Abstract
TOC and Rock-Eval analyses were conducted on cutting samples (111) from various Paleogene formations (Ed3, Es1 and Es3) in the Qinnan sag. The average values of total organic carbon (TOC) content are 1.11, 1.64 and 2.29% for Ed3, Es1 and Es3 samples, respectively. The Es1 and Es3 source rocks are of relatively high S2 values, ranging from 0.42 to 46.01 and 2.46–61.01mgHC/Rock, respectively. The Ed3 rocks have lower generative potential with S2 values ranging from 0.9 to 9.3 mg HC/g Rock. Moreover, Tmax values indicate that these source rocks are sufficiently mature for petroleum generation. These analyses suggest that Es1 and Es3 are potential source rocks for oils produced from the QHD29 field.Eighteen oil samples from the QHD29 field were analyzed by GC and GC–MS; and 84 QHD29 oil (13) and source rock (71) samples were employed for stable carbon isotope analysis. Based on hierarchical cluster analysis of selected biomarker parameters, the QHD29 oils can be identified into two groups. Group I and group II oils are both derived from the Eocene Shahejie Formation (Es1 and Es3), displaying remarkable difference to the Oligocene Ed3-derived oils. In comparison with Group II oils, Group I oils display relatively low 4MSI and high G/H, indicating that group I oils have important contributions from Es1 source rock, deposited under more alkaline-saline environment. Moreover, these two group oils can be clearly separated by δ13C values, and Group I oils are isotopically lighter than Group II oils. Difference occurs in stable carbon isotope distribution between Es1 and Es3 source rock extracts as well, and Es1 source rocks are characterized by relatively light carbon isotopic composition. This implies that Group I oil shares more Es1-derived oil, which is consistent with the results of biomarker analysis.
Published Version
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