Wells in the Midland Basin in West Texas 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.
The operator adopted the use of STAR SHIELD® 500 at 8 lb/bbl in the oil-based mud (OBM) circulating system to create a shield against the rock-fluid interface. The operator was able to successfully drill the lateral interval to total depth (TD) through the Upper Spraberry, and cement casing on bottom while maintaining zero mud losses or hole instability.
The operator successfully drilled the lateral interval to TD through the highly depleted Spraberry formation without encountering any mud losses or influxes. Low concentrations of STAR SHIELD 500 were more effective than high concentrations of conventional lost circulation materials (LCM’s). The operator ran casing to bottom and cemented with full returns.