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Drilling Bit Introduction and bit Selection (Part 2)

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(PART 1,2 & 3)
1. Drilling mechanisms
2. Bit classifications (fixed cutter and roller cone bits)
3. IADC code descriptions
4. Tri-cone bits life time
5. Geometrical analysis of roller cone bits
• Fundamentals of bit design
• Basics of cone geometry design
• Oversize angle
• Offset
• Teeth and inserts
• Additional design criteria: tooth to tooth and groove clearances and etc.
• Cone-shell thickness
• Bearings factors
• Rock bit metallurgy
• Heat treatment
• Legs and cones material
• Tungsten carbide materials
• Legs and cones hard facing
• Tungsten carbide grade selection for inserts
• Bearings, seals and lubrication
• Bearing shape
• Bearing precisions and geometry
• Seal systems and seal details
• Dull grading system
6. Geometrical analysis of PDC bits
• PDC materials and constructions
• Matrix materials testing
• Differs between matrix & steel body
• Matrix body bits manufacturing
• Steel body bits manufacturing
• PDC bit design parameters: mechanical, hydraulic, rock properties
• Weld strength of PDC bits and cutters
• PDC cutter manufacturing process
• Tsp cutter properties vs PDC
• The influences of bit profile and profile elements
• PDC forces
• PDC bit stability
• PDC bit steer-ability
• Back rake
• Side rake
• Depth of cut
• Cutter exposure
• Cutter density
• Thermal damage and degradation of cutters
• Cutting mechanics
• PDC cutter substrate and its thickness
• Cutting structure elements
• Single set bladed cutting structures
• Plural set bladed cutting structures
• Dull grading system
7. ROP management based on drilling parameters
• WOB
• Rpm
• Sold content of mud
• Mud weight
• Cutter shape
• Cutters geometry
• Depth
• Abnormal pressure
• Drilling formation properties

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Drilling Bit Introduction and bit Selection (Part 2)

