柴北缘大煤沟组七段(J_2d~7)页岩油资源潜力评价——以大煤沟地区为例

通过对大煤沟地区4口钻井和侏罗系标准剖面的40件大煤沟组七段泥页岩样品进行有机地球化学特征、岩矿特征、储集性能等实验分析。结果表明:样品的总有机碳含量平均值为5.22%;干酪根类型为I-II型,以腐泥质为主;样品有机质成熟度平均值为0.52%,主要为未成熟—低成熟样品;样品的储集空间类型多样、微裂缝发育,有利于页岩油的吸附、存储,矿物组成中大于40%的脆性矿物含量有利于后期的生产压裂。另外,在荧光下,样品断面及层理面具有好的荧光显示,为页岩油的存在提供了直接证据。综合分析认为,大煤沟地区大煤沟组七段具备页岩油形成的地质条件,是中侏罗统页岩油发育的最有利层段。并且在柴北缘范围内,该层段泥页岩单层厚度大,平面上横向分布稳定,结合已有研究成果,初步预测冷湖地区、赛什腾凹陷、鱼卡凹陷、大柴旦—大煤沟地区为柴北缘该层段的页岩油发育有利区。

The potential evaluation of shale oil in the seventh member of Dameigou Formation(J2d7)on the northern margin of Qaidam Basin: A case study of Dameigou area

This study used 40 shale samples from the seventh member of Dameigou Formation in 4 drilling wells and the Jurassic standard profile in the Dameigou area to illustrate the organic geochemical characteristics, the petrographic and mineralogical features, and the reservoir properties. According to the results obtained, the average content of total organic carbon is 5.22%; the kerogen is of I-II type, dominated by sapropel; the average value of organic maturity is 0.52%, belonging mainly to immaturity to low maturity; the reservoir space has various types, and micro-fractures are developed in favor of the adsorption and storage of the shale oil, and the content of brittle minerals in the mineral composition is more than 40% in favor of the production fracturing in the future. In addition, the fracture surface and the bedding planes with fluorescent provide the direct evidence for the presence of shale oil. A comprehensive analysis shows that the seventh member of the Dameigou Formation in Dameigou area with the geological conditions of the shale oil formation is the most favorable section for the development of Middle Jurassic shale oil. Moreover, the single layer of the shale in this member has larger thickness and the lateral distribution of this member is stable in the plane within the northern margin of Qaidam Basin. Combined with the existing results, it is tentatively held that the favorable areas for the shale oil development are Lenghu area, Saishiteng depression, Yuka depression and Dachaidan-Dameigou area.