Wells drilled in the Midland Basin have a high potential to encounter whole mud losses while drilling through the mechanically weak sandstones in the Spraberry formation. Efforts to keep mud weights lower than the fracture gradient while drilling through the extremely fragile Spraberry formation can be challenging with narrow pore pressure and fracture gradient windows.
An operator incorporated the use of STAR SHIELD 500 at 8 lb/bbl in the oil-based mud circulating system to create a shield against the rock-fluid interface. The operator was able to successfully drill the lateral interval to TD through the Upper Spraberry, and cement casing on bottom while maintaining zero mud losses or hole instability. Production casing was run, set and cemented with full returns.
-Successfully drilled the lateral interval to total depth through the highly-depleted Spraberry formation without encountering any mud losses or influxes.
-Successfully ran casing to bottom and cemented with full returns.
-Low concentrations of STAR SHIELD 500 were more effective than high concentrations of conventional LCM’s.