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对珠江口盆地东部原油和烃源岩抽提物进行了详细的生物标志化合物检测,结果发现存在两类不同特征的原油,第一类原油含有丰富的C304-甲基甾烷,而C19三环萜烷、双杜松烷(主要是T构型)等代表陆生高等植物生源的分子化合物浓度低,与典型湖相沉积的文昌组烃源岩有良好的可比性;另一类原油具有高丰度的双杜松烷和C19三环萜烷以及较高的Pr/Ph值等,代表着偏氧化环境下以高等植物生源为主的恩平组湖沼相烃源岩的贡献,但这类原油中同时也不同程度地含有只是在文昌组岩石中才有的C304-甲基甾烷,因而认为这类油是两套烃源岩的混源产物,恩平组原油的混合比例最高可达80%以上,主要分布在惠州凹陷及其南边的西惠地凸起上。原油配比实验表明,即使在文昌组生成的原油中加入50%-80%的恩平组原油,混合油仍表现出文昌组生源的特征。因此,4-甲基甾烷的存在不能作为判识珠江口盆地东部油源主要是文昌组的唯一证据。文昌组烃源岩对珠-坳陷商业性油藏的贡献是普遍的,但恩平组烃源岩对惠州凹陷周边凸起上的油田/油藏的显著贡献不容忽视。正是由于恩平组生成的原油的再次注入,使得早期发生生物降解了的油藏再次充满,使油质变轻。
A detailed biomarker test was conducted on the crude oil and source rock extracts in the eastern Pearl River Mouth Basin. As a result, two different types of crude oil were found. The first type of crude oil was rich in C304-methylstestane, whereas the C19 tricyclic The concentration of molecular compounds, such as terpene and dicudone (mainly T configuration), which represent the terrestrial higher plant biomass, is low and comparable with that of the Wenchang Formation source rocks deposited by typical lacustrine facies. The other type of crude oil has high The abundance of biocurdane and C19 tricyclic terpanes and higher Pr / Ph values represent the contributions of the Enping Formation lacustrine facies source rocks in the partial oxidation environment. However, Crude oil also contains to varying degrees C304-methyl sterane, which is only found in the rocks of Wenchang Formation. Therefore, it is considered that this oil is a mixed product of two sets of source rocks, and the mixing ratio of Enping Formation crude oil is up to More than 80%, mainly distributed in the huizhou depression and the west of huixi convex. Crude oil ratio experiment shows that, even if 50% -80% of Enping Formation crude oil is added to the crude oil produced in Wenchang Formation, the mixed oil still shows the characteristics of Wenchang Formation source. Therefore, the existence of 4-methylstestane can not be used as the only evidence to identify the main source of Wenchang Formation in the eastern Pearl River Mouth Basin. The contributions of Wenchang Formation source rocks to commercial reservoirs in the Pearl-Depression are common, but the significant contributions of Enping Formation source rocks to the oil fields / reservoirs on the periphery of the Huizhou Sag can not be ignored. It is precisely because of Enping formation of the re-injection of crude oil, making early biodegradable reservoirs filled again, so that light oil lighter.