Evaluating Efficiency of Scaling Inhibitors in Geothermal Fluids at High Pressures and Temperatures

Abstract

Mineral precipitation (scaling) such as sulfates and carbonates is a well-known phenomenon in geothermal plants. Scaling can damage plant equipment (e.g. heat exchangers) or reduce the injectivity of the reservoirs and thus the operation lifetime of such installations. Reduction or prevention of scaling is commonly achieved by injecting scaling inhibitors into the geothermal circuit. However, most highly efficient scale inhibitors are toxic and persistent in the reservoir. In this context, the use of environmental friendly, non-toxic, and degradable scaling inhibitors has become attractive. In this study, a scale inhibitor based on ecologically friendly polycarboxylates was examined with respect to its efficiency to inhibit calcite scaling under high pressure/high temperature (HPHT) conditions. Efficiency tests were carried out in a static batch experiment applying an autoclave system equipped with a sensor monitoring the pH-value. This system allows measurements at pressures and temperatures up to 150 bar and 125 °C. The results were compared with efficiency test under normal ambient conditions.