Modelling the Massive Scaling Phenomena in Upper Mahiao and South Sambaloran Using Solveq/Chim-XPT

Massive mineral deposition along geothermal Fluid Collection and Re-cycling System (FCRS) facilities has caused losses in the operation of Upper Mahiao and South Sambaloran sectors in Leyte Geothermal Production Field due to recurring shutdowns conducted to remove these deposits. It is important to provide the proper mitigating measure to prevent such occurrence and this can be done by understanding the process by which this massive scaling forms. Geochemical modelling software like SOLVEQ and CHIM-XPT are useful tools to model and understand the process by which mineral deposition occurs. Results of the simulation using the software showed that the modelling was able to match the identity of most of the deposits that were observed in the field and the mechanism by which massive scale formation occurred. Modelling simulation showed that massive deposition in Upper Mahiao two-phase header was due to the mixing of the acidic (pH = 3.7) amorphous silicasupersaturated fluid, from Well 2D with the less acidic (pH=6) fluid from Well 1D. The resulting fluid was supersaturated with amorphous silica but with a less acidic pH of 5. The increase in pH resulted to faster oligomerization that caused massive scale formation. Separation of the branch-lines was recommended to prevent the massive scaling. While for the case of South Sambaloran, the massive deposition in Separator 6 brine line, based on the simulation, was due to the flashing of the brine. Flashing caused amorphous silica to become supersaturated and form massive deposits.