Wells are constructed in subterranean formations in an effort to extract hydrocarbon fluids such as oil and gas. A wellbore may be drilled with a rotary drill bit mounted at the lower end of a drill string. The drill string is assembled at the surface of a wellsite by progressively adding lengths of tubular drilling pipe to reach a desired depth. The drill bit is rotated by rotating the entire drill string from the surface of the well site and/or by rotating the drill bit with a downhole motor incorporated into a bottomhole assembly (BHA) of the drill string. As the drill bit rotates against the formation, cutters on the drill bit disintegrate the formation in proximity to the drill bit. Drilling fluid (“mud”) is circulated through the drill string and the annulus between the drill string and the wellbore to lubricate the drill bit and remove cuttings and other debris to surface.
Rotary drill bits are generally categorized as fixed cutter (FC) bits having discrete cutters secured to a bit body at fixed positions (i.e., fixed cutters), roller cone (RC) bits having rolling cutting structures (i.e., roller cones), or hybrid bits comprising both fixed cutters and rolling cutting structures. A fixed cutter is typically secured to the bit body with the cutting table at a particular orientation and position, thereby exposing some portion of the cutting table to the formation. A fixed cutter traditionally has a cylindrical overall shape with a round, flat cutting table. However, as diamond manufacturing continues to improve, more nuanced cutting table shapes continue to be developed that provide various technical advantages.
These drawings illustrate certain aspects of some examples of the present disclosure and should not be used to limit or define the disclosure.
Various shaped cutters are disclosed for use on a drill bit or other wellbore forming tool. The shaped cutters may be fixed cutters, formed as a polycrystalline diamond compact (PDC) utilizing one or more high-pressure, high-temperature press cycle. The design of the disclosed shaped cutter includes various functional aspects to enhance rock removal while drilling. The shaped cutter may cut rock by shearing, and by virtue of its shape, may also enhance other rock failure modes, including but not limited to indentation, impacting, scraping and grinding. In one aspect, the shaped cutter includes multiple peripheral cutting teeth on the cutter face to increase a stress level to the rock. The plurality of peripheral cutting teeth may generate multiple cracks in the formation. The cutter geometry may also modify a back rake angle for the cutter engaging the formation as compared with the back rake angle of a conventional cylindrical cutter at the same relative orientation on the bit body. The cutter geometry may also provide a sharper indentation angle than would otherwise be present in a conventional cutter.
The shape of the disclosed cutters may also make productive use of the presence of vibrations in the drill string, which may include both torsional and axial vibration components. Aspects of the disclosed cutter designs were conceived, in part, on a recognition that a PDC bit has almost always some type of vibration in drilling, especially in relatively hard formations. Vibration in a cutting direction may help the teeth to generate more cracks in the formation in front of the teeth. Energy may be distributed over the multiple cracks to increase a frequency and/or reduce an amplitude of a vibration frequency while drilling. Torsional vibrations propagating to a drill bit may be used to enhance cutting with the use of a non-planar (e.g., tapered) cutter surface at locations where a conventional cutter may otherwise have a planar surface. Axial vibrations propagating to the drill bit may also be used to enhance cutting with a sharper cutting angle to increase cutter indentation.
The drill bit 114 may be a fixed-cutter or hybrid drill bit having one or more fixed cutters, including one or more shaped cutters as disclosed herein to enhance rock removal. A pump 120 (e.g., a mud pump) circulates drilling fluid 122 through a feed pipe 124 and to the kelly 110, which conveys the drilling fluid 122 downhole through the interior of the drill string 108 and through one or more orifices in the drill bit 114. The drilling fluid 122 is then circulated back to the surface via an annulus 126 defined between the drill string 108 and the walls of the wellbore 116. At the surface, the recirculated or spent drilling fluid 122 exits the annulus 126 and may be conveyed to one or more fluid processing unit(s) 128 via an interconnecting flow line 130. After passing through the fluid processing unit(s) 128, a “cleaned” drilling fluid 122 is deposited into a nearby retention pit 132 (i.e., a mud pit). While illustrated as being arranged at the outlet of the wellbore 116 via the annulus 126, those skilled in the art will readily appreciate that the fluid processing unit(s) 128 may be arranged at any other location in the drilling rig 100 to facilitate its proper function, without departing from the scope of the scope of the disclosure.
The bit body defines a bit axis 215 about which the drill bit 114 may rotate while drilling. The bit axis 215 may coincide at least approximately with a center of mass of the drill bit 114. The bit axis 215 may be generally aligned with an axis of a drill string or other conveyance to which the drill bit 114 is coupled. Drill bits may be connected in any of an unlimited number of ways to a drill string, coiled tubing, or other conveyance to allow for rotation about the bit axis 215. In this example, the drill bit 114 may include a metal shank 204 with a mandrel or metal blank 207 securely attached thereto (e.g., at weld location 208). The metal blank 207 extends into bit body 210. The metal shank 204 includes a threaded connection 206 distal to the metal blank 207 for securing the drill bit 114 to a drill string, which connection may generally align the bit axis 215 with an axis of the drill string or other desired axis of rotation.
