Overcoming Challenges for Drilling High-Dogleg-Severity Curves

Abstract Shale-gas plays and other unconventional resources have gained significant prominence in the USA and several other parts of the world. Maximizing well productivity and improving drilling efficiency remains a major challenge. Well placement in the sweet spot and extended laterals help maximize productivity. Drilling a high-dogleg-severity (DLS) curve maximizes the length of lateral in the productive zone. Wells in US shale-gas plays and other unconventional resources require a DLS of 10° to 14°/100 ft. Achieving high DLS with steerable motors presents numerous drilling challenges. Rotating a steerable motor with high adjustable kickoff (AKO) sub settings could result in fatigue failure. Alternate drilling in slide-rotate modes reduces drilling efficiency, increases tortuosity, and limits well placement in the productive zone. In the past, drilling high-DLS curves with rotary steerable systems (RSS) was a challenge. These challenges led to the development and ultimately the successful testing of a new high-dogleg RSS. Using the new system enabled drilling all sections, including high-DLS curves, tangents and laterals with one bottom hole assembly (BHA). Using closed-loop control and a short steering sleeve that decouples steering functionality from drilling dynamics, the system can drill high-DLS curves and extended reach laterals with precise well placement and improved borehole quality. The authors will discuss the design, and field test results in different environments such as shale-gas plays and tight sands. The new system significantly improves drilling performance with excellent directional control. Drilling high-DLS curves increases the length of laterals by several hundred feet, enabling additional recovery of hydrocarbons. The ability to drill all sections with one system and elimination of slide drilling significantly reduces drilling time and eliminates trips to make changes to the BHA. By minimizing wellbore tortuosity, the new system enables setting casing easily and quickly, leading to early production. Minimized tortuosity in the lateral also enables faster drilling out of completion plugs with coil tubing. The innovative system can be used in similar areas of the world to drill complex wells with high DLS and straight laterals with precision and efficiency.