Reservoir Characteristics And Diagenesis Of Upper Paleozoic Reservoir On The West Margin Of The Ordos Basin

This thesis mainly based on the special"reservoir analysis and evaluation of old wells on the west margin of the Ordos basin". Most test data of casting slice, SEM, mercury intrusion, granularity analysis, CLM, bireflectance of vitrinite, X-ray diffraction of clay minerals have been used; in combination with the Reservoir physical properties, the thesis evaluated the upper Paleozoic reservoir on the west margin of the Ordos basin being guided by the new achievements of sedimentary theory, clastic reservoir research and international oil-gas field exploration.According to the comprehensive research on structural features, sedimentary facies, reservoir characteristics and diagenesis of the upper paleozoic clastic reservoir on the west margin of the Ordos basin, following conclusions have been achieved:1. The upper Paleozoic reservoir on the west margin of the Ordos basin mainly distribute from Shihezi formation to Shanxi formation. Shanxi formation is dominated by meandering river, river-dominated delta and lake sedimentary system. Shihezi formation is dominated by meandering river, braided delta and lake sedimentary system.2. This is the reservoir of low porous and low permeableoir, interganular pores and secondary dissolution pores are dominated, permeability is rather low. The diagenesiss in this area mainly includes compaction, pressure solution, cementation, and phase transition of clay minerals etc.,3. Secondary pores in this area have been analyzed by studying the feldspar dissolution, tuffaceous volcanics dissolution and the effect of thrust on reservoir, in combination with the diagenesis evolvement. Secondary pores mainly formed in the period A at the late diagenetic stage, as the K-feldspar dissolved into kaolinite and quartz due to the rise of ground temperature and participation of acid medium, the bulk has been decreased and the secondary pores were developed. However, once the volcanic materials, especially the fine volcanic ash filled in the holes in the reservoir have been compacted, it could both avoid kaolinization and restrict the dissolution; therefore, the sandstone are usually compact and deeply affect the porosity-permeability and the inhomogeneity of reservoir. The complex distribution of effective reservoir in this area most probably generated from this.4. After the comprehensive analysis and evaluation, it is considered that the best reservoir may be exist in Shanxi formation around Lucan 1 well and Shihezi formation around Tianshen 1 well in this area.