US3314490A

US3314490A - Diamond drill bit

Info

Publication number: US3314490A
Application number: US444272A
Authority: US
Inventors: Alexander B Hildebrandt
Original assignee: Exxon Production Research Co
Current assignee: ExxonMobil Upstream Research Co
Priority date: 1965-03-31
Filing date: 1965-03-31
Publication date: 1967-04-18
Anticipated expiration: 1984-04-18

Description

April 1967 A. B. HILDEBRANDT v 3,314,490

DIAMOND DRILL BIT F iled March 31, 1965 FIG. 2

BYW E. L

ATTORNEY United States Patent 3,314,490 DIAMQND DRILL BIT Alexander B. Hiidehrandt, Tulsa, Okla, assignor to Esso Production Research Company, a corporation of Delaware Filed Mar. 31, 1965, Ser. No. 444,272 4 (Ilairns. (Cl. 175-329) The present invention relates to rotary bits for drilling boreholes in the earth and is particularly concerned with diamond bits for drilling oil wells, gas Wells and similar boreholes.

The typical diamond bit employed in the petroleum industry includes a body provided with a steel shank and a crown composed at least in part of a metallic matrix in which the diamond cutting elements are embedded. The matrix is generally formed by the liquid phase sintering of tungsten carbide or a similar refractory hardmetal powder in the presence of a softer binder metal. Experience has shown that erosion of the matrix by the fluid used to remove cuttings from the borehole is a serious problem. Efforts to avoid this problem through the use of improved tungsten carbide compositions, more erosionresistant binder metals, higher tungsten carbide-to binder metal ratios, and other changes in the crown metallurgy have been only partially successful. Further improvements which will facilitate the use of high circulation rates to secure adequate cleaning of the diamonds and will permit high drilling rates without severe erosion and premature loss of the diamonds are needed.

It is therefore an object of the present invention to provide improved diamond bits for drilling oil wells, gas wells and similar boreholes in the earth. Another object is to provide diamond bits which will facilitate the use of high fluid circulation rates to secure better bit performance during rotary drilling operations carried out in the petroleum and mining industries. A further object is to provide bits which are less susceptible to matrix erosion and loss of the diamonds than diamond drilling bits available in the past. Still other objects will become apparent as the invention is described in greater detail hereafter.

In accordance with the invention, it has now been found that the performance of a diamond drill bit can be improved by providing an elongated throat opening which extends across the lower surface of the tool and feeds the discharged drilling fluid into substantially parallel waterways extending outwardly from the throat opening to the gage surfaces. This arrangement of the throat opening and waterways reduces erosion of the matrix in the critical area of the throat where severe erosion normally takes place and promotes more effective distribution of the fluid to the diamond-bearing surfaces between the waterways than can generally be obtained with bits having radial or spiral waterways of conventional design. This in turn facilitates the use of higher fluid circulation rates to promote better bit performance.

The nature and objects of the invention can best be understood by referring to the fol-lowing detailed description of one embodiment of the improved bit and to the accompanying drawing in which:

FIGURE 1 is a vertical elevation, partially in section, of a diamond drill bit constructed in accordance with the invention; and,

FIGURE 2 is a bottom view of the bit shown in FIG- URE 1.

The diamond bit depicted in the drawing includes a cylindrical body 11 having an upper shank 12 on which external threads 13 have been cut to permit attachment of tool to the lower end of a rotary drill string or the outer rod of a mining drill. The body will normally be cast or machined from steel or a similar tough, shock from about 50 to about of the crown diameter.

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resistant metal. If the tool is intended for use in the petroleum industry, the shank dimensions and threads will generally be selected to provide a standard API tool joint pin. Standards are similarly available for tools to be employed in the mining industry. In lieu of a shank having external threads as shown, a tool joint box containing internal threads may be provided. The body includes an axial passageway 14 which extends through the body from an opening in the upper shank and permits the circulation of drilling fluid to the tool. The body is provided with external threads 15 at its lower end to facilitate attachment of the crown before it is Welded in place at the lower end of the body. The welded joint is designated by reference numeral 16 in FIGURE 1.

