Cutting Structure (MT or TCI) Teeth shape and projection Bearing type (sealed or open) Bearing type (friction or roller) Compensation system Arm shape and protection
RC Bit Geometry – Journal (or Pin) Angle
Centerline of Bit
Basic element in the design of cone Angles – Soft formations - 33° – Hard formations - 36°
Journal Angle Journal
Influences the cone contour (profile) and aggressiveness
Journal (Pin) Angle
Soft Formation
Hard Formation Of Bit
Of Cone & Journal Journal Angle
Of Cone &Journal
Cone Angle Cone Angle
Journal Angle
Oversize Angle
Oversize Angle
Cone Angle Large Cone Angle – Soft to Medium Formation – Rounder cone profile – Gouging & Scrapping Small Cone Angle – Hard Formation – Flatter cone profile – Crushing
Offset (Skew Angle) Direction of Rotation - Bit
Offset
Direction of Rotation - Cone
Offset Soft Formation Offset
Increased ROP in soft formation More offset increases gouging and scraping (action on bottom)
Hard Formation
Less offset for medium formations Little or no cone offset for hard formation Weight applied to crushing rock
Hard formation bits – little to no oversize angle –
Reduces action on gage, cone diameter, reaming
Intermesh Intermesh clearance
Prevents packing of formation Better use of space for the cutting structure Greater cone shell thickness Extended tooth/insert length Larger bearing size
Projection and Pitch Projection
Projection is the height of the tooth (Aggressiveness) Pitch
Pitch is the spacing between the teeth (Agressiveness and Antitracking feature)
Insert Bit Cutting Structure Diamond Enhanced Inserts Maintain Bit Gage Diamond surf protection used in 33% (D), 50% (D2) and 100% (D3) increments Reduce shirttail wear in directional and horizontal applications
Diamond
33% Increment
50% Increment
100% Increment
Roller Cone Technology
Cutting Efficiency Optimization
Roller Cone General Design Characteristics
Mill Tooth Attributes vs. Performance
Insert Attributes vs. Performance
Roller Bearings
Large Diameter Bits Larger than 13 ½” Low friction Reduces heat Sealed and non-sealed
Non-Sealed Roller Bearing
Tooth cutting structures Generally for top hole and cement drilling applications
Double Sealed Roller Bearing
Rollers captured in arm Single compensation system Insert and Tooth Generally for rotary and motor applications
Roller-Ball-Roller (RBR) • Radial seal Spring-loaded face seal
Premium Double Sealed Roller Bearing
Roller-Ball-Roller (RBR)
• Tandem radial seals
Larger than 15” Rollers captured in cone Dual compensation system Insert and Tooth Generally for motor or high energy applications
Sealed Journal Bearings
Smaller Diameter Bits
13 1/2” and smaller Insert and tooth O-ring Seal Friction bearing High load capacity Silver plated to reduce friction Motor and rotary
Improve Bearing lubrication through enhanced grease communication (Heat cooling and pressure compensation)
Standard
High Energy
Advanced Diamond Hardfacing
Ample hardfacing is applied to flanks, crests and gage surfaces for maximum wear resistance Steel teeth are sculptured in high wear areas for added hardfacing material
Gage
Flank
Fluid Circulation Purpose – Remove cuttings – Keep the cutting structure clean – Cool the bit – Stabilize the borehole wall – Shales inhibition – …etc Drilling fluid – Liquid (water or oil-based) – Air, Aerated Mud – Foam
Bit Hydraulics • With high pressure drop across the nozzles, high velocity fluid flows past the cones and impacts against the formation, flushing out cuttings in the hole
Drilling Fluid
Nozzle Arm
Center Jet (if equipped)
Roller Cone bit Selection vs Formation Hardness
R ock H a rd n e s s V e ry s o ft S o ft m e d iu m H a rd V e ry h a rd
c o m p r e s s iv e s t r e n g t h ( p s i) < 4 ,0 0 0 4 , 0 0 0 - 8 ,0 0 0 8 ,0 0 0 - 1 6 , 0 0 0 1 6 ,0 0 0 - 3 2 , 0 0 0 > 3 2 ,0 0 0
Lower impact damage to CS Extended Bearing / Seal life by reducing wobble motion of cones Improved Directional Responsiveness Increased ROP Force Balancing
Double Positive Seals • Dual compensation system permits use of two positive seals to extend bearing life • The high aspect ratio seals provide additional squeeze with low stress levels resulting in lower operating temperatures
Seal Design Improvements 487 Double Seal
C29 Double Seal
C49 Double Seal
• Radial seal and spring-loaded face seal
• Radial seal and modified face seal
• Tandem radial seals
• Grease hand-packed in cavity between seals
• Grease hand-packed in cavity between seals
• Cavity between seals vacuum filled with lubricant
• No means to equalize pressure between seals
• Series of small filtering holes in outer seal to equalize between seals pressure
• Dedicated reservoir to equalize pressure between seals
Roller Bearing Radial Load distribution • Greater distance between roller bearing
Typical loading diagram
centers improves load distribution • Longer roller bearing elements increase bearing capacity • Combined improvements extend expected bearing life M
9.4
Relative life expectancy
8.8
7.1
A B
5.4
2.9
1.0
A
B
487
A
B
A
B
C49 C29 Bearing code
Bearing loads calculated as resultants of moments generated from weight on bit
Optimizing Technology
Bearings system optimized using Bearing Simulation Software, FEA and custom laboratory testers for bearing materials, seals and full scale bit testing.
Optimized Contact Pressure Profile Seal • Highest contact pressures at the edge of sealing interface where it is needed. • Lower contact pressures reduce heat and torque at center of sealing face. • In controlled laboratory testing: • • •
53% increase in seal life 24% reduction in torque 16% decrease in temperature
Optimized Contact Pressure Profile Sealing mechanics. High Aspect Ratio Seals Developing improved thermally stable and wear resistant elastomers 400
Dome compensation and mechanical pressure relief Increased reliability & repeatability Reduced hysteresis Improved seal condition due to consistent pressure Flexibility with mechanical spring to adjust relief pressure
Optimizing Technology Enhanced and Directed Hydraulics – Remove cutting from crucial areas (sealing area & CS) – Improved arm geometry – Directed flow channels
