FIG. 1 MECD CHANGE: NORMAL-FAULTING STRESS REGIME
0.84
0.80
0.76
0.72
0.68
0.63
0.59
90
75 60 45
30 15 0 90 75 60 45 30 15
0
Inclination angle, degrees Relative azimuthal angle, degrees
M
ax
im
u
mE
CD,
g/
c
c
TECHNOLOGY
Combining circumferential stresses with additional stresses
produced by fluid seepage creates a new model which can
be combined with the conventional model to fully describe
in-situ stress regimes’ influence on wellbore stability during
underbalanced drilling (UBD) of horizontal wells.
This article finds the effects of in-situ stress regimes on
wellbore stability by comparing them with a conventional
model that does not take fluid seepage into consideration.
It then demonstrates how fluid seepage creates greater well-
bore instability and that different in-situ stress regimes im-
pact wellbore stability in both models.
Shiming He
Wei Wang
Ming Tang
Southwest Petroleum University, Chengdu
Ruifeng Zhang
PetroChina, Renqiu
UBD creates wellbore
instability in horizontal wells
DRILLING &
PRODUCTION
