Fractionation of hydrocarbon generation induced by organic-mineral interactions in fine-grained sediments

Abstract

Hydrocarbon (HC) generation is closely related to the properties of organic matter (OM), however, rare concern has been paid to the exact influence from its contiguous minerals in fine-grained sediments. Here we employed the physical-chemical sequential treatments and Rock-Eval pyrolysis and pyrolysis gas chromatography determination of shale samples to address the issue. Our results show that the OM type, HC generation potential, Tmax, gas-oil ratio, and ratio of light to heavy HCs (∑C14−/∑C15+) of shales are regularly successively changed after sequential treatments. These successive changes suggest that OM with strong interaction strength with minerals has poor OM quality and HC generation potential, and the strong strength of organic-mineral interactions (OMIs) can decrease the geothermal requirement for HC generation and move forward the onset timing of HC generation. Light and heavy HCs are mainly generated from the tight and weak mineral-combined OM, respectively, and more light or mobile oil can be found if a source rock has experienced the stronger OMI strength. Our study reveals the important influence of different OMI strengths on the fractionation of HC generation in fine-grained sediments, which is significant to improve the understanding of petroleum resource assessment and the carbon cycle.