Background
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This disclosure relates generally to the field of wellbore drill bits used for drilling subsurface earthen formations. More particularly, the disclosure relates to fixed cutter wellbore drill bits having shear type cutting elements ("cutters") and pick or gouging type cutters.
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Fixed cutter bits known in the art include polycrystalline diamond compact ("PDC") bits, wherein a plurality of PDC cutters are affixed to a bit body in a selected arrangement on one or more blades formed in the bit body.
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Gouging type cutters are used in drill bits for drilling mine shafts or tunnels, among other uses. Such bits are known in the art as "claw" bits, one example of which is sold under the trademark QUI-KLAW, which is a trademark of Drillhead, Inc. Such bits are known to be useful in drilling clay, unconsolidated sand, loose rock and gravel.
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U.S. Patent No. 8,505,634 issued to Lyons et al. describes a drill bit having gouging cutters disposed adjacent to shear cutters on a blade on the bit body. The shear cutters have a planar cutting face, while the gouging cutting elements have a non-planar cutting face, e.g., dome shaped or cone shaped.
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Another type of fixed cutter drill bit that has both shear cutters and gouging cutters is sold under the trademark PEXUS, which is a trademark of Shear, Bits, Ltd., 407 2nd St. S.W., Suite 300, Calgary AB T2P 2Y3, Canada. It has been observed that such drill bits may exhibit premature wear on the shear cutters disposed on radially outward (from the center of rotation of the bit) portions of blades (the "profile"). Such wear is believed to be a result of being shielded from high velocity drilling fluid flow by the gouging elements, such that such shear cutter overheat and wear more quickly than expected. In applications where a drill bit designer would select low cost shear cutters on conventional PDC bits, such gouging and shear cutter bits need cutters made from more heat resistant and therefore more expensive cutters to avoid premature cutter wear due to thermal degradation (i.e., overheating of the cutters).
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It has also been observed that the foregoing drill bits using shear and gouging type cutters may generally drill through subsurface formations at slower rates lower than conventions fixed cutter (e.g., PDC) drill bits. It is believed that such slower drilling rates are related to the hydraulic energy of the drilling fluid pumped through the drill bit courses or nozzles in the bit body being directed less at the PDC cutters than at the gouging elements. Such slower drilling rates may also be due to addition of gouging elements to a full shear cutter drill bit cutting structure may add excessive cutter surface area in contact with the earthen formations. The present disclosure is directed to the subject-matter of the appended claims, an object of which is to overcome, at least in part, the above-mentioned drawbacks of the prior art devices.
Brief Description of the Drawings
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- FIG. 1 is a top view of one example embodiment of a drill bit according to the present disclosure.
- FIG. 2 is a side view of the example embodiment of FIG. 1.
- FIG. 3 shows a top view of another example embodiment of a drill bit.
- FIG. 4 shows an oblique view of the example embodiment of FIG. 3.
- FIG. 5 shows a coplanar view of a surface profile defined by gouging cutters and shear cutters.
Detailed Description
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An example embodiment of a wellbore drill bit according to the present disclosure is shown in top view (viewed from the cutting end) in FIG. 1. The drill bit 10 may include a bit body 12 having features (FIG. 2) for connection to a drill string or drilling tools for drilling a wellbore in subsurface formations. The bit body 12 may be formed from steel and have an abrasion resistant coating such as tungsten carbide applied to certain wear susceptible areas (not shown) on the bit body 12. The bit body 12 may also be made, for example, from carbide matrix of compositions known in the art.
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The present example embodiment may include one or more circumferentially, primary blade(s) 14. The one or more primary blade(s) 14 may extend radially from a first selected radial distance (D in FIG. 2) from a center of rotation C of the bit body 12 to a gage portion 14A located substantially at the radius of the bit body 12. If more than one primary blade 14 is used, such primary blades 14 may be azimuthally, circumferentially or angularly spaced apart. The first selected distance D may be the same for each primary blade 14 or may be different. Any one or more of the primary blade(s) 14 may include at least one, and may include a plurality of shear cutters 20. The shear cutters 20 may be PDC cutters of any type known in the art. The shear cutters 20 may also be made from any other material known in the art to be used for shear cutters on a fixed cutter drill bit. The shear cutters 20 may be affixed to the bit body 12 at a rake angle selected for the expected subsurface formations to be drilled by the drill bit.
