GB2307699A - Rotary drag bit - Google Patents

Abstract

A rotary drag bit for drilling subterranean formations comprises a plurality of layers of matrix material secured together to define a bit body, a plurality of cutting elements secured to a bit face on said bit body and a tubular, externally threaded bit shank secured to said bit body opposite said bit face.

Description

ROTARY DRAG BIT This invention relates to a rotary drag bit. This application is divided from co-pending application 9504547.2 (Serial Number 2287959). The general background to the present invention is discussed in the specification of the parent application. The present invention is set out in claim 1.

Examples of the invention will now be described with reference to the accompanying drawings in which: FIG. 1 is a perspective view of a solid or three-dimensional model of a drill bit as might be designed by a CAD system; FIG. 2 is an enlarged perspective view of the drill bit of FIG.

1, sliced transversely to the longitudinal bit axis to expose an interior section; FIG. 3 is an enlarged top elevation of the uppermost slice or layer of the drill bit segment depicted in FIG. 1; FIG. 4 is a schematic of a first preferred computer-controlled layering apparatus suitable for use in fabrication of a drill bit according to one preferred embodiment and FIGS. 4A-4E are schematics depicting use of the apparatus in the manufacture of a bit; FIG. 5 is a top elevation of the surface of a single slice or layer of another drill bit model, depicting the use of several different powders to provide different physical characteristics for various portions of the bit slice or layer and contiguous portions of adjacent slices or layers; FIG. 6 is a schematic of a second preferred layering apparatus suitable for use in fabrication of a drill bit according to another preferred embodiment;; and FIG. 7 is a schematic bottom elevation of a wing- or blade-type drill bit formed of interlocked components.

Referring now to FIGS. 1 to 3 of the drawings, an exemplary drill bit 10 as three-dimensionally modelled by a state of the art CAD system. Such systems are well known and widely used, and a particularly suitable commercially available CAD system for implementation of the present invention is the Pro/ENGINEER, offered by Parametric Technology Corporation. Drill bit 10, as shown, includes a variety of external and internal components, such as bit body 12 secured to a tubular bit shank 14 having a threaded pin connection 16 at the free end thereof and six blades or wings 18 carrying cutting elements 20 placed in sockets 22 and supported from the rear by inclined buttresses 24. Gage trimmers 26 are set immediately adjacent and above (as depicted in the drawing figures) gage pads 28.Blades 18 are separated by generally radially extending fluid courses 30 leading to junk slots 32, fluid courses 30 and junk slots 32 being provided in operation with drilling fluid ("mud") from the drill string through shank 14 communicating with internal fluid passages 34 leading to nozzles 36 in cavities 38 opening onto anid courses 30. Blades 18, fluid courses 30 and the topographical details thereof collectively define what may be termed the "bit face," being the surface of the bit in contact with the undrilled formation at the bottom of the borehole. The extcrior shape of a diametrical cross-section of the bit body 12 taken along the longitudinal bit axis 40 defines what may be termed the bit or crown profile.

As shown in FIG. 2 of the drawings, a CAD system may numerically "slice" the three-dimensional bit model along any desired plane, and in this instance along a plane perpendicular to the longitudinal axis 40 of bit 10. Looking at surface 42 in FIG. 2, it is readily apparent that the model of bit 10 may be readily numerically characterized as a series of superimposed primarily twoimensional thin layers of gradually varying cross section, which two-dimensional layers, when completely stacked, define the three-dimensional drill bit model depicted in FIG.

1. As shown in both FIGS. 2 and 3, surface 42 indudes apertures or voids where segments 34' of internal fluid passages 34 exist, the contiguous segments 34' in superimposed layers or slices comprising complete passages 34 in the bit model as representative of drill bit 10. FIG. 2 also shows voids 44 in the surface of the bit body where gage trimmers 26 have been deleted, providing a bit body ready for the addition of cutting elements 20, gage trimmers 26 and nozzles 38.

