Characteristics and hydrocarbon potential of source rocks in the Late Permian Linxi Formation, northern Songliao Basin

Thick sequences of dark mudstone of the Upper Permian Linxi Formation are developed in northern Songliao Basin. To assess the hydrocarbon potential of this formation in the area, multiple geological survey wells were drilled and encountered a large suite of dark mud slate. Geochemical analyses, including source rock geochemistry and saturated hydrocarbon gas chromatography-mass spectrometry (GC-MS), were conducted to evaluate its geochemical characteristics, organic matter type, and depositional environment. The results indicate that the source rocks exhibit relatively high organic matter abundance, rating as fair to good. The organic matter is predominantly Type Ⅱ and has reached a high to over-mature thermal evolution stage. The average illite crystallinity is 0.54(>0.42), indicating a diagenetic stage without metamorphism. Biomarker data point to a strongly reducing to reducing depositional environment, favorable for organic matter preservation, with a mixed organic input derived from higher plants and lower aquatic organisms such as algae. The source rocks in the Upper Permian Linxi Formation have entered the gas-generation window, representing a promising interval for deep hydrocarbon exploration in the Songliao Basin and offering potential for shale-gas exploration.