Research on the collapse pressure of an elliptical wellbore considering the effect of weak planes

Owing to stress concentration and anisotropy, the actual shape of a borehole is oval instead of what is usually treated – circular. In this study, a collapse pressure model for an elliptical vertical wellbore is established. The influences of ellipticity and weak planes on the wellbore collapse pressure are analyzed. The results reveal that the collapse pressure increases with the wellbore ellipticity and decreases as the weak planes' strength increases. Additionally, the collapse pressure depends strongly on the attitude of the weak planes. The present study achieves a more accurate prediction of the wellbore collapse pressure in a layered formation.