Hole Opening Bits - Bicenter Technology
3 3/4" x 4 1/8" TO 14 3/4" x 17 1/2" (95.25 mm x 104.8 mm TO 14.34 mm x 444.5 mm) - In Matrix
Varel’s bicenter bits are designed to enlarge the well bore, drilling 15 to 25% larger than the pass through well bore in all types of PDC drillable formations. The bicenter bits are used to increase lateral diameter, to replace under reaming, to help control trouble zones, and for expandable tubulars. The matrix material construction resists erosion and abrasion found when drilling oilfield applications. The one-piece design shortens the overall bit length for better directional control. Varel bicenter bits also have an innovative force balanced cutting structure which minimizes cutter and casing damage when drilling out. Additionally, Varel’s unique design minimizes bit vibrations often experienced with conventional hole opening tools thereby resulting in longer downhole tool life and reduced drilling costs.
One-Piece Construction
Varel's unique design, shortens the overall bit length for better directional control and eliminates the need to have a connection and weld between the pilot bit and the reamer section of the bicenter. The one piece construction also allows for optimal hydraulic configuration with pilot and reamer blade alignment, optimizing cuttings removal and improving ROP.
Hydraulic Design
Nozzle placement, pilot bit and reamer blade alignment provide a direct flow path to the annulus. The junk slot area is maintained or increased, resulting in no decrease in fluid velocity and improved cuttings removal between the pilot and reamer.
Spiraled Blades
Varel's bicenter bits are designed with spiral blades to provide better contact with the casing during drill out. Spiral blades stabilize the bit ensuring less damage to the casing and resulting in better well bore quality.
Varel's bicenter was recognized as a finalist for a best mechanical engineering award by ASME-IPTI at the 2005 Offshore Technology Conference.
Cutting Structure Drill-Out Feature
Varel's Casing Saver Design cutting structure feature provides a reliable drill-out mode while protecting the cutting structure inside the casing. Because of the bicenter bits unique application, the bit design is not symmetrical. When drilling out from casing, the bit rotates on the casing centerline and not the bit centerline. This off center rotation of conventional bits can cause damage to cutters located near the center of the pilot bit. This cutter damage is due to backward rotation of cutters located between the bit centerline and the casing centerline in the pilot bit. However, Varel has repositioned cutters between the two centerlines in the nose of the pilot bit. Our design minimizes the possibility of cutter damage while inside the casing in drill out mode. As the bit transitions to formation drilling the cutters begin to rotate normally about the bit centerline and cut the formation. This small but unique design philosophy prevents cutter damage when drilling out allowing efficient rock-cutter interaction during formation drilling.
Force Balancing
During the design process, the pilot and reamer cutting structure are force balanced as a single unit. This provides increased drilling efficiencies in both vertical and deviated wells. Improved ROP, increased durability and better directional control are all benefits of Varel's force balancing.
Casing Saver Design
Pilot bit design, spiral blades, non contact gage cutters and casing saver technology all result in minimal casing damage during drill-out.
