Molecular and experimental study on hydrogen sulfide formation mechanism during Chang 7 type-II oil shale kerogen pyrolysis

Hydrogen sulfide is a volatile toxic gas associated with oil and gas production, causing corrosion to surface equipment such as wellbores and doing harm to the environment. This study aims to investigate the formation mechanism of hydrogen sulfide during the pyrolysis process of Chang 7 type-II oil shale kerogen. XPS spectra are obtained with the usage of Kratos Analytical Axis UltraDLD to analyze the occurrence forms of hybrid atoms. S 2p XPS spectrum and its fitted curves are gained from full spectrum wide spectrum scanning and narrow spectrum scanning of the sulfur element. The pyrolysis characteristics and processes of kerogen with three initial structures under different temperatures are implemented with ReaxFF. The results of the hydrogen sulfide formation pathway are tracked. The sulfur element in Chang 7 II kerogen is mainly in the form of organic sulfur, with a molar ratio of 77.74%. The kerogen initial structure with fewer C--C bonds containing more H atoms has a higher oil yield. The desulfurization rate sharply increases with the increase in pyrolysis temperature. Hydrogen sulfide production is affected by sulfur-containing functional groups (aliphatic sulfur, aromatic sulfur, sulfoxide, sulfone). Hydrogen sulfide formation paths mainly include capturing H radicals through HS radicals and capturing H radicals through high sulfur to form-SH2-.

Automated summary

This study investigates the formation mechanism of hydrogen sulfide during the pyrolysis process of Chang 7 type-II oil shale kerogen. XPS spectra were obtained to analyze the forms of hybrid atoms, and the pyrolysis characteristics were studied using ReaxFF. The sulfur element in the kerogen was mainly in the form of organic sulfur, and the desulfurization rate increased with higher pyrolysis temperatures. Hydrogen sulfide production was influenced by various sulfur-containing functional groups.