This slicing or layering technique permitted by CAD systems has been adapted to manufacturing techniques primarily employed in the fabrication of non-metallic prototypes of three-dimensional objects, such as engine parts, and of molds for casting liquified metals and other materials in low-volume production of solid objects. It appears, however, that such techniques are limited and shortsighted in comparison to the potential for the adaptation of such techniques to the fabrication of the ultimate desired end-product, in the present instance a rotary drag bit.

Referring now to FIG. 4 of the drawings, a first preferred exemplary apparatus 100 for tht fabrication of a rotary drag bit in accordance with the present invention is schematically illustrated. Apparatus 100 includes a horizontal platen 102 on which a bit body is to be formed. The platen 102 is preferably vertically movable in precise increments, as by a stepper motor assembly or other means 104. A particulate spreader, comprising a lineariyextending feed head 106 at the bottom of hopper 108 is horizontally movable across and above platen 102 to deposit a layer of particulate material on platen 102.Hopper 108 may be vibrated to facilitate the flow of particulate material and to render the flow more uniform, if desired. Vertically-fixed, horizontallyextending roller or scraper bar or blade 110 is also horizontally movable across platen 102, and may, if desired, be suspended from hopper 108. Fixative head 112, movable in at least the X and Y planes and also preferably in the Z plane, is suspended above platen 102 Fixative head 112 may comprise one of a variety of assemblies, depending upon the nature of the particulate material 120 and the desired binder alternative employed.Fixative head 112 may comprise, for example and not by way of limitation, a laser an inkjet nonle or a metal spray gwL The sequence of operation and movements of platen 102, hopper 108, roller 110 and fixative head 112 are controlled by a computer 114 employing a suitable machine control program as is currently known in the art Computer 114 may comprise a commerdafly vniable personal computer employing an Intel 486-series microprocessor. Vendors offering suitably-programmed computers employing stereolithography (SIA) systems responsive to CAD .S II file formats and associated hardware adaptable to the method of the present invention include DTM Corporation, Austin, Texas; Soligen, Inc, Northridge, California; Stratasys, Inc, Eden Prairie, Minnesota; and Helisys, Inc of Torrance, California The particulate material 120 comprises resin-coated metal particles such as tungsten carbide, iron, steel, Invar, ceramics or a mixture of any of the foregoing, which particulate material 120 comprises resin-coated metal particles.such as tungsten carbide, iron, steel, Invar, ceramics or a mixture of any of the foregoing, which particles 120 are deposited by the horizontal movement of hopper 108 over platen 102 with the latter in its uppermost deposition. Roller or scraper 110 spreads and smooths particles 120 into a first thin layer 122 of substantially uniform thickness (e.g. .076 - 0.51 mm (.003 to .020 inches)).Thereafter, fixative head 112, which comprises a laser, is directed toward and moved across particulate layer 122 in a regular horizontal pattern representative of a first or lowermost transverse layer or slice of the drag bit body as numerically defined and stored in computer 114. The laser beam is directed to impinge on layer 122 in those areas where bit body is comprised of solid material, and avoids those areas wherein a segment 34' of an internal fluid passage 34 or other void (for example, a plenum) exists within bit body. As shown in FIG. 4A, the laser melts the resin and fuses the metal particles together, resulting in what may be termed a preform layer 122' having. the peripheral outline of bit body at that vertical or longitudinal level, apertures or voids in that layer remaining as loose, unfused particles 120. With some metal powders, sintering may also occur.The laser is.then withdrawn and, as shown in FIG. 48, platen 102 indexed downwardly a vertical distance equal to the thickness of layer 122, a second layer 124 of particles - 120 is deposited by feed head 106 of hopper 108, then spread and smoothed by roller or scraper 110 as previously described. As shown in FIG. 4C, the laser is again directed, this time at the second layer 124 of FIG. 4B, to follow-a-horizontal pattern representative of a second, higher layer or slice of the drag bit body as numerically defined, and stored in computer 114, fusing the second layer 124 of FIG. 4B into second preform layer 124' which is also simultaneously fused to first preform layer 122'. It will be appreciated that layers 122' and 124' have been exaggerated in thickness for purposes of illustration.Since the crown profile of bit body is not cylindrical but tapered and the internal fluid passages extend laterally as well as longitudinally within bit body, the net result is that preform layer 124', while contiguous with layer 122', may not be identical thereto.

