中口子盆地侏罗系煤系烃源岩地球化学特征及生烃潜力评价

甘肃-内蒙古交界处的北山盆地群侏罗系是我国西北地区潜在的油气勘探新领域。为加深对该盆地群资源潜力的认识，以有机地球化学分析数据为基础，探讨了其中煤系烃源岩的沉积环境、有机质来源，建立了该烃源岩生烃潜力评价标准。研究结果表明，中口子盆地侏罗系烃源岩干酪根类型以Ⅱ₁-Ⅱ₂型为主，生烃母质主要是陆生植物，含少量的藻类和水生生物，主要形成于三角洲平原沼泽或湖侵期的间湾湖泊等氧气量适中的弱氧化-弱还原沉积环境。生烃潜量和氢指数是衡量煤系源岩有机质丰度、生烃潜力和生油潜力最有效的指标，根据生烃潜力评价标准：黑帐房凹陷侏罗系暗色泥岩多属于中-差烃源岩，南泉凹陷暗色泥岩生烃潜力级别优于黑帐房凹陷，主要为中-好烃源岩；南泉凹陷炭质泥岩大多数属于中等-好油源岩，煤岩大多属于差油源岩。

Evaluation of Hydrocarbon Generation and Geochemical Characteristics of Coal-Measure Source Rocks,Zhongkouzi Basin in Beishan Area

The Jurassic system of Beishan basin group at the junction of Gansu and Inner Mongolia is a new potential field for oil and gas exploration in Northwest China. On the basis of systematic sample collection,the characteristics of organic matter and biomarker of the Jurassic source rocks in Zhongkouzi basin were analyzed in detail by means of testing technology and geochemical analysis. The results show that the kerogen type of the Jurassic source rocks in the middle mouth basin is mainly typeⅡ₁-Ⅱ₂, and the source material of hydrocarbon generation is mainly terrestrial plants, containing a small amount of algae and aquatic organisms. It is mainly formed in a weak oxidation-weak reduction sedimentary environment with moderate oxygen content, such as swamps or transgressive lakes in delta plain. According to the evaluation criteria of hydrocarbon generation potential, most of the Jurassic dark mudstones in Heizhangfang sag belong to the source rocks with poor or medium hydrocarbon generating potential. The hydrocarbon generating potential of the dark mudstones in Nanquan sag is medium or high,better than that in Heizhangfang sag. Based on the analytical data in Zhongkouzi basin and the discussion on sedimentary environment and sources of organic matter, the evaluation criteria for hydrocarbon generation potential of source rocks in coal measures are established. This study can provide a comparative reference for the study of the Jurassic sedimentary paleo-environment and resource potential in Northwest China.