准噶尔盆地玛湖凹陷烃源岩和原油生物标志物与碳同位素组成及其意义  

Biomarker and carbon isotopic compositions of source rock extracts and crude oils from Mahu Sag,Junggar Basin

作　　者：黄攀[1] 任江玲[2] 李二庭[2] 马万云[2] 徐浩[1] 于双[1] 邹艳荣[1] 潘长春[1] 

机构地区：[1]中国科学院广州地球化学研究所有机地球化学国家重点实验室,广东广州510640 [2]中国石油新疆油田公司实验检测研究院地质实验中心,新疆克拉玛依834000

出　　处：《地球化学》2016年第3期303-314,共12页Geochimica

基　　金：国家油气专项专题(2011ZX05008-002-50);国家自然科学基金(41372136)

摘　　要：对准噶尔盆地玛湖凹陷6个下二叠统风城组(P_1f)烃源岩抽提物和10个原油样品进行了色谱、色谱-质谱和色谱-同位素比值质谱分析。依据分子和碳同位素地球化学特征,将10个原油样品分为三组。第一组具有如下特征:(1)Pr/nC_(17)和Ph/nC_(18)值较高;(2)几乎不含Ts、C_(29)Ts和C_(30)重排藿烷;(3)伽马蜡烷和胡萝卜烷相对含量高;(4)三环萜烷分布模式为C_(20)<C_(21)<C_(23)或C_(20)>C_(21)<C_(23);(5)正构烷烃单体δ^(13)C值随碳数增加而变重。该组油样是Ⅰ类原油的端元代表,来源于"典型"下二叠统风城组(P_1f)烃源岩。第二组油样的特征与第一组油样明显不同:(1)较低的Pr/nC_(17)和Ph/nC_(18)值;(2)相对较低的伽马蜡烷和胡萝卜烷含量;(3)三环萜烷分布模式为C_(20)<C_(21)>C_(23);(4)正构烷烃单体δ^(13)C值则随碳数增加而变轻。该组油样是Ⅱ类原油的端元代表。第三组油样为介于Ⅰ类和Ⅱ类原油之间的过渡类型。6个烃源岩样品抽提物分子指标与该凹陷"典型"下二叠统风城组(P_1f)烃源岩及Ⅰ类原油具有一定的差异,而与之前认为的中二叠统下乌尔禾组(P_2w)烃源岩及Ⅱ类原油类似。烃源岩抽提物之间正构烷烃单体δ^(13)C值具有较大的差异,并且比10个原油样相对偏轻。在玛湖凹陷至今尚未钻遇有较大生油潜力的下乌尔禾组烃源岩样品,风城组烃源岩既是Ⅰ类原油的油源,也可能是Ⅱ类原油的主要油源。由于有机岩相及成熟度的差异,导致来源于同一套烃源岩的原油具有不同的生物标志物和碳同位素组成。GC, GC-MS and GC-IRMS analyses were performed on six extracts from source rocks within the Lower Permian Fengcheng Formation （P1f） and ten oils collected from the Mahu Sag, Junggar Basin. Based on molecular and carbon isotopic compositions, the oils can be classified into three groups. Group I oils are characterized by： （1） high Pr/nC17 and Ph/nC18 ratios, （2） negligible amounts of Ts, C29Ts and C30 diahopane, （3） high relative concentrations of gammacerane and carotanes, （4） tricyclic terpane distribution pattern of C20〈C21〈C23 or C20〉C21〈C23, and （5） δ13C values of individual n-alkanes increasingly heavier with carbon number of n-alkanes. Group 1 oils are representatives of the end member of type I oils, which are derived from ＂typical＂ source rocks within the Lower Permian Fengcheng Formation （P1f）. In contrast, group 2 oils are characterized by： （1） low Pr/nC17 and Ph/nC18 ratios, （2） low relative concentrations of gammacerane and carotanes, （3） tricyclic terpane distribution pattern of C20〈C21〉C23, and （4） δ13C values of individual n-alkanes increasingly lighter with carbon number of n-alkanes. Group 2 oils are representatives of the end member of type 1I oils. Group 3 oils are of intermediates between types I and II oils. The six source rock extracts are more or less different from the ＂typical＂ source rocks within the Lower Permian Fengcheng Formation （Plf） and type I oils, but similar to source rocks within the Middle Permian Lower Wuerhe Formation （P2w） and type lI oils in molecular compositions. δ13C values of individual n-alkanes among the six source extracts vary significantly, and are relatively lighter than those of the 10 oils. So far, source rocks with a high oil generative potential have not been penetrated from the Lower Wuerhe Formation by boreholes. Both the type I and II oils were possibly mainly generated from the source rocks within the Fengcheng Formation （Plf）. The differences in molecular and carbon isotop

关 键 词：风城组烃源岩 生物标志物 单体烃碳同位素 玛湖凹陷 

分 类 号：P593[天文地球—地球化学]