Subhorizontal Geothermal doublet Completed at Cachan, Paris Basin. A demonstrator for the future

New Well Architecture — A World Geothermal Premiere

On March 20, GPC IP successfully tested the second subhorizontal geothermal (injection) well, GCAJ2, at the Paris suburban Cachan site, thus validating this innovative well architecture, initiated on the previously drilled production well, GCAH1, recorded as a World Première.

Well design features two 1001 (GCAH1) / 1 005 m (GCAH2) long, 87 to 93° slanted, 8"^1/2 openhole drains, drilled in the Dogger (mid Jurassic)/Bathonian oolithic limestone at 1 550 m true vertical (TVD) and 3 000 m drilled (mD) depths.

Targeted at 450 (nominal) and 500 m³/h (maximum) productive and injective capacities, the new doublet, managed by a DALKIA (EDF Group)/City of Cachan J.J (DALKIA operator), will replace two existing, ageing (33 years) doublets rated 180 and 170 m³/h (total 350 m³/h) respectively.

The concept pioneered by GPC IP, first published in February 2011 at the Stanford Geothermal Engineering Workshop and later developed at the 2016 European Geothermal Conference (September 2016, Strasbourg), raises considerable interest among geothermal operators reclaiming areas undergoing moderate to poor (by geothermal standards) reservoir performance.

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