Boring or penetrating the earth – Bit or bit element – Specific or diverse material
Reexamination Certificate
1998-12-04
2001-01-23
Mai, Lanna (Department: 3619)
Boring or penetrating the earth
Bit or bit element
Specific or diverse material
C175S434000
Reexamination Certificate
active
06176333
ABSTRACT:
TECHNICAL FIELD
This invention relates in general to earth-boring bits and particular to an earth-boring bit having tungsten carbide cutting elements with diamond caps.
BACKGROUND ART
The success of rotary drilling enabled the discovery of deep oil and gas reservoirs. The rotary rock bit was an important invention that made rotary drilling economical.
In drilling boreholes in earthen formations by the rotary method, rock bits typically fitted with three rolling cutters are employed. The bit is secured to the lower end of a drill string that is rotated from the surface or by downhole motors or turbines. The cutters mounted on the bit roll and slide upon the bottom of the borehole as the drill string is rotated, thereby engaging and disintegrating the formation material to be removed. The roller cutters are provided with teeth or cutting elements that are forced to penetrate and gouge the bottom of the borehole by weight from the drill string. The cuttings from the bottom and sidewalls of the borehole are washed away by drilling fluid that is pumped down from the surface through the hollow, rotating drill string and are carried in suspension in the drilling fluid to the surface.
It has been a conventional practice for several years to provide diamond or super-hard cutting elements or inserts in earth-boring bits known as PDC, or fixed cutter bits. The excellent hardness, wear, and heat dissipation characteristics of diamond and other super-hard materials are of particular benefit in fixed cutter or drag bits, in which the primary cutting mechanism is scraping. Diamond cutting elements in fixed cutter or drag bits commonly comprise a disk or table of natural or polycrystalline diamond integrally formed on a cemented tungsten carbide or similar hard metal substrate in the form of a stud or cylindrical body that is subsequently brazed or mechanically fit on a bit body.
Implementation of diamond cutting elements as the primary cutting structure in earth-boring bits of the rolling cutter variety has been somewhat less common than with earth boring bits of the fixed cutter variety. In the rolling cutter variety, generally a diamond cap is formed on a cylindrical tungsten carbide base. The cap may be conical, hemispherical, or other shapes. While successful, improvements in wear resistance and penetration rate are desired.
DISCLOSURE OF INVENTION
In this invention, the cutting elements have cylindrical bases of tungsten carbide. Each cutting element has a diamond cap extending upward from a junction with the base, terminating in a rounded apex. Flats are formed in the sidewall of the cap surrounding the apex. Each flat is located in a single plane and has a perimeter which is oval in shape. A portion of each perimeter is contiguous with adjacent flats, creating sharp edges.
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Baker Huges Incorporated
Bradley James E.
Felsman, Bradley, Vaden, Gunter & Dillon L.L.P.
Gort Elaine
Mai Lanna
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