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Investigation of thermo-hydro-geochemical processes in a standing column well intersected by a fracture

Eppner, Fanny
Pasquier, Philippe
Baudron, Paul
Local thermal and chemical conditions may favor minerals' scaling which can cause undesirable operational problems to standing column well systems. Precipitation may reduce heat exchange in the well and the heat exchanger and increase pressure drops in the systems components, as well as the drawdown in the well. In this paper, a coupled thermo-hydro-geochemical model simulating the operation of a standing column well is used to illustrate the link between the temperature and the reaction rate of calcite. The results demonstrate that bleeding only 10% of the pumped water allows to get rid of calcium ions in solution in the well and reduces substantially the precipitated calcite mass. Our simulations clearly indicate that groundwater flow induced by the bleed mainly occurs in the fracture since significant chemical variations are observed downstream of the fracture. We expect that the findings presented in the paper will help demystify the complex thermo-hydro-geochemical behaviour of standing column wells installed in sedimentary rocks.