Van Steene, Marie (Schlumberger Logelco Inc.) | Povstyanova, Magdalena (Schlumberger) | Al-Attar, Haitham (BP-GUPCO) | Abu El Gheit, Diaa (BP-GUPCO) | Abutaleb, Moamen (BP-GUPCO) | Lantz, Jim (BP-GUPCO) | Abdel Kareem, Salah (GUPCO)
Multiple wellbore stability projects in the Western Desert of Egypt identified a strong sensitivity of the breakout gradient to wellbore inclination and a weak sensitivity to wellbore azimuth, from the Abu Roash to the Alam El Bueib formations. The breakdown gradient shows strong sensitivity to both wellbore inclination and wellbore azimuth. Tensile failures are a problem only in high deviation wells (deviation more than 55-60) where the breakdown gradient will in general be lower. For highly deviated wells, the occurrence of tensile failure can be reduced by drilling close to the minimum horizontal stress direction.
Breakout can be tolerated to some extent, so planning the drilling mud weight to completely eliminate it is not necessary. The extent to which breakout can be tolerated depends on the well deviation, as cuttings become more difficult to evacuate as the well deviation increases.
As losses are very common in most of the Western Desert formations, the optimum drilling mud weight should be formulated as a balance between the risks caused by breakout and mud loss.
Understanding the main causes of rock failure and applying the recommended failure mitigation measures resulted in successfully drilling four deviated wells in the area.