Evaluation of residual oil content, composition, and evolution of marine shale from the Middle Ordovician Pingliang Formation, Erdos Basin, China

A grain-based microscale sealed vessel pyrolysis method to a whole rock sample from Pingliang (PL) marine shale was used to investigate the residual oil contents, fractional compositions and evolutions at different temperatures and maturities. The maximum residual oil of PL marine shale can reach 116.86 mg/g TOC. In oil window, PL marine shale residual oil is mainly composed of saturates, aromatics, and resins, but less asphaltenes showing higher shale oil prospective. In wet and dry gas windows, its residual oil is mainly made up of saturates, resins, and asphaltenes, showing higher gas generation potential at high maturities.