Scale Control in Geothermal Wells—What Are the Options for Effective and Economic Scale Management?

Summary The drive towards net zero by 2050 has led to the development of alternative energy sources, with a focus on geothermal energy projects. Geothermal brines often contain dissolved minerals and gases that cause scale deposition in wells and plant equipment, leading to decreased efficiency in thermal energy production and reduced flow capacity in injection wells. Geothermal plant conditions and brine chemistry of each geothermal plant vary greatly, making the selection of a suitable scale management process crucial for sustainable energy production. Prevention through chemical inhibition or removal is preferred over costly mechanical methods, though nonchemical alternatives are attractive for reducing the CO2 footprint. Chemical treatment options include continuous topside injection, scale squeeze, or batch treatment in injection/production wells. High temperatures and water throughput in geothermal wells challenge chemical scale control and removal. Selected inhibitors/dissolvers must be thermally stable up to 250°C, preferably biodegradable, and effective against calcium carbonate and silica/silicate scales. Geothermal brines contain dissolved CO2 and H2S, making fluids corrosive. Therefore, the interaction between scale and corrosion inhibitors must be considered in any management strategy, possibly requiring modified laboratory test methods, especially for plants with water reinjection. This paper will review geothermal scale and its mechanisms of formation and management options, including chemical and nonchemical treatments. It also discusses the impact of well completion, high water production, corrosion, CO2 footprint, and the challenges of chemical treatments regarding thermal stability and laboratory testing.