藏北羌塘盆地QK-1井中侏罗统烃源岩地球化学特征

QK-1天然气水合物钻探试验井位于西藏羌塘盆地毕洛错地区，主要钻遇中侏罗统夏里组粉砂质泥岩和布曲组灰岩。其有机质丰度、有机质类型、有机质成熟度等有机地球化学特征表明，南羌塘地区中侏罗统烃源岩的有机质丰度偏低，夏里组泥岩TOC介于0.26%~0.38%之间，达到差-中烃源岩标准，而布曲组灰岩TOC介于0.02%~0.08%之间，仅局部达到差烃源岩标准；两个组的烃源岩有机质类型主要为Ⅱ₂型及Ⅲ型，较利于天然气的生成，其中夏里组的生气能力优于布曲组；该区烃源岩热演化程度较高，Ro为1.31%~1.63%之间，均达到高成熟阶段，而夏里组有可能已进入干气阶段。基于冻土区天然气水合物成藏条件分析，综合考虑夏里组烃源岩及沉积厚度特征，认为中侏罗统夏里组具备良好的天然气水合物勘探前景。

Geochemical Characteristics of Hydrocarbon Source Rocks in the Middle Jurassic of Borehole QK-1 in the Qiangtang Basin,Northern Tibet

The borehole QK-1, one of the scientific drilling holes of gas hydrate, is located at Biluocuo area in the Qiangtang Basin of northern Tibet, in which the silty mudstones of Xiali Formation(J₂x) and limestones of Buqu Formation (J₂b) were drilled. The geochemical characteristics of the abundance, type and maturity of organic matters of the source rocks reveal the following aspects: the organic matter abundance of source rocks in Middle Jurassic is lower; the silty mudstones in Xiali Formation have reached be poor-medium source rocks with TOC of 0.26% to 0.38%, and the TOC values of limestones in Buqu Formation are between 0.02% and 0.08%, part of which has reached to be poor-hydrocarbon source rocks; the types of organic matters for source rocks in Xiali and Buqu formations are mainlyⅡ₂ type or Ⅲ type, which are beneficial to gas formation, and the source rocks of Xiali Formation is superior to that of Buqu Formation. The value of R_o for source rocks in this area is from 1.31% to 1.63%, showing that the organic matter has undergone a high-degree thermal evolution and is in a high-maturity stage, and the organic matter in Xiali Formation is even in an over-maturity stage. Combining all factors favorable for the genesis of gas hydrates, it comes to the conclusion that Xiali Formation is a potential exploration target.