  1. 1. Cone bit Course
  2. 2. Introduction to Roller Cone Bits • First Roller Cone bits:
  3. 3. ROLLER CONE BIT TERMINOLOGY
  4. 4. ROLLER CONE BIT TERMINOLOGY
  5. 5. ROLLER CONE BIT TERMINOLOGY
  6. 6. FUNDAMENTALS OF BIT DESIGN • Available Space • Basics of Cone Geometry Design Journal Angle: It influences the design of many key bit features, including: • Depth of intermesh, • Insert extension and milled tooth depth, • Heel surface length and angle, • Gage contact and length, • Cone diameter, (oversize angle), • Cone shell thickness, • Space available for bearings, • Leg strength and,
  7. 7. Basics of Cone Geometry Design • Oversize Angle: • Oversize angle, is provided when it is desired to increase the diameter of a cone. • Increasing oversize angle enlarges a cone and increases scraping action on the borehole wall. • This, in turn, requires that the gage tip be moved toward the center of the bit to prevent over- gage geometry. • This results in a degree of scraping by the gage inserts on a cone having an oversize angle; if the amount of oversize is reduced, scraping will be decreased.
  8. 8. Basics of Cone Geometry Design • Offset: • "Offset" is the horizontal distance between the axis of the bit and a vertical plane through the axis of the journal. • To increase scraping, bit designers generate additional working force by offsetting the centerlines of the cones so that they do not intersect at a common point on the bit. • In abrasive formations, offset can reduce cutting structure service life to an impractical level. As a result, bits designed for these applications typically utilize a relatively small offset in order to minimize scraping.
  9. 9. Basics of Cone Geometry Design • Teeth and Inserts: • Structural requirements for the tooth or insert, and, • Formation requirements
  10. 10. Basics of Cone Geometry Design • Teeth and Inserts: • Structural requirements for the tooth or insert, and, • Formation requirements
  11. 11. Basics of Cone Geometry Design • Teeth and Inserts: • Structural requirements for the tooth or insert, and, • Formation requirements
  12. 12. Additional Design Criteria • Tooth-to-tooth and tooth-to-groove clearances, • Bottom-hole coverage, • Cone-shell thickness, and, • Bearing configuration.
  13. 13. Additional Design Criteria • Cone-Shell Thickness • Cone-shell thickness is of crucial importance from a strength standpoint. • Insufficient cone-shell area can result in cone failure and down-hole loss of components. • Varying shell thicknesses are used for different bit types. • The design engineer must adhere to established, minimum values, however.
  14. 14. Additional Design Criteria • Bearings Factors • The primary function of the balls is to secure cones to leg journals; under certain loading, balls can resist thrust loading, however. • Roller cone bit bearings must normally withstand extremely high values of unit and impact loading. • Within the limited space available, overly large roller and ball bearings necessitate reduced journal diameters. This condition decreases the wear life of the journal and increases its potential for fatigue failure.
  15. 15. Materials • Important physical property requirements for legs and cones include: • Legs are forged from aircraft grades of wrought material • Nickel-chrome or nickel-chrome-molybdenum steel is used to produce case-harden able journals that provide both optimum resistance to wear and to structural failures in bearing races caused by spalling. • Hardenability • Forge ability • Chemical and grain structure uniformity and cleanliness • Machinability and weld ability • Impact resistance • Especially tough steels, characterized by high resistance to chipping • or breaking at high hardnesses, are used for ball and roller bearings.
  16. 16. ROCK BIT METALLURGY • Physical properties of a bit component: • Type of heat treatment • Material from which the component is made • structural requirements need for abrasion / erosion resistance. • WHY FORGED COMPONENTS? • When forgings (both legs and cones) are purchased, it is specified that they be made from wrought material. This means that cast ingots from • the steel mill have been rolled. Rolling results in grain refinement that, when correctly oriented, improves forging and end product structural strengths.
  17. 17. HEAT TREATMENT • Carburizing, • Heating and Quenching • Tempering • Cones and legs are subjected to all three processes. Ball and roller bearings and thrust buttons are not carburized, but do undergo heating, quenching, and tempering treatments.
  18. 18. Carburizing • the carbon content of the surfaces of the steel is increased by heating the material in an atmosphere made up of gases having high carbon content. The purpose of developing such a carbon layer is to provide a tough, wear- resistant "skin" or case.
  19. 19. Heat Treatment • Heat treatment increases material hardness to a maximum. All roller cone bit components are heat treated. In heat treatment, the properties of a material (steel in the case of roller cone bits) are altered to meet functional requirements of the part without appreciable change in its chemical composition.
  20. 20. Tempering • All rock bit components are tempered. • Tempering, (or drawing), takes place at relatively low temperatures. • Tempering is the final operation in the overall heat-treating process; it consists of reheating a hardened material after the heating and quenching cycle to relieve high residual stresses formed during quenching. • Without tempering, heat-treated parts tend to be brittle and have low toughness or impact strength.
  21. 21. HARDFACING • Steel is a relatively soft material that has poor resistance to abrasive and erosion wear. • To improve service life, some bit components that are subjected to this wear are hard-faced with tungsten carbide particles. • In general, hard-facing or Hard-metal is applied to the leg shirttail, and bearing surfaces on roller cone bits. • It is welded to the base material.
  22. 22. TUNGSTEN CARBIDE MATERIALS • Tungsten carbide is a brittle material with very high hardness and high compressive strengths; the compressive strength of tungsten carbide is approximately three times its tensile strength. • Tungsten carbide will cut most natural and man-made materials. • It cannot, conversely be cut or abraded by most materials other than diamond materials. • The cobalt binding provides the strength and toughness to mask the brittleness of pure tungsten carbide and make it useful for drilling.
  23. 23. Tungsten Carbide Grade Selection For Inserts • Inner insert rows commonly use softer, tougher insert grades to cut rock formation by crushing, compressing, gouging and scraping actions. • Gage insert rows commonly use harder, and wear resistant grades to cut rock and maintain gage. • Heel and TruCut gage insert rows commonly use the hardest carbide grades to maintain gage toughness, and higher impact and tensile strengths.
  24. 24. TUNGSTEN CARBIDE HARDFACING • The process is not complex: a hollow steel tube is filled (at manufacture) with appropriately sized grains of tungsten carbide. The tube is then held in an oxyacetylene flame until the steel rod melts and bonds, by surface melting, with the bit feature to be hard faced. In the process, the contained tungsten carbide grains flow onto the bit as a solid and do not melt. • This process is highly temperature critical. Excessive temperature will cause degradation of tungsten carbide grain boundaries and will result in decreased abrasion resistance and binder toughness. • Insufficient temperature will not result in a quality bond between the steel of the bit and that of the hard-facing rod that holds the tungsten carbide grains in place.
  25. 25. Components • BEARINGS, SEALS AND LUBRICATION • Ductility is an important property in a roller cone bit journal bearing because of high loading and bit vibration characteristics.
  26. 26. Bearing Shape
  27. 27. Bearing Precisions and Geometry
  28. 28. SEAL SYSTEMS • Seals have two functions in roller cone bits: – To prevent foreign materials (mud, cuttings, chemicals, water, etc.) from entering the bearings. (This function is called the “exclusionary” function.), – To prevent bearing lubricant stocks from escaping the bit and eventually leading to operation with un-lubricated bearings and seals. • The separation of these two, extremely different, functions is only a plane through the point of contact between them. Yet, if either of the functions breaks down, the bearings are destined for failure! This is a tough order that demands quality engineering. • Seal Environment – Seals must operate in an unusually harsh environment.
  29. 29. Seal Details • The two working sides of a seal are called: – The energizer, and, – The dynamic wear face.
  30. 30. Seal Details
  31. 31. BEARING AND SEAL LUBRICATION
  32. 32. BEARING AND SEAL LUBRICATION

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  • RaviKumar5340

    Nov. 28, 2019
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    May. 25, 2020

(PART 1,2 & 3) 1. Drilling mechanisms 2. Bit classifications (fixed cutter and roller cone bits) 3. IADC code descriptions 4. Tri-cone bits life time 5. Geometrical analysis of roller cone bits • Fundamentals of bit design • Basics of cone geometry design • Oversize angle • Offset • Teeth and inserts • Additional design criteria: tooth to tooth and groove clearances and etc. • Cone-shell thickness • Bearings factors • Rock bit metallurgy • Heat treatment • Legs and cones material • Tungsten carbide materials • Legs and cones hard facing • Tungsten carbide grade selection for inserts • Bearings, seals and lubrication • Bearing shape • Bearing precisions and geometry • Seal systems and seal details • Dull grading system 6. Geometrical analysis of PDC bits • PDC materials and constructions • Matrix materials testing • Differs between matrix & steel body • Matrix body bits manufacturing • Steel body bits manufacturing • PDC bit design parameters: mechanical, hydraulic, rock properties • Weld strength of PDC bits and cutters • PDC cutter manufacturing process • Tsp cutter properties vs PDC • The influences of bit profile and profile elements • PDC forces • PDC bit stability • PDC bit steer-ability • Back rake • Side rake • Depth of cut • Cutter exposure • Cutter density • Thermal damage and degradation of cutters • Cutting mechanics • PDC cutter substrate and its thickness • Cutting structure elements • Single set bladed cutting structures • Plural set bladed cutting structures • Dull grading system 7. ROP management based on drilling parameters • WOB • Rpm • Sold content of mud • Mud weight • Cutter shape • Cutters geometry • Depth • Abnormal pressure • Drilling formation properties

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