The particle deposition, smoothing and selective fusing of each successive preform layer is continued under computer control for hundreds or even thousands of layers until a recognizable three-dimensional structure as depicted in FIG. 2 gradually emerges, and the layering process is further continued until a completed bit body 12 as depicted in FIG. 1 (but without cutting elements 20, gage trimmers 26 and nozzles 36) is achieved, as shown in FIG. 4D. The bit body 12 at this stage is a porous, sponge-like or open-celled matrix 130 which is to be intrated with a binder.In order to effect the infi2tration, matrix 130 may be sprayed with a sealer to close the exterior pores of the bit crown and those opening onto any interior voids within matrix 130, then inverted and positioned in a mold casing 140 as shown in FIG. 4E A hardenable liquid 1427 such as Cotronics 770 (a ceramic), is then poured into casing 140 and permitted to harden into a solid mold form 144 resistant to temperatures above that at which a binder liquifles, the mold form 144 both surrounding the exterior of matrix 130 and filling internal fluid passages 34 and other internal voids.The mold may then be preheated to vaporize the resin in the matri A hardenable liquid binder is then mass infiltrated into matrix 130 in the manner well known in the art to fill the pores or cells therein, and permitted to harden, the finished product comprising the bit body. The mold form is then broken off the bit body and the mold material filling internal passages 34 and other voids is removed.

It is also contemplated that a "soft" or unconsolidated mold may be employed to support the bit body during infiltration. For example, casting sand or graphite powder may be poured around the bit body in a casing 140, and the casing vibrated to consolidate the sand or other particulate material around and within the bit body, eliminating unwanted voids before infiltration is effected.

A polymeric binder such as a polyester or epoxy resin, or even glass may be employed to infiltrate matrix 130. In some instances, the infiltration may thus be carried out substantially at room temperature by pouring the liquefied binder into the mold casing 140. Alternatively, a more traditional metal binder, such as a copper-based alloy, or a high melting-point nonmetallic binder such as glass may be placed on top of matrix 130 and the mold casing 140 with. matrix 130 and binder placed into a furnace until the binder melts and infiltrates downwardly into matrix 130. A particularly suitable copper alloy is disclosed in U.S. Patent 5,000,273. If desired, with any type of binder a vacuum may be pulled at the bottom of mold casing 140 to eliminate air pockets and attendant potential structural defects in the end product bit body.

It is possible to employ a preformed bit blank as used in prior art fabrication techniques for matrix bits, the blank being placed on platen 102 and the layers of particles deposited around the blank. Of course, with this variation of the method, use of a roller or scraper IS not practicaL Therefore, spreading and smoothing of each particle layer 122, 124 and so on may be effected by vibration of platen 102, and the volume of particulate material more carefuily controlled A premix of powdered matrix material and powdered binder may be deposited in layers on platen 102 as described above.However, in lieu of a complete mass binder infiltration process as previously described, the laser is employed to effect what may be termed a preliminary in = layer by layer infiltration process by heating and liquefying the binder to bond the top layer of unconsolidated matrix particles to each other and to the previously bonded layers below. By employing such a method, the bit body is finished at the ennEsion of the layering process and only infiltration with additional binder is required to eliminate voids in the bit body, if some porosity cannot be toierated. The powdered binder may be, as previously described, either nonmetallic or metallic Instead of prinking matrix and binder powder, separate layers of each may be applied (first matrix powder, then binder powder before the binder is liquefied by laser heating and penetrates between the underlying matrix partides).A further alternative, to avoid potential uneven distribution of matrix and binder particles in a premix, is to employ bindersoated matrix particles to ensure that each matrix particle is wetted by binder and bonded to an adjacent matrix partide. The coated particles are heated by laser to melt the binder and consolidate the matrix particles with each other and with the layer below.

