Drill bit

Abstract: A drill bit is provided which includes cutting elements cooperatively arranged with apertures in the bit to define flow paths for hydraulic flow proximate each cutting element. Cutting elements are preferably arranged in cutting pads which generally surround the apertures, such that hydraulic flow is forced to flow across the entire surface of the cutting pad. The dimensions of the cutting pad may be varied so as to control the hydraulic flow.

Description: The present invention relates to a drill bit as set forth in the preamble of claim 1. US-A-3 322 218 disclosing a bit of the kind referred to teaches the inducing fluid flow across the top or surface of the lands using a pressure differential. The cutters used in US-3 322 218 are natural diamonds or other abrasive particles embedded in the matrix forming the lands. The cutters protruding above the surface of the lands are passed by the fluid emerging from the discharge parts within the lands and flowing across the lands. Object of the present invention is to provide a drill bit which facilitates covling and cleaning of the cutters and which is practical for use with a variety of types and sizes of cutting elements. The invention is a drill bit as characterized in claim 1. Several further embodiments are claimed in claims 2-22. Figure 1 depicts a drill bit of the kind referred to in the preamble of claim 1, illustrated in an upward-looking perspective view, Figures 2A-B depict a first embodiment of a cutting pad for use on a drill bit in accordance with the present invention, depicted in Figure 2A in a perspective view and in Figure 2B in a segmented exploded view. Figure 3 depicts the cutting pad of Figure 2A in vertical section. Figure 4 depicts an alternative configuration of a cutting pad in accordance with the present invention. Figure 5 depicts another alternative embodiment of a cutting pad in accordance with the present invention. Figure 6 depicts an alternative arrangement of cutters on a cutting pad in accordance with the present invention. Figure 7 depicts another alternative arrangement of cutters on a cutting pad in accordance with the present invention. Figures 8A-B depict another alternative embodiment of a cutting pad for use on a drill bit in accordance with the present invention. Figure 9 depicts another alternative embodiment of a drill bit in accordance with the present invention illustrated from a side view. Figure 10 depicts another alternative embodiment of a drill bit in accordance with the present invention, illustrated from a side view. Referring now to FIGS. 1 drill bit 10 includes a body 12 which includes cutting pads, indicated generally at 14, and gage pads, indicated generally at 16. Gage pads 16 may serve a cutting function, but normally would not unless extending radially beyond those portions of cutting pads 14 extending to the gage. Body 12 is preferably a molded component fabricated through conventional metal matrix infiltration technology. Body 12 is coupled to a shank 18 which includes a threaded portion 19. Shank 18 and body 12 are preferably formed to be functionally integral with one another. Drill bit 10 includes an internal recess (not illustrated), through which hydraulic flow will flow. Each cutting pad 14 is formed of a continuous land 20 which includes a plurality of surface-set diamond cutting elements 22 secured thereto. Diamond cutting elements 22 are preferably embedded in the matrix of body 12 and project a desired distance from the surface of continuous land 20. Surrounding each continuous land 20 are channels or recesses 24. In this embodiment, recesses 24 represent nominal contours of body 12, relative to which continuous lands 20 are elevated. Body 12 includes apertures 26 within the interior of each continuous land 20. Each aperture 26 provides a path for hydraulic flow from the interior to the exterior of drill bit 10. The relative elevation of continuous lands 20 provides a flow area adjacent the periphery of each land 20. Each continuous land 20 is formed in a generally "wedge shape," with an inwardly extending leg, indicated generally at 28, approaching the central axis of drill bit 10 from a central portion along the outer periphery 30 of the wedge. This conformity places an increased area of land 20, and therefore of cutting elements 22, proximate the outer radial portion of bit 10. Accordingly, because the outermost portions of the radius of a diamond drill bit are subjected to increased abrasion and wear relative