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The present example embodiment may include one or more secondary blades 15. The one or more secondary blades 15 may extend from a second, respective radial distance (D2 in FIG. 3) from the center of rotation C of the bit body 12 and may extend radially outward to a gage portion 15A substantially at the gage radius of the bit body 12. The one or more secondary blade(s) 15 may include one or more shear cutters 20. The one or more shear cutters 20 on the secondary blade(s) may be the same composition and structure as the shear cutters 20 on the one or more primary blades 14, or may be a different structure or composition. The one or more shear cutters 20 on the one or more secondary blade(s) 15 may also be made from any material known in the art to be used for shear cutters on a wellbore drill bit.
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Any or all of the one or more shear cutters 20 may be affixed to a pocket or similar mounting feature formed into the one or more primary blades 14 (and the secondary blade(s) 15 if shear cutters are used thereon) using any attachment method or device known in the art. Such methods or devices may include, but are not limited to brazing.
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In the present example embodiment, at least one or a plurality of gouging cutters 16 may be affixed to the bit body 12 rotationally, circumferentially or azimuthally displaced from the primary blade(s) 14 by a selected azimuthal angle along a direction of rotation 11 of the bit body 12, the direction of rotation 11 being that which bit is rotated in a wellbore to drill through subsurface formations. In the present example embodiment, the one or more gouging cutters 16 may be rotationally ahead of a corresponding primary blade 12, that is, rotationally displaced in the direction of rotation to be rotationally forward of a cutting surface (20A in FIG. 3) of the one or more shear cutters 16. The gouging cutters 16 may be any type of gouging cutter known in the art, for example, the structure of the QUI-KLAW brand gouging cutters described in the Background section herein. In some embodiments, the gouging cutters 16 may comprise ballistic shaped tungsten carbide inserts. The gouging cutters 16 may be affixed to the bit body 12 using any attachment means or device known in the art for attaching gouging cutters to a bit body, including, without limitation, brazing, welding or using a locking ring.
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The terms "azimuthally" and "circumferentially" and "rotationally" may mean angularly displaced referenced to the direction of rotation 11. "Rotationally ahead of" may mean angularly advanced along the direction of rotation 11. "Rotationally behind" may mean angularly in back of with reference to the direction of rotation 11. In order to avoid ambiguity, with reference to the shear cutters 20, "ahead of" the shear cutters 20 rotationally, azimuthally or circumferentially means ahead in the direction of rotation 11 with respect to a cutting surface of the shear cutters.
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In the present example embodiment, the gouging cutters 16 may be affixed to the bit body 12 in any suitable geometric arrangement for gouging cutters used in a fixed cutter drill bit having at least one shear cutter. For purposes of describing a drill bit according to the present disclosure, a first group 16A of shear cutters may be disposed rotationally displaced from, e.g., rotationally ahead of one of the primary blades 14, this particular primary blade being shown at 24 in FIG. 1. One or more drilling fluid orifices or jets 18 may be disposed azimuthally, circumferentially or rotationally between the first group 16A of gouging cutters 16 and the one 24 of the primary blades. The fluid orifices or jets 18 may be oriented such that drilling fluid pumped through the drill bit 10 during drilling is oriented toward the one or more shear cutters 20 on the one 24 primary blade.
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The example embodiment shown in FIG. 1 includes one or more shear cutters 20 on the at least one secondary blade(s) 15. Other embodiments of a drill bit may include at least one shear cutter only on the one or more primary blade(s) 14. Such embodiments will be explained in more detail with reference to FIGS. 3 and 4.
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A side view of the example embodiment shown in FIG. 1 is shown in FIG. 2. The bit body 12 may include features, such as threads 12B to couple the bit body 12 to a drill string (not shown) or a drilling tool (not shown). The bit body 12 may also include features such as flats 12A for applying torque to the bit body 12 to engage the threads 12B with the drill string (not shown) and apply a selected torque to the bit body 12 to ensure suitable engagement of the threads 12B. The at least one primary blade 14 is shown extending from the first selected distance D from the center of rotation C to the gage portion 14A substantially at the radius of the drill bit. The gage portion 14A may include one or more gage inserts 22 therein. The gage inserts 22 may be made from any hard, wear resistant material known to be used for gage inserts, including without limitation, polycrystalline diamond, tungsten carbide and cubic boron nitride.
