羌塘盆地北羌塘坳陷晚三叠世发育了一套分布广、厚度大的黑色泥岩,对油气勘探具有重要意义.为明确北羌塘坳陷东缘巴贡组黑色泥岩的有机地球化学特征,采集了石油沟地区61块浅井岩心和64块手钻柱塞样品,开展地球化学和矿物学技术分析,对烃源岩生烃潜力、沉积环境进行了评价.结果表明:①巴贡组黑色泥岩TOC分布在0.06，～5.81，之间,整体为一套差―中等烃源岩,部分达到优质烃源岩标准,形成于弱氧化―弱还原环境,有机质类型为Ⅱ2―Ⅲ型,以混合型有机质为主,Ro分布在0.95，～1.90，之间,处于成熟晚期至高成熟阶段.②巴贡组烃源岩有机质丰度较高,有机质类型好,成熟度适中,生烃潜力大.③巴贡组烃源岩与上覆雀莫错组底部砂砾岩形成"下生上储"的源储组合,为大中型油气田的形成奠定了基础,同时巴贡组也是页岩油勘探的有利层系.这套烃源岩对北羌塘坳陷东缘常规油气和非常规油气勘探均具有重要意义.

The Qiangtang Basin,located in the eastern part of the Tethys domain,is the only large-scale superimposed basin in China where no industrial oil or gas fields have been discovered.Based on the new round of comprehensive research on oil and gas geology in recent years,a set of widely distributed black mudstone with large thickness(600-800 m)of Bagong Formation is found being developed in the front delta-shallow water shelf during the foreland basin stage of Late Triassic in Qiangtang Basin,which is of great significance for oil and gas exploration.In order to study the organic geochemical characteristics of the black mudstone of Bagong Formation in the eastern margin of the North Qiangtang Depression,61 core samples from shallow well and 64 hand-drilled plunger samples are collected to carry out geochemical and mineralogical analysis,and the source rock potential and sedimentary environment are evaluated.The results show that:(1)The black mudstone of the Bagong Formation,with TOC of 0.06，-5.81，,is poor-medium source rock on the whole,and some reach the standard of high-quality.Formed in weak oxidation-weak reduction environment,the organic matter type is Ⅱ2―Ⅲ,mainly belonging mixed organic matter.It is in the late mature to high mature stage with Ro of 0.95，-1.90，.(2)The Bagong source rock has great hydrocarbon generation potential,due to high organic matter abundance,good organic matter type,and moderate maturity.(3)There developed a source-reservoir assemblage of"lower generation and upper reservoir"between the Bagong source rock and the glutenite reservoir at the bottom of the Quemocuo Formation,which lays a foundation for the formation of large and medium-size oil and gas fields.Besides,the Bagong mudstone is a favorable layer for shale oil exploration.In general,the Bagong source rock is of great significance for conventional and unconventional oil and gas exploration in the eastern margin of the North Qiangtang Depression.