Scaling and blockage risk in geothermal reinjection wellbore: Experiment assessment and model prediction based on scaling deposition kinetics

Wellbore scaling affects the high-efficient geothermal reinjection. It is important to predict the scaling risk accurately in the reinjection wellbore and take effective anti-scaling measures. In this study, using the geothermal water in Xining Basin, China, a series of scaling experiments were carried out to explore the scaling amount of geothermal water, the scaling adhesion ratio on the pipe wall, and the influences of related factors. An improved prediction model of scale layer thickness in reinjection wellbore was established based on the scaling deposition kinetics, and the scaling and blockage risk in the reinjection wellbore at different conditions were assessed. The results show that there is a large-scale adhesion ratio on the pipe wall at a static condition. But in a real reinjection wellbore, the water scaling tendency will decrease significantly because of the small temperature rise in the wellbore. Only a very small amount of scale particles can attach to the pipe wall, while most of them will invade the formation and damage the injectivity. Long injection time, large injection rate, and high injection temperature can eliminate the scaling risk in the wellbore totally, which is the most economical anti-scaling measure.