Evolution of Plastic Zone around Inclined Wellbores Using Finite Element Simulation with Generalized Plane Strain Model

This paper presents a specialized finite element procedure to analyze the elastoplastic response of rock surrounding an inclined wellbore. The procedure enables this special three-dimensional problem to be solved using a 2-D finite element mesh. The only assumption made in this model is that the properties of the rock and the far-field stress do not vary significantly along the wellbore axis over the region of interest. The resulting procedure allows for a significant reduction in numerical computation over three dimensional elements without suffering any loss of generality for analyzing inclined wellbores. The Drucker-Prager yield criterion for perfectly plastic material is then incorporated into the finite element code in order to simulate the evolution of the plastic zone around a pressurized wellbore. The spread of the yielding region around vertical, inclined, and horizontal wellbores subjected to various levels of pressures of drilling mud can then be examined to study the progressing and extent of failure in the rock surrounding the borehole.