Amongst all issues plaguing drilling operations, wellbore instability and failure is still a leading contributor to drilling non-productive time (NPT). Failure can result from misunderstanding the wellbore conditions, improper drilling practices, unavailability of geomechanical properties or improper interpretation of those values. For maximum long-term production, it is desirable to avoid uncertainties associated with wellbore integrity during drilling. Wellbore integrity deals with identifying the optimal drilling fluid properties and formulations to avoid unwanted surprises while drilling. It is well-documented that near-wellbore stresses can be altered by adopting different approaches to maintain or increase wellbore integrity while staying within the drilling window (pore pressure and fracture gradient).

The results from testing methods for curing wellbore instability using drilling fluids containing products like gilsonite/asphaltene were input into a numerical simulator to understand their stabilizing effect on wellbore. Increase in the near-wellbore stresses was observed for certain drilling fluids; however, a destabilizing effect was observed for a few fluids. The wellbore strengthening technique includes inducing fractures in problematic zones like depleted formations and inter-bedded sand layers. The fractures are then propped open with lost circulation materials (LCM) to sustain the increase in the near-wellbore effective tangential stresses. Different combinations of LCM were tested to indentify the optimal combination. Enhanced performance was observed after the addition of high aspect ratio material in LCM pill.

This paper presents comprehensive information on the different mechanisms employed to improve wellbore integrity. Application of different laboratory methods and materials in combination with numerical simulator analysis are provided to demonstrate different approaches for wellbore integrity management in various scenarios.

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