The crown of the bit depicted in the drawing extends outwardly beyond the upper part of the body to provide gage surfaces 17 which contact the borehole wall and assist in maintaining the desired borehole diameter. The crown includes a generally tubular crown blank 18 of steel or similar metal to which the body is attached, a matrix 19, and diamond cutting elements 20. The matrix is bonded to both the inner and outer surfaces of the crown blank. These surfaces may be roughened or indented to promote better bonding. The crown is normally formed by placing the diamonds in shallow depressions in the wall of a refractory mold of the desired shape, positioning the crown blank in the mold, surrounding the blank with finely ground tungsten carbide powder or a similar hardmetal, and then infiltrating a molten copper-nickel alloy or equivalent binder metal into the interstices between the powder granules. The binder employed will generally have a melting point between about 1550 F. and about 2450 F. and in the molten state should have the ability to wet the hardmetal granules. As the binder metal cools following the infiltration step, a metallurgical bond between the steel surfaces and the carbide granules is formed. The diamonds are held in place by the surrounding matrix. The crown may then be removed from the mold, sand blasted to remove surface irregularities, and thereafter attached to the body. An alternate procedure which may 'be utilized in lieu of that described involves the liquid phase sintering of an intimate mixture of carbide powder and bonding metal at high pressure and elevated temperature. These and other fabrication methods and matrix compositions which may be employed are described in greater detail in the Diamond Drill Handbook by I. D. Cumming, 1956 edition, published by J. K. Smit & Sons of Canada, Ltd, Toronto.

Below the gage surfaces, the lower part of the crown shown is rounded to give a generally concave lower surface or drilling face 21. As can be seen more clearly from FIGURE 2 of the drawing, this surface includes an elongated slot-like throat opening 22 which communicates with passageway 14 in the body and upper part of the crown. The opening extends a substantial distance across the crown, preferably through a distance equivalent to It decreases in depth toward its outer ends and is generally of substantially uniform width. Alternatively, the depth may be substantially uniform and the width may decrease toward the bit periphery. The diamonds 20 which serve as cutting elements are embedded in lands 23 which extend at substantially right angles to the longitudinal axis of the throat opening. Each land contains one or more rows of diamonds. At the center of the bit, the lands extend inwardly beneath the bit axis to permit drilling out of the formation at the center of rotation and thus avoid the formation of a core. The diamond concentration at this point will generally be somewhat greater than at other points on the tool because relatively little motion takes place between the diamonds and underlying formation. The two outermost lands 24 at the ends of the throat opening on the bit shown contain no diamonds and extend a short distance below the other lands to divert the flow of drilling fluid. In lieu of these diversion lands, lands similar to those elsewhere on the bit may be utilized. Waterways 25 extending outwardly from the throat opening at substantially right angles to the longitudinal axis of the opening separate the adjacent lands. The waterways and intervening lands extend upwardly on the gage surfaces to provide lateral stability and permit the escape of drilling fluid into the annular space surrounding the body of the bit. The cross-sectional areas of the waterways may decrease toward the outer ends of the throat opening to secure more uniform fluid distribution. Each waterway may also be tapered to control the pressure drop along its length if desired. Junk slots 26 are provided in the gage surface adjacent the diversion lands 24' to serve as passageways through which particles produced by the diamonds may escape without being reground between the gage surfaces of the tool and the surrounding borehole wall. The bit shown includes two diametrically opposed junk slots but a single slot or more than two may be provided if desired.

As can be seen from the cross-sectional view in FIG- URE 1, the bit depicted is provided with a concave lower surf-ace having a radius of curvature substantially equivalent to the radius of the borehole. The rim surrounding the concave spherical surface is rounded to avoid excessive forces on the diamonds near the bit periphery. This type of configuration reduces the tendency of the bit to walk" or tilt in response to wob-bling of the drill collars above it and minimizes variations in the forces acting on the diamonds. This reduces diamond losses and promotes longer bit life. p

- In drilling with the tool of the invention, drilling fluid is circulated downwardly through the drill string to which the bit is connected. The fluid passes through passageway 14 in the body and upper part of the crown and emerges into throat opening 22 in the lower part of the 'tool. Because of the relatively large cross-sectional area of this opening, there is littletendency for the emerging fluid to erode away the matrix. In conventional diamond bits, on the otherhand, erosion is normally severe at points around the throat where the fluid first flows between the matrix surface and the underlying formation. The fluid thus supplied to the throat opening flows outwardly through waterways 25 into the annulus above the crown, carrying with it cuttings produced by the diamonds. Because the fluid is fed from the enlarged throat opening into a series of parallel waterways across which the pressure drop does not. vary widely, fluid welocities beneath the cutting surfaces are substantially uniform. Better fluid distribution is obtained than can be secured with a tool having radial or spiral waterways extending outwardly from a relatively small throat opening. The use of junk slots facilitates the removal of solids beneath the bit without repeated regrinding and also simplifies tripping of the bit into and out of the borehole.