It is possible to use uncoated particles of metal or other suitable material deposited on platen 102 as previously described. In this instance, however, fixative head 112 may comprise one or more ink-jet nobles such as are employed in printing mechanisms or alternatively a metal spray gun Fixative head 112 deposits a liquid binder over the powder particles, penetrating therebetween and solidifving, thus bonding the particles of the uppermost layer to each other and to the underlying layer which has previously been consolidated. If an ink-jet type binder deposition process is employed, the binder may comprise a non-metallic binder such as a polymer compound.Alternatively, a metallic binder such as a copper or zinc alloy or Kirksite, a proprietary alloy available through Industrial Modern Pattern and Mold Corp., may be employed. In the case of a metal alloy, the binder may be supplied in wire form which is liqitied (as by electric arc heating) and sprayed onto the uppermost particulate layer. Another alternative is to liquify the distal end of the binder wire with a laser or other heating means immediately above the unconsolidated powder layer rather than using a metal spray.

Further variations are also contemplated. For example, different matrix powders may be separately deposited on the platen at appropriate and desired locations, in order to provide different portions of the drill bit with different physical characteristics. Specifically, particles of tungsten carbide, a ceramic, or other hard material may be deposited by a hopper or other deposition device controllably moved in the X-Y plane at the periphery of a layer being formed on the platen or on an underlying layer to provide an abrasion- and erosion-resistant outer shell for the bit body, and at the CAD-indicated locations for internal fluid passage segments to provide a similarly abrasion- and erosion-resistant wall segment surrounding the passage segment.The other matrix particles employed in the layer being formed may comprised iron, steel, Invar or other tough and ductile materials to so enhance the toughness and ductility of the bit body. After the two types of powders have been deposited (two types being only by way of example and not limitation), the powder layer may be sintered or otherwise bonded, the end result being a layer or slice 200 of a bit body as depicted in FIG. 5 of the drawings. layer 200, shown in the finished form as it would be as a part of the bit body,includes a hard outer periphery 202 and passage wall segments 204 for the passage segments, and a tough and ductile major portion 206 providing the desired robust physical characteristics for the bit body as a whole. Aside from the use of the two powders, the method is performed in the manner disclosed above.

As an alternative to selective placement of different powdered materials in a layer and bonding of the entire layer at once, the same result may be achieved by a variation of the method which is easier to effect in practice and which may provide more precise boundaries between the different materials in a layer.

In the variation, a first powdered material is deposited over the entire crosssection of a bit body layer, and then selectively bonded as by a laser in desired locations. Powder in the unbonded areas of the layer is then removed and recovered by vaawning, and a second powdered material is then deposited over the entire cross-section and selectively bonded, with unbonded material again removed by vacuuming.A third material, etc, may also be deposited and selectively bonded Using selective placement or selective bonding of powdered materials with differing physical characteristics reduces the volume of relatively expensive tungsten or tungsten carbide required for the bit body, as such would be used only where necessary, and may reduce the size of the blank required or eliminate the need for a conventional blank altogether due to the employment of an inherently tough and ductile matrix material throughout the majority of the bit body volume.

Only a short "stab" blank may thus be required for welding the threaded shank to the bit body, or the relatively low or even ambient temperatures employed in the bit fabrication process may permit the matrix to be secured (sintered, fused or mechanically secured) to a combination blank/shank during the matrix formation process without adversely affecting the physical characteristics of the blank/shant It should further be recognized that yet a third type of powder 208 as shown in FIG. 5 may be deposited in a controlled manner to build a simulated "blank" within the bit body if such is desired.

With any of the foregoing embodiments of the present invention, and particularly those wherein the metal or other powder defining the bit body matrix is fairly porous and easily machined, the layered and consolidated (but not finally infiltrated) bit body is drilled, milled or otherwise machined to provide a receptacle to accept a bit blank of desired configuration. The blank is then inserted, and bonded into the bit body during the infiltration thereof.

Another alternative is to avoid fusing the particulate material in the regions wherein a blank is to be inserted into the bit body, to define a blank receptacle in the same manner that fluid passages are defined.

