Fig. 3

Mohr–coulomb failure envelopes on shear stress (τ) versus normal stress (σ) plots for Bentheim sandstone. Legend is the same for all three panels. The pink area labelled R_MC indicates the uncertainty which was estimated based on the repeat experiments. Slope (friction coefficient µ ~ 0.8, see Table 2) and intercept (cohesion S₀ ~ 19 MPa, see Table 2) are unaffected by fluid type. a sandstone with water; b sandstone with inhibitor 1 (3000 ppm); c sandstone with inhibitor 2 (3000 ppm)