It will be understood that the invention disclosed herein is not limited to the specific tool shown in the drawing. The junk slot configurations, the number and size of the waterways, the fluid diversion lands and other features may be modified without departing from the invention. Cutting elements other than diamonds, regular or irregular shaped particles of tungsten carbide, a multiple carbide or similar hardmetal for example, may be employed if desired. These and other modifications of similar nature will readily suggest themselves to those skilled in the art.

What is claimed is: a

1. A rotary drill bit comprising:

(a) a body member containing an axial passageway for the transmission of drilling fluid, said member including means for connecting said bit to the lower end of a drill string;

(b) a crown connected to the lower end of said body member and extending laterally beyond said memher, said crown including (i) a lower face for contasting the formation at the bottom of a borehole, (ii) an elongated slot-like throat opening in said lower face, said throat opening communicating with said passageway in said body member near the longitudinal axis of said bit, (iii) a plurality of waterways in said lower face extending from said throat opening to the crown periphery at substantially right angles to the longitudinal axis of said opening, and (iv) diversion lands extending at substantial right angles to the longitudinal axis of said throat opening at the ends thereof; and,

(c) a plurality of diamonds embedded in lands on said lower face between said watercourses.

.2. A bit as defined by claim 1 wherein said throat opening is of substantially uniform Width and decreases in depth toward each end thereof.

3. A bit as defined by claim 1 wherein said throat opening is of substantially uniform depth and decreases in width toward each end thereof.

4. A bit as defined by claim 1 wherein said throat opening extends at least halfway across said crown.

References Cited by the Examiner UNITED STATES PATENTS 791,264 5/ 190 5 Hardsocg 4l7 X 2,264,440 12/1941 H-avlick 175329 2,545,195 3/1951 Crake 175-330 2,998,088 8/ 1961' Pennington 175-329 3,153,458 10/1964 Short 175-329 CHARLES E. OCON'NELL, Primary Examiner.

R. E. FAVREAU, Assistant Examiner.

Claims

1. ROTARY DRILL BIT COMPRISING: (A) A BODY MEMBER CONTAINING AN AXIAL PASSAGEWAY FOR THE TRANSMISSION OF DRILLING FLUID, SAID MEMBER INCLUDING MEANS FOR CONNECTING SAID BIT TO THE LOWER END OF A DRILL STRING; (B) A CROWN CONNECTED TO THE LOWER END OF SAID BODY MEMBER AND EXTENDING LATERALLY BEYOND SAID MEMBER, SAID CROWN INCLUDING (I) A LOWER FACE FOR CONTACTING THE FORMATION AT THE BOTTOM OF A BOREHOLE, (II) AN ELONGATED SLOT-LIKE THROAT OPENING IN SAID LOWER FACE, SAID THROAT OPENING COMMUNICATING WITH SAID PASSAGEWAY IN SAID BODY MEMBER NEAR THE LONGITUDINAL AXIS OF SAID BIT, (III) A PLURALITY OF WATERWAYS IN SAID LOWER FACE EXTENDING FROM SAID THROAT OPENING TO THE CROWN PERIPHERY AT SUBSTANTIALLY RIGHT ANGLES TO THE LONGITUDINAL AXIS OF SAID OPENING, AND (IV) DIVERSION LANDS EXTENDING AT SUBSTANTIAL RIGHT ANGLES TO THE LONGITUDINAL AXIS OF SAID THROAT OPENING AT THE ENDS THEREOF; AND, (C) A PLURALITY OF DIAMONDS EMBEDDED IN LANDS ON SAID LOWER FACE BETWEEN SAID WATERCOURSES.