北黄海盆地LV井侏罗系烃源岩特征及油源对比

Geochemical Characteristics of Jurassic Source Rocks from Well LV and Oil-source Correlation in North Yellow Basin

对北黄海盆地LV井中、上侏罗统烃源岩及上侏罗统原油(油砂抽提物)进行常规有机地球化学分析和碳同位素测试,分析研究烃源岩和原油的地球化学特征并探讨原油的来源问题。测试结果显示,侏罗系烃源岩达成熟—高熟阶段,有机质类型以Ⅲ型为主。中侏罗统烃源岩有机碳含量较高,但生烃潜能、氯仿沥青"A"及总烃含量低值,属于差的烃源岩。干酪根碳同位素总体偏重(-24.4‰^-23.5‰),与原油碳同位素特征(-29‰左右)差异显著,排除与原油的母岩关系。上侏罗统烃源岩有机碳含量较中侏罗统低,但生烃潜能、氯仿沥青"A"及总烃含量高值。上侏罗统烃源岩抽提氯仿沥青"A"碳同位素(-26‰^-21.5‰)特征、单体烃碳同位素分布模式及甾萜烷生物标志物特征都与原油相似,综合分析认为原油应该来源于上侏罗统中干酪根类型较好、母质为混源的成熟烃源岩。

Jurassic source rocks and oil sands from Well LV has been analyzed by usual organic geochemical methods and stable carbon isotopic detection in the North Yellow basin,in order to study the geochemical characteristics of the source rocks and the crude oils and oil-to-source correlation. The results show that the maturity of Jurassic source rock is higher,its kerogen type is maily Ⅲ. Middle Jurassic source rocks are higher in organic carbon and lower in hydrocarbon yields,chloroform bitumen ＂A＂and HC,which means they are relatively poor source rocks. The kerogen carbon isotope of the middle Jurassic source rocks is heavy. There is a remarkable difference of carbon isotopic values of middle Jurassic source rocks（-24.4‰ ^-23.5‰） and crude oils（ about-29‰）. Therefore,there is no relationship among them. However,TOC content of the upper Jurassic source rocks is lower than that of the middle Jurassic source rocks,but hydrocarbon yields,chloroform bitumen ＂A＂and HC of the upper Jurassic source rocks are higher. The character of chloroform bitumen ＂A＂carbon isotope,distribution pattern of carbon isohopic distributions of individual n-alkanes and biomarkers of upper Jurassic source rocks are similar to crude oils. Comprehensive analysis could draw a conclusion that there is closely relationship between crude oil and the upper Jurassic hydrocarbon source rock,which has good kerogen type and mature parent materials from both higher plants and lower aquatic organisms.