Downhole Outer Drill Bit

Abstract

A downhole drill bit, of the type used to bore into the earth when searching for or extracting subterranean resources, may comprise a working face opposite an attachment end and an opening passing from the attachment end through to the working face. A protrusion on one end of a bottom hole assembly may extend through the opening and be exposed at the working face when the drill bit is attached to the end of the bottom hole assembly. In various embodiments the exposed portion of the protrusion may house conduits or nozzles for handling fluids; sensors, transmitters or wires for handling electrical signals; or mechanical hammers, motors or cutters for degrading an earthen formation. In this way, the protrusion may bring such elements from the bottom hole assembly to the working face of the drill bit.

Description

BACKGROUND

When exploring for or extracting subterranean resources such as oil, gas, or geothermal energy, it is common to form boreholes in the earth. Such boreholes are often formed by suspending a specialized drill bit from a derrick or offshore platform and rotating the drill bit to engage and degrade the earth as it turns. The drill bit may be suspended by coiled tubing or a series of drill pipe sections connected end to end to form a drill string, and rotated at the derrick/platform or by a downhole motor disposed towards an end of the drill string. If a drill bit becomes dull or damaged it may cease to drill efficiently and may need to be replaced before drilling continues.

In many situations, it may be desirable to gain access to the drill bit as it drills. For example, it may be desirable to discharge drilling fluid flowing through a drill string at a drill bit. This may be done to cool, clean or lubricate the drill bit or carry debris created by the drill bit engaging an earthen formation up a borehole. In another example, it may be desirable to place sensors at a drill bit as it drills. This may be done to gather information about the formation being drilled as far in front of the drill bit as possible or to get the most accurate possible measurements of how the drilling process is progressing. These sensors may measure natural conditions of an earthen formation or responses to energy transmitted into a formation from transmitters also disposed at the drill bit. In yet another example, it may be desirable to control a trajectory of a drill bit as it bores into a formation by manipulating degradation of the formation at the drill bit. This may be accomplished, for example, by placing cutters on an offset mechanical hammer or rotational motor exposed at a drill bit and activating it alternatingly as the drill bit rotates.

While placing these types of equipment as close to the drill bit as possible may be desirable, placing them on the drill bit may become prohibitively expensive as drill bits may need to be replaced regularly, if not frequently. Accordingly, tools providing access to a drill bit that need not be replaced as often as drill bits may be valuable.

BRIEF DESCRIPTION

A downhole drill bit may comprise a working face, capable of engaging and degrading tough earthen formations, opposite an attachment end, fashioned to attach to a bottom hole assembly. The drill bit may further comprise an opening passing from the attachment end through to the working face. A protrusion on one end of a bottom hole assembly may extend through the opening and be exposed at the working face when the drill bit is attached to the end of the bottom hole assembly. This exposed portion of the protrusion may provide access for equipment housed within the bottom hole assembly to the working face while drilling. For example, in various embodiments, the protrusion may accommodate conduits or nozzles for handling fluids; sensors, transmitters or wires for handling electrical signals; or mechanical hammers, motors or cutters for degrading an earthen formation. In such configurations, the drill bit may be replaced when dull or damaged without requiring replacement of this additional equipment.

DRAWINGS

FIG. 1 is an orthogonal view of an embodiment of a drilling operation comprising a drill bit secured to an end of a drill string suspended from a derrick.

FIG. 2 is a perspective view of an embodiment of a bottom hole assembly comprising a protrusion on one end thereof and a drill bit capable of attachment to the end of the bottom hole assembly.

FIG. 3 is a perspective view of the embodiment of the drill bit shown in FIG. 2 attached to the end of the bottom hole assembly such that the protrusion extends through an opening in the drill bit.

FIG. 4 is an orthogonal face view of an embodiment of a drill bit with a protrusion extending through an opening therein and an exposed portion of the protrusion comprising a generally circular exposed surface.

