The relatively new concept of wellbore strengthening was introduced to tackle the issues of lost circulation and narrow drilling window complications. Wellbore strengthening is intended to increase the effective formation strength and its resistance to drilling-induced fracture formation. The ultimate goal of this concept is reduce trouble time associa and in many cases, allow drilling to continue past zones that would have required casing to be set in order to proceed. Numerous techniques that vary in their effectiveness and applicability were created. Therefore, there is a clear need for a tool that will help cast a critical eye on the use of these techniques.
The model described in this work aims to provide a practical tool that evaluates and predicts the performance of wellbore strengthening techniques in practical situations. The wellbore strengthening techniques covered by the model use stress changes around the wellbore as the primary criteria for enhancing the fracture pressure and effectively enlarging the drilling window. The model relies on geometric principles, basic rock mechanics data, linear elasticity plane stress theory, drilling fluid data, and geological data. It also provides a process for the proper selection of candidates for wellbore strengthening. To achieve that goal, the model creates all of the possible scenarios in terms of well placement, surface location, and trajectory based on input data to define the scenario that will yield maximum results using a specific wellbore strengthening technique.
The results produced by the model are based on a specific case study. They show practical advantages of applying the model in the well planning phase. The analysis performed using the model demonstrates the applicability of a certain wellbore strengthening technique, the effectiveness of the technique, and the best parameters for the technique. Therefore, the analysis shows not only the best case scenario for applying a wellbore strengthening technique, but it also illustrates the cases where applying the technique should be avoided due to a predicted detrimental effect.
A key finding from the model results is the effect of the direction of drilling on the performance of the highlighted strengthening techniques. It is shown that implementing certain strengthening techniques can cause the paths of the largest drilling window and the narrowest drilling window to switch directions.