differences in geochemical parameters, such as ∑C22−/∑C23+, Pr/Ph, Pr/nC17, Ph/nC18, OEP1, OEP2, CPI, and hopane distribution. Additionally, the carbon isotopic compositions of the fractions varied by less than 1‰, indicating that the TCM and DCM: MeOH regents did not significantly affect the results of the oil–source correlation.