辽西金羊盆地北票组油砂芳烃地球化学特征及其地质意义

Geochemical Characteristics and Geological Significance of Aromatic Hydrocarbons in Oil Sand of Beipiao Formation in Jinyang Basin in Western Liaoning Province

作为原油和烃源岩沥青抽提物的重要组成部分,芳烃蕴藏着反映可溶有机质的母质类型、沉积环境和成熟度的地质地球化学信息。对辽西金羊盆地北部SZK02井中发现的4件油砂样品进行了气相色谱-质谱(GC-MS)分析,研究了油砂芳烃组成特征,并探讨了油砂成因。结果表明,下侏罗统北票组油砂主要形成于弱氧化的淡水湖相沉积,为成熟油砂;芳烃化合物组成以菲系列为主,其次为三芴、萘、[艹屈]系列,其中,上部2件油砂与下部2件油砂特征有所差异,表现为下部油砂中四甲基萘、二甲基联苯、三芳甾烷含量明显高于上部;总体认为,上部油砂与下部油砂在成因上存在一定差异,这与饱和烃地球化学特征具有一致性。

As an important component of bitumen extracts from crude oil and source rocks,aromatic hydrocarbons contain geological and geochemical information reflecting the parent material type,sedimentary environment and maturity of soluble organic matter.The aromatic fraction of four oil sand samples found in SZK02 well from the north part of Jinyang basin in the western Liaoning province were analyzed by the gas chromatography-mass spectrometry analysis(GC-MS)for the research of the aromatic composition characteristics and the origin of oil sand.The results show that the oil sand of the Beipiao Formation of the lower Jurassic is mainly formed in the weakly oxidized freshwater lacustrine sedimentary environment,which is mature oil sand.The aromatic compounds are mainly composed of phenanthrene series,followed by trifluorene,naphthalene and flexion series.Among them,the characteristics of the upper two oil sand samples are different from that of the lower two oil sand samples,showing that the contents of tetramethylnaphthalene,dimethyl biphenyl and triaromatic sterane in the lower part are significantly higher than that in the upper part.It is generally believed that there are some differences in the cause of formation between the upper oil sand and the lower oil sand,which is consistent with the geochemical characteristics of saturated hydrocarbon.