Physical properties and percolation characteristics of Neogene Lantian−Bahe Formation thermal reservoir in Guanzhong Basin

Guanzhong Basin is rich in geothermal resources, and its development and utilization will help to adjust the energy structure, reduce haze and improve the environment.The Neogene Lantian−Bahe Formation is the main stratum exploited at present. It is of great significance for effective development and reinjection of geothermal energy to clarify reservoir physical properties and seepage mechanism. Through core data and logging data, combined with mercury injection, casting thin section, nuclear magnetic resonance and other related testing methods, the physical property, pore structure and seepage characteristics of the Neogene Lantian−Bahe Formation in the Weihe Basin are analyzed in detail. The results show that: ①The porosity in the plane of Lantian Bahe Formation is 7%~30%, with an average of 15%; permeability changes greatly, 0.05~5689 mD, generally more than 30 mD. ②The pores of Lantian−Bahe Formation are mainly primary intergranular pores and intergranular residual pores, with a small amount of microcracks and feldspar dissolution pores can be seen locally.The pore throat distribution is relatively uniform, mainly between 10 and 16 μm. The contribution value of permeability is high. The water yield can reach 80 m³/h, and the unit water inflow of sandstone with unit thickness can reach 0.0035 m³/(h·m²) with good water yield and seepage characteristics.③The reservoir type of Lantian−Bahe Formation belongs to Class Ⅱ reservoir, which is comprehensively evaluated as high porosity permeable layer, and is the most favorable geothermal development interval.