to inner portions along the radius, drill bit 10 provides an increased density of cutting elements to optimize distribution of such abrasion and wear. One cutting pad 14' extends to the center of drill bit 10 to assure full coverage of a cutting surface across the face of bit 10. Additionally, as can be seen in FIG. 1, cutting pads 14 extend from the bottom cutting surface of bit 10 around to the gage cutting surface. Accordingly, bit 10 provides for dedicated hydraulic flow across cutters cutting the gage of the borehole. In some applications where particular deflection of the bit from the gage of the borehole is anticipated, such as in navigational drilling, it may be desirable to increase the widths of continuous lands 20 on the gage of the bit relative to other locations to maintain optimal hydraulic flow characteristics around the surface of cutting pad 14. During the use of drill bit 10 in a drilling operation, fluid will be pumped down the drill string and out apertures 26 in drill bit 10 to cool cutting elements 22 and to flush the cuttings uphole. The hydraulic flow will typically be pumped at a level such as 500 to 3000 psi above the hydrostatic pressure at the bit. The pressure existing in recesses or channels 24 adjacent cutting pads 14 will be generally at hydrostatic pressure. Because the formation being penetrated by drill bit 10 will have a contour which complements that of bit 10, continuous lands 20 function, with the earth formation, to form a restriction to fluid flow which is, in this embodiment, generally constant. The pressure drop of the drilling fluid to hydrostatic pressure is, therefore, also generally uniform around continuous lands 20. Accordingly, the hydraulic flow will be generally uniform around the surface of continuous lands 20, and by each cutting element 22. Accordingly, the arrangement of continuous lands 20 around hydraulic flow apertures 26 allows for a portion of the hydraulic flow from each aperture 26 to be distributed to each set of cutters on the respective land 20. Referring now to FIGS. 2A-B and 3, therein is depicted a cutting pad 60 for a drill bit in accordance with the present invention. Cutting pad 60 includes a plurality of cutting elements 62 retained in the leading-facing surfaces of continuous land 64. A plurality of flow channels 66 are distributed across the width of continuous land 64. Flow channels 66 are preferably distributed with one on each side of each individual cutting element 62. Cutting pad 60 surrounds a central aperture 68. In this embodiment, hydraulic flow will pass from central aperture 68 across cutting pad 60, primarily through flow channels 66. Flow will therefore be established proximate each cutting element 62, thereby facilitating cooling and cleaning of each cutting element. FIG. 3 depicts cutting pad 60 in horizontal section along line 3-3 in FIG. 2A. Referring now to FIGS. 4 and 5, therein are depicted alternative cooperative arrangements between cutting elements and flow channels which may be utilized in bits in accordance with the present invention. The embodiment of FIG. 4 is similar to that of FIG. 2A, in that land 70 has a cutting element 72 retained proximate its leading face and that cutting element 72 is flanked on each side by a flow channel 74. However, flow channels 74 are oriented so as to be convergingly aligned relative to cutting element 72. Accordingly, hydraulic flow through channel 74 will converge proximate face 76 of cutting element 72 and will evidence relatively increased turbulence proximate face 76 of cutting element 72 to improve cleaning and cooling of cutting element 72. FIG. 5 depicts a configuration where cutting pad 80 includes cutting elements 82 retained on land 84 immediately adjacent flow channels 86. Cutting elements 82 and flow channels 86 each extend across the width of land 84. Cutting elements 82 and flow channels 86 may be at any desired position relative to the radius of the bit, from generally perpendicular to the radius of the bit to generally parallel to the radius of the bit. Additionally, cutting elements 82 may be angled or contoured in any desired manner. The arrangement of cutting elements 82 immediately adjacent flow channels 86 assures that there is a direct flow path along each cutting element 82. FIGS. 6 and 7 show two arrangements for cutting elements on a cutting pad in which the cutting elements are elevated above the surface of the cutting pad. In FIG. 11, cutting pad 100 includes land 102 which has a plurality