Geogard SX: A silica scale inhibitor for geothermal brine

Abstract

Geogard SX has been developed primarily for the control of silica scaling in geothermal brine. When first tested at the Malitbog Test Facility, this antiscalant - an aqueous solution based on a phosphino carboxylic acid copolymer - achieved 38.1% to 95.7% inhibition efficiency at varying low concentrations of 5 to 10 ppm using brine with high silica saturation indices of 2.3 to 2.5. Subsequent successful testing at 10 ppm with the Botong separated brine, which contains an ultra high concentration of silica of more than 1,100 ppm, led to the first commercial application of the inhibitor. Inspection after 17 mo. of continuous dosing of Geogard SX revealed minimal deposition along the Botong Fluid Collection and Disposal System (FCDS). As for the low excess silica brine, Geogard SX at 0.5 ppm dosing, the test facility trials attained ca 70% inhibition efficiency. If applied to the Malaunay sector of Palinpinon-I FCDS, Geogard SX would reduce the O&M (operating and maintenance) cost by US$250,000/yr. Geogard SX is the first efficient and cost-effective silica scale inhibitor for geothermal brine.