Near-Wellbore Stress Analysis and Wellbore Strengthening for Drilling Depleted Formations

摘要

Alhough lost circulation has provided a challenge for drilling, especially for drilling depleted formations, its mechanism has not been well studied or fully understood. Aided by analytical and numerical solutions, this paper identifies the role of hydraulically conductive cracks in low near wellbore pressure containment. It also demonstrates that the lost circulation frequently encountered when drilling depleted formations occurs when both near wellbore pressure containment and far field pressure containment are low. The numerical method is used to investigate the improvement of wellbore pressure containment by propping fractures with particulate lost circulation materials to strengthen the wellbore. The results demonstrate that the wellbore pressure containment can be improved to a level beyond that of the ideal wellbore pressure containment defined by the Kirsch’s tangential stress equation.