Factors controlling the termination of a 3-Mw-pilot power plant in the Chingshui Geothermal Field, Taiwan

Taiwan is located at the margin of young orogenic belt which the Philippine Sea plate collides with Asian continental margin. It is characteristic that the geothermal outcrops and hot springs are widely distributed in this island and has great potential to explore and develop the geothermal heat for power plant. A 3-Mw pilot power plant, therefore, was constructed in 1981 in the Chingshui area, northeastern Taiwan. However, due to rapid decline of power generation from 1.2 Mw to 0.2 Mw and shortage of economic efficiency, this plant was terminated in 1993. Most of the engineers and researchers considered the important reason for termination may be resulted from carbonate scaling, based on the findings of calcite deposits inside well pipe. In 2005, the Bureau of Energy of Taiwan restarted geothermal exploration and developed a plan for future power generation in the Chingshui geothermal field. A production well with the depth 1,500 m has been drilled into the reservoir of slate host rocks and raises 200 m cores between 600 m to 800 m in depth. Many calcite or aragonite minerals filled up the fractures, veins and open cracks have been found in the cores. Meanwhile, surface survey on outcrops shows that there are many quartz veins occurred in slate formation, but a few or no calcite veins. Those lines of evidence strongly suggest that the termination of power plant in the Chingshui geothermal field is due to formation scaling rather than carbonate precipitations inside the wells. A solution reducing the formation scaling will be sought in the future to restart power generation of the Chingshui geothermal field.