The staged hole opener (SHO) incorporates precision-engineered cutting structures to ensure fast, smoothly drilled, high-quality, concentric hole openings under a wide range of application conditions. SHO tools are successfully run on rotary and rotary steerable assemblies in both straight and deviated holes.
While the overall cutting structure is balanced, it is divided into four sections, each serving a specific purpose:
- Pilot bit
Using either a fixed-cutter or roller cone bit, the pilot bit drills the initial hole diameter. A bull nose can also be used to follow a predrilled pilot hole. SHO assemblies can be used with multiple pilot configurations for specific applications and can be positioned for various drillstring configurations.
- SHO pilot section
The pilot section consists of one or two rows of cutting structures to recondition the pilot hole and remove any swelling clays or moving halites. Gauge pads provide initial stabilization as the SHO begins the staged reaming process to reduce stick/slip, whirling, or off-center tendencies.
- SHO pilot conditioning section (PCS)
The cutting structure is designed to minimize work rates on each cutter position for maximum durability. By stress relieving the formation with this intermediate stage, larger-hole drilling can be done at a more aggressive ROP. This section recentralizes the SHO on the given well trajectory in both vertical and directional applications.
- SHO reaming section
This cutting structure completes the final hole diameter. With the formation already stress relieved, the reaming section remains aggressive, even in more competent formations. Gauge trimmers and spiraled gauge pads ensure good hole quality. Gauge pads in this section are kept short in length for directional responsiveness.