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Geothermal Energy

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Fig. 8 | Geothermal Energy

Fig. 8

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. 8

Stress–strain relationships in hydrostatic compression tests. a Bulk volumetric strain is the response of the tested volume to compressive stress during loading. Limestones generally show higher deformation than dolomitic limestones and dolostones. b Drained bulk modulus \({K}_{\mathrm{d}}\), calculated as the slope of the stress–strain curve at an effective pressure of 25 MPa, shows a distinct positive correlation with uniaxial rock strength. c With increasing porosity more pore volume can be compressed and the drained bulk modulus \({K}_{\mathrm{d}}\) decreases significantly due to the weakening of the rock structure

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