| Title | Geothermal Silica Scale Inhibition and Control Using Phosphino Carboxylic Acid Copolymer in Bacon-Manito Geothermal Business Unit |
|---|---|
| Authors | Baltazar, Almario D. Jr.; See, Fidel S.; De Guzman, Richard C.; Solis, Ramonito P.; Salonga, Noel D. |
| Year | 2014 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | GSX; silica; scaling; geothermal |
| Abstract | Silica scaling is a common and real problem in the operation of water-dominated geothermal systems of Energy Development Corporation (EDC) in the Philippines. To help operate the fields such as the Bacon-Manito Geothermal Business Unit (BGBU), EDC focused and conducted experiments on the use of polymers Geogard SX (GSX - a phosphino-carboxylic acid copolymer) to inhibit silica scale formation in the geothermal facilities. Initial field experiments using low concentration of GSX for five (5) months resulted to treatment efficiency of 64-98%. This was based on silica concentrations of 1000-1300 ppm in various sampling points of the test rig. The established efficiency helped BGBU to manage and operate the Botong Power Plant for about 10 years (1998-2008) with the silica scale inhibition technology. In this operation, GSX was delivered using high pressure pump into the two-phase header (~165°C) and followed a cold injection scheme that is unique in BGBU prior to injection. Several GSX studies in BGBU and Leyte Geothermal Business Unit (LGBU) were undertaken for hot injection testing. Based on the BGBU results, hot injection scheme for Botong with inhibitor dosing of 10 ppm is a technically feasible option. Comparison of GSX against commercial inhibitor, F3680 also revealed that the average deposition rate of silica in GSX treated brine is better than any tested concentration of F3680. In LGBU, the GSX test with 0.5 ppm dosing showed very low thickness of silica scale and deposition rates (2.4-11.9 mm/yr). These were also confirmed by flow rate, formation weight, petrologic analysis and brine chemistry monitoring. The GSX was further tested for low temperature brine injection scheme during a simultaneous discharge test (SDT) of wells TW1D and TW4D in BGBU. The process supersaturates dissolved amorphous silica at the silencer weirbox (T~ 90°C) to 753 and 694 ppm with a silica saturation index (SSI) of 2.42 and 2.28. A treatment concentration of 8ppm was found effective as the deposition rates of silica decreased significantly with an inhibition efficiency of 71%. |