Skip to main content
Geothermal Energy

Science – Society – Technology

Fig. 1 | Geothermal Energy

Fig. 1

From: Stress sensitivity of porosity and permeability under varying hydrostatic stress conditions for different carbonate rock types of the geothermal Malm reservoir in Southern Germany

Fig. 1

Test setup for the hydrostatic tests. a Specimen was saturated by â‘  raising the upstream pore pressure to 1 MPa and waiting for pressure equalization, while the downstream flow port is closed. The specimen was flushed after opening the downstream fluid port â‘¡ to remove trapped air. b Cycling of confining pressure for reduction of inelastic effects and closure of microcracks. The strain shows irreversible deformation and relaxation hysteresis during unloading. c Permeability was determined after reaching stationarity for hydrostatic pressure steps of 5 MPa. Permeability shows a further decrease during the holding phase at maximum pressure due to creep and hysteresis at the beginning of the unloading cycle. Permeability cannot completely recover at the end of the unloading cycle as a result of irreversible sample deformation. d Change in fluid and bulk volume was measured during hydrostatic loading and unloading at drained conditions with fixed pore pressure and indicates a reduction in porosity

Back to article page