Page 114 - Reservoir Geomechanics

98 Reservoir geomechanics

a.
300
Mohr–Coulomb criterion
250 C 0 = 325 MPa
m i = 0.4
Mean misfit = 9.5 MPa
200
(MPa) 150

t
100

50

0
0 100 200 300 400 500
s (MPa)

b.
800
700

600 s 3

500 s 3
(MPa) s 3 s 3
400 s 3
s s 3
300 s 2
s 1 (MPa)
s 3
= 0
s 3
200 = 6
s 3
= 15
s 3
Modified Lade criterion = 24
s 3
100 C = 325 MPa = 46
0 s 3
= 72
m i s 3
0
0 100 200 300 400 500 600 700 800
(MPa)
s 2
Figure 4.10. Best-fitting solution for the Solenhofen limestone using the triaxial test data;
(a) Mohr–Coulomb criterion; (b) modified Lade criterion. After Colmenares and Zoback (2002).
Reprinted with permission of Elsevier.
m and s. After studying a wide range of experimental data, Hoek and Brown (1980)
proposed that the maximum principal stress at failure is given by

σ 3
σ 1 = σ 3 + C 0 m + s (4.9)
C 0
where m and s are constants that depend on the properties of the rock and on the extent
to which it had been broken before being tested. Note that this form of the failure law