Petrological characteristics and potential damage factors of mid-deep geothermal reservoirs in Guanzhong Area

To get clear about potential damage factors of mid-deep geothermal reservoirs in Guanzhong area, the rock sample from geothermal reservoirs of Lantian-Bahe formation is taken as the research object. By means of casting thin sections, granularity analysis, scanning electron microscopy, CT scan and X-ray diffraction method, the studies on interstitial material, physical properties and pore structure are carried out based on the lithology classification, the relationships between sensitivity minerals, permeable-storage space and geothermal reservoirs damage are analyzed. The results showed that the order of clay mineral content of all kinds of geothermal reservoir rocks from the highest to the lowest was below: siltstone, fine sandstone, medium sandstone, glutenite. There was a positive correlation between permeability and porosity. According to lithology, the physical properties of geothermal reservoir rocks were in the order of glutenite, medium sandstone, fine sandstone. The higher the matrix content, the worse the physical properties of the geothermal reservoir rocks. The large-size pore throat in various types of geothermal reservoir rocks contributes greatly to permeability. When the formation particles in the rocks, especially clay minerals, contact with external fluids or their environment is changed, it is easy to disperse and migrate, causing damage to the reservoir. The characteristics of loose cementation of geothermal reservoir rocks aggravate its particle migration.