A further preferred embodiment of the present invention which may employ at least two different powders in the matrix differs from the variations described above in that only an outer bit shell (an illustrative layer thereof being element 200 in FIG. 5) is formed by thc layering process, and the shell is then later fitted with preforms for defining the internal fluid passages, filled with the second powder and the assembly infiltrated with binder. The shell thus forms a mold for casting the vast majority of the bit body, and then becomes an integral part thereo To perform this particular method, tungsten carbide or ceramic particles (either resin-coated, bindercoated or mixed with a resin or a binder) may be deposited on the platen in a ring approximating the outer periphery of the first, lowermost layer of the bit body. A laser is then used to bond the powder particles, and a subsequent controlled deposition of particles then effected to define the second layer, which is then formed and simultaneously fused to the first layer.To promote more uniform layering, complete planar layers of tungsten carbide or ceramic may be deposited instead of a ring, and (if a second material is to be used for the bit interior) the unbonded material later recovered, placed in the hopper and used for formation of the next bit. If such a practice is followed, it also becomes relatively easy to define all of the internal fluid passages of the bit body by building "stacked" passage wall segments 204 (see FIG. 5). It is further contemplated that if the "shell" embodiment of the present invention is employed, the interior volume of the bit body may comprise a hardenable liquid such as molten iron, steel, or a non-metallic substance such as a polymer, and the second powder and infiltration thereof may be eliminated altogether.

It is also contemplated that the method may be employed to form bit body parts or components which may later be assembled together in abutting relationship and placed in a mold to be infiltrated into a single body. In such a manner, highly complex bit body configurations may be readily achieved. If desired, the parts or components may be configured to physically interlock to facilitate assembly and infiltration.

As depicted in FIG. 7 of the drawings, a wing- or blade-type drill bit or other complex bit body configuration may be fabricated by forming a central component 400 with grooves, channels or cavities 402 therein adjacent the gage 410. Wings or blades 404 may also be formed to extend over the face 412 of the bit. The assembly 406, maintained together by the interlocking of the key portions 408 of blades 404 with grooves 402, is then infiltrated as previously described to form a complete unit. Central component 400 may also be formed without grooves 402, and wings or blades 404 without key portions 408, and the components merely placed in abutment in a mold for infiltration.

Components may be adhered together for infiltration, or held together mechanically by fasteners if desired. In lieu of forming a central component and separate blades, components configured as halves, quarters or other equal or unequal fractions or portions of bit bodies may be separately formed for subsequent assembly and unification. In short, bit body components may be defined at will using the CAD system in any manner desired.

It is also contemplated that components machined or cast from metal or other materials may be secured to components fabricated by the layering techniques described above by infiltration. In addition, thermally stable diamond cutting elements, such as natural diamond or thermally stable polycrystalline diamond compacts (PDC's) may be adhered to the layered bit body prior to infiltration and secured thereto during the infiltration process.If a suitable low-temperature binder is employed to infiltrate the bit body, non-thermally stable PDC's may be secured during infiltration Other cutting elements known in the art, such as hot isostatic pressed diamond-impregnated cutting elements, cubic boron nitride cutting elements, or diamond film cutting elements may also be assembled with a bit body or bit body components of the present invention, infiltrated therewith and bonded thereto by a suitable binder. Of course, any and all types of cutting elements may be secured to a bit body after formation and infiltration, as known in the art. As used herein, the term "bit body components" specifically contemplates, without limitation, cutting elements and cutting structures.

It is possible to employ sheet material, rather than powders or particulates, to form the bit body matrix. As depicted in FIG. 6 of the drawings, an apparatus 300 for effecting the method includes at least a platen 302, means 304 for moving platen 302 in vertical increments, sheet feeder 306, laster head 308 and control computer 310.

