Impact of diagenetic on evolution of reservoirs of Taiyuan Formation limestone in Ordos Basin
Limestone in the Taiyuan Formation in the Ordos Basin has good gas-bearing properties,but the key types of diagenesis that help the reservoir evolve remain unclear.This study investigates the characteristics of the reservoir and its evolution due to its diagenesis by examining thin-section samples from its core through cathode luminescence,scanning electron microscopy,and LA-ICP-MS.The results showed the following:(1)The limestone reservoir in the Taiyuan Formation was dominated by bioclastic limestone that had undergone many types of diagenesis,including micritization,five-stage cementation,penecontemporaneous karstification,mixed-water dolomitization,and siliceous metasomatism.(2)A comparison of the elemental geochemical characteristics of the limestone matrix and the key diagenetic products of each stage led to the identification of a four-stage environment for the fluid:"sealed seawater"in the period of shallow burial,"atmospheric fresh water"in the penecontemporaneous period,"mixed water"in penecontemporaneous-to-shallow burial period,and"residual fresh water"in the burial period.(3)The dissolution of"atmospheric fresh water"in the penecontemporaneous period was the key force driving the development of the reservoir in the area,while various kinds of cementation and small-scale dolomitization caused continuous damage as the reservoir was filled.A diagenetic model of limestone in the Taiyuan Formation controlled by fourth-and fifth-order high-frequency cycles can help predicted areas favorable for exploration and extraction.
Taiyuan Formation limestonediagenetic fluid tracingdiagenetic evolution of reservoircontrolling diagenesis model of reservoirsOrdos Basin
万方数据
维普