of cutting elements 104 secured thereto through use of backing segments 106. Backing segments 106 may be molded extensions which are integral with land 102, or may be backing slugs on which the cutting elements are mounted and which, in turn, are set within the body of the drill bit. The arrangement of cutting pad 100 allows fluid flow directly across the cutting face 108 of each cutting element 104. The embodiment of FIG. 6 is functionally identical to that of FIG. 7, with the exception that backing segment 106' has been reduced in dimension across a diagonal, thereby allowing cutting elements 104 to be placed closer to one another while still facilitating full fluid flow across face 108 of each cutting element 104. Referring now to FIGS. 8A-B, therein is depicted yet another alternative embodiment of cutting pad 170 in accordance with the present invention. Each cutting pad again includes a continuous land 172 having a plurality of cutting elements 174 arranged thereon. In the illustrated embodiment, cutting elements 174 are polycrystalline diamond cutters presenting a generally hemispherical exposed cutting surface. In the depicted embodiment, continuous land 172 is graduated between two sections of varying heights 176 and 178, respectively. Lower height section 176 is on the leading side of continuous land 172 and includes cutting elements 174. Transitional sections 180, 181 leading to upper height section 178 are on the radially inner and outer portions of pad 172. In this embodiment, upper height section 178 of continuous land 172 does not include any cutting elements. Additionally, upper height section 178 of continuous land 172 is of an increased width relative to the width of lower heigth section 176. In the illustrated embodiment, cutting elements 174 are preferably comprised of a polycrystalline synthetic diamond table 182, mounted, bonded or otherwise fixed to a metallic backing slug 184 although other types of cutting elements, such as natural diamonds or thermally stable synthetic diamonds, may be employed in lieu of or in combination with the cutting elements as shown. The metallic backing slug 184 is in turn set within continuous land 172 as a part of the infiltration molding process. These cutters 174 present a relatively high exposure relative to the nominal surface 188 of the bit. Accordingly, higher portion 178 of continuous land 172 (with increased width as well as heigth), serves as a "dam" which effectively closes the path for hydraulic flow to areas other than those proximate cutting elements 174. Thus, notwithstanding the relatively high exposure of cutters 174, adequate hydraulic pressure and flow may be maintained proximate cutters 174. Land 172 will preferably be formed, at least in part, of an abradable matrix which will wear as cutting elements 174 wear, and may itself include cutting elements thereon, such as natural diamonds, diamond grit or thermally stable synthetic diamonds, all of such being known and commercially available. For example, land 172 is depicted as being formed of an abradable matrix cutter as previously described herein with respect to Figure 9. It should be readily understood that although a cutting pad of varying heights and widths is described in combination with polycrystalline diamond cutters, such varying pad dimensions may be utilized to control and regulate fluid dynamics with a variety of cutting elements types and designs. FIGS. 9 and 10 depict alternative shapes, and distributions of shapes, of cutting pads which may be utilized in drill bits in accordance with the present invention. One skilled in the art will recognize that these exemplary embodiments shown are illustrative only, and that a virtually infinite number of cutting pad configurations may be utilized within the scope of the present invention. The embodiment of FIG. 9 is depicted as including natural diamond cutting elements. Alternatively, this embodiment could include other types of cutting elements and or flow channels, including those exemplary configurations depicted in FIGS. 1-8. Although each exemplary embodiment depicted herein, depicts hydraulic flow apertures which extend to the boundaries of the cutting pad or land which surrounds them. It should be readily understood that these apertures may be singularly smaller, or may be divided into a plurality of smaller apertures within the pad, so as to control the hydraulic flow regime. For example, the sizes of apertures within various cutting pads on a bit may be