ABSTRACT
In rock salt, linear (pressure solution) creep is recognized as an important deformation mechanism under low differential stress conditions (below ~5 MPa), where it takes over from power law (dislocation) creep processes that dominate at higher stresses. In salt caverns, such low differential stress levels occur in the far-field, or following shut-in and abandonment after production stops. It is therefore crucial to incorporate linear creep in numerical simulations assessing cavern behavior. However, theoretical models of pressure solution and microstructural observations suggest that this process does not act below a certain ‘threshold’ stress, which for rock salt is proposed to lie in the range 0.07-0.7 MPa (Van Oosterhout et al., this volume). By means of numerical finite element (FE) modelling of single-cavern systems, implementing an Ellis-type creep law extended with a user-defined threshold for the linear creep component, we show that pressure solution and its threshold strongly influences creep-induced cavern convergence and subsidence behavior, and should therefore be considered when assessing the effects of salt production or storage applications. Additionally, this threshold may explain certain discrepancies between previous cavern scale modeling studies and field observations (e.g. the rebound predicted for Barradeel by Breunese et al. 2003).
