The characteristics and significance of biomarker compounds in the Permian Lucaogou Formation hydrocarbon source rock on the southern margin of the Junggar Basin

The accuracy of the evaluation result for the surface outcrop hydrocarbon source rock in the lower exploration degree area by using the traditional method is doubtful. Based on a study of such biomarkers as GC and GCMS, the authors evaluated the sedimentary environment, source rock kerogen type and maturity of the Permian Lucaogou Formation on the southern margin of the Junggar Basin.The Pr/Ph ratio of the hydrocarbon source rocks with an average of about 1 shows weak oxidation and weak reduction of sedimentary environments. The average value 0.15 for the gammacerane index and the high content of pregnanes indicate that the sedimentary environment was of high salinity, which was favorable for the enrichment of organic matter to a certain salinity for a weak redox sedimentary environment. The sterane C₂₉20S(20S + 20R), C₂₉αββ/(αββ + ααα) and C₃₁ hopanes αβ22S/(22S+22R) values and some maturity parameter analysis show that the source rocks in the study area remain in the low mature to mature stage. Emergence of tetracyclic terpane organic matter in source rocks and small regular sterane/17α(H)-hopane ratio parameters show that the early organic matter of the source rock was subjected to a certain degree of biodegradation.