Case History: Casing Collapse During Concentric Drilling Operation Leads to New Casing Design Approach for HP/HT Wells with Low Reservoir Pressure and/or N2 Injection

Abstract

This paper describes the events leading to the collapse of a 9 7/8" liner over a 7 5/8" casing while drilling a depleted fractured reservoir (high inclination, 150°C BHST) using the concentric injection technique and Managed Pressure Drilling (MPD) in well "A" in the South of Mexico. It also illustrates the investigation process conducted aimed at the identification of the potential failure scenarios. Finally, a new casing design approach for wells under these challenging conditions based on limit state design and deterministic load estimate has been developed and implemented as a result.