Abstract
This paper presents a new model that integrates relevant aspects of geomechanics and drilling fluids to provide practical solutions for wellbore strengthening. This integrated approach accounts for the influence of stress state, rock properties, wellbore design parameters, and the impact of particle-laden fluids on the creation, growth, and arrest of an induced fracture. A dimensionless parameter called the Wellbore Strengthening Index (WSI) is introduced as a measure of desired strengthening normalised to the rock stiffness. WSI is used to estimate the concentration of wellbore strengthening material (WSM) required for a given application. A semi-empirical correlation then relates solids loading to the length of an induced fracture at time of sealing. A closed-form equation is proposed to estimate fracture width using this calculated fracture length. Once induced fracture dimensions are determined, appropriately sized WSM is selected for efficient sealing. The model is relatively straightforward to code into a practical and user-friendly design tool for wellbore strengthening. Two case studies are presented to show successful implementation of the new model.
