Wellbore Stability in Shale Formation Using Analytical and Numerical Simulation

Optimization of drilling fluid parameters such as mud weight, salt concentration, and temperature is essential to alleviate instability problems during drilling through shale sections. The selection of suitable mud parameters can benefit from analyses that consider significant instability processes involved in shale-drilling–fluid interactions. This paper describes the development of analytical and numerical method for describing shale deformation. Appropriate and optimum mud pressure in which the highest consistency happens is calculated with analytical and numerical methods. It was found that, the predicted mud pressures obtained from two methods are approximately equal. The stress condition is considered non-hydrostatic. From the analytical and extensive numerical simulation it was concluded that with applying any mud pressure the well shape changes from spherical to elliptical. As the selection of the optimum mud pressure is based on the less movement and maintaining the well shape constant.