An analytical solution for wellbore stability problem using strain hardening Drucker-Prager plasticity model

Document Type

Conference Proceeding

Publication Date

1-1-2016

Abstract

In this paper, an exact analytical solution for the wellbore boundary value problem is derived, in an elastoplastic porous rock formation. The rock is modelled as Drucker-Prager material with the incorporation of hardening behaviour depending on the evolving of the plastic deviatoric strain. By adopting the small strain deformation in the elastic region while large strain deformation in the plastic region, the wellbore stability problem under undrained condition is formulated as solving a system of first order ordinary differential equations in the plastic zone. The illustration numerical example shows the distributions of stress components and the pore pressure around the borehole, in addition to the evolving stress path for a rock point at the borehole surface due to the wellbore drilling. The major advantage of the calculated wellbore drilling curve lies in the fact that it can track the deformation responses of the borehole surface from elastic to elastoplastic states and down to the ultimate strength condition if needed, thus providing much more flexibility and more appropriate mud pressure design over the conventional elastic-brittle models.

Publication Source (Journal or Book title)

50th US Rock Mechanics / Geomechanics Symposium 2016

First Page

2328

Last Page

2334

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