生物降解作用对辽河盆地原油中三芴系列相对组成的影响

借助于定量GC—MS分析技术，系统分析了一组取自辽河油田生物降解程度不同的原油芳烃馏分中三芴系列的组成特征。结果表明在生物降解过程中三芴系列化合物很容易遭受生物降解。母体三芴化合物在原油轻微降解阶段抗降解能力相似，其相对组成保持基本稳定，仍可指示沉积环境的性质；但进入中等及以上程度降解作用后，抗生物降解能力出现差异，相对组成发生变异，失去其环境意义。在甲基三芴系列中，甲基硫芴的抗降解能力强于甲基芴和甲基氧芴，降解速率不一致，组成特征不断变化，使甲基三芴系列相对组成不能指示沉积环境的性质。“三芴系列”被细菌消耗的速率不同，整个生物降解过程中其相对组成都在发生变化，因此对生物降解原油而言，无论其降解程度如何，“三芴系列”相对组成特征均不能有效的指示沉积环境的性质。

Influence of Biodegradation on the Compositional Characteristics of Fluorene, Dibenzofuran and Dibenzothiophene and Their Methyl Homologues in Crude Oils from the Liaohe Basin

The concentrations and the relative proportions of fluorene, dibenzofuran and dibenzothiophene and their methyl homolognes (Fs, OFs and SFs) in a series of crude oils with different degrees of biodegradation from the Liaohe basin have been quantified and studied by GC-MS. The results show that fluorene, dibenzofuran and dibenzothio-phene and their methyl homologuesare sensitive to biodegradation influence. In slightly biodegraded oils, the concen-trations of fluorene, dibenzofuran and dibenzothiophene without alkyl side chain decreased at almost similar rate, but their relative proportions could remain constant and could be used as depositional environment indicator. In moderate or severely biodegraded oils, because of the variation of their ability to resistant biodegradation, their relative propor-tions have been altered and lost their original geochemical significance. However, as for their methyl homologues, the ability to resist biodegradation of methyl dibenzothiophene is more than methyl fluorene and methyl dibenzofuran, re-sulting in differently biodegraded rate, their relative proportions varied from slightly to severely biodegraded oils and could not be used to indicate the features of depositional environment. Although the concentrations of Fs, OFs and SFs in differently biodegraded oils were decreased during biodegradation, their rates differed significantly, their relative proportions varied with biodegradation all time. Therefore, for biodegraded oils, the cautions should be taken when their relative proportions of Fs, OFs and SFs are used to determine the depositional environment.