Abstract:

There have been controversies whether or not the Carboniferous has the potential of hydrocarbon generation in Qaidam Basin. Based on a great deal of geological field surveys and lab tests, this paper obtained the related evidence for the Carboniferous hydrocarbon generation in the basin. Recently, thick-layered oil sands were firstly found in many Carboniferous outcrops in peripheries of Qaidam Basin and they are mainly distributed within interlayers and fractures of the thick Carboniferous Huaitoutala Formation biogenic limestone, especially in bioherms and fossil belts. On the basis of comparison and analysis of biomarker parameters for source materials, sedimentary environments and thermal maturity, the oil-source correlation testified that these oil sands have no affiliations with any Mesozoic or Cenozoic source rocks of the basin but a good comparability with Carboniferous source rocks. Therefore, the oil in these Carboniferous oil sands originates from Carboniferous source rocks in Qaidam Basin. This evidence shows that Carboniferous source rocks have a hydrocarbon generation process, and probably generate oils that accumulated in Carboniferous traps. Therefore, there would be a great exploration potential in the Carboniferous of Qaidam Basin.

Key words: Qaidam Basin, Kunbei fault-terrace belt, oil genesis, biomarker, formation stage of reservoir

摘要：

柴达木盆地石炭系是否具有生烃潜力一直存在争议，本文在大量野外地质调查与实验室样品分析的基础上，找到了石炭系生烃的相关证据。首次在盆地周边露头区多处石炭系中发现油砂出露，油砂主要分布在石炭系怀头他拉组灰岩中，沿厚层生物灰岩层间和裂缝发育，在生物礁和化石带中尤为突出。通过烃源岩和油砂反映成烃母质来源、沉积环境及成熟度3个方面的生物标志化合物参数对比研究，表明油砂与中生界-新生界烃源岩没有亲缘关系，而与石炭系烃源岩具有良好的可对比性，确定石炭系中的油砂来源于石炭系烃源岩。这证实柴达木盆地石炭系烃源岩有过生烃过程，并可能形成石炭系油气藏，从而揭示了柴达木盆地石炭系具有广阔的生烃前景。

关键词: 柴达木盆地, 昆北断阶带, 原油成因, 生物标志化合物, 成藏期次