Silica Scaling Field Experiments

Abstract

The deposition of silica from geothermal fluid discharged from a high temperature New Zealand geothermal field was investigated at temperatures between 120 and 180°C. At these temperatures the corresponding silica supersaturation ratios were between 2.7 and 1.4. The fluid was passed through 25 mm diameter pipes and 150 mm diameter gravel beds at 3 and 30 l/min. At 160 and 180°C before the onset of polymerization the deposition rate was uniform across the length of the pipes and beds and there was little difference between the two flows. At the lower temperatures where the silica was rapidly polymerizing there was a large reduction in the deposition rate between the pipe inlet and outlet and in the gravel beds a soft voluminous silica deposited right at the fluid inlet. There appeared to be no substantial enhancement of scaling rate due to the high polymer concentrations at 120°C and the deposition rate in the pipes appeared to be independent of flow rate.