Abstract: Qingtang Basin is a large Mesozoic marine sedimentary basin located on northern Qingzang plateau and has the widespread and thick source rocks. The source rocks of Xiaochaka Formation in the upper Triassic and Buqu Formation and Xiali Formation in the middle Jurassic were researched by organic geochemistry means. It is found that the organic matter type of source rocks is good, and abundance of organic matter is large. The maturity of organic matter varies from mature to over-mature, and the burial conditions of source rocks are relatively good. The simulation of hydrocarbon-generation process revealed that source rocks had two periods of hydrocarbon generation and hydrocarbon expulsion. The production of hydrocarbon is extremely large. The fossil-reservoir belt located in dolomite of Buqu Formation in the Bilongcuo-Angdaercuo region has a length of 100 kilometers and a width of 20 kilometers. It is a long and narrow humid swarm with light oil. The organic geochemistry characters of oil-source rocks show that oil and gas of the fossil-reservior come mainly from the hydrocarbon rock in the lower Jurassic. The discovery of the fossil-reservoir belt implied that Qiangtang Basin had large-scale migration and accumulation of oil and gas. It will have a good prospect for exploration of oil and gas.

Key words: Tibet area, Qiangtang Basin, Mesozoic, hydrocarbon source rock, fossil-reservoir belt, geochemistry characters, perspective exploration of oil and gas

摘要： 羌塘盆地是青藏高原北部的大型中生代海相沉积盆地,发育有厚度大、分布广的烃源岩.用有机地球化学方法,分析了羌塘盆地上三叠统的肖茶卡组、中侏罗统布曲组、夏里组和索瓦组烃源岩结果发现,其有机质类型好、丰度高,成熟度从成熟到过成熟均有分布,埋藏条件较好.生烃过程模拟结果表明,羌塘盆地烃源岩有两次生烃、排烃过程,且生烃量巨大.于2000年发现的位于羌塘盆地羌南坳陷比隆错—昂达尔错地区布曲组白云岩中的古油藏带,东西长约100km,南北宽约20km,为一狭长湿状、具有强烈油气味的轻质油苗群.根据油—岩地球化学特征,分析并确定,古油藏带主要来源于下侏罗统烃源岩.古油藏带的发现进一步说明了羌塘盆地曾有大规模的油气运移和成藏,具有良好的油气勘探远景.

关键词: 西藏, 羌塘盆地, 中生代, 烃源岩, 古油藏带, 地球化学特征, 油气勘探远景