Operators in this region of the Middle East drill curves using rotary steerable systems in what is referred to as “manual mode.” This involves a sequence applied repeatedly to control the curve trajectory and comprises multiple interventions and downlinks from the directional driller at the surface for steering force, toolface (TF) orientation, and measurements. And the sequence alone can involve up to 20 minutes to cycle, all leading to lost time, tortuous curves, and slow ROP.
Schlumberger recommended deploying a BHA with autonomous downhole control system (ADCS)—in this specific instance, the auto-curve component. This capability bundles all the steps of manual mode into a single downhole autonomous control process that begins with the directional driller downlinking the dogleg severity (DLS) and TF as required on the well plan. The RSS receives the command downhole and alone automatically adjusts its steering force and TF to match the demanded DLS and TF.
Additionally, the BHA tracks its continuous inclination and azimuthal using sensors close to the bit (3-axis inclinometers and triple 3-axis magnetometers).
With the addition of downhole ROP data, auto-curve enables the tool to compute its resulting DLS and TF. Each second, the tool adjusts its steering parameters to meet the designated trajectory. Autonomous downhole controls function without the need for surface intervention, which means fewer downlinks and less time lost to the cycle. The technology makes frequent and small adjustments, resulting in less tortuosity compared with the infrequent and violent surface control. Freed from trajectory concerns, the directional driller can focus on drilling efficiency.
This is the first time the auto-curve capability was used, enabling a PowerDrive Orbit G2 RSS to drill a curve in each of four wells in their respective 81/2-in sections. Results observed across these land wells were compared with nearby offsets and those curves drilled in manual mode. Downlinks to the RSS were reduced 49% in each of the four wells as compared with offsets using manual mode. And ROP increased 37% while drilling the curves with auto-curve.