羌塘盆地白垩系黑色岩系生烃母质研究

羌塘盆地白垩系是该区域新近发现的潜在烃源层系,通过有机岩石学和地球化学相结合的方法研究了其生烃母质。结果表明,根据观测到的各类生烃母质形状、大小、聚集形式以及荧光等特征综合分析,其成烃生物组合由高到低主要包括底栖生物、细菌、浮游藻类和高等植物4大类,并以底栖藻类占主要地位。这种以底栖藻类为主的烃源岩系与国内外其他同类烃源岩特征类似,在地球化学特征上表现为有机质丰度高(TOC大于2.0%,达到好烃源岩质量标准)、有机质类型较差(Ⅱ₂型),据此认为这套黑色岩系形成于海相环境。结合其在区域上的热演化特征,认为其具有良好的生烃潜力,特别是生气潜力,值得在今后的油气勘探和地质研究中加以重视。

Bio-precursors of Cretaceous black shales in the Qiangtang Basin,Tibet

A new sequence of hydrocarbon source rock has been discovered recently in the Qiangtang Basin, Tibet, i.e., the Cretaceous black shales. We investigated the bio-precursors of the shales by an integrated method of organic petrology and geochemistry to improve the understanding of their resource potential. Results showed that the bio-precursors of the shales can be classified into four types in general based on their shapes, sizes, accumulation forms and fluorescence. They include marine benthic algae and zooplankton, bacteria, phytoplankton and terrestrial higher plants in decreasing order of abundance. Benthic algae are the dominant precursors. Similar to source rocks of the same type worldwide, these benthic algae dominant source rocks have high organic matter abundance (TOC>2.0%), reaching the level of good quality and belonging to organic matter type Ⅱ₂, indicating that they were deposited in a marine environment. Combined with the regional thermal evolution of the shales, we deduced that the black shales have a good hydrocarbon resource potential and are likely to produce dominantly gas. They may comprise a good exploration target and merit further geological research.