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

Bohnsack, Daniel; Potten, Martin; Freitag, Simon; Einsiedl, Florian; Zosseder, Kai

doi:10.1186/s40517-021-00197-w

Geothermal Energy

Science – Society – Technology

Table 1 Pore size characteristics of the rock samples investigated by mercury intrusion porosimetry (MIP)

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

Sample	Lithology	Facies	Pore classification					Pore throat classification
			\({\varPhi }^{i}\)	Predominant pore type		Subordinate pore type		\({d}_{\varPhi }^{\mathrm{min}}\)	\({d}_{\varPhi }^{\mathrm{med}}\)	\({d}_{\varPhi }^{\mathrm{max}}\)	Micro	Meso	Macro	Mega
			(%)	Predominant pore type		Subordinate pore type		(µm)			(in % of total pore throats)
L1	Limestone	Grainstone	13.0	inter-P	50–200 µm	v	< 1 mm	0.02	0.1	44.9	67.9	10.5	12.0	9.6
L2	Limestone	Grainstone	14.5	inter-P	50–200 µm	v	< 1 mm	0.02	17.8	64.0	11.3	18.4	59.4	10.9
L3	Limestone	Grainstone	18.1	inter-P	50–100 µm	oo-mo	> 150 µm	0.13	0.7	2.5	18.9	74.0	2.1	5.1
L4	Limestone	Rudstone	12.7	inter-P	100–300 µm	Mi	< 0.4 µm	0.08	0.5	2.0	29.1	66.6	2.2	2.1
dL1	Dolomitic limestone	Grainstone	13.0	inter-P	20–150 µm	inter-X	< 5 µm	0.04	0.8	16.2	16.7	67.5	11.8	4.0
dL2	Dolomitic limestone	Grainstone	15.0	inter-X	20–150 µm	intra-P & mo	20–120 µm	0.07	0.4	1.7	54.7	40.9	2.0	2.5
D1	Dolostone	Fine-X	14.9	inter-X	< 25–125 µm	el. inter-X	< 500 µm	1.09	5.9	12.3	1.4	83.9	12.2	2.5
D2	Dolostone	Fine-X	9.8	inter-X	< 25–125 µm	el. inter-X	< 500 µm	0.81	2.4	11.3	3.4	85.7	7.2	3.7
D3	Dolostone	Medium-X	8.9	inter-X	< 50 µm	el. inter-X	< 250 µm	0.05	7.9	101.2	11.5	38.6	38.9	11.0
D4	Dolostone	Medium-X	8.2	inter-X	< 24 µm	el. inter-X	< 500 µm	0.05	25.4	126.1	8.7	30.9	36.5	23.9
D5	Dolostone	Medium-X	2.3	v	250 µm–2 mm	inter-X	< < 100 µm	0.01	13.6	138.4	11.6	16.8	43.6	28.1
D7	Dolostone	Coarsely-X	4.0	mo-v	250 µm–2 mm	inter-X	< 50 µm	0.01	32.1	198.8	16.6	15.2	27.8	40.4
D8	Dolostone	Coarsely-X	3.7	v	250 µm–1 mm	inter-X	< 50 µm	0.03	13.9	142.0	32.5	11.5	17.3	38.7

Bold values indicate predominant magnitude of the pore throats
X crystalline, \({\varPhi }^{i}\) initial porosity, inter-P interparticle pores, intra-P intraparticle pores, inter-X intercrystalline, el. inter-X elongate intercrystalline pores, v vugs, mo-v moldic vugs, oo-mo oo-moldic pores, mo moldic pores, mi micropores, \({d}_{\varPhi }^{\mathrm{min}}\) minimum diameter, \({d}_{\varPhi }^{\mathrm{med}}\) median diameter,\({d}_{\varPhi }^{\mathrm{max}}\) maximum diameter

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