Testing of New Silica Inhibitor at Botong Reinjection System, Bacon-Manito Geothermal Production Field, Philippines

Abstract

A polyacrylic copolymer-based silica inhibitor (F3680), was tested in the Botong Reinjection System (BRS) of the Bacon-Manito Geothermal Production Field (BGPF) using the brine separated at 0.70 MPa with about 45% oversaturation with respect to amorphous silica. The test was aimed to determine the inhibition property and applicability of F3680 and as an alternative silica inhibitor chemical for GSX at the current cold injection set-up and the proposed hot injection scheme. The chemical was dosed at an effective concentration of A ppm at the two-phase fluid tapped from the header of the production wells before the main separator vessel.

Treating the brine with F3680 at the cold injection set-up achieved an inhibition efficiency of 55.8% or an average deposition rate of 1.76 mm/day as compared with 3.98 mm/day of the untreated line. The new chemical reduces silica deposition and produced layered and less adherent to surface type of deposits, to granular and soft gel-type form.

In the hot injection scheme, yellowish slurry type of deposits is produced along the hot line and in the retention vessel. The deposition rate is measured based on weight difference method since the type of deposits are loose and non-adherent to the pipes. Minimal deposits are formed along the pipes with highest deposition rate of 0.15 g/day measured in the inspection spools.

Based on the nature of deposits formed, F3680 is a promising silica inhibitor that can replace the existing chemical inhibitor.