DRILLING TECHNOLOGY

Extreme drilling environment forces evolution of rotary steerable systems and bits

Multiple changes in bit design and BHA configuration lead to record directional runs through difficult Wilcox sections.

Bronwyn Cox and Louis Romo, BP America; Brett Champion and Osman Maung, Schlumberger; and Kirk Card and Steve Barton, Reed-Hycalog

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. Directional operations in the intermediate or drilling liner sections have cost an incremental spend of up to $3 million on some wells and a 30�45-day delay to first production.

This article describes improvements over a five-year period using Powered Rotary Steerable Systems (PRSS) coupled with rotary steerable bit technology. The performance step-change reduced days per 10,000 ft (d/10k) drilled through systematic learning. .