Reactive transport model predicting calcite precipitation: Case of a dynamically operated standing column well

Abstract

The sanding column well is a promising ground heat exchanger. Nevertheless, hard water can lead to scaling problems. The aim of this study is to calibrate a thermo-hydro-chemical model on experimental data to quantify the factors influencing the scaling. Groundwater samples were collected during 70 days on a standing column well operated jointly with a groundwater treatment unit. A coupled thermo-hydro-chemical model integrating nine aqueous species, calcite mineral reactions, CO2 degassing, and temperature dependent reactions was developed and calibrated on the experimental measurements. Calibration results indicated a precipitated calcite mass of a few nanograms per day. It was observed numerically that when bleed is not active, treating only 2% of the flowrate avoids calcite precipitation. If sealing the wellhead and limiting CO2 degassing are possible, the simulation results indicate a reduction in precipitated calcite masses of 36%.