Clogging detection and productive layers identification along boreholes using Active Distributed Temperature Sensing

Fiber-Optic Active Distributed Temperature Sensing (FO-ADTS) experiments were performed on an Aquifer Thermal Energy Storage system (ATES) site located on the university campus of Bordeaux, France. The experiments consisted in heating the steel core of the FO cable while monitoring the rate of temperature increase during the heating periods. The changes in temperature, that were monitored through time at every depth under various hydraulic conditions and in different boreholes, were used to evaluate both aquifer properties and wells conditions. A first ADTS experiment was conducted under cross borehole configuration using a pumping well and a monitoring well separated by a distance of 8.5 meters. Then, to check the reciprocity of the results, a second experiment was conducted by switching the monitoring and the pumping well. The results obtained through the use of analytical solutions for reproducing and interpreting the data lead to the following conclusions: (i) ADTS can be used to estimate both thermal conductivity and Darcy velocity distribution along boreholes, crucial properties for ATES performance. (ii) The proposed method is a promising tool to detect clogging locations in the boreholes when it occurs. This can be of great practical interest to maintain systems performance, since, once FO cables deployed, experiments could be easily repeated without opening boreholes and stop the system operation.

Automated summary

Fiber-Optic Active Distributed Temperature Sensing (FO-ADTS) experiments were conducted on an ATES site in Bordeaux, France. The experiments involved heating the FO cable's steel core and monitoring the rate of temperature increase. The results showed that ADTS can estimate thermal conductivity, Darcy velocity distribution, and detect clogging in boreholes, offering potential benefits for maintaining ATES system performance without the need for extensive drilling or system shutdown.