European HDR research programme at Soultz-sous-Forêts (France) 1987–1996

The site at Soultz-sous-Foreà ts (France) has been selected as the future European HDR research site (Garnish, J., Baria, R., BaumgaÈ rtner, J., GeÂrard, A., 1994. GRC Trans. 18, 431±438; Baria, R., 1990. Proceedings of Camborne School of Mines. International HDR Conference, June 1989, p. 613. Robertson Scienti®c Publications, London). Since 1987, extensive testing of the underground has been carried out using a single well (GPK1), initially to a depth of 2000 m and then to a depth of around 3590 m. From 1995 onwards the testing of the underground has utilized two deep wells. The hydraulic tests carried out in 1993±1994 demonstrated the potential of the site as a future European Scienti®c Prototype. In particular, the tests showed that in the Rhine graben the fracture network in the basement is well-developed, with a degree of permeability. While some minor ¯uid movement occurs naturally, hydraulic simulation has been shown to increase substantially the overall transmissivity. The Soultz site has been used for testing a modi®ed or alternative facet of the concept of HDR developed in recent years. The geological setting also o€ers other advantages in terms of relatively low stimulation pressures, a characteristic that may simplify the task of developing a promising circulation system. A second deep well (GPK2) was drilled late in 1994, with the aim of developing circulation between the two deep wells. In 1995, GPK2 was stimulated for the ®rst time and a short circulation test was attempted between the two deep wells. During 1996, GPK2 was stimulated again using higher ¯ow rates to improve the injectivity further. It is planned to install the necessary infrastructure 0375-6505/99/$20.00 # 1999 CNR. Published by Elsevier Science Ltd. All rights reserved. PII: S0 37 5 -6 50 5 (9 9) 00 0 36 -X Geothermics 28 (1999) 655±669 * Corresponding author. Fax: +33-38880-5351. E-mail address: baria@soultz.net (R. Baria) to carry out, during 1997, a 4-month circulation test at around 25 kg/s, using a downhole pump to produce from GPK2 and reinjecting the produced ¯uid into GPK1. # 1999 CNR. Published by Elsevier Science Ltd. All rights reserved.