A Test of Calcium Carbonate Scale Inhibition in Chingshui Geothermal Field, Taiwan

A 3MWe geothermal power plant at Chingshui geothermal field was built in 1981 and was decommissioned in 1993 due to continued declines in well production. Deposit and plugging wellbore caused by calcium carbonate scale was a major reason for reduced production. The purpose of this study was to investigate the inhibition efficiency of representative wells IC-9, IC-13 and IC-19 in Chingshui geothermal field. A downhole geothermal fluid sampler was conducted at a representative depth of 800 m in IC-19 to gather data on the formation fluid and for the analysis of scaling potential. Two kinds of inhibitors, Sodium Polyacrylate and Polyacrylate Acid, were tested in-situ. The difference of calcium concentration before and after dosage was used as an index for inhibition efficiency calculations. The inhibition efficiency of Sodium Polyacrylate was better than Polyacrylate Acid, but not significantly different. The exponential relationship between inhibitor concentration and efficiency was obtained; it can be a reference for maintenance cost calculation of Chingshui geothermal power plant.