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    萍乐坳陷上二叠统乐平组泥页岩储层特征

    Reservoir characteristics of Upper Permian Leping Formation shale in Pingle depression

    • 摘要: 为了探讨萍乐坳陷地区乐平组泥页岩的储层特征,以野外地质调查、老井复查资料及样品的分析测试结果为基础,对研究区泥页岩的分布特征、地球化学特征、矿物组成特征及微孔隙特征等进行了较深入分析。结果表明:乐平组泥页岩在研究区分布广泛,平均厚度在100m以上。泥页岩的有机碳含量较高,介于0.21%~23.4%,平均为1.74%,Ro为0.7%~4.06%,平均为1.88%,处于成熟-高成熟阶段,干酪根类型以II2型为主。泥页岩中脆性矿物含量较高,以石英为主,平均为47。94%,表明泥页岩具有好的压裂潜力。黏土矿物含量中等,平均为34.93%,主要为伊利石和伊蒙混层。泥页岩的孔隙度平均为3.5%,渗透率平均为0.01×10-3μm2,反映了乐平组泥页岩储层物性较好。扫描电镜下观察泥页岩微孔隙类型主要为粒间孔、粒内孔和有机质孔。孔隙形态呈较开放状态,以细颈状墨水瓶孔和四边开放的平行板状孔等为主。进一步分析表明乐平组泥页岩微孔隙发育主要受有机碳含量和石英矿物含量控制,有机碳含量越高,微孔和中孔越发育,石英含量则对宏孔贡献明显。

       

      Abstract: On the basis of field geological investigation, old well reexamination and analysis results, the reservoir characteristics of Leping Formation shale in Pingle depression was discussed in such aspects as distribution characteristics, geochemical characteristics, mineral composition features and micro-pore features. The results show that Leping Formation shale is widely distributed and its thickness is above 100 m. The total organic carbon content of shale is high, reaching up to 0.21%-23.4%, averagely 1.74%, the thermal evolution degree of shale is also high, with Ro in the range of 0.7%-4.06%, averagely 1.88%, and the organic matter type is mainly of type II2. The shale has abundant brittle minerals consisting mainly of quartz(averagely 47.94%)and shows a good fracturing potential; the clay minerals content is moderate(averagely 34.93%)composed mainly of illite and andreattite. The shale reservoirs have an average porosity of 3.5% and average permeability of 0.01×10-3μm2, implying a good physical property. The types of micropores include intergranular pores, intragranular pores and organic pores, as shown by scanning electron microscope. Shale reservoir pore shapes show opening state, including two-end opened cylindrical shape and four sides opened parallel pores. Further analyses show that the organic carbon content and quartz content were the major factor to control the shale reservoir porosity development, the effect of total organic content on shale micro-pores was mainly manifested in the development of micropores and mesopores, and the quartz mineral content contributed to macropores.

       

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