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Geothermal Energy

Science – Society – Technology

Fig. 9 | Geothermal Energy

Fig. 9

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. 9

taken from Meng et al. (2019) for comparison of the results and show a similar stress dependency for both parameters

Stress-dependent porosity and permeability reduction of all investigated samples during hydrostatic testing. a Porosity reduction is characterized by the Eulerian porosity \({\varPhi }^{E}\) and normalized to the initial porosity \({\varPhi }^{i}\) for comparison. With increasing effective stress, \({\varPhi }^{E}\) decreases almost linearly. The porosity reduction is relatively small (< 2.5%) and for limestone samples generally more pronounced than for dolomitic limestone and dolostone. b Stress-induced reduction of permeability \(k\) (normalized to initial permeability \({k}^{i}\)) is significantly stronger than for porosity indicating a higher stress sensitivity of permeability (up to 57%). The “Indiana limestone” data were

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