Separation and characterization of squalene and carotenoids derived sulfides in a low mature crude oil

Abstract

An unusual distribution on molecular composition of organic sulfur compounds (OSCs) was found in a crude oil from the Bohai Bay Basin (China) that contains negligible thiophenic sulfur compounds but abundant in C30 and C40 sulfides. The sulfides were separated from the crude oil by methylation/demethylation method and characterized by gas chromatography-mass spectrometry (GC–MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). A novel series of C30 OSCs that possess a bio-precursor of squalene were identified. The lexene (C33) derived OSC was also identified for the first time in the crude oil, which indicates a strictly anaerobic condition during the early diagenesis of the source rock. Most C40 sulfur compounds were verified to be sulfides having a β-carotane skeleton. Most identified sulfides possess a thiolane group with a quaternary carbon atom or a thiane group within their carbon skeletons.