Extreme drilling environment forces evolution of rotary steerable systems and bits ///

Wells drilled in the Tuscaloosa Trend near Baton Rouge, Louisiana, have long been recognized for the extreme nature of the High Pressure, High Temperature (HPHT) operating environment and for well control problems. This article describes drilling of the highly abrasive formations in the intermediate and drilling liner sections to depths of ± 20,000 ft. These sections are a major cause of bit, directional tool and drillstring failures. Wells' directional complexity has increased in recent years due to surface location constraints and reservoir compartmentalization. New drills are directional to penetrate multiple stacked targets, fault-out depletion and to adhere to regulatory constraints. Directional control in the intermediate section requires drilling through the abrasive Wilcox formation and risks wellbore drift out of the target. Below the intermediate section, drillers encounter significant directional tool constraints, because temperatures range from 300-400°F. Poor directional response, low penetration rates and increased motor failures have resulted in long and costly sections.

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