Degassing of Geothermal Fluids: A Geochemical Model

Abstract

Liquid geothermal fluids entering a wellbore generally flash during their ascent to the surface as a consequence of temperature and pressure drops, which strongly affect fluid chemistry. The chemical behavior of brine nowadays seriously preoccupies engineers and research workers because of its repercussions on well production: fluid chemistry affect fluid physical properties and thus hydrodynamic, and is closely linked to scaling, well plugging and corrosion problems. We have there fore developed a computer program, TPDEGAZ, to model the chemical behavior of the brine. It takes into consideration salts, steam and noncondensable gases. It predicts the flash pressure and , the amount of steam, composition of the gas phase, pH, modalities of aqueous species and saturation degrees of the fluid with minerals at wellhead and at every intermediate thermodynamic conditions. A test of the model on a low enthalpy geothermal well in the Paris basin (France) is detailed.