Hydrochemical Characteristics of High‐Temperature Geothermal Fluids and Quantitative Assessment of Wellbore Scaling in the Yangbajain Geothermal Field, Tibet

Severe calcium carbonate scaling occurs in the wellbores of high‐temperature geothermal wells in the Yangbajain Geothermal Field. Based on sampling and laboratory analysis of the geothermal field, this study investigates the hydrogeochemical characteristics of the geothermal fluids, estimates the reservoir temperature, and reconstructs the bottom‐hole fluid composition. Combined with field discharge tests and scaling characteristics, a prediction model for the flash horizon in the wellbore and a coupled quantitative evaluation model for calcium carbonate scaling are established to forecast the scaling location and amount. The results indicate that the shallow reservoir temperature is 190 ° C ± 20 ° C, with an initial pH between 5.3 and 6.7. The high‐temperature geothermal water is of Na‐Cl type, and the CO 2 in the geothermal fluid primarily originates from high‐temperature decarbonation of deep metamorphic sedimentary rocks and marine carbonates. Higher CO 2 content leads to a greater scaling rate and amount. For the typical geothermal well ZK303, the predicted flash horizon is at a depth of 126.8 m, with the most severe scaling occurring 10–20 m above the flash horizon. The maximum scaling rate is 0.1214 mm/d, with scaling thicknesses of 0.85 mm (7 days) and 3.64 mm (30 days), and scaling amounts of 342.65 kg (7 days) and 1468.52 kg (30 days).