Differentiating depositional environments and maturity of crude oils using GC-AED benzothiophenic spectra

Organosulfur compounds of crude oils and light oils (condensates), collected from ten Chinese petroleumbearing basins and representing different sedimentary environments, were analyzed and identified using a newly-developed GC-AED technique. The results show that the distributions of organosulfur compounds of crude oils from different sedimentary environments are of obvious difference. The crude oils from marine carbonates are rich in organosulfur compounds and those from the source rocks in an ocean-land interchanging facies and a littoral facies have a high abundance of organosulfur compounds, while no or less organosulfur compounds of crude oils from a fresh-water lacustrine facies and a swamp facies were detected in the detectable abundance range of the instrument. This analysis gives a new effective method for oil-source correlation. We also tried to relate the various parameters of benzothiophenic compounds of crude oils with the methane carbon isotope of associated natural gases to discuss the thermoevolutionary degree of crude oils and natural gases.