Sheet feeder 306 may comprise a photocopier-type feeder and provide individual sheets, or may comprise a roll-type feeder with a feed roller and a take-up roller, as desired. In either case, a sheet of matrix material 312 (which may be imperforate or comprise a screen or perforated or porous sheet) of a suitable metal such as iron or steel or a non-metallic material such as a composite, is placed on platen 302. Laser head 308, under control of computer 310, cuts an outline of the periphery of that layer of the bit body being formed. The surrounding sheet material may then be removed, if desired, and a second uncut sheet 312 placed over the first, is bonded to the first by suitable means after which laser head 308 cuts the perimeter outline of the second layer of the bit body.If desired, the laser may be used rapidly to heat the second layer and bond it to the first before the second layer sheet 312 is cut at its periphery. The more usual method, however, employs a heated roller 314 which is pressed and rolled over the uppermost layer 312 before the layer periphery is cut.

Such bonding can be effected by sintering if the sheet material is metal, or may be adhesive in nature. For example, the top, bottom (or both sides) of each sheet may be coated with a heat-activated or meltable bonding substance. A further alternative is the use of layers of sheet material comprising a screen-like, perforated or porous sheet of matrix material impregnated with a binder which may be melted or otherwise activated by laser head 308 and/or heated roller 314. Yet another alternative is to alternate sheets 312 of matrix material with sheets of a binder material, or powdered layers of a binder material, or even to spray a binder material on the top of each sheet 312 before the next is placed.Further, and if desired, sheets of matrix material may include a ring of a different material than the main body of the sheet, and the laser employed to cut the layer periphery so that the ring material forms the outer shell of the bit. It is also contemplated that the laser may be used to cut internal fluid passage segments 34' in each layer after placement. As with the other, previously-described embodiments of the invention, bit body components may be formed for subsequent assembly with other components to form a bit body.

Other variations in the bit and its method of manufacture are envisaged. For example, a stationary platen may be employed, and the associated hopper, roller, fixative head, sheet feeder, etc. may be made vertically movable. An electron-beam welding head may be used in lieu of a laser in appropriate circumstances. Bits may be fabricated entirely from non-metallic materials, if desired. A mixture of matrix powder and a liquid adhesive or binder may be sprayed in layers, or the matrix powder and adhesive or binder sequentially sprayed (see U.S.

Patent 4,884,477). Powdered matrix material may be produced in sheet form with a flexible polymeric binder (see U.S. Patent 4,919,013) to form the layers of the bit body, the periphery and desired voids in each layer cut, and the polymer burned off with a laser and the powder sintered, or the polymeric vaporized by hot metal liquid binder when the bit body is infiltrated. Bit bodies may be subsequently machined to receive cutting elements on the face thereof, such as natural diamonds or thermally stable products (TSP's), which are then bonded to the bit body during infiltration thereof. Diamond particles may be mixed with tungsten carbide and selectively deposited at the periphery of each layer defining the bit face to provide so-called impregnated bits. Large cavities, grooves or other receptacles may be formed on the bit face or gage and prefabricated cutter assemblies, natural diamond gage pads or tungsten carbide blocks secured to the bit body during the infiltration process or subsequent thereto, as by brazing or other means known in the art.

Claims (9)

1. A rotary drag bit for drilling subterranean formations, comprising: a plurality of layers of matrix material secured together to define a bit body; a plurality of cutting elements secured to a bit face on said bit body; and a tubular, externally threaded bit shank secured to said bit body opposite said bit face.

2. A rotary drag bit as claimed in claim 1 further comprising a binder material within and between said layers of matrix material.

3. The rotary drag bit as claimed in claim 1 wherein said layers of matrix material comprise consolidated particulate material.

4. The rotary drag bit as claimed in claim 1 wherein said layers of matrix material comprise preformed sheet material.

5. The rotary drag bit as claimed in claim 1 wherein at least some of said matrix material layers are comprised of at least two different materials.

6. The rotary drag bit as claimed in claim 1 wherein said bit body is comprised of separately-formed components secured together after formation thereof.

7. The rotary drag bit as claimed in claim 6 wherein said separately-formed components include cutting elements.

8. A component for a rotary drag bit for drilling subterranean formations, comprising a plurality of layers of matrix material secured together in a predetermined three-dimensional shape.

9. A rotary drag bit as claimed in claim 1 substantially as hereinbefore described with reference to the accompanying drawings.