Drill bit types advantages and disadvantages

Drill bit types advantages and disadvantages

1. Drill Bit Types Advantages and Disadvantages Presented By Jyoti Anischit Tribhuvan University Msc in Engineering Geology

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

3. 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 )

4. Common Types of Drilling Bits

5. DRILL BITS TYPES OF DRILL BITS- Detachable bits- Removable from the drill when required . Forged bits- Made up of single length of drill steel and are available at several shapes.

6. Bits Types of Bit Drag Bit Roller Cutter Bit Drill Bit Classification Drag Bit Classification Roller Cutter Bit Classification Drill Bit Grading Tooth Wear/Loss Bearing Wear Gauge Wear

7. Contd. A steel-toothed piece of equipment attached to the lower end of the drillstring in order to : crush, scrape and, grind formation loose. The two types available are : drag bits rolling cutter bits

8. Drag bit They consist of fixed cutter blades that are integral with the body of the bit and rotate as a unit with the drillstring . The cutting element consists of steelcutters , diamond, or polycrystalline diamond compact (PDC). Steelcutter bits the serrated steel blades are set at different angles(e.g. a fishtail bit). Natural diamond bits the face or crown of the bit consists of many diamonds set in a tungsten carbide matrix . Polycrystalline diamond compact (PDC) bits a layer of synthetic PDC is bonded to a cemented tungsten carbide, it contains many diamond crystals bonded together. The sintered PDC compact is bonded either to a tungsten carbide bit-body matrix or to a tungsten carbide stud that is mounted in a steel bit. Thermally stable polycrystalline (TSP) bits these bits are manufactured in a similar fashion to PDC bits but are tolerant of much higher temperatures than PDC bits.

9. Roller Cutter Bits They 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. The 3-cone rolling cutter bit is by far the most common. Important factors to consider in this type of bit are: structural materials, bearing-seal-lubricating design, cutting structure arrangements, and hydraulic arrangements.

10. Types of Bits 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.

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

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

13. Drag Bits Advantages 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

14. Fishtail Drag Bit

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

16. Drag Bits Types of Drag Bits Steel cutter bits ( Fishtail Type) Diamond bits Polycrystalline diamond bits

17. Best for Soft formations Uniform formations unconsolidated formations Now, replaced by other types in all area Steel Cutter Bits

18. 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

19. 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 Bits

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

21. 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 Bits

22. 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 Bits

23. Top View of Diamond Bit

24. Side View of Diamond Bit

25. Natural Diamond Bits PDC Bits

26. Natural Diamond bit junk slot cuttings radial flow high D p across face

27. Soft Formation Diamond bit Larger diamonds Fewer diamonds Pointed nose

28. Hard Formation Diamond bit Smaller diamonds More diamonds Flatter nose

29. 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

30. PDC bits Courtesy Smith Bits

31. 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)

32. 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

33. 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

34. 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.

35. 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

36. 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

37. 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

38. Rolling Cutter bits

39. ROLLING CUTTER BITS Rolling Cutter Bits Steel Tooth (milled tooth) Carbide Tooth (tungsten carbide insert) Introduced in 1909 by Howard Hughes 2 - cone bit Not self-cleaning

40. Tungsten Carbide Insert Bit Milled Tooth Bit

41. ROLLING CUTTER BITS The three-cone rolling cutter bit is by far the most common bit Large variety of tooth design and bearing types Maximum use is made of limited space Cone offset to stop rotating periodically to scrape the hole like (PCD) bits It increases drilling speed but tooth wears faster. (4 for soft, 0 for hard)

42. ROLLING CUTTER BITS Shape of teeth: long widely spaced steel teeth are used for drilling soft formations As the rock type gets harder the tooth length and cone offset must be reduced to prevent tooth breakage Tooth action = Scraping and twisting Zero offset cones action = Crushing Smaller tooth allows more room for the construction of stronger bearings

43. Classification of Tricone Bits (a) Milled tooth cutters (b) Tungsten carbide insert cutters Hard facing on one side of the tooth allows self sharpening Chipping tends to keep tooth sharp Intermeshing is advantageous. Heel teeth = outer-raw very difficult job it wears it leads to out of gauge bit (hole)

44. Example tungsten carbide insert cutter used in rolling cutter Bits

45. ROLLING CUTTER BITS Improvements 3 - cone bit (straighter hole) Intermeshing teeth (better cleaning) Hard-facing on teeth and body Steel Tooth (milled tooth) Carbide Tooth (tungsten carbide insert) Change from water courses to jets Tungsten carbide inserts Sealed bearings Journal bearings

46. ROLLING CUTTER BITS Advantages For any type of formation there is a suitable design of rock bit Can handle changes in formation Acceptable life and drilling rate Reasonable cost

47. Fluid flow through water courses in bit Proper bottomhole cleaning is very important

48. Fluid flow through jets in the bit (nozzles)

49. ROLLING CUTTER BITS Milled Tooth Bit (Steel Tooth) Long teeth for soft formations Shorter teeth for harder formations Cone off-set in soft-formation bit results in scraping gouging action Self-sharpening teeth by using hard-facing on one side High drilling rates - specially in softer rocks

50. Milled Tooth Bit (Steel Tooth)

51. ROLLING CUTTER BITS Tungsten Carbide Insert Bits Long life cutting structure in hard rocks Hemispherical inserts for very hard rocks Larger and more pointed inserts for softer rock Can handle high bit weights and high RPM Inserts fail through breakage rather than wear Tungsten carbide: very hard, brittle material

52. Tungsten Carbide Insert Bits

53. Roller Cone Bearings

54. Bearings Ball Bearings (point contact) Roller Bearings (line contact) Journal bearing (area contact) Lubrication by drilling fluid . . . or . . .

55. Bearings Sealed Bearings (since 1959) Grease lubricant (much longer life) Pressure surges can cause seal to leak! Compensate? Journal Bearings (area contact) Wear-resistant hard surface on journal Solid lubricant inside cone journal race O - ring seal Grease

56. Grading of Dull Bits How do bits wear out? Tooth wear or loss Worn bearings Gauge wear

57. Grading of Dull Bits How do bits wear out? Steel teeth - graded in eights of original tooth height that has worn away e.g. T3 means that 3/8 of the original tooth height is worn away

58. Grading of Dull Bits Broken or Lost Teeth Tungsten Carbide Insert bit e.g. T3 means that 3/8 of the inserts are broken or lost

59. Grading of Dull Bits How do bits fail? Bearings: B3 means that an estimated 3/8 of the bearing life is gone Balled up Bit Cracked Cone

60. Grading of Dull Bits How do bits fail? Washed out Bit Lost Cone

61. Grading of Dull Bits How do bits wear out? Gauge Wear: Bit is either in-Gauge or out-of-Gauge Measure wear on diameter (in inches), using a gauge ring BIT GAUGE RING

62. Thank you for ur kind attention Email me at [email protected] Jyoti Anischit TU EGEO, 2 nd semester Roll no. 12