Characteristics of source rocks and hydrocarbon resource prospects of Permian Linxi Formation in northern Songliao Basin

In order to explore the oil and gas resource prospects in the Carboniferous–Permian strata in northern Songliao Basin, geological survey boreholes (HFD 1 and HFD 2) were drilled in the area, and thick dark mudstone and slate of the Upper Permian Linxi Formation were encountered. Source rock geochemistry analysis of the samples show that the organic matter abundance of the Upper Permian Linxi Formation source rock in the north of Songliao Basin is high, which belongs to medium to good source rock. The organic matter belongs to type Ⅱ, and it is in the evolution stage of highly mature to over mature. The Pr/Ph ratios of the source rocks range from 0.16 to 0.93, with an average of 0.53. The phytane predominance is obvious, and indicates a strong reduction to reduction sedimentary environment, which is conducive to the preservation of organic matter. Pr/nC₁₇, Ph/nC₁₈ and C₂₇–C₂₈–C₂₉ regular steranes indicate that the organic matter was derived from a mixture of vascular plants and aquatic organisms such as algae, and is mainly contributed by phytoplankton. Through comprehensive analysis, it is considered that the source rocks of the Upper Permian Linxi Formation in northern Songliao Basin have entered the gas generation stage and have shale gas exploration prospects.