Drill a high-DLS curve in the zone of exclusion
Needing to drill a high-dogleg severity (DLS) curve section for a well in
the Northeast Basin, an operator was faced with the compounding
challenge of orienting the wells in the zone of exclusion (ZOE)—a narrow
north–south window with azimuths between 160° to 200° (southerly) and
340° to 20° (northerly). The danger is that the ZOE can further destabilize
azimuthal headings already stressed by the formation’s inherent shock and
Drilling curves with RSSs requires what is referred to as “manual mode.”
This involves a sequence repeatedly applied 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. Cycle times for downlinks can be as long as 20 minutes and
impair drilling efficiency, which is especially challenging through the ZOE.
Use advanced ABSS with autonomous drilling capabilities
Schlumberger recommended deploying the NeoSteer CL curve and
lateral at-bit steerable system with the auto-curve and auto-tangent
components of the autonomous downhole control system.
These capabilities bundle all the steps of manual mode sequence into a single
downhole autonomous control that begins with the directional driller
downlinking the DLS and TF as required on the well plan. The NeoSteer CL
ABSS receives the command downhole and alone automatically adjusts
its steering force and TF to match the demanded DLS and TF.
Using sensors close to the bit (3-axis inclinometers and triple 3-axis
magnetometers), NeoSteer CL ABSS tracks its continuous inclination and
azimuth. The autonomous downhole control system uses ROP data that
enables the ABSS to compute its resulting DLS and TF. The tool adjusts
its steering parameters every second to ensure it meets the designated
trajectory and it functions without the need for surface control, which
means fewer downlinks and less time lost to the cycle. Making frequent
and small adjustments means less tortuosity compared with the infrequent
and violent surface control.
Autonomously drilled high DLS through ZOE while increasing ROP
Results observed were compared with nearby offsets drilled in manual
mode. Downlinks to the NeoSteer CL ABSS were reduced 21%. In fact,
the auto-curve engaged for a 10°, three-part build, proceeding all the
way to horizontal landing. The curve began with a 2D build to 7,250-ft MD, followed by a 2D turn to 7,750 ft, and then a final 3D build and turn. Auto-tangent engaged and drilled to the landing point at 8,250 ft. ROP also increased 34%.