北黄海盆地LV井侏罗系油砂抽提物地球化学特征

对北黄海盆地侏罗系两块含油砂岩的抽提物进行了常规的有机地球化学分析和碳同位素测试,结果表明它们具有不同的地球化学特征:埋藏较深的油砂抽提物属正常原油,饱和烃以正构烷烃为主,色谱图显示单峰型正态分布;而埋藏较浅的油砂抽提物,在饱和烃色谱图中有明显的UCM鼓包,同时含有完整的低碳数的正构烷烃、姥鲛烷和植烷,全油及族组成碳同位素分布范围广,为-24.7‰~-32.3‰,其中,全油及沥青质碳同位素偏重,饱和烃和芳烃碳同位素轻,反映出遭受了强烈的生物降解作用。与成熟度相关的生物标志物参数显示,原油已进入成熟—高成熟阶段。生物标志物和碳同位素组成表明,母质是在水体较浅的湖相环境下沉积的,受陆源高等植物和低等水生藻类的双源控制。综合判断,研究区存在两期油气充注。

Geochemical Characteristics of Extracted Hydrocarbon from Jurassic Oil Sandstone Reservoirs in Well LV,North Yellow Sea Basin

Samples are two oil-bearing extracts from Jurassic oil sandstone reservoirs in Well LV in North Yellow Sea basin. By analysis results of conventional organic geochemical methods and stable carbon isotopic detection, it is shown that their geochemical characters are different. The deeper oil extract belongs to common oil, in which the n-alkane is predominant fractional composition of saturate hydrocarbon, and the n-alkane curve shows normality distribution with low carbon number predominance. While the shallower oil extract indicates strong biodegrade. The gas chromatograms (GC) of the saturate hydrocarbon raises baseline from UCM, and also contains the complete low carbon number n-alkane, Pr and Ph. The carbon isotope(δ13C) values of whole oil (oil sandstone extract) and group composition ranges from-24.7‰ to-32.3‰. The δ13C values of whole oil and asphaltene have heavy carbon isotopic ratio, while saturate hydrocarbon and aromatic hydrocarbon have light carbon isotopic ratios. The biomarkers relating with maturity parameter show that the two oil sandstone extracts have arrived to mature or highly mature stages. Deduced from biomarkers and carbon isotopes, the matrix of the oil sandstone extracts were deposited in a shallow lacustrine environment so that it was controlled by terrestrial higher-plant debris and the lower aquatic organisms. Comprehensive analysis indicates that hydrocarbon was charged twice in these areas.