Relative Abundance and Parameters of Aromatic Hydrocarbon Series in Retained Oil

The geochemical significance of phenanthrene series compounds within tricyclic aromatic hydrocarbons (TAHs) remains controversial, particularly regarding the relative control of thermal maturity and depositional environment. This study focused on variations in phenanthrene series parameters during thermal evolution and their controlling mechanisms. Lacustrine shale samples from the Shahejie Formation (Es₄) of well X in the Bohai Bay Basin were subjected to closed-system pyrolysis using a DK-III thermal simulation apparatus at seven temperature points (275 ℃–450 ℃) for 48 h. Aromatic fractions of expelled oil were analyzed via gas chromatography-mass spectrometry (GC–MS) to determine the distribution and evolution of polycyclic aromatic hydrocarbons (PAHs).