GEOCHEMICAL SIGNIFICANCE OF ORGANIC SULFUR COMPOUNDS IN THE TARIM OILS

Aromatic fraction in more than 30 representative oils from the Tarim Basin are analyzed using GC/MS and gas chromatography with atomic emission detector(GC/AED).The analytical data shows that various kinds of oils are significantly different in concentration and distribution of organic sulfur compounds.Compared with the terrestrical oils,the marine oils are characterized by high amount of dibenzothiophenes(20%)and high dibenzothiophene/phenanthrene ratio(>0.35).By their higher values of these two para meters,Tazhong restricted bay(lagoon)oils can be distinguished from Tabei marine platform oils.These marine oils are poor in dibenzothiophene(DBT)compared to dimethylated homologs(DBDBT),reflecting the difference in oringinal organic matter and depositional enviroment.It is noted that the abundance benzothiophenes(BTs)relative to dibenzothiophenes(DBTs)varies in oils from different source rock lithologies,with oils derived from carbonate having higher value.MDR,a maturity indicator based on dibenzthiophenes in oils,is affected by mineral matrices,with coal derived oil having anomalous high value,and MDR₁ and MDR_2,3 are related to depositional environment and organic matter type.