The Haute-Sorne Project began in 2017 with drilling Glovelier-1 (GVL-1), the first of a 2-well geothermal doublet connected through an EGS. Water was circulated between the two wells, in a closed-loop system used for power generation. GVL-1 also proved the feasibility of the Geo Energie Suisse downhole heat exchanger concept.
GVL-1 is drilled to a total vertical depth of 5 000 m. The final bottom hole static temperature (BHST) must be a minimum of 170 °C. The well was drilled vertically until the top of the granite basement was reached and steered to intersect a maximum number of natural fissures and deviated to 55° from vertical.
The injection/production drain is not cased. The open hole drained was sectioned with a completion string using water swelling elastomer and slickline operated mechanical sleeves. The planned completion design called for 30 individual sections spread over a 1 500 m long drain. Each section was stimulated independently by injecting defined volumes of fresh water, according to a pumping sequence. An extensive seismic monitoring programme was planned, that would take place before, during and after the drilling, completion and stimulation operations.