Calcite scaling potential of Kangding geothermal field, W-Sichuan plateau, China

Abstract

High temperature geothermal systems in China are mainly along the Himalaya tectonic zone, which extends from Xinjiang to Tibet, western Sichuan Plateau, and Yunnan. One of the main problems during energy production is calcite scaling. This report presents a general calcite scaling potential assessment of the Kangding geothermal fields in the western Sichuan Plateau. Results show that the reservoir fluid reconstructed is slightly over-saturated with respect to calcite and scaling and sinters have been observed in some of the boreholes or springs. Taking fluid from well BH6 as an example, it is saturated with respect calcite in the reservoir conditions and with boiling at different temperatures, it evolves to over-saturated and precipitates in the pipeline. The boiling depth is evaluated to be about 150 m (not considering CO2 and salinity) and 440 m (considering CO2 and salinity) using the HOLA and WELLSIM programmes, respectively. The calcite scale quantity is calculated with three methods and is about 151-300 kg and the thickness is about 1- 3 cm which is almost consistent with the observed thickness in the surface pipeline from the production test. Calcite scale removal and prevention methods are reviewed based on their formation mechanisms and for calcite scaling in the Kangding geothermal field, a probable inhibitor injection from laboratory and a field test is suggested with consideration of the reservoir temperature and fluid chemistry.