Single Trip Curve-Lateral Drilling with High Dogleg RSS

This paper discusses the design of an attitude controller embedded in a high dogleg, fully-rotating rotary steerable system (RSS). While drilling with a high dogleg capable RSS at high rate of penetration (ROP), directional control may become challenging along tangent sections, thus, making it difficult to drill vertical, curve, and lateral sections within a single trip with low tortuosity. To ensure tight inclination and azimuth control along tangent sections with high dogleg RSS, we introduce an on-board robust attitude control system and discuss its performance over several curve-lateral case studies drilled at high ROPs. The downhole navigation and control system consists of a multiplicity of accelerometers, a magnetometer, and gyroscopes that are used to precisely measure borehole attitude via sophisticated sensor fusion algorithms. The attitude measurements representing borehole direction in a three-dimensional frame are fed back to the controller, which communicates a corrective control command to a high-bandwidth actuation system to minimize deviation from the target attitude. This corrective control command is generated by an advanced control method that is optimized to provide good attitude tracking performance and necessary robustness against potential formation pushes during high ROP drilling. Several case histories from wells drilled using the automatic attitude control feature of the high dogleg RSS will be shared in the paper and discussed in detail. The cases include single-trip curve-lateral runs from onshore North America (Marcellus Shale) drilled at high ROPs. The entirety of the lateral sections of these wells, each longer than 10,000 ft, are drilled with the automatic attitude control mode. While generating consistently over 12°/100ft dogleg severity in curve sections, the RSS was able to drill smooth lateral sections with an average of over 200 ft/hr ROP and by keeping the average dogleg severity at approximately 1.2°/100ft. The attitude-hold controller enables the high dogleg capable RSS to drill smooth vertical sections, tangents, and extended laterals, along with the curve sections, in just a single run. This technology has the potential to offer cost savings on several fronts: (1) reducing non-drilling time due to tripping in and out between different sections of the well; (2) allowing for drilling at an increased ROP by maintaining tight directional control and, therefore, reducing the drilling time; and (3) increasing operational efficiency by shifting the steering decision-making process to the downhole given target attitude.