Development of New Silica Inhibitor -- Laboratory and Field Study

Abstract

In many parts of the world Silica is the critical limiting factor in harvesting geothermal energy and water reuse. Silica scale is extremely tenacious, highly insulating, and very difficult to remove. Generally, in the production well silica does not cause any fouling due to high temperature and relatively lower pH. However, in the surface equipment, multi-flash plants, binary plants, and the injection well, as the brine cools down and may also be accompanied by higher pH, silica/silicate precipitation can plug the surface equipment and the close down injection well. Most common solution has been either removing silica by precipitation with magnesium lime and landfill or acidified the brine to prevent precipitation. Both these solutions are very costly and compromise safety and equipment integrity. Acidified brine is highly corrosive to the equipment and the well casing. Thus the silica inhibitor is highly desirable. The laboratory study showed that silica inhibition depended on both time and product dose. These results do show the importance of kinetics and residence time to determine the optimum dose to inhibit silica deposition. Hydrothermal stability of the silica inhibitor showed excellent performance at least up to 300 °C. Laboratory study provided guidance for the field study in geothermal fields, the results of which are presented in this paper.