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In some embodiments, the one or more primary blade(s) 14 and the one or more secondary blades 15 may be shaped to include a tapered face 14C below (in the viewing direction of FIG. 2) the gage portion 14A. The tapered face 14C may include one or more shear cutters 20 of the same or different construction as the shear cutters located elsewhere on the drill bit. The one or more primary blades 14 is shown each extending from its respective first selected distance D from the center of rotation C. The respective first selected distance D may be as small as the smallest distance known in the art to be used for shear cutters disposed on a fixed cutter drill bit. The second selected distance will be explained with reference to FIG. 3.
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In embodiments that have one or more shear cutters 20 on the one or more secondary blades 15, such shear cutters 20 may define a profile surface that is, at corresponding radial distances from the center of rotation C, located a selected distance H lower (in the plane of view of FIG. 2) along the longitudinal dimension L of the drill bit than a corresponding surface profile defined by the gouging cutters 16.
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FIG. 3 shows a top view of another example embodiment of a drill bit 10A according to the present disclosure. The example embodiment of FIG. 3 may be substantially the same as the embodiment shown in FIG. 1, the exception being that the one or more secondary blades 15 may exclude shear cutters. In embodiments such as the one shown in FIG. 3, the one or more secondary blades 15 may define a surface profile that is at corresponding radial distances from the center of rotation C located a selected distance H lower (in the plane of view of FIG. 4) along the longitudinal dimension L of the drill bit than a corresponding surface profile defined by the one or more gouging cutters 16. FIG. 3 more clearly shows the second selected distance D2 from which the one or more secondary blades 15 begins with reference to the center of rotation C. The selected radial distance D2 may be larger than the first selected distance (D in FIG. 2). The selected radial distance D2 may be different for each secondary blade 15. Both the one or more secondary blades 15 and the one or more primary blades 14 may extend from the respective selected distances D2, D to a gage radius defined by a respective gage portion 15A, 14A. Nozzles or jets may be disposed at similar positions as in the embodiment explained with reference to FIG. 1, that is, generally rotationally between the gouging cutters 16 and a rotationally behind the selected one of the one or more primary blades 14.
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FIG. 5 shows a planar view of the surface profile P2 defined by shear cutters 20 on one of the primary blades (14 in FIG. 2). The view in FIG. 5 is such that all the shear cutters 20 are rotated to the same plane. A side view of some of the gouging cutters 16 rotated to the same plane as the view of the shear cutters 20 is also shown in FIG. 5. The gouging cutters 16 define a different surface profile P1. Thus the view in FIG. 5 represents the axial position (position along the longitudinal dimension L) of each cutter 16, 20 with respect to its radial position referenced to the center of rotation (C in FIG. 3). As may be observed in FIG. 5, the gouging cutter profile surface P1 is advanced in the longitudinal direction L by a distance H beyond the shear cutter surface profile P2. In some embodiments, the gouging cutters 16 may be positioned on the bit body (12 in FIG. 2) such that they do not extend to the gage radius defined by the gage portions (14A, 15A in FIG. 2).
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A side view of the example embodiment shown in FIG. 3 is shown in FIG. 4. The present example embodiment may also include features on the bit body (e.g., threads and flats) to couple the drill bit to a drill string or drilling tool.
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In example embodiments such as shown in FIGS. 3 and 4, the one or more primary blade(s) 14 may include one or more shear cutters 20 as shown in the figures. Although both embodiments shown and described herein, i.e., with reference to FIGS. 1 and 2, and FIGS. 3 and 4, respectively, have six blades (3 primary, 3 secondary) equiangularly spaced apart from each other, different embodiments may use more or fewer blades, generally but not exclusively in a range of two to twelve total blades. Such other embodiments may have the same or different circumferential, azimuthal or angular spacing between adjacent blades. Gouging cutters may be affixed to the bit body on a part thereof separate from any blade structure, e.g., as shown in FIGS. 1 and 3.
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A drill bit according to the present disclosure having one or more gouging cutters on a drill bit having shear cutters may include one or more of the following:
- (i) protects the shear cutters from impact damage;
- (ii) create large fractures in the formations which are more efficient for drilling than shearing in some types of formations;
- (iii) drills formations with a smoother torque response than a comparable drill bit having shear cutters alone; and
- (iv) enables the bit drill to successfully drill through formations that conventional fixed cutter (shear cutter only) drill bits cannot drill.
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While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
