Methods for Detecting Perforations in Casings of Wells Exploiting Geothermal Fluids

Abstract

The geothermal installations exploiting the Dogger aquifer in the Paris Basin experience problems of corrosion and scaling in the well casings. When localized, corrosion can lead to perforations in the casing, thereby increasing the risk of contamination by geothermal fluids of freshwater aquifers (Albian, Chalk) traversed by the wells. To detect perforations, for which there are numerous scenarios, several different methods can be used. For this particular geothermal application, two methodologies have been adapted: Analysis of samples taken at the production wellhead of the geothermal well or at the freshwater pumping station, allows us, for some chemical species, to detect a volumetric proportion of Albian water in Dogger water of as little as 1%, and even less than 0.5% in the opposite case. 2) Remote monitoring of the different operating parameters (flowrate, pressure, temperature, etc.) allow us to determine, in some cases and almost in real time, the probability of perforation. Emergency measures can then be taken.