Modeling Of Inelastic Failure Leading To Borehole Breakout

Abstract

Inelastic deformation is an irreversible process that is not adequately described with linear elastic-brittle approach. The classical linear elastic-brittle approach systematically overestimates the stress concentrations on the borehole wall, because inelastic deformation is underestimated. A continuum damage mechanics (Cdm) Concept is implemented in a finite element software abaqus to model the complex fracturing process and inelastic deformation in the development of the borehole breakout. The proposed approach explicitly models dissipative behavior of the material due to cracking and its evolution which leads to an inhomogeneous redistribution of material properties and stresses in the vicinity of the borehole wall. We are able to represent several characteristics of the failure processes during the breakout development as observed in experimental results, e.G. Localized cracks distribution in the vicinity of borehole wall, damage evolution which shows a widening process in the beginning followed by subsequent growth in depth, shear-fracturing-dominated breakout in sandstone. Furthermore, a good agreement between the geometry of the breakout resulted from our numerical simulations and the laboratory experiments is achieved.