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.

Notes: __________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________

__________________________________________________________