Transient Thermo-Poroelastoplasticity Finite Element Analysis of Inclined Wellbore Stability

Wellbore instability is a crucial concern problem in highly inclined well drilling, extended reach well drilling and horizontal well drilling, particularly in high temperature and high pressure (HPHT) formations. However, few studies have concentrated on the three-dimensional inclined wellbore instability analysis considering the influence of thermo-poroelastoplasticity and filter cake. In the present study, a three-dimensional inclined wellbore stability model fully coupling thermo-poroelastoplasticity and considering filter cake is created and analyzed using finite element analysis. This model can be used for the wells with any deviation angle and azimuth angles simply by changing the far field stresses and boundary conditions. The distribution of pore pressure and wellbore stress under various deviation angles, consolidation time and temperature gradients are investigated. The research results show that, the wellbore instability problem is generally severe in the inclined wells comparing to the vertical wells. The wellbore becomes unstable as the consolidation time increases, and it is more unstable under positive temperature gradient than under negative; the filter cake can reduce the pore pressure and stress around the wellbore, it prevents the wellbore from shear failure in vertical well (deviation 0o), and prevents the wellbore from tensile failure in inclined well especially in the horizontal well (deviation 90o). The results obtained in this paper can benefit a deeper understanding of the instability mechanism of inclined wellbore.