Drilling Bit Part One PDC ,Tricone Function

Drill bits ,PDC tricone ,function

1. PETE 203
DRILLING ENGINEERING
Chapter 5Chapter 5
Drilling BitsDrilling Bits

2. Contents:
•Various bit types available (classification).
•Criteria for selecting the best bit for a given situation.
•Standard methods for evaluating dull bite
•Factors affecting bit wear and drilling speed.
•Different Rock Failure mechanisms
•Optimization of bit weight and rotary speed
•Relative Costs of Bits

3. Ideal Bit (Lowest Cost $/ft)
•High drilling rate
•Long life
•Drill full-gauge, straight hole
•Moderate cost

4. Selecting Ideal Bit
•Drilling Cost per foot
•Drillability
•Abrasiveness
•Type of Reservoir
•Cost of the Bit
•Depth

5. Improving Bit Performance
•Stabilize the Bit
•Maintain minimum mud weight, sand & solids
•Maintain adequate bottom hole cleaning
•Protect the seals - avoid pressure surges
•Thoroughly inspect bit before re-running
•Keep oil from the mud, and from the seals
•Follow manufacturers recommendations (e.g.
6,000 lb/in of diameter and 40-60 RPM)

6. Common
Types of
Drilling
Bits

7. Types of Bits
1.Drag Bits: Fixed cutter blades
Consist of fixed cutter blades that are integral
with the body of the bit and rotate as a unit
with the drill string (19
th
century).
2.Rolling Cutter Bits: Rock bits - with cones
(1909) have two or more cones containing the
cutting elements which rotate about the axis of
the cone as the bit is rotated at the bottom of
the hole.

8. Drag Bits
•Design Features
–Number & shape of cutting blades/stones
–Size and location of the water courses
–Metallurgy of the bit and cutting elements

9. Drag Bits
–Drilling is achieved by physically blowing
cuttings from the bottom of the bore-hole

10. AdvantagesAdvantages
–No rolling parts which require strong clean
bearing surfaces
–Because it is made from one solid piece of steel
there is less chance of bit breakage, which would
leave junk in the bottom of the hole
Drag Bits

11. Fishtail Drag Bit

12. Drag Bits
•Cutter may be made from:
–Steel
–Tungsten carbide
–Natural diamonds
–Polycrystalline diamonds (PDC)

13. Drag Bits
•Types of Drag BitsTypes of Drag Bits
– Steel cutter bits (Steel cutter bits (Fishtail Type)
– Diamond bitsDiamond bits
– Polycrystalline diamond bitsPolycrystalline diamond bits

14. •Best for
–Soft formations
–Uniform formations
–unconsolidated formations
•Now, replaced by other types in all
area
Steel Cutter BitsSteel Cutter Bits

15. When Using Natural Diamond Bit?
•Penetration rate of rock bit < 10 ft/hr
•Hole diameter < 6 inches
•When it is important to keep the bit and pipe
in the hole
•When bad weather precludes making trips
•When starting a side-tracked hole
•When coring
•When a lower cost/ft would result

16. –Best for hard non-brittle formations
–The face or crown of the bit consists of many
diamonds set in a tungsten carbide matrix
–Fluid courses are provided in the matrix to
direct the flow of drilling fluid over the face of
the bit.
Diamond BitsDiamond Bits

17. •Shape of crown profit:
– Step type
– Long taper (straight hole, high wt.)
– Short taper (easier to clean)
– Non taper (directional drilling)
Diamond BitsDiamond Bits

18. •Size and number of diamonds, depend on the
hardness of the formation
–Hard formations:
•Many small stones
•0.07-0.125 carrot
–Soft formations:
•Few large stones
•0.75-2.0 carrot
Diamond BitsDiamond Bits

19. •Pressure drop across the face of the bit
•Pump pressure measured with the bit off
bottom-pump pressure with the bit drilling =
500 : 1000 psi
•Manufacturer usually provide estimate of
approximate circulating rate required establishing
the needed pressure drop across the bit.
Diamond BitsDiamond Bits

20. Top View of Diamond Bit

21. Side View of Diamond Bit

22. Natural Diamond Bits PDC Bits

23. Natural
Diamond
bit
junk slot
cuttings
radial flow
high p
across face

24. Soft
Formation
Diamond bit
 Larger diamonds
 Fewer diamonds
 Pointed nose

25. Hard
Formation
Diamond bit
 Smaller diamonds
 More diamonds
 Flatter nose

26. PolyCrystalline Diamond (PCD) Bits
•Since mid 1970’s a PDC Bits has been made possible
by the introduction of a sintered polycrystalline
diamond drill blanks, as a bit cutter element
•The drill blanks consist of a layer of a synthetic
polycrystalline diamond about 1/64 in. thick that is
bonded to a cemented tungsten carbide substrate in a
high-pressure high-temperature (HPHT) process

27. PDC
bits
Courtesy
Smith Bits

28. PolyCrystalline Diamond (PCD) Bits
•It contains many small diamond crystals bonded
together
•The PCD is bonded either to a tungsten carbide
bit-body matrix or to a tungsten carbide stud that is
mounted in a steel bit body
•They perform best in soft, firm, and medium-hard,
non-abrasion formations (not gummy)

29. PolyCrystalline Diamond (PCD) Bits
•Good results are obtained in carbonates or
evaporates that are not broken up with hard shale
stringers.
•Also good in a sandstone, siltstone, shale
•Design of crown profile is important, double-cone
and flat profile
•Size, shape, number of cutters and angle of attack
back rake, side rake and exposure

30. PolyCrystalline Diamond (PCD) Bits
•Advantages:
–Increase penetration rates in oil & gas wells
–Reduce drilling time and costs
–Cost 5-15 times more than roller cone bits
–1.5 times faster than those 2 years earlier
–Work better in oil based muds; however, these
areas are strictly regulated

31. At about $10,000-150,000 a
piece, PDC bits cost five to
15 times more than roller
cone bits
PDC Bits

32. Relative Costs of Bits
Diamond WC Insert Milled
Bits Bits Tooth Bits
$/Bit
• Diamond bits typically cost several times as much as tri-
cone bits with tungsten carbide inserts (same bit diam.)
• A TCI bit may cost several times as much as a
milled tooth bit.

33. Grading of Worn PDC Bits
CT - Chipped Cutter
Less than 1/3 of cutting
element is gone
BT - Broken Cutter
More than 1/3 of cutting
element is broken to the
substrate

34. Grading of Worn PDC Bits – cont’d
LT - Lost Cutter
Bit is missing one or
more cutters
LN - Lost Nozzle
Bit is missing one or
more nozzles

35. Table 7.7 - Commonly Used Bit Sizes For
Running API Casing
Casing Size Coupling Size Common Bit
(OD in.) (OD in.) Sizes Used (in.)

4 1/2 5.0 6, 6
1/8
, 6
1/4
5 5.563 6
1/2
, 6
3/4
5 1/2 6.050 7
7/8
, 8
3/8
6 6.625 7
7/8
, 8
3/8
, 8
1/2
6 5/8 7.390 8
1/2
, 8
5/8
, 8
3/4
7 7.656 8
5/8
, 8
3/4
, 9
1/2
7 5/8

8.500 9
7/8
, 10
5/8
, 11
8 5/8

9.625 11, 12
1/4
9 5/8

10.625 12
1/4
, 14
3/4
10 3/4 11.750 15
13 3/8 14.375 17
1/2
16 17 20
20 21 24, 26