四川江油厚坝油砂产出于侏罗系沙溪庙组下段,含油砂层沿北东方向延伸约25 km.露头和岩芯油砂样抽提得到氯仿沥青“A”含量为0.4％～33％.抽提物饱和烃GC-MS分析得到的分子有机地球化学特征表明,油砂油遭受严重生物降解,饱和烃分布呈现双大鼓包,正构烷烃和异构烷烃基木被降解；三环萜烷含量丰富,孕甾烷和升孕甾烷含最也较高,规则甾烷具C29优势；芳烃组分中富含噻吩类化合物和烷基菲,露头和岩芯样品氯仿沥青“A”碳同位素值小于-34‰.厚坝油砂分子地球化学特征、碳同位素组成和川西北地区地质构造特征表明,原油可能主要来自震旦系和寒武系烃源岩,母质来源以藻类和细菌为主.%Oil sand is widely cropped out at Houba region of Sichuan Province. The lower member of the Jurassic Shaximiao Formation is the main oil reservoir, which is composed of sandstone beds stretching towards north-east orientation for as long as roughly 25 km. Tar sand oil contents of cropped and drilled samples range from 0.4% to 3.3%. Characteristics of saturated hydrocarbon component analyzed by GC-MS showed that tar sand oils were severely biodegraded, which was featured by the disappearance of n-alkanes and iso-alkanes. Biomarkers like tricyclic terpane, pregnane and homo-pregnane have relatively high contents. Meanwhile, the content of C29 regular steranes is relatively high compared to its C27, C28 series. Mass chromatograms of aromatic hydrocarbons were characterized by prolific alkylated phenanthrenes and thiophene series. Bulk oil carbon isotope components of the tar sand oils from drilled and cropped samples are depleted ( < -34%°). Features for both biomarkers and carbon isotope ratios of the Houba oil sand imply that these oils may have originated from Sinian-Cambrian source rocks and had biological sources comprising of algae and bacteria.
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