utilized to regulate the proportion of the total hydraulic flow which is dedicated to that cutting pad. For example, smaller apertures might be placed within gage cutting pads to provide sufficient but reduced fluid flow relative to the flow dedicated to cutting pads cutting the bottom of the hole. FIG. 9 depicts a drill bit 180 in accordance with the present invention. Drill bit 180 includes a plurality of cutting pads 182 which may be considered to form cutting surfaces which are generally spiraled around the bottom and gage periphery of drill bit 180. Each cutting pad 182 again surrounds a central aperture 184. Drill bit 180 includes cutting pads 182 which may be considered to form the general contours of the lower portion of bit body 186. Accordingly, bit body 186 includes grooves or channels 188 adjacent the outer periphery of cutting pads 182. Upper chamfer section 190 of bit body 186 again provides a relative recess for fluid flow adjacent the outer periphery of cutting pads 182. Accordingly, during operation of bit 180 fluid within relative recesses 188, 190 will be generally at hydrostatic pressure thereby allowing optimal fluid distribution around cutting pads 182. Additionally, bit 180 demonstrates another embodiment of a bit providing dedicated hydraulic flow proximate cutters cutting the gage, i.e., those cutters above gage line 192. The extension of cutting pads 182 and central apertures 184, and recesses 188, both above and below gage line 192, coupled with chamfer 190 serve to provide hydraulic flow across the face of the gage cutting elements. Referring now to FIG. 10, therein is depicted an alternative embodiment of bit 200 including gage cutters 202 with dedicated hydraulic flow. Gage cutters 202 are each formed of a raised cutting pad 204 surrounding a central gage aperture 206. Gage cutting pads 204 serve to provide optimal hydraulic flow characteristics to the gage cutters, rather than their being left to cooling from incidental flow around bit 200, as is typical with conventional designs. Many modifications and variations may be made in the techniques and structures described and illustrated herein within the teaching of the invention as defined in the claims. For example, in addition to the placing of nozzles within the perimeter of the cutting pads, nozzles may be oriented at desired locations on the exterior of the cutting pads. Additionally, bits may be constructed to include both cutting pads with a dedicated hydraulic flow as described herein and conventionally irrigated cutters subjected to either radial or nozzle-oriented hydraulic flow. Further, cutting pads incorporating more than one type of cutting element and bits having a plurality of cutting pads thereon, each having a single type of cutting element but different than the cutting elements on at least one other pad, are contemplated as within the scope of the present invention. Accordingly, the techniques and structures described and illustrated herein are exemplary only and are not to be considered as limitations on the present invention.

Claims: A drill bit (10,180,200) comprising a body member (12) including at least one aperture (26) therethrough surrounded by a generally continuous land (20,64,70,84,102,172) being elevated to provide a restriction to fluid flow discharged from said aperture (26) said land having a plurality of cutting elements (22,62,72,88,104,174) associated therewith, characterized in a plurality of flow channels (66,74,86) formed in and extending across said land for directing hydraulic flow from said aperture (26) proximate to individual cutting elements (62,72,88,104,174). The drill bit (10, 180, 200) of claim 1, wherein said body member (12) includes a plurality of apertures (26) and a plurality of generally continuous lands (20, 64, 70, 84, 102, 172), and wherein each of said generally continuous lands (20, 64, 70, 84, 102, 172) generally surrounds one or more of said apertures (26). The drill bit (10, 180, 200) of claim 1, wherein said generally continuous land (20, 64, 70, 84, 102, 172) includes an increased surface area proximate an outer radial portion of said drill bit (10, 180, 200) relative to the surface area of said generally continuous land (20, 64, 70, 84, 102, 172) proximate an inner radial portion of said drill bit (10, 180, 200). The drill bit (10, 180, 200) of claim 1, wherein said generally continuous land (20, 64, 70, 84, 102, 172) is elevated relative to the portion of said drill bit (10, 180, 200) adjacent the outer