Page 195 - Reservoir Geomechanics
P. 195
177 Compressive and tensile failures in vertical wells
a.
150 s qq
Stress at wellbore wall (MPa) 100 s zz
50
s rr
0
0 90 180 270 360
Angle around the hole (from south)
b.
W
BO
0 50
Required C 0
Figure 6.5. (a) Stress concentration at the wellbore wall and (b) zone of compressive failure around
the wellbore (similar to Figure 6.3) when the mud weight has been raised 10 MPa above the
mudweight. Figure 6.3b compares the width of breakouts for the two cases. Note that raising the
mud weight decreases the size of the breakouts considerably. The area in white shows the region
where tensile stresses exist at the wellbore wall.
