Abstract
Predicting the full compositional makeup of subsurface oil and gas reservoirs is crucial for evaluating their fluidity, phase behavior, and recoverability, but effective techniques remain scarce. Given that n-alkanes (n-C) are among the most significant components of hydrocarbons generated at certain maturities, this study conducted gold-tube pyrolysis experiments on source rocks from the Songliao Basin. These experiments quantified and analyzed the full composition of n-alkanes in the samples. Based on this data, a comprehensive evaluation of n-C composition under geological conditions was conducted using various analytical methods, and a chemical kinetic model for the generation of individual n-C components was established and validated. By integrating the Sedimentary burial and thermal history of the target area, this model quantitatively assessed and predicted the distribution and evolution of n-C composition at different stages of geological evolution. Additionally, the PVTsim software was used to predict the subsurface phase behavior and evolutionary trends of Gulong shale oil and gas. The results revealed inconsistencies in methane composition between n-C components derived from pyrolysis experiments and those from naturally evolved samples. An empirical correction based on pressure-core component data effectively addressed this discrepancy. The corrected compositions highlighted that methane has the highest activation energy, with the activation energy and frequency factor decreasing as the carbon number or molecular size of n-alkanes increases. These results, combined with geological conditions, identified the current phase behavior of the reservoir as a gas condensate state. This research lays a foundation for advancing the prediction of full hydrocarbon compositions and provides a basis for assessing the phase behavior, mobility, and recoverability of subsurface oil and gas under geological conditions.
Paper Information：
Bo Song, Haitao Xue, Shuangfang Lu*, Min Wang, Fangwen Chen, Jinbu Li and Nengwu Zhou, 2025, Simulation experiment evaluation and chemical kinetics prediction of the composition of n-alkanes components. Fuel, https://doi.org/10.1016/j.fuel.2025.135620.
