Wpływ właściwości odkształceniowych soli kamiennej na powstawanie stref o podwyższonej przepuszczalności w otoczeniu podziemnego magazynu gazu
Abstract
Influence of rock salt strain behavior on origin of increased permeability zones around underground gas storage
A b s t r a c t . The presented description of rheological behavior in rock salt together with nondilatancy criterion is more accurate for underground structures design and prognosis of processes due to long-term utilization (Flisiak 2000). Many research centres specializing in construction of underground storages in rock salt are confident in ability to load resistance with preservation large ductile deformation without failure, while the triaxial tests show that at whole range of stresses and temperature which are accompanying exploitation of underground caverns, exists the clear boundary between compressibility and dilatancy domains (Flisiak, 2007). The effect of increase of irreversible volumetric strain is a rapid growth of creep rate with power dependence of stress and approaching a brittle failure as a result of creep (Flisiak 2000; Kortas 2008). Laboratory compressing and creep tests show also that this process is becomes highly intensified (Fig. 1) when rock salt deformation properties are anisotropic (Kortas 2008; Grzybowski et al. 2008). In practice, change of gas pressure and stresses in rock around caverns may be the cause of increase of salt permeability, creep activation and even a local falling. To confirm this thesis the nondilatancy criterion was used and numerical modeling of processes in rock salt with strain anisotropy around underground gas storage was realized. They enable to define potential directions of permeability with hazard of gas migration.
A b s t r a c t . The presented description of rheological behavior in rock salt together with nondilatancy criterion is more accurate for underground structures design and prognosis of processes due to long-term utilization (Flisiak 2000). Many research centres specializing in construction of underground storages in rock salt are confident in ability to load resistance with preservation large ductile deformation without failure, while the triaxial tests show that at whole range of stresses and temperature which are accompanying exploitation of underground caverns, exists the clear boundary between compressibility and dilatancy domains (Flisiak, 2007). The effect of increase of irreversible volumetric strain is a rapid growth of creep rate with power dependence of stress and approaching a brittle failure as a result of creep (Flisiak 2000; Kortas 2008). Laboratory compressing and creep tests show also that this process is becomes highly intensified (Fig. 1) when rock salt deformation properties are anisotropic (Kortas 2008; Grzybowski et al. 2008). In practice, change of gas pressure and stresses in rock around caverns may be the cause of increase of salt permeability, creep activation and even a local falling. To confirm this thesis the nondilatancy criterion was used and numerical modeling of processes in rock salt with strain anisotropy around underground gas storage was realized. They enable to define potential directions of permeability with hazard of gas migration.