F3680 Silica Inhibitor Testing in Botong Sector, Bacon-Manito Geothermal Production Field, Philippines

摘要

A polyacrylic copolymer based silica inhibitor (F3680), were tested at varying concentrations from 5-20 ppm using Botong separated brine at 0.70 MPa with about 45percent oversaturation with respect to amorphous silica to determine its efficiency and inhibition property at the current cold injection set-up. Geogard SX (GSX), the existing silica inhibitor being used by the Botong Reinjection System (BRS) was also tested in the same set-up to compare the two inhibitors and determine if F3680 can be used as an alternative to GSX. The chemical inhibitor was dosed at the two-phase fluid tapped from the header of all production wells before the main separator. F3680 reduces silica deposition within the cold section of BRS with an average deposition rates ranging from 1.76 to 2.76 mm/ day as compared to 3.98 mm/day of the untreated line. Treating the brine with 10ppm of F3680 achieved the highest inhibition efficiency of 55.8percent. Brine treated with F3680 produced poorly formed, layered, and thin but moderately hard silica deposits, to granular and compact and soft gel-type that settles and friable. GSX treated brine produced silica deposits that are much more dense, very hard, and massive. The deposits are also adherent to the metal surface and alter to globular and grainy habits downstream of the test facility. Average deposition rate of GSX-treated brine is 1.27 mm/day, which is higher than any concentration of F3680 treated brine. The efficiency is consequently higher at 68percent. Results of the tests using F3680 is promising and can be used to replace GSX as long as regular cleaning of the sumps will be implemented.