Hydrocarbon generation kinetics and expulsion efficiency evaluation of lacustrine source rocks: A case study of the Qingshankou Formation in the Songliao Basin

The lacustrine source rocks of the Qingshankou Formation in the Songliao Basin represent an important tight oil potential play in Northeast China, and their hydrocarbon generation kinetics and expulsion efficiency are crucial for resource potential evaluation and exploration deployment. Based on gold-tube pyrolysis experiments and organic geochemical analyses, this study systematically investigates the hydrocarbon generation potential, kinetic parameters, and expulsion efficiency of Type I kerogen source rocks from the Qingshankou Formation. The results indicate that the maximum hydrocarbon generation yield reaches approximately 600 mg/g·TOC, with the main generation stage occurring at EasyRo values of 0.5%–1.2%. Kinetic analysis shows an average activation energy of 218.8 kJ/mol, with heavier fractions generally exhibiting lower activation energies than lighter fractions. Combined with thermal history modeling of Well YX58 and geological model reconstruction, the current hydrocarbon conversion rate of the formation is estimated at 40%–60%, corresponding to an actual hydrocarbon yield of 240–360 mg/g·TOC and an expelled hydrocarbon yield of about 150–200 mg/g·TOC, with an expulsion efficiency of approximately 60%. In summary, the Qingshankou Formation source rocks possess significant tight oil potential, and the established methodological framework for hydrocarbon generation kinetics and expulsion efficiency evaluation provides theoretical and technical support for the quantitative assessment, favorable area prediction, and exploration target optimization of lacustrine source rocks.