Weaker when wet: The influence of water saturation on the rock-mass strength of the Permo-Triassic sandstones at the Soultz-sous-Forêts geothermal site (France)
The presence of aqueous fluids within the void space of rock—a combination of pores and cracks—is known to influence their short-term mechanical behaviour. Therefore, laboratory deformation experiments performed on dry samples, the standard method to assess the strength of reservoir rock, may overestimate intact rock strength and rock mass strength asssessments provided by the generalised Hoek-Brown failure criterion. We present here a systematic experimental study on the influence of water saturation on the strength of the Permo-Triassic sediments sampled from exploration well EPS-1 at the Soultz-sous-Forêts geothermal site (France). Future work will involve upscaling these strengths, using the generalised Hoek-Brown failure criterion, to provide "wet" and "dry" rock mass strengths of the Buntsandstein.