Abstract The Barnett Shale field of North Texas is one of the most prolific and fastest growing natural gas fields in North America with a multi-trillion cubic feet equivalent upside potential. However, the area presents numerous drilling challenges. In the vertical section, roller cone bits had unacceptable low penetration rates while PDC bits suffered premature damage. High torque and drag along with low penetration rates hampered drilling the curve and lateral sections. To address these challenges, a detailed engineering analysis was performed utilizing sophisticated BHA and drill string modeling software. Engineers studied offset wells and drillstring modeling including buckling load analysis, critical speed analysis, and torque and drag analysis. As a result of the study, engineers determined that bit whirl and stick-slip were resulting in premature bit damage and reduced ROP while drillstring buckling resulted in inefficient transfer of weight on bit. Modeling helped design a BHA that mitigated buckling while optimized drilling parameters avoided critical speeds. The improvements resulted in 42% to 121% higher penetration rates with minimal damage to the PDC bits. The 83/4" vertical section was drilled in one PDC run in 60 out of 104 wells resulting in significant reduction in rotating hours and average cost per foot. The new BHA reduced drillstring buckling and significantly reduced torque and drag while drilling the curve and lateral sections. The authors will describe the significance of applying principles of buckling load and torque and drag analysis; to design technically sound BHA's. They will also discuss how to utilize drillstring dynamics to avoid critical speeds.

Typically S/J type directional land wells of North America utilize steerable downhole motors. This selection has some limitations: trips to adjust AKO for build/tangent/drop sections, potentially less than optimal hole quality from string rotation, possible drillstring/BHA/casing wear, potential hole enlargements requiring increased cement volumes and high torque/drag due to wellbore tortuosity. Closely spaced wells require precise control of wellpath to prevent collision. Multiple corrections to wellpath may increase wellbore tortuosity. Rotary steerable systems (RSS) requiring rotation of drill string are typically cost prohibitive for this application/environment. To overcome these challenges research, field testing and ten years of experience gained with other rotating/non-rotating rib steering systems has culminated in the development of a new state-of-the-art directional drilling system. The system, specifically designed for low inclination 3-D wellbores, utilizes an automated rib-steering closed loop system with a non-rotating drill string. Since the introduction of this innovative/sophisticated system many wells have been drilled in North America with build/drop of 3°/100 ft. Vertical/build/tangent and drop sections can be drilled without tripping. Tangent section inclination remained within 0.2°. Wellpath corrections were made while drilling by system's automatic closed loop control. The new system has reduced drilling/completion time, minimized hole enlargements, reduced torque/drag to help deliver smooth high quality wellbores and increased efficiency of cementing operations. This has allowed the operator to log and set tubulars easily and quickly, leading to early production. The innovative system has potential applications in many similar areas of the world to drill simple/complex S/J type wells without string rotation. Low-inclination wells can be drilled with precision and efficiency due to the closed loop's constant control over wellpath, and the ability to drill long sections without tripping for BHA changes.