A numerical investigation into the propagation of acid-etched wormholes in geothermal wells

Carbonate geothermal reservoirs are widespread in the Beijing-Tianjin-Hebei region, and acidification stands out as the most effective method to enhance the heat recovery potential of these reservoirs. To understand the propagation patterns of acidized wormholes in geothermal reservoirs, a pore-Darcy scale mathematical model of acidizing reactions in geothermal reservoirs has been established. A normal random distribution function is introduced to depict the reservoir's heterogeneity. Using the finite element method, the study simulated the impact of injection rate, acid concentration, diffusion coefficient, and acid-rock reaction rate on wormhole morphology. The findings indicate that the reaction is uniform in the early stage of acidification, becoming non-uniform in the late stage, ultimately forming distinctive wormhole structures. The acidification radius is more extensive along a particular direction post-acidification. Increasing the acid injection rate, acid concentration, and initial specific surface area proves beneficial in enhancing the acidizing effect. The outcomes of this study hold theoretical and technical significance for optimizing the thermal recovery efficiency of geothermal reservoirs.