While drilling, an axial force such as weight on bit (WOB) may be applied in a direction of the bit axis 215, such that the cutters 300 engage the formation being drilled. Simultaneously, the drill bit 114 is rotated about the bit axis 215 to engage the earthen formation to cut material (“rock”) from the formation. The shaped cutters 300 have particular shapes, such as disclosed below in specific examples, that may enhance the removal of rock while drilling. Drilling fluid circulated downhole may lubricate the drill bit 114 and remove the cuttings and other fluid contaminants to the surface, such as generally described above in relation to
The peripheral cutting teeth 322 are equidistant from the cutter axis 315 at a radius “R” and are equally spaced circumferentially at a tooth spacing “C.” The tooth spacing C is illustrated as a center-to-center tooth spacing in this example. The peripheral cutting teeth 322 may taper inwardly as shown in a radial direction toward the center of the cutting table coinciding with the cutter axis 315. Thus, a circumferential tooth width “W” according to the taper decreases from the outer portion of the peripheral cutting teeth 322 to the inner portion of the peripheral cutting teeth 322 at the radius R.
A portion of the cutting table 320 radially inward of the peripheral cutting teeth 322 is an open region 326 having no cutting teeth. The open region 326 is a generally circular region of radius R that traverses the cutter axis 315 and fully spans the portion of the cutting table 320 radially inward of the peripheral cutting teeth 322. In at least some embodiments, the open region 326 may span at least seventy percent of an overall cutter diameter D and may occupy at least fifty percent of a projected circular surface area (˜π/4*D2) of the cutter. This relatively small proportion of the total cutter diameter and surface area occupied by the peripheral cutting teeth 322 helps to heighten the indentation force of the cutting table 320 on the formation.
All or at least a majority of the open region 326 may be recessed axially (into the page of
The peripheral cutting teeth 422 in each teeth grouping 430 optionally have an equal circumferential tooth spacing “C” between adjacent teeth in that group. Optionally, the circumferential tooth spacing C is the same in all of the teeth groupings 430. A group spacing “G” between adjacent teeth groupings is greater than the circumferential tooth spacing C in each of the adjacent teeth groupings. By this convention, the group spacing G and tooth spacing C in the figure are measured as the center-to-center distance of the respective teeth whose spacing is measured. However, the group spacing and tooth spacing could alternatively be measured as the closest points on the respective teeth being compared.
Aside from differences in the arrangement of the peripheral cutting teeth 422, other aspects of the cutting table 420 may be similar to aspects of the cutting table 320 of
The peripheral cutting teeth 522 may be arranged according to the examples of
The peripheral cutting teeth 622 are equidistant from the cutter axis 615. The open region 626 is recessed with respect to the peripheral cutting teeth 622. The open region 626 comprises a tapered portion 628A that is non-orthogonal to the cutter axis 615. In this case, the tapered portion 628A extends all the way from the peripheral cutting teeth 622 toward the cutter axis 615 at an internal back rake angle φ with respect to the interface plane 617. The internal back rake angle φ is preferably within a range of between five to ten degrees in one or more embodiments, although an angle outside this range is also within the scope of this disclosure. Alternative embodiments may have an open region in which one portion is perpendicular to the cutter axis 616 and another portion is tapered. The taper 628A results in a concavity, in that the taper 628A extends axially inwardly in a radial direction towards the cutter axis 616. In this case the open region 626 is generally frustoconical, wherein the taper 628A extends linearly in the radial direction toward the cutter axis 616. However, a concavity with a curved profile in the radial direction toward the cutter axis 616, such as shown in dashed lines at 628B, may alternatively be formed in the open region 626.
However, as better seen in the enlarged detail view of
However, the shaped cutting table 320 in
Therefore, a shaped cutter is disclosed along with a drill bit and a drilling method utilizing such a shaped cutter. The shaped cutter may include peripheral cutting teeth and an open region that is optionally tapered. The shaped cutter, drill bit and drilling method may include any combination of features including but not limited to those in the following examples.
Example 1. A shaped cutter for a wellbore forming tool, the shaped cutter comprising: a substrate having a proximal end and a distal end and defining a cutter axis passing through the proximal and distal ends; and a cutting table secured to the proximal end of the substrate at a cutter-substrate interface, the cutting table having a cutting end comprising a plurality of peripheral cutting teeth circumferentially arranged along a periphery of the cutting table equidistant from the cutter axis, and an open region spanning a portion of the cutting table radially inward of the peripheral cutting teeth.
Example 2. The shaped cutter of Example 1, wherein the open region defines a transverse plane orthogonal to the cutter axis that fully spans the portion of the cutting table radially inward of the peripheral cutting teeth.
Example 3. The shaped cutter of Example 1, wherein the open region comprises a tapered portion having an internal back rake angle from the peripheral cutting teeth toward the cutter axis.
