Stress solutions for short- and long-term wellbore stability analysis

Abstract

Numerous models have been proposed to address the time-delayed wellbore collapses or untimely mud losses that have been widely reported in the field. There is still reluctance in applying them in real-time field operations due to their complex mathematical appearance. In this technical note, we address the effective stress solutions for short- and long-term wellbore stability analysis. We present the poroelastic, porothermoelastic, and porochemoelastic wellbore effective stress solutions at t→0+ and t→∞. The concise expressions of these solutions are simple to implement into computational codes for the ease of engineering field data interpretation. We also improve a generic algorithm for calculating mud weight windows. Application of the asymptotic solutions and the algorithm in an example with a random set of data indicates that the long-term collapse and fracturing mud weights can be 32.5% higher and 25.6% lower than the short-term ones, respectively. Conventional time-independent elastic models cannot capture these behaviors.