Charactristics of the Biomarkers from Nonmarine Crude Oils in China—A Review

The present paper deals with the biomarker characteristics of crude oils and source rocks from different environments(fresh,fresh-brackish and salt waters)of nonmarine depositional basins of different ages in China.Their characters are summarized as follows:1)Souce rocks and crude oils derived from fresh-water lacustrine facies have an odd/even predominance of n-alkanes and high pristine/phytane ratios.Oils from the fresh-water lacustrine facies differ from typical marine oils in the relative contents of total steranes and terpanes,the concentrations of hopanes and organic sul-phur compounds and the values of methylphenanthrene indices and C,H,S stable isotopes.2)The source rocks and crude oils derived from saline lacustrine facies possess an even/odd predominance of n-alkanes and high phytane/pristine ratios.There are also some differences between saline lacustrine oils and freshwater lacustrine oils in the concentrations of steranes,tricyclic terpanes and organic sulphur compounds,as well as in the values of methylphenanthrene indices and C,H,S stable isotopes.3)Oils derived from fresh-brackish water lake facies differ from oils from fresh-water lacustrine or samline lacustrine environments in respect of some biomarkers.According to the various distributions of these biomarkers,a number of geochemical parameters can be applied synthetically to differentiating and identifying the nature of original depositional environments of crude oils and source rocks and that of organisms-primary source materials present in those environments.

Characteristics of the biomarkers from nonmarine crude oils in China — A review

The present paper deals with the biomarker characteristics of crude oils and source rocks from different environments (fresh, fresh-brackish and salt waters) of nonmarine depositional basins of different ages in China. Their characters are summarized as follows: 1 ) Source rocks and crude oils derived from fresh-water lacustrine facies have an odd / even predominance of n-alkanes and high pristane / phytane ratios. Oils from the fresh-water lacustrine fecies differ from typical marine oils in the relative contents of total steranes and terpanes, the concentrations of hopanes and organic sulphur compounds and the values of methylphenanthrene indices and C, H, S stable isotopes. 2) The source rocks and crude oils derived from saline lacustrine fecies possess an even / odd predominance of n-alkanes and high phytane / pristane ratios. There are also some differences between saline lacustrine oils and freshwater lacustrine oils in the concentrations of steranes, tricyclic terpanes and organic sulphur compounds, as well as in the values of methylphenanthrene indices and C, H, S stable isotopes. 3) Oils derived from fresh-brackish water lake facies differ from oils from fresh-water lacustrine or saline lacustrine environments in respect of some biomarkers. According to the various distributions of these biomarkers, a number of geochemical parameters can be applied synthetically to differentiating and identifying the nature of original depositional environments of crude oils and source rocks and that of organisms — primary source materials present in those environments.