Laboratory Study on the Effect of Fluid Pressurization Rate on Fracture Instability

Figure 4

Stress-displacement evolution in nonstepping injection-induced shear tests. (a–c) Tests T1, T2, and T3. (d) Mohr-Coulomb failure envelopes obtained by fitting the shear strengths (solid red circle) from the displacement-driven shear tests, and the stress states of sawcut fractures before the fluid injection (solid green five-pointed star) and at the onset of injection-driven fracture instability (solid pink five-pointed star). Please notice the difference in the coordinate scale.

(a) T1

(b) T2

(c) T3

(d) Mohr-Coulomb failure envelopes