Oil generation character of Mesoproterozoic Xiamaling formation during stepwise pyrolysis

Abstract

The exploration potential of Mesoproterozoic petroleum system has getting increasingly attention and the oil generation character of Mesoproterozoic source rock is still uncertain. To solve the problem, this study choose sample from Mesoproterozoic Xiamaling formation from north China, using the stepwise gold tube pyrolysis method to study the oil generation character and the composition of liquid pyrolysates, and choose sample from Mesozoic Yanchang formation in middle China as a comparison to study their differences in oil generation character. The results showed that oil generation window of Mesoproterozoic Xiamaling sample in this research was earlier and narrower, with an earlier oil generation peak, this maybe the result of the single source of organic matter and its labile chemical bound. Furthermore, mainly source of organic carbon, like cyanobacteria and acritarchs, were lack of lipid compounds, perhaps this could make the relative concentration of saturated hydrocarbon in liquid pyrolysates of Mesoproterozoic Xiamaling sample much lower than the Mesozoic Yanchang sample with the same kerogen type, nonpolar fraction of liquid pyrolysates in the oil generation window were mainly aromatic hydrocarbon. Maybe the results mean that although Mesoproterozoic Xiamaling formation is still in low maturity stage, it may has already started oil generation, and type of oil generated by Mesoproterozoic source rock in oil generation window may have significant difference from the Phanerozoic source rock.