Characteristics and mechanism of the calcite scaling and plugging in DZK02 geothermal well, western Sichuan, China

The issue of calcite scaling and plugging in geothermal wellbores and pipelines significantly hinders the development and utilization of geothermal energy. During an 8-day blowout test of the DZK02 geothermal well in Kangding, western Sichuan, China, it was observed that the scaling thickness reached 1 to 3 cm in the surface pipeline. This phenomenon involves complex processes such as multiphase flow, reactive solute transport, and mineral particle migration and deposition. In this study, we have incorporated the functionality of multiphase flow in wellbores into the general-purpose reactive transport program TOUGHREACT while integrating crystal scaling and particle scaling theories. We applied this program to analyze DZK02 geothermal well with a focus on investigating the mechanisms, characteristics, and influencing factors associated with calcite scaling and plugging. With limited information available on the wellhead conditions, we estimated bottom conditions and reproduced the entire blowout process. Our findings indicate that CO₂ partial pressure at the bottom ranges from 15 to 25 bar, which positively correlate with flash and scaling occurring at the depth. Most of the scale accumulates as particles within the surface pipeline because of the diameter change. This study presents a robust numerical simulation method for analyzing calcite scaling issues within geothermal systems, while providing valuable insights for future utilization strategies concerning DZK02 well.