Abstract
Accurate prediction of hydrocarbon composition is essential for evaluating hydrocarbon quality and recoverability. However, research on pre-drilling prediction of subsurface fluid phase behavior for medium to highmaturity shale oil remains limited. Given that compositional kinetics can effectively evaluate and predict the compositional evolution of shale oil and gas reservoirs, this study focuses on the first member of the Qingshankou Formation (K2qn1) in the Songliao Basin. Based on gold-tube hydrocarbon generation simulation experiments, a compositional generation and cracking kinetic model, and a methane correction model derived from pressurized coring, we accurately predicted the phase behavior of medium to high maturity shale oil in the Songliao basin. The results indicate that the difference in methane content between natural and experiment samples is not caused by migration-induced fractionation. Instead, it is likely due to the relatively high temperature and pressure in the experiments, which may cause hydrocarbon fluids to enter a single gas phase prematurely, thereby suppressing methane generation. The discrepancy between the corrected predicted phase diagram and the PVT experiment phase envelope is attributed to light hydrocarbon loss during PVT experiments, as supported by phase envelope simulations under varying degrees of light hydrocarbon depletion. The predicted phase diagram shows that the present day Gulong Sag is a volatile oil reservoir and that a single episode of hydrocarbon migration and fractionation occurred around 66 Ma. This study provides a basis for assessing the phase behavior, mobility, and recoverability of medium- to high-maturity shale oil and gas reservoirs under geological conditions.
Paper Information:
Bo Song, Fangwen Chen*, Shuangfang Lu**, Min Wang, Ming Li, Jinbu Li, Nengwu Zhou and Wenbiao Li, 2026. Phase behavior prediction of medium to high maturity shale oil in the Songliao Basin: Insights from compositional generation kinetics. Journal of Analytical and Applied Pyrolysis,194,107547-107547.https://doi.org/10.1016/J.JAAP.2025.107547.