FIGS. 5-1, 5-2, 5-3 and 5-4 are longitude-sectional views of different embodiments of bottom hole assemblies comprising various types of equipment housed therein and exposed at a working face of a drill bit by a protrusion passing through an opening in the drill bit.

FIG. 6 is a perspective view of an embodiment of a bottom hole assembly comprising a protrusion on one end thereof and a drill bit capable of attachment to the end of the bottom hole assembly.

FIG. 7 is an orthogonal face view of the embodiment of the drill bit shown in FIG. 6 with the protrusion extending through an opening therein and an exposed portion of the protrusion comprising a generally non-circular exposed surface.

FIG. 8-1 is a longitude-sectional view of an embodiment of a bottom hole assembly comprising a protrusion with a periphery surface parallel with a central axis of the bottom hole assembly. The protrusion is aligned with a drill bit capable of attachment to the end of the bottom hole assembly.

FIG. 8-2 is a longitude-sectional view of the embodiment of the drill bit shown in FIG. 8-1 attached to the end of the bottom hole assembly with a locking mechanism.

DETAILED DESCRIPTION

FIG. 1 shows an embodiment of a drilling operation comprising a drill string 110 suspended from a derrick 112 into the earth 114. A bottom hole assembly 100 may be disposed adjacent a distal end of the drill string 110 and comprise any of a number of mechanical, electrical, or fluid systems known in the art to aid in increasing rate of penetration of drilling; steering; gathering, storing, or communicating data; or sensing. A drill bit 118 may be secured to the bottom hole assembly 100 capable of engaging and degrading the earth 114 as it is rotated to form a borehole 116 allowing for the drill string 110 to advance. In many situations, it may be desirable to position the various systems housed within the bottom hole assembly 100 as close to a working face of the drill bit 118 as possible.

FIG. 2 shows an embodiment of a bottom hole assembly 200 comprising a generally elongate shape. A protrusion 220 may be disposed on one end of the bottom hole assembly 200 and extend out therefrom. The protrusion 220 may be attached to the bottom hole assembly 200 by a spider 228 allowing drilling fluid traveling through the bottom hole assembly 200 to pass the protrusion 220. In the embodiment shown, the protrusion 220 extends from a threaded pin 227 comprising a generally circular cross section surrounded by threads 221. The threaded pin 227 may be received by an attachment end 222 of a drill bit 218 comprising a threaded box (hidden). While the present embodiment comprises a threaded pin 227 and box combination, other attachment mechanisms may be similarly suitable. A working face 223 may be disposed on the drill bit 218, opposite the attachment end 222, and comprise a plurality of cutters 224, formed at least partially of superhard material (e.g. polycrystalline diamond), secured thereto. The working face 223 may also comprise a plurality of blades 225 extending therefrom allowing the cutters 224 to dig into a formation to be degraded and debris generated during the degradation to exit through spaces between each of the blades 225. Additionally, an opening 226 may pass completely through the drill bit 218 from the working face 223 to the attachment end 222.

FIG. 3 shows the embodiment of the drill bit 218, shown in FIG. 2, attached to the end of the bottom hole assembly 200. When attached, the protrusion 220 may extend through the opening 226 passing through the drill bit 218 to be exposed at the working face 223. In the embodiment shown, an exposed portion 330 of the protrusion 220 comprises a generally circular exposed surface. The exposed portion 330 may also be generally flush with the working face 223.

FIG. 4 shows an exposed portion 430 of a protrusion 420 surrounded by a working face 423 of a drill bit 418. At least one cutter 444, comprising superhard material (e.g. polycrystalline diamond), may be disposed on the exposed portion 430 of the protrusion 420. In the embodiment shown, the cutter 444 is positioned within an organized pattern, such as along a blade, with some of the plurality of cutters 424 disposed on the working face 423. As the drill bit 418 is rotated, those of the plurality of cutters 424 positioned closer to an exterior 441 of the working face 423 may travel at a higher speed relative to a formation being degraded, due to an increased radius, than cutters 424 positioned closer to an axis of rotation 442 of the drill bit 418. Because of this higher speed, cutters 424 positioned closer to the exterior 441 may be more likely to receive wear or damage than those positioned closer to the axis of rotation 442. When worn or damaged, the drill bit 418 may be replaced. However, any equipment exposed at the working face 423 through the protrusion 420, which is also less likely to receive wear due to its position closer to the axis of rotation 442, may be left in place.

