Abstract
The risk of voluminous silica scaling limits many geothermal energy plants to steam and brine separation temperatures above the saturation limit for silica in the separated brine. The impact of these limits are compounded in the face of demand for secondary heat extraction using binary plant that can significantly increase energy efficiency from geothermal fluids. Options for additional energy extraction include (i) increase in pH to increase the solubility limit for silica and (ii) decrease in pH to delay the time for onset of polymerization reactions for colloidal silica sufficient to allow reinjection to a reservoir where elevated temperature will lower the silica saturation index. These two scale-control methods can have significant impact on localized corrosion in chloride rich brines. Conditions for scale control and the risk of corrosion can both be modeled theoretically to predict ideal conditions for enhanced energy production with minimal risk of corrosion. However, prudent operators can benefit from confirmation testing of scaling and corrosion risks using a pilot plant that mimics planned operating conditions. Repeated testing of the thermodynamic models will improve the developed model prediction capabilities.
