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230 Reservoir geomechanics

0

1000

2000
Depth (mRKB TVD)

3000
S Hmax

4000 P p S hmin

HYDROSTATIC S v
PORE PRESSURE

5000
0 20 40 60 80 100 120
Stress (MPa)

Figure 7.13. Similar to Figure with estimates of S Hmax (dots with error bars) determined from
analysis of drilling-induced tensile fractures in the Visund field of the northern North Sea (after
Wiprut, Zoback et al. 2000). Reprinted with permission of Elsevier.

S Hmax is greater than the overburden. As shown, there is a significant amount of uncer-
tainty in the estimates of S Hmax . Brudy, Zoback et al. (1997) pointed out that the value of
S Hmax required to induce drilling-induced tensile fractures (after correcting for excess
mud weight and cooling) must be considered as a lower-bound estimate. This is because
the drilling-induced tensile fractures might have occurred even if there had been no