10-15
0.4
permeability (m2)
10-16
Coefficient of Friction Normalized Permeability
0.3
10-17
0.25
0
30 40 50 70 80 60 effective stress (MPa) Intact Natural Mudstones: Exhibit strong permeability reduction as a function of effective stress (above). There is no systematic difference in permeability with increased in situ sample depth or smectite to illite transformation; increased depth of samples is shown by colors from red (shallowest) to yellow - green - purple - brown (deepest).
10
-17
10
-18
10
-19
10
-20
10
-21
0.01
0.05
0
10
0.1
0.1
10-20
-16
10 1
0.15
10-19
10
100
0.2
10-18
-15
A
Montmorillonite/Quartz
0.35
10
0
0
5
20
Montmorillonite/Quartz Illite Shale Chlorite Schist
10 20 30 40 50 60 Effective Normal Stress (MPa)
Experimentally Sheared Samples: Permeability as a function of normal stress for 3 experimentally sheared synthetic gouge mixtures (left). Permeability was measured before (open symbols) and after (filled symbols) shearing. We find that shearing decreases permeability to a larger extent than effective normal stress, though both are important.
70
0.001
P1608
10
15
20
B
Illite Shale
0.35
25 100 10
0.3 0.25
1
0.2 0.1
0.15
0.01
0.1 0.05 0
0.001 0
5
10 15 20 Shear Strain
25
30
Experimentally Sheared Samples, Effects of Shear Strain: Our results show that the major decrease in permeability of experimental fault zones occurs after shear strains of ~3-5. This correlates with attainment of residual shear strength in the layer, indicating indirectly that the reduction in permeability is associated with fabric development and clay mineral alignment.
