Test Results of Another Silica Scale Inhibitor in Malitbog Geothermal Brine, Tongonan, Leyte

Abstract

Silica scale inhibitor Geosperse CSXSl 10 was fesfed in Malitbog low-pressure (P - 0.6 MPag) and slightly oversaturated brine (SS/ = 1 .1 -1 .2) using a silica inhibition fesf set-up. Iesf runs in short durations using 5.0 ppm (1 1 days),0.5 ppm (5 days) and 10,0 ppm (31 days) dosing concentrations were conducted to evaluate the inhibitor's suitability to address the recurrent capacity decline of injection wells 5R1D and 5R4 due to silica deposition. All test runs showed the formation materials coated with distinct powdery silica deposifs in contrast with the hard, cemented type and rough-edged silica deposition of the baseline (untreated) fesfs. The powdery deposifs do not significantlya ttach to the inspection pipesi nner walls. The presence of silica depos/fs loosely coating the formation materials with no significant change in the brine'st otal silicac oncentrationsa cross fhe fesf sefup suggesfs the mechanism of molecular deposition may a/so be as important as silica deposition due to polymerization. The inhibitor acts as a drspersant to prevent the growth of silica particles bigge r than the critical size necess ary for the polymers fo drop out in the brine solution and deposit in the inspection pipes and formation materials. Furthermore, the inhibitor may have interfered in the formation of hard deposifs produced through cross-/rkni ng of silica particles. Additional fesfs are to be conducted to validate the preliminary results and evaluate whether the type of deposifs may be acceptable to PNOC-EDC operations.