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为分析生物降解原油中甾烷生物标志物分子发生选择性蚀变的先后顺序及生物降解作用对甾烷分子成熟度参数的影响,在渤海湾盆地东营凹陷广饶潜山油藏选择了发生不同程度生物降解作用的原油,利用色谱质谱(GC-MS)仪对其中甾烷进行了定量测试分析和对比。结果发现在生物降解过程中,不同级别的生物降解作用对甾烷具有不同程度的影响:6级以下的生物降解作用对甾烷的降解能力有限,甾烷及其相关化合物比值没有可以识别的改变;6级以上的严重生物降解作用会对甾烷生物标志物的相关参数产生显著的影响。在严重生物降解原油中(级别≥6):甾烷系列被降解和蚀耗的先后顺序为,ααα20R>αββ20R>αββ20S≥ααα20S,C27>C29>C28,规则甾烷优先于重排甾烷发生降解,C27,C28,C29甾烷优先于C20,C21甾烷发生降解;甾烷生物标志物分子参数C2920S/(20S+20R),C29ββ/(ββ+αα)会发生显著升高,不能真实反映成熟度大小。研究结果为正确评价生物降解原油的成熟度及甾烷生物标志物分子的选择性蚀变提供了新的科学依据。
In order to analyze the sequence of selective alteration of sterane biomarker molecules in biodegradable crude oil and the effect of biodegradation on the maturity parameters of sterane, we selected different degrees of occurrence in Guangrao buried hill reservoir in Dongying Sag of Bohai Bay Basin Biodegradability of crude oil, the use of chromatographic mass spectrometry (GC-MS) of the steranes were quantitative test analysis and comparison. The results showed that different levels of biodegradation had different effects on sterane in the biodegradation process: the biodegradation below 6th grade had limited ability to sterane degradation and there was no identifiable change in the ratio of sterane and its related compounds ; Severe biodegradation above grade 6 has a significant effect on the relevant parameters of the sterane biomarker. In severe biodegradable crude oils (Grade ≥6), the order of degradation and erosion of the sterane series is that ααα20R> αββ20R> αββ20S> ααα20S, C27> C29> C28, and regular steranes preferentially degrade steranes , C27, C28 and C29 steranes take precedence over C20 and C21 steranes. Sterane biomarker molecular parameters C2920S / (20S + 20R) and C29ββ / (ββ + αα) are significantly increased and can not truly reflect the maturation Degree size. The results provide a new scientific basis for the correct evaluation of the maturity of biodegradable crude oil and the selective alteration of sterane biomarkers.