Laboratory experiments on inhibition of silica particulate deposition in a porous column by dosing of chemical reagents into reinjection water (2): Prevention and dissolution of silica deposits by alkali dosing

In order to develop a method for prevention of silica deposition in a reinjection zone, laboratory experiments using reinjection water from the Kakkonda geothermal field were conducted. In the experiments, the reinjection water was cooled from about 130°C to 120°C or 95°C, and then introduced to a porous column that was packed with zirconia beads. Permeability decrease of the column due to deposition of solid onto the beads was monitored by measuring pressure values along the column. Observation of the solid deposits on the beads indicated that aggregation of silica particles on the beads was the predominant deposition process. To prevent or dissolve the silica deposits in the column, an alkaline solution was injected into the reinjection water upstream of the column. The alkali dosing at a specified rate prevented and dissolved the silica deposits. The experiments further proved the ability of the intermittent dosing to dissolve the silica deposits. We concluded that the intermittent dosing can be a practical method for inhibiting silica deposition in the reservoir, because the intermittent addition will reduce the amount of alkali to be used, and hence the cost.