In order to observe wellbore collapse process visually, by using the real triaxial simulation experiment system, the borehole enlargement rate and the borehole collapse changing laws were tested through exerting triaxial stress on the samples under different conditions including the stress state, deviation angle and azimuth of the wellbore. The results show that the borehole enlargement rate increases with the increase of vertical crustal stress and azimuth angle, while formation stability decreases with them; and the borehole enlargement rate decreases with the increase of deviation angle, while formation stability increases with them. The conclusion could provide references for the field drilling operation.
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