Geothermal applications by drilling. Operational interference control.

Geothermal drilling on aquifers consists in feeding heat exchangers with water from the aquifer to produce heat or cold on the surface using thermodynamic machines (heat pumps, refrigeration pumps).

Such a thermodynamic machine can only function correctly in the Carnot cycle if the two external heat sources (hot and cold) remain at an almost constant temperature over the long term.

Geothermal regulations for open heat exchangers supplied with aquifer water by producer wells require that all geothermal water produced must be reinjected into the same aquifer via injector wells .

The geothermal water is reinjected into the aquifer at a different temperature (around 5 to 7°C higher or lower, depending on whether the thermodynamic machines are producing cold or heat).

The risk involved in operating geothermal well doublets (producer-injector) would therefore be that reinjection water of different temperatures would eventually migrate to the drainage zone of the producer wells. This would seriously impair the thermodynamic performance of the machines and eventually lead to plant shutdown ( , p. 8 and 56).

The complex models used to calculate the evolution over time of hydraulic or thermal drainage zones (also known as plumes or clouds) in the aquifer of producing or injecting wells are described in the literature ( . The essential results that can be obtained using these methods are presented in reference ,...