Long-Term Performance and Sustainability of Geothermal Doublets

Abstract

The reinjection of the cooled water in geothermal doublet operation causes thermal drawdown in an expanding volume which propagates to the production well, where the temperature will decrease after the breakthrough time. Corresponding long-term calculations for the doublet operation in Riehen near Basel, Switzerland show that only a moderate temperature drop is to be expected even for decades of production. The maximum value will be about -0.7 K in one decade. After produchon stop the heat production capacity of the reservoir will recover. Corresponding calculations show a recovery of the heat production capacity of the Riehen reservoir by 35%-40% after a 40 year production and a subsequent similar recovery hme. The thermal drawdown as well as the recovery occurs in an asymptotic manner. Shorter production-recovery cycles produce more thermal energy.