Example 4. The shaped cutter of Example 3, wherein the tapered portion extends fully from the peripheral cutting teeth to the cutter axis.
Example 5. The shaped cutter of Example 3, wherein the tapered portion extends partially from the peripheral cutting teeth toward the cutter axis, and wherein the open region further comprises a transverse plane orthogonal to the cutter axis radially inward of the tapered portion of the open region.
Example 6. The shaped cutter of Example 3, wherein the internal back rake angle is within a range of between 5 to 10 degrees.
Example 7. The shaped cutter of Example 1, wherein the peripheral cutting teeth are arranged in a plurality of teeth groupings, with an equal circumferential tooth spacing between the peripheral cutting teeth in each teeth grouping, and with a group spacing between adjacent teeth groupings that is greater than the circumferential tooth spacing in each of the adjacent teeth groupings.
Example 8. The shaped cutter of Example 7, wherein the teeth groupings comprise at least three teeth groupings of three peripheral cutting teeth per teeth grouping.
Example 9. The shaped cutter of Example 7, having four teeth groupings of five peripheral cutting teeth per teeth grouping.
Example 10. The shaped cutter of Example 1, wherein the cutting table comprises an outer diameter equal to a diameter of the substrate.
Example 11. The shaped cutter of Example 1, wherein the periphery of the cutting table defines a generally cylindrical outer profile.
Example 12. The shaped cutter of Example 11, wherein the peripheral cutting teeth extend parallel to the cutter axis in an axial direction away from the cutter-substrate interface.
Example 13. The shaped cutter of Example 1, wherein the peripheral cutting teeth are angled radially inwardly.
Example 14. The shaped cutter of Example 13, wherein the periphery of the cutting table defines a generally frustoconical surface that flares radially outwardly in an axial direction away from the cutter-substrate interface.
Example 15. The shaped cutter of Example 13, wherein the periphery of the cutting table defines a generally frustoconical surface that flares radially inwardly in an axial direction away from the cutter-substrate interface.
Example 16. A drill bit comprising: a bit body comprising one or more blades each having one or more cutter pockets; one or more shaped cutters disposed in a respective one of the cutter pockets, each shaped cutter comprising a substrate having a proximal end and a distal end and defining a cutter axis passing through the proximal and distal ends, and a cutting table secured to the proximal end of the substrate at a cutter-substrate interface, the cutting table having a cutting end comprising a plurality of peripheral cutting teeth circumferentially arranged along a periphery of the cutting table equidistant from the cutter axis, and an open region spanning a portion of the cutting table radially inward of the peripheral cutting teeth.
Example 17. The drill bit of Example 16, wherein the bit body defines a bit axis about which the bit body rotates during drilling, and wherein at least one of the shaped cutters has an inwardly tapered surface defining an internal back rake angle and is secured to the bit body at an orientation that defines an actual back rake angle with the inwardly tapered surface of the cutting table.
Example 18. The drill bit of Example 17, wherein the inwardly tapered surface has an internal back rake angle of between 5 to 10 degrees.
Example 19. A drilling method, comprising: rotating a drill bit about a bit axis, the drill bit comprising a bit body with one or more blades each having one or more cutter pockets and one or more shaped cutters secured in a respective one of the cutter pockets, each shaped cutter comprising a substrate having a proximal end and a distal end and defining a cutter axis passing through the proximal and distal ends, and a cutting table secured to the proximal end of the substrate at a cutter-substrate interface, the cutting table having a cutting end comprising a plurality of peripheral cutting teeth circumferentially arranged along a periphery of the cutting table equidistant from the cutter axis, and an open region spanning a portion of the cutting table radially inward of the peripheral cutting teeth; and axially engaging a formation to be drilled with the drill bit while rotating the drill bit.
Example 20. The drilling method of Example 19, further comprising using the plurality of peripheral cutting teeth to simultaneously generate multiple cracks in the formation.
It should be understood that, although individual examples may be discussed herein, the present disclosure covers all combinations of the disclosed examples, including, without limitation, the different component combinations, method step combinations, and properties of the system. It should be understood that the compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces.
For the sake of brevity, only certain ranges are explicitly disclosed herein. However, ranges from any lower limit may be combined with any upper limit to recite a range not explicitly recited, as well as, ranges from any lower limit may be combined with any other lower limit to recite a range not explicitly recited, in the same way, ranges from any upper limit may be combined with any other upper limit to recite a range not explicitly recited. Additionally, whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range are specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values even if not explicitly recited. Thus, every point or individual value may serve as its own lower or upper limit combined with any other point or individual value or any other lower or upper limit, to recite a range not explicitly recited.
Therefore, the present examples are well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular examples disclosed above are illustrative only, and may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Although individual examples are discussed, the disclosure covers all combinations of all of the examples. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. It is therefore evident that the particular illustrative examples disclosed above may be altered or modified and all such variations are considered within the scope and spirit of those examples. If there is any conflict in the usages of a word or term in this specification and one or more patent(s) or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.