Page 28 - Reservoir Geomechanics

a. Stress or pressure d. Stress or pressure
0 20 40 60 80 MPa 0 20 40 60 80 MPa
0 0
200 4000 6000 8000 10000 12000 psi 2000 4000 6000 8000 10000 12000 psi
0
Normal faulting Normal faulting
1000 1000 overpressure at depth
4000 hydrostatic 4000
S v ≥ S Hmax ≥ S hmin S v ≥ S Hmax ≥ S hmin
6000 2000 6000
2000
Depth (meters) 8000 Depth (meters) 8000 S hmin S Hmax

3000
10000 S v 3000 10000 P p
(~23 MPa/km) S v
P p
(~1 psi/ft)
12000 (feet) S hmin S Hmax 12000
4000 4000
(~10 MPa/km)
(~0.44 psi/ft)
b. Stress or pressure e. Stress or pressure
0 20 40 60 80 MPa 0 20 40 60 80 MPa
0 0
2000 4000 6000 8000 10000 12000 2000 4000 6000 8000 10000 12000 psi
Strike-slip faulting
Strike-slip faulting
1000 1000 overpressure at depth
4000 hydrostatic 4000
S Hmax ≥ S v ≥ S hmin
S Hmax ≥ S v ≥ S hmin
Depth (meters) 2000 6000 Depth (meters) 2000 6000 S hmin
8000
8000
S Hmax
3000 3000 P p
10000 10000
S Hmax
12000 (feet) 12000 (feet) S v
4000 S hmin S v 4000
P p

c. Stress or pressure f. Stress or pressure
0 20 40 60 80 MPa 0 20 40 60 80 MPa
0 0
2000 4000 6000 8000 10000 12000 psi 2000 4000 6000 8000 10000 12000 psi
Reverse faulting Reverse faulting
1000 hydrostatic 1000 overpressure at depth
4000 4000 S Hmax ≥ S hmin ≥ S v
S Hmax ≥ S hmin ≥ S v
Depth (meters) 2000 6000 S hmin Depth (meters) 2000 6000 S hmin

8000
8000
P p S v S Hmax
3000 S Hmax 3000 10000
10000
S v
12000 (feet) 12000
4000 4000
P p

Figure 1.4. Variation of stress magnitudes with depth in normal, strike-slip and reverse faulting
stress regimes for hydrostatic (a–c) and overpressure conditions (d–f). Note that the difference
between principal stresses increases with depth (due to the increase of the frictional crustal strength
of the crust with depth – see Chapter 4)but decreases as severe overpressure develops due to the
decrease of frictional strength with elevated pore pressure (also discussed in Chapter 4).