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PDC Bits Slide
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Fixed Cutter Bits
Early Diamond Bit History
• Prior to 1940 natural diamonds were “peened”into a steel head to create a diamond bit.
• Due to the high cost and marginal manufacturing technique, diamond drill bit were rarely used.
• The primary diamond application was in core bits.
Milestones• 1947 - Christensen Develops matrix bit
technology for practical attachment of natural diamonds to a drill or core bit head.
• 1954 - GE is the first to synthesize diamond.• 1975 - First practical application of man-made
diamond with introduction of GE’s “Stratapax”polycrystalline diamond compact (PDC) stud cutter.
• 1981 - Introduction of thermally stable polycrystalline (TSP) cutters.
PDC Design Presentation• Cutter Technology• PDC Bit Design
• Profiles and Blades• Cutter Orientations• Hydraulics• Bit Gauge
• Bit Mechanics• Design Optimization
Natural Diamond Cutters
• Original diamond cutting element.• Monocrystalline diamond.• Different size and quality diamonds for different applications.
• Size range expressed as stones per carat (SPC).
Natural Diamond Cutters• Natural diamonds are furnaced into the bit head.
• Versatile application range when synthetic diamonds are not applicable.
• Medium to very hard formations.
• Fixed TFA.
BallasetCutters
• Thermally Stable Polycrystalline (TSP) diamond cutters.
• Extension of PDC cutter technology.• Cutter size expressed as stones per carat
(SPC).
Ballaset Cutters• Thermal stability allows
cutters to be directly furnaced into the bit.
• Developed for medium to hard applications, particularly carbonates.
• Fixed Total Flow Area (TFA).
Impregnated Cutters
• Diamond grit is “hot-pressed” into tungsten carbide matrix to form impregnated segments.
• Diamond grit is synthetic diamond material.
• Pre-formed segments furnaceddirectly into bit crown.
• Grinding tool for very hard and abrasive applications.
• Especially effective at high rotation speeds.
Impregnated Cutters
Polycrystalline Diamond Compact
Diamond Table
TungstenCarbide
Substrate
Conventional PDC Cutter
PDC Cutter Sizes
0.529” - 13.3 mm 0.323” - 8.2 mm
0.642” - 16 mm
0.750” - 19 mm
0.315” - 8 mm 0.315” - 8 mm
Sharp vs. Chamfered Cutting Action
Failure Plane Failure Plane
Built-Up Edge
Polished Cutter
Polished Cutters
Carbide Supported Edge
CSE Geometry Strengthens The Diamond Edge Against The Cutting Force
Chamfer Angle
Cutting Force
Tungsten Carbide Body
Standard CutterCSE Cutter
Materials & Bit Construction
Nozzles
Junk SlotArea
PDC Cutters
API Connection
WeldBlank
Blank Blade
Matrix Body
PDC GaugeCutters
PDC FaceCutters
Cone Nose
Shoulder
Nozzle
Gauge Pad
Crown Chamfer
Breaker Slot
Stamp Area- Serial #- Style- TFA - ND/Ballaset
Bit Profiles• Bit profile and cutter layout are closely related. • Layout is a compromise between the following:
• Maximum number of cutters (longer bit life)
• Lowest blade count (better hydraulics, penetration rate)
• Shortest possible profile (better bit stability and cleaning)
Volume of Rock Removed
• Volume of rock removed is a function of• Cutter radius• Depth of cut• Width of cut
• There is a direct relationship between the volume of rock removed and the work rate of a cutter.
• The volume of rock removed is calculated for a given penetration rate (depth of cut).
• We use profile and blade count to manipulate the amount of work done in each area of the bit.
Cutter #60 RPM, 60 ft./hr
Vorr
(in3 )
Volume of Rock Removed
0
1
2
3
4
5
1 2 3 4
LIGHT MEDIUM HEAVY
Blade Count & Cutter Density
• Tapered blades provide optimum strength and hydraulic efficiency
• The blade strength is calculated using the blade height, width, length and the leading edge root radius.
• Blade strength is given as a percentage of the API connection strength. (i.e., 204%)
Blade Strength
Blade Width
Root Radius
Force
BladeLength
BladeHeight
Conventional Blade Configuration
Backrake & Siderake
• A cutter will see a different magnitude & direction of forces depending on it’s location on the bit profile.
Depth of Cut
F Torque
Fwob
Fwob
FsFwob
Fn
Fn
Fs
Single Cutter Forces
Force Vector Groups Force Vector Summation
Group #1
Group #2
Group #3
Group #4
Net Imbalance Force
Group #3
Group #4
Group #1
Group #2
Resultant Cutter Force Vector
• The gauge is considered the stabilizing, full hole section of a bit.
• Gauge begins at the gauge point and continues up to the crown chamfer.
• Typical materials include natural diamonds and tungsten carbide segments.
• For optimum stability a flush set gauge pad is used.
Gauge Design
PDC Bit Gauge
• Cutter layout & orientation are purposely designed to create a net imbalance force, pushing the bit against the hole wall and creating a stable rotating condition.
Anti-Whirl Force Balancing
PDC Applications
Quartzite(metamorphic)
Granite(Igneous)
Marble(metamorphic)
Sandstone LimestoneMarlstone
10,00020,00030,00040,00050,00060,00070,00080,00090,000
100,000U
CS
(psi
)
SEC PDC Application Limit
Standard PDC Limit
IADC Dull Grading System
Cutting Structure Bearing Gauge Comments
Inner Rows
Outer Rows
Dull Characteristic
Location Bearing & Seal
Gauge Other Characteristic
Reason Pulled
X
Cutter Wear
Bit Dull / Other Characteristics
BC - Broken ConeBF - Bond FailureBT - Broken Teeth/CuttersBU - Balled UpCC - Cracked ConeCD - Cone DraggedCI - Cone InterferenceCR - CoredCT - Chipped Teeth/CuttersER - ErosionFC - Flat Crested WearHC - Heat CheckingJD - Junk DamageLC - Lost ConeLN - Lost Nozzle
LT - Lost Teeth/CuttersNR - Not RerunnableOC - Off-Center WearPB - Pinched BitPN - Plugged Nozzle/Flow AreaRG - Rounded GaugeRO - Ring OutRR - RerunnableSD - Shirttail DamageSS - Self-Sharpening WearTR - TrackingWO - Wash Out on BitWT - Worn teeth/CuttersNO - No Other Major Dull
Characteristics
Fixed Cutter Bit Profiles
A - All overC - Cone - shown on all profilesN - Nose - Part of profile that would rest on the table if bit set upside downT – Taper – Straight portion tangent to nose and shoulderS - Shoulder - Outer area adjacent to the nose and gauge areasG - Gauge - Area ground to API specifications and cuts a “gauge” hole
Worn Cutter
Diamond Lip
Worn Cutter
Chipped Cutter
Broken Cutters
Lost Cutters
Heat Checking
Erosion
Ring Out
Junk Damage
Cored
Broken Blade
Balled
Plugged Nozzle
Acknowledgement
We wish to thank the Hughes Christensen division of Baker Hughes for their valuable assistance in the preparation of this material.
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