Transcripción del resumen del autor: One of the problems during drillingoperation is wellbore instability. Many parameters affect the wellborestability. Some of these parameters are related to the properties of drilling mud and its interaction with the formation and some of them are related to the mechanical properties of the formation and the magnitude and distribution of the forces around the wellbore. Generally the wellbore instability is calssified as mechanical, physico-chemical or both. This paper is an attempt to investigate the mechanical and physico-chemicalaspects of wellborestability during drillingoperations