Objective: to understand the hydrodynamic, chemical and bacteriological processes leading to the decrease of productivity of the drilling and to the fault of the hydraulics of the submerged pump.
31m deep catchment borehole in PVC-coated casing. Arrival of water from the flint gray chalk.
Understanding of the hydrodynamic regime (variation of the water level) prevailing in the drilling from the lithological description, the technical cut of the drilling, the pumping tests carried out at the end of the drilling and the operating conditions.
Analyzes on geothermal water: physico-chemical parameters, dissolved and total iron, cations and major anions.
Analyzes on the ocher deposit taken from the hydraulic pump: count of sulphate-reducing bacteria (BSR) and thiosulfato-reducing (BTR), microscopic observation of ferrobacteria (BFO).
Analyzes of crystallized phases in X-ray diffractometry deposits.
Proposal for curative solutions: cleaning procedure for sludge drilling, technical rechecking cut, estimation of the new critical operating flow, recommendation to use the geothermal system for heating and cooling the building in order to avoid the proliferation of ferrobacteria .
Photo caption: observation of the partially clogged strainers of the PVC casing in contact with the geothermal water by bacteria of the iron cycle of the Gallionella genus