柴达木盆地北缘侏罗系页岩气地质条件

    Geological conditions of the Jurassic shale gas on the northern margin of Qaidam Basin

    • 摘要: 侏罗系泥页岩是柴达木盆地的主力烃源岩之一, 具备形成页岩油气的地质条件。对采自柴北缘鱼卡、大煤沟、小煤沟、开源、绿草沟、大头羊等煤矿附近地表露头的11块中侏罗统泥页岩样品进行单样品多参数实验分析, 探讨了陆相页岩有机地化、储层物性、含气量等参数之间的关系, 建立了页岩气资源评价参数体系。结果表明, 柴达木盆地北缘中侏罗世处于浅湖-半深湖湖相沉积, 断裂较发育, 泥页岩富含有机质, 具有低孔、低渗、低熟、较高含气量等特点, 具备形成页岩油气的地质条件, 进一步的勘查开发需优选地层压力系数高、保存条件较好、脆性矿物含量高的页岩气甜点区。

       

      Abstract: Jurassic shale is one of the main hydrocarbon source rocks in Qaidam Basin and possesses the geological conditions for the formation of shale oil and gas. Eleven samples collected from the surface outcrops of Jurassic shale near some coal mines on the northern margin of Qaidam Basin such as Yuqia, Dameigou, Xiaomeigou, Kaiyuan, Lvcaogou and Datouyang. The authors carried out single multi-parameter experimental analysis of these samples and investigated the relationship between the organic geochemstry, petrophysical properties and gas content of lacustrine shale. On such a basis, the shale gas resource evaluation parameter system was established. The results show that the northern margin of Qaidam Basin was characterized by shallow lake-semi-deep lake lacustrine sediments in Jurassic, with well-developed fractures. During that time, shale was rich in organic matter, and had such characteristics as low porosity, low permeability, low maturity, low brittleness, and high gas content, thus having geological conditions for the formation of shale oil and gas. Further exploration and development of Jurassic shale should choose shale gas areas with high formation pres-sure coefficient, relatively favorable storage conditions and high content of brittle minerals.

       

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