In experiments, flow rates through porous media were measured using raw brine (pH = 6.5, [SiO2] = 1130 mg/L) at Sumikawa Geothermal Power Plant in 2016. The flow rates decreased by up to 25% of the initial flow rate after 11 days. A geochemical clogging model with data from 2003 was used to predict the permeability reduction due to silica precipitation. This model considers the type of silica deposited (amorphous and aluminum-silica scales) and calculates the optimized conditions for keeping the concentration of SiO2 below 300 mg/L to lessen the reduction of permeability during the reinjection of geothermal brines.