藏北羌塘盆地上三叠统典型剖面烃源岩地球化学特征研究

Geochemical characteristics of Upper Triassic source rocks from typical sections in Qiangtang Basin,northern Tibet

依据露头样品和测试数据,从有机质丰度、有机质类型及成熟度方面对羌塘盆地上三叠统烃源岩特征进行了评价。结果表明:沃若山和扎那陇巴剖面有机质丰度较高,为中等—好烃源岩,有机质类型以Ⅱ_2型为主,处在高成熟阶段,以生成凝析油和湿气为主;而藏夏河剖面和肖茶卡剖面有机质丰度低,生烃能力较差,有机质类型为Ⅱ_2型,处在过成熟阶段,主要生成干气。总体来看,羌塘盆地上三叠统存在中等-好烃源岩,尤其是盆地凹陷区,可能存在好的烃(气)源岩,这对于羌塘盆地以后的油气勘查具有重要意义。

According to the outcrop samples and analytical data of Upper Triassic source rocks from Qiangtang Basin, the authors evaluated the hydrocarbon generation capacity based on the abundance of organic matter, the type of organic matter and maturity of organic matter. The result reveals that the abundance of organic matter is high in Woruoshan section and Zanalongba section, and the rocks are medium-good source rocks, the type of the organic matter is 112, the maturity is high and it mainly generates condensate and moisture. The abundance of organic matter is low in Duoseliangzi section and Xiaochaka section, and it has poor generation capacity, the type of organic matter is I12, the maturity is over-maturity and it mainly generates dry gas. Overall, the Upper Triassic source rocks in Qiangtang Basin have good hydrocarbon generation capacity, especially in the depression area. The results achieved by the authors have important significance for the future exploration in Qiangtang Basin.