西藏伦坡拉盆地古近系页岩油资源潜力初探

摘要

Based on the measured profile of the Paleogene Niubao Formation and Dingqinghu Formation in northwestern Jiangriacuo sag, northwest Lunpola Basin, Tibet, the authors analyzed the organic matter abundance, types and maturity of the source rocks. The Niubao Formation and Dingqinghu Formation were characterized by high organic matter abundance with the TOC values ranging from 0.91% to 5.53% and the chloroform "A" ranging from 0.03% to 0.63%. The organic matter is of type I, with averageTmax being 428℃, which suggests that the source rock is at the early stage of oil generation, and the Niubao Formation is better than the Dingqinghu Formation in this aspect. The results indicate that the Niubao Formation in the work area is the most favorable source rock. A comparison with typical shale layers in China and abroad shows that it possesses the basic geological condition of generating shale oil although the maturity is slightly lower. It is inferred that the higher maturity the deposition center of Jiangriacuo sag is the greater the shale oil potential would be.%本文在西藏伦坡拉盆地蒋日阿错凹陷西北部古近系牛堡组和丁青湖组实测剖面的基础上,通过对烃源岩有机质丰度、有机质类型、有机质成熟度及生标化合物等进行分析,认为牛堡组和丁青湖组烃源岩有机质丰度中等,有机碳含量TOC在0.91%~5.53%之间,氯仿沥青"A"在0.03%~0.63%之间,有机质类型主要为Ⅰ型,Tmax平均值为428℃,烃源岩处于未成熟-低成熟阶段.综合分析认为,研究区牛堡组是古近系最有利的烃源岩层段,与国内外典型页岩层各项指标对比,牛堡组具备页岩油形成的基本地质条件,但成熟度略低,推断位于蒋日阿错凹陷沉积中心的牛堡组烃源岩厚度更大、成熟度更高,页岩油潜力更大.