Abstract

Wellbore instability costs includes billions of dollar per year worldwide because of down hole drilling problems and majority of problems occurring are related to mechanical instability of wellbore. When the stresses exceed the limit of rock strength it fails and if failure is too severe drilling problems occur. It is nearly impossible to drill perfectly gauge hole without any wellbore breakouts, but our aim should be to avoid catastrophic failure and to keep the borehole in the ambit of modest intensity of breakouts and successfully drill the well with limited complications. Each drilled well provides tremendous amount of information about stresses around wellbore. If subsurface Geological and Geophysical data is studied clinically, prevention of catastrophic wellbore failure can be ensured.