开鲁盆地钱家店凹陷姚家组砂岩中烃类地球化学特征及来源探讨

对开鲁盆地钱家店地区下白垩统姚家组砂岩中吸附烃和包裹体烃类进行色谱—质谱测试,分析了它们的地球化学特征,并讨论其可能的来源。吸附烃和包裹体烃生物标志物成熟度参数,C₂₉ααα甾烷20S/(S+R)、C₃₁αβ藿烷22S/(S+R)比值基本达到平衡值,显示含矿砂岩中的烃类已接近成熟—成熟热演化阶段;物质来源及沉积环境参数,ααα20R甾烷百分含量C₂₇>C₂₈29,C₂₅/C₂₆三环萜烷、规则甾烷/17αC_29-33藿烷比值显示相对低值,结合伽马蜡烷指数、C₃₅升藿烷指数等参数,综合反映了其来源应为弱氧化—还原环境下的腐殖—腐泥型湖相有机质。这些特征与该凹陷侏罗系九佛堂组烃源岩地球化学特征相似,因而,油源可能来自九佛堂组烃源岩。 

GEOCHEMICAL CHARACTERISTICS AND ORIGIN OF INCLUSIONS AND ADSORBED HYDROCARBONS IN YAOJIA FORMATION SANDSTONES IN QIANJIADIAN AREA, THE KAILU BASIN

Inclusion hydrocarbons and adsorbed hydrocarbons were observed under microscope and UV fluorescence in Lower Cretaceous Yaojia Formation sandstones in Qianjiadian area,the Kailu Basin.Subsequently,these sandstone samples were washed,crushed,extracted for hydrocarbons and analyzed by GC and GC-MS.The results showed that ratios of C₂₉ ααα sterane 20S/(20S+20R) and C₃₁ αβ hopane 22S/(22S+22R) of the hydrocarbons were closed to respective equilibrium values,suggesting that the hydrocarbons were marginally mature to mature.Among C₂₇,C₂₈ and C₂₉ ααα20R steranes,C₂₇>C₂₈29.Ratios of C₂₅/C₂₆ tricyclic terpane and regular steranes/17αC_29-33 hopanes were relatively low.The values together with those of gammacerane index and homohopane index consistently indicated that the inclusion oils and adsorbed hydrocarbons were derived from humic-sapropel type organic matter under poor reducing freshwater to semi-saline environment.The features were similar to those of organic matter extracted from the Upper Jurassic Jiufotang Formation source rocks in the Kailu Basin.Thus,it could be concluded that the inclusion oils were mainly derived from the Upper Jurassic Jiufotang Formation source rocks of lacustrine facies.