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

Geothermal Energy

Science – Society – Technology

Table 4 Poroelastic parameters resulting from drained hydrostatic tests at an effective pressure of 25 MPa

Sample	Lithology	\(\Delta {\varPhi }_{\mathrm{rel}}\)	\(\Delta {\varPhi }_{\mathrm{abs}}\)	\(\Delta {k}_{\mathrm{rel}}\)	\(\Delta {k}_{\mathrm{abs}}\)		\({k}_{\mathrm{rec}}\)
Sample	Lithology	%	% p.u	%	mD	m²	%
L1	Limestone	1.41	0.18	43.2	1.975	1.9E⁻¹⁵	94.27
L2	Limestone	2.13	0.31	56.7	2.128	2.1E⁻¹⁵	–
L3	Limestone	1.15	0.21	46.4	2.054	2.0E⁻¹⁵	–
L4	Limestone	1.24	0.16	33.0	0.053	5.2E⁻¹⁷	79.08
L5	Limestone	1.00	0.16	Test failed			–
dL1	Dol. limestone	0.96	0.13	27.7	0.207	2.0E⁻¹⁶	86.26
dL2	Dol. limestone	0.98	0.15	52.3	0.282	2.8E⁻¹⁶	84.90
D1	Dolostone	0.70	0.10	28.3	0.365	3.6E⁻¹⁶	90.89
D2	Dolostone	0.95	0.09	24.2	0.233	2.3E⁻¹⁶	77.83
D3	Dolostone	0.72	0.06	17.3	0.771	7.6E⁻¹⁶	83.19
D4	Dolostone	Test failed		19.3	0.157	1.5E⁻¹⁶
D5	Dolostone	0.87	0.02	38.8	0.001	9.9E⁻¹⁹	–
D6	Dolostone	0.72	0.07	32.5	0.141	1.4E⁻¹⁶	–

\(\Delta {\varPhi }_{\mathrm{rel}}\) relative porosity reduction, \(\Delta {\varPhi }_{\mathrm{abs}}\) absolute porosity reduction, \(\Delta {k}_{\mathrm{rel}}\) relative permeability reduction, \(\Delta {k}_{\mathrm{abs}}\) absolute permeability reduction, \({k}_{\mathrm{rec}}\) permeability recovery