柴东欧南凹陷石炭系烃源岩有机质富集的影响因素

柴达木盆地东部地区欧南凹陷是石炭系油气运聚成藏的有利构造单元,具有一定勘探潜力,但对有机质富集机理认识不清导致对优质烃源岩分布的预测缺乏有效指导,制约了油气勘探进程.基于地球化学分析、XRD、SEM等分析测试,对石炭系烃源岩矿物组分、 有机质丰度、 干酪根类型、 热演化程度、 形成环境、TOC与主要矿物关系等进行了综合...

The factors influencing the enrichment of organic matters in the Carboniferous source rocks, Ounan depression, eastern Qaidam basin

The Ounan depression is a favorable structural unit for the Carboniferous hydrocarbon migration and accumulation, which demonstrates certain exploration potential. However, the organic matter enrichment mechanism is still unclear, which results in the absence of effective guidance for predicting the distribution of high-quality source rocks and restricts the process of oil and gas exploration. Based on geochemical analysis and XRD, SEM and other tests, the main factors influencing the enrichment of organic matters in Carboniferous source rocks have been identified through a comprehensive investigation into the aspects such as mineral composition, organic matter abundance, kerogen type, thermal evolution degree, formation environment, and the relationship between TOC and primary minerals. The results reveal that shales and carbonate source rocks have been developed in the Carboniferous, a large quantity at poor-medium level and a few at good or above level. They were deposited in the environment of intercontinental shelf with saline-water, arid-hot climate and weak oxidation and reduction. The dispersed organic matters are composed of mixed marine and terrestrial origins, which are overall in a "maturity-high maturity stage". The Carboniferous clastic source rocks are mainly residual type Ⅲ kerogen, but the extracted chloroform bitumen "A" is mainly derived from type Ⅱ kerogen.TOC values increase with the growing of quartz minerals because the high-abundance source rocks are rich in siliceous biological fossils. The SiO₂ in the high-SiO₂ source rocks has been identified as biogenic, suggesting that the participation of siliceous organisms in the Carboniferous cause the enrichment of marine organic matters and greatly improve the primary productivity of the sediments. This study provide the basis for predicting the distribution of Carboniferous high-quality source rocks and the deployment of oil and gas resources in the study area.