Abstract

Casing wear caused by rotating drill strings can lead to reduced well integrity or increased well maintenance. Furthermore, excessive casing wear can lead to remedial actions, expensive non-productive time, failed casing, or safety hazards. Mechanical casing wear is a function of drill pipe contact pressure, drill pipe revolutions, and wear factor. Casing wear can be an issue anywhere in the world, but this paper examines these challenges in a particular well in the Bolivia's sub-Andean region. The historically low rate of penetration (ROP) of 1.3m/hr caused nine months of drilling operations inside the production casing. As a result, the production casing was exposed to 11.3 million drill pipe rotations. The operator with extensive experience drilling wells in this region identified the critical importance to mitigate casing wear. The strategy was to implement the use of Non-Rotating Protectors (NRPs) after the production casing was set in the hole to drill the last two hole sections. While casing wear reached 13.2%, an analysis indicates the wear would have reached 80% had NRPs not been used.

Additional challenges were expected due to high temperature and pressure in the lower sections. By using tools suited for these extreme conditions, one of the deepest wells in Bolivia was successfully drilled.

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