Simulation experiments on the generation of organic sulfide in the Shengli crude oil

Shengli crude oil sample was investigated using a comprehensive method to characterize and identify the formation and distribution of the organic sulfide. A full compositional model uses an autoclave on the system of Shengli crude oil and magnesium sulfate under high temperature and pressure conditions. Gas chromatography (GC) and microcoulometry were used to describe characteristics of gas phase products. The results show that the ratio of methane in the gas composition and the content of hydrogen sulfide improved by increasing temperature, which suggested that with the reaction temperature growing, the extent of the thermochemical sulfate reduction (TSR) process is deepened gradually. With the analysis of oil phase products by fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and gas chromatography-pulsed-flame photometric detector (GC-PFPD), the distribution of organic sulfide can be detected in detail. The contents of organic sulfide especially as mercaptan, sulfoether and thiophene were detected by GC-PFPD. Through FT-ICR MS, sulfide species were characterized by class, type, and carbon number. The results show that, with increasing temperature, the content of mercaptan, became dramatically dominated, sulfoether and thiophene gradually increasing too. Types of sulfur compounds in the oil phase identified by FT-ICR MS are mainly S1, S2, N1S1, O1S1 and O2S1. The S1 species are the most dominated. All of the results suggest that, as the reaction temperature is growing, the evolution process of organic sulfur compounds is originally changed from thiophene series to the benzothiophene series gradually and then to dibenzothiophene series. The products of solid phases were analyzed by FT-IR and XRD. The results show that the content of sulphur in magnesium sulphate decreased. This fenomenon demonstrated transformation of inorganic sulfur compounds into organic sulfur compound. According to the reaction model, the calculated activation energy is 57.91 kJ mol−1 and the frequency factor A is 0.21 s−1.