periphery of said generally continuous land (20, 64, 70, 84, 102, 172). The drill bit (10, 180, 200) of claim 1, wherein said generally continuous land extends along a bottom cutting portion and along the gage of said drill bit (10, 180, 200). The drill bit (10, 180, 200) of claim 1, wherein said drill bit (10, 180, 200) further comprises cutters to cut along the gage of said drill bit (10, 180, 200), and wherein said gage cutters are placed on said generally continuous land (20, 64, 70, 84, 102, 172). The drill bit (10, 180, 200) of claim 1, wherein said at least one aperture (26) comprises a plurality of apertures (26), and wherein said drill bit (10, 180, 200) further includes a plurality of generally continuous lands (20, 64, 70, 84, 102, 172) each surrounding at least one of said apertures (26), and wherein each generally continuous land (20, 64, 70, 84, 102, 172) includes a plurality of cutting elements (22, 62, 72, 88, 124, 174) cooperatively arranged with said generally continuous land (20, 64, 70, 84, 102, 172), and a plurality of flow channels (66, 74, 86) formed in each of said generally continuous lands (20, 64, 70, 84, 102, 172) to provide fluid flow from said respective apertures (26) proximate to each cutting element (22, 62, 72, 88, 124, 174) of said plurality of cutting elements (22, 62, 72, 88, 124, 174). The drill bit (10, 180, 200) of claim 7, wherein at least one of said generally continuous lands (20, 64, 70, 84, 102, 172) is adapted to cut along the gage of said drill bit (10, 180, 200). The drill bit (10, 180, 200) of claim 1, wherein said generally continuous land (20, 64, 70, 84, 102, 172) varies in height relative to portions of said drill bit (10, 180, 200) adjacent the outer periphery of said generally continuous land (20, 64, 70, 84, 102, 172). The drill bit (10, 180, 200) of claim 1, wherein said cutting elements (22, 62, 72, 88, 124, 174) comprise synthetic diamond cutting elements. The drill bit (10, 180, 200) of claim 10, wherein said synthetic diamond cutting elements are retained in a sintered matrix. The drill bit (10, 180, 200) of claim 1, wherein each of said flow channels (66, 74, 86) lies immediately adjacent one cutting element (22, 62, 72, 88, 124, 174) of said plurality of cutting elements (22, 62, 72, 88, 124, 174). The drill bit (10, 180, 200) of claim 1, wherein said aperture is in the form of a nozzle. The drill bit (10, 180, 200) of claim 1, wherein said plurality of flow channels (66, 74, 86) are distributed with one of said flow channels (66, 74, 86) on each side of each said cutting element (22, 62, 72, 88, 124, 174). The drill bit (10, 180, 200) of claim 14, wherein said flow channels (66, 74, 86) on each side of each said cutting elements (22, 62, 72, 88, 124, 174) converge toward one another at the outer periphery of said generally continuous land (20, 64, 70, 84, 102, 172). The drill bit (10, 180, 200) of claim 1, wherein at least some of said cutting elements (22, 62, 72, 88, 124, 174) are arranged within said flow channels (66, 74, 86). The drill bit (10, 180, 200) of claim 16, wherein all of said cutting elements (22, 62, 72, 88, 124, 174) are arranged within said flow channels (66, 74, 86). The drill bit (10, 180, 200) of claim 1, wherein said plurality of flow channels (66, 74, 86) are arranged so that fluid flow from said aperture (26) will pass proximate each of said cutting elements (22, 62, 72, 88, 124, 174). The drill bit (10, 180, 200) of claim 1, wherein said aperture (26) includes a nozzle. The drill bit (10, 180, 200) of claim 1, wherein said generally continuous land (172) is elevated relative to selected adjacent portions of said body member (12), said land (172) includes a first portion (176) and a higher, second portion (178); and said plurality of cutting elements (174) are arranged on said first portion (176) of said land (172), whereby said higher, second portion (178) of said land (172) directs fluid flow from said aperture (26) across said first portion (176) of said land (172) and said cutting elements (174) arranged thereon. The drill bit (10, 180, 200) of claim 20, wherein said second portion (178) of said land (172) is wider than said first portion (176) of said land (172). The drill bit (10, 180, 200) of claim 20, wherein said second portion (178) of said land (172) includes an abradable surface.

Inventors: TIBBITTS GORDON A, TIBBITTS, GORDON A.
Applicants: EASTMAN TELECO CO, EASTMAN TELECO COMPANY
Application year: 1989
Main classification: E21B10
IPC codes: E21B10