One example of equipment that may be housed within a bottom hole assembly and exposed at a working face of a drill bit by a protrusion passing through an opening in the drill bit is fluid handling equipment as shown in FIG. 5-1. Specifically, FIG. 5-1 shows drilling fluid 550-1 traveling through a hollow center of a bottom hole assembly 500-1. A conduit 551, passing through a protrusion 520-1 extending from the bottom hole assembly 500-1, may channel a portion of the drilling fluid 550-1 to a nozzle 552, secured on an exposed portion 530-1 of the protrusion 520-1, where it may be discharged at a working face 523-1 of a drill bit 518-1. The drill bit 518-1 may be replaced when worn or damaged without affecting the fluid flow path.

Another example of equipment that may be exposed at a working face by a protrusion is electrical equipment as shown in FIG. 5-2. In the example shown, wires 553 may pass through a protrusion 520-2 and transmit electrical signals to and from a transmitter 554 and a sensor 555 positioned on an exposed portion 530-2 of the protrusion 520-2 at a working face 523-2 of a drill bit 518-2. The transmitter 554 may send energy in any of a variety of forms, such as for example a magnetic field or gamma rays, into a formation being drilled that may reflect off of the formation, be altered by the formation or cause a reaction in the formation that may be sensed by the sensor 555. In alternate embodiments, a transmitter may not be necessary and a sensor alone, such as for example an accelerometer or thermometer, may sense naturally occurring phenomena at a working face.

Yet other examples of equipment that may be exposed at a working face by a protrusion are extra degradation tools such as those shown in FIGS. 5-3 and 5-4. For example, FIG. 5-3 shows at least one cutter 544-3 extending from an end of an exposed portion 530-3 of a protrusion 520-3. The cutter 544-3 may be secured to a hammer mechanism 556 capable of vibrating the cutter 544-3 for the purpose of increasing a rate of penetration of a drill bit 518-3, steering the drill bit 518-3, sending an acoustic signal into a formation or for other reasons. In the embodiment shown, a motor 558-3 may actuate a valve 559-3 to alternating route drilling fluid 550-3 traveling through a hollow center of a bottom hole assembly 500-3 to the hammer mechanism 556 causing the cutter 544-3 to extend and retract. In other embodiments, other types of hammer mechanisms may achieve similar results.

In another example, FIG. 5-4 shows at least one cutter 544-4 extending from an exposed portion 530-4 of a protrusion 520-4 and secured to a motor 557 capable of rotating the cutter 544-4 about an axis. Similar to the hammer mechanism 556 shown in FIG. 5-3, the motor 557 may increase a rate of penetration, steer, send signals into a formation or perform other tasks. In the embodiment shown, the motor 557 comprises a rotor 558-4 rotated relative to a stator 559-4 by a drilling fluid 550-4 traveling through a hollow center of a bottom hole assembly 500-4. Rotation of the rotor 558-4 may be passed to the cutter 544-4 to increase degradation of a formation. In other embodiments, other types of rotational mechanisms may achieve similar results.

FIGS. 6 and 7 show an embodiment of a drill bit 618 that may be attached to a bottom hole assembly 600 and allow a protrusion 620 of the bottom hole assembly 600 to pass through. An exposed portion 630 of the protrusion 620 may comprise a non-circular shape. In order to fit the drill bit 618 over the noncircular shape, the protrusion 620 may comprise a periphery surface 661 parallel with a central axis 663 of the bottom hole assembly 600. The periphery surface 661 may extend from a boundary 662 of the exposed portion 630 at a working face 623 of the drill bit 618 toward the bottom hole assembly 600.

