Studying of shale organic matter structure and pore space transformations during hydrocarbon generation

Abstract

In this study, we focus on organic matter structure and its interaction with the pore space of shales during hydrocarbon (HC) generation. Rock samples collected from Domanic horizon of South-Tatar arch were heated in the pyrolyzer to temperatures closely corresponding to different catagenesis stages. X-ray microtomography method was used to monitor changes in the morphology of the pore space and organic matter structure within studied shale rocks. By routine measurements we made sure that all samples had similar composition of organic and mineral phases. All samples in the collection were grouped according to initial structure and amount of organics. They were processed separately to: (1) study the influence of organic matter content on the changing morphology of the rock under thermal effects; (2) study the effect of initial structure on the primary migration processes for samples with similar organic matter content. After heating the morphology of altered rocks was characterized by formation of new pores and channels connecting primary voids. However, it was noted that the samples with a relatively low content of the organic matter had less changes in pore space morphology, in contrast to rocks with a high organic content. Second part of the study also revealed significant differences in resulting pore structures depending on initial structure of the unaltered rocks and connectivity of original organics.