生物降解原油中UCM成因机理研究

Oil biodegradation is common and the biodegraded oil is widely occurred. One of the important features of this type of oil is that there is a wide occurrence of unresolved complex mixtures (UCM) present in the one-dimensional gas chromatograms of saturated hydrocarbon or aromatic hydrocarbon, which have significant geological and geochemical implications. However, the UCM study is very difficult because it is unresolved in general, and thus, it is one of the research challenges in the study of petroleum geology and geochemistry. This will be addressed in this project. Here we will attempt to obtain cultures from biodegraded oils and select favorable biodegradation conditions. Then, biodegradation simulation experiments will be conducted on the different hydrocarbon components which were divided by different hydrocarbon adduction techniques. The products (UCM in particular) of the simulation experiments will further be analyzed by advanced methods including gas chromatography and two-dimensional gas chromatography with time-of-flight mass spectrometry. The UCM will be compared to that in the oils with different biodegraded levels. Thus, the difference of UCM that is produced in different types of biodegradations can be obtained and, thus, the general features and mechanisms of the UCM formation can be summarized. These will provide theoretical base for comprehensive and precise understandings on the UCM and its geological and geochemical applications, which in turn have practical significance for the exploration and exploitation of biodegraded oils. In addition, the results can also provide theoretical information for the environmental restoration of oil spills and petroleum compositional studies.

原油的生物降解作用普遍存在，生物降解原油分布广泛，其烃类一维气相色谱图中出现大量未可分辨的复杂混合物（UCM）是该类原油的典型特征，具有重要地质地球化学意义，但因未可分辨故而研究程度低，是油气地球化学领域的研究难点。本项申请，拟从生物降解原油中提取菌种，优选降解条件，对石油烃采用烃类络合技术细分为不同组分，并分别进行细菌降解模拟实验，再应用气相色谱和全二维色谱-飞行时间质谱等先进分析技术剖析实验产物中的UCM，并与不同降解级别原油的UCM进行对比，分析细菌降解产生UCM的差异性，总结细菌降解产生UCM的规律，从而揭示生物降解原油中UCM的成因机理，为全面准确认识UCM并进行地质地球化学应用奠定理论基础，这对生物降解原油的勘探与开发具有重要实际应用价值，也可为溢油污染环境修复和石油组成学研究提供理论参考。

生物降解油普遍存在，其中烃类色谱图常出现“鼓包”化合物（简称之为UCM），其组成复杂，目前尚未完全认识，形成机理更不清楚。本项目以正常原油为研究对象，以自然降解油为参照，用人工模拟生物降解方法，利用全二维气相色谱-飞行时间质谱等先进的分析手段，对正常原油及其组分开展人工降解，并深入剖析降解产物的UCM组成特征及差异性，从而揭示UCM的形成机理。.本项目首先在对必需的样品的地球化学特征分析基础上，对正常原油进行组分分离和制备，同时从自然界降解油中提取出有效菌种，并进行人工降解条件试验；然后，用最佳降解条件对分离制备的样品实施人工降解，并分离出降解产物中的烃类化合物；最后，利用为自行建立的反相柱系统分析方法来剖析人工降解产物中的UCM组成，以揭示UCM形成机理。.通过研究，获得以下认识和成果：①在国内石油系统中较早地建立了反相柱系统全二维色谱-质谱分析方法，并对原油中常见的烃类化合物进行了详细的鉴定和识别，为生物降解油中的鼓包化合物（UCM）剖析奠定了良好的基础；②在分析自然生物降解油时，分离出以往不为明显的两个化合物，一个是三甲基金刚烷异构体，它的有效分离，大大提高了金刚烷成熟度参数计算的准确性；另一个是C27四环萜烷，发现在生物降解油中丰度较高，且与降解程度有明显的正相关性。研究认为它是由五环三萜烷在C17位和C21位键断裂降解而成，且陆相原油比海相原油丰富。对自然降解样品中的UCM做过详细剖解，显示出反相柱系统法的优越性；③成功分离制备出原油族组分，并相应地进行了人工生物降解模拟实验，剖解了降解产物中的UCM组成，初步揭示了生物降解油中UCM的组成和形成机理。认为生物降解油中的UCM主要由原油的饱和烃组分降解形成，原油的芳烃组分对UCM产生有一定的贡献，但主要出现在低分子量化合物端，而原油的胶质组分只能产生零星的甾萜等多环烷烃类化合物，且含量很低。这可能与以烃类为碳源的微生物对胶质很难发生降解有关。