Analysis of wellbore stability using diffenrent rock failture criteria

Abstract

Wellbore stability analysis during drilling operation is an essential step in order to minimize possible risks, thereby reducing drilling costs and ensuring safety for the environment and for the people. The aim of this paper is to analyze the stability of the wellbore using different failure criteria such as Mohr-Coulomb, Tresca and Von Mises. The Mohr-Coulomb failure criterion is an evaluation method based on dynamic friction and tension models in materials. According to the Tresca criterion, if the difference between the highest and the lowest tension stress on the shear plane exceeds the shear stress limit of the material, the material will crack or become permanently deformed. According to the Von Mises criterion, if the Von Mises stress exceeds the strength limit of the material, it may be permanently deformed or destroyed. The results of this study show that if only the pore pressure is used for the lower boundary of the drilling mud window, there will be unstable sections because the collapse pressure has not been considered in the analysis. Similarly, if we use only the fracture gradient for the upper boundary of the drilling mud window, there will also be sections that cause wellbore collapse. Therefore, in order to cover all possibilities of potential collapse in the wellbore, we should simultaneously use different failure criteria, which are Mohr-Coulomb, Tresca and Von Mises. This study also considered the inclination of the well trajectory in the analysis, so that appropriate failure criteria can be used for various wellbore segments. The contributions of this study are therefore not only about the academic aspect but also the practical aspect because the process can be applied in real life to find out the most optimal and safest drilling fluid density.