The drill bit 618 may comprise a rotatable locking mechanism 667 to secure the drill bit 618 to the bottom hole assembly 600. While a rotatable locking mechanism 667 is shown in the present embodiment, other styles of locking mechanisms may achieve similar results. As also seen in this embodiment, the working face 623 may comprise at least one cutter 624 disposed encroaching on the boundary 662 of the noncircular exposed surface. It is believed that in some situations this encroachment may aid in maintaining an organized pattern of cutters between the exposed portion 630 of the protrusion 620 and the working face 623. Some blades 625 extending from the working face 623 may also continue uninterrupted onto the exposed portion 630 in an elevated section 664 of the exposed portion 630.

FIGS. 8-1 and 8-2 show an embodiment of a drill bit 718 comprising a rotatable locking mechanism 767 that may secure the drill bit 718 to a bottom hole assembly 700. The rotatable locking mechanism 767 may rotate freely relative to a remainder of the drill bit 718 thanks to a plurality of ball bearings 770 secured within tracks 771. This relative rotation may permit the locking mechanism 767 to thread onto a threaded pin 727 of the bottom hole assembly 700 while allowing the remainder of the drill bit 718 to remain rotationally stationary relative to a protrusion 720.

In the embodiment shown, the protrusion 720 is held onto the bottom hole assembly 700 by a removable retainer 772. Using such a removable retainer 772 for attachment may allow for simpler construction and easier maintenance or replacement. For example, in the embodiments shown, at least one snap ring may act as a removable retainer 772 holding the protrusion 720 on the end of the bottom hole assembly 700.

Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.

Claims

1. A downhole drilling assembly, comprising:

a bottom hole assembly comprising an elongate shape and a protrusion on an end thereof; and

a drill bit comprising a working face opposite an attachment end and an opening passing from the working face to the attachment end; wherein

when the attachment end of the drill bit is attached to the end of the bottom hole assembly the protrusion extends through the opening and is exposed at the working face.

2. The downhole drilling assembly of claim 1, wherein when the attachment end of the drill bit is attached to the end of the bottom hole assembly an exposed portion of the protrusion is generally flush with the working face.

3. The downhole drilling assembly of claim 2, wherein the working face comprises at least one blade extending therefrom that continues on the exposed portion of the protrusion.

4. The downhole drilling assembly of claim 1, further comprising a conduit disposed within the protrusion allowing drilling fluid passing through the bottom hole assembly to exit at the working face through an exposed portion of the protrusion.

5. The downhole drilling assembly of claim 1, further comprising a wire disposed within the protrusion capable of communicating an electrical signal from the bottom hole assembly to an exposed portion of the protrusion at the working face.

6. The downhole drilling assembly of claim 1, further comprising a sensor disposed on an exposed portion of the protrusion at the working face.

7. The downhole drilling assembly of claim 1, further comprising a transmitter disposed on an exposed portion of the protrusion at the working face.

8. The downhole drilling assembly of claim 1, further comprising at least one cutter comprising superhard material disposed on an exposed portion of the protrusion at the working face.

9. The downhole drilling assembly of claim 8, further comprising a hammer disposed within the bottom hole assembly capable of vibrating the at least one cutter.

10. The downhole drilling assembly of claim 8, further comprising a motor disposed within the bottom hole assembly capable of rotating the at least one cutter about an axis.

11. The downhole drilling assembly of claim 8, wherein the cutter disposed on the exposed portion of the protrusion is positioned within an organized pattern with other cutters comprising superhard material disposed on the working face.

12. The downhole drilling assembly of claim 1, wherein the end of the bottom hole assembly comprises a threaded pin and the attachment end of the drill bit comprises a threaded box.

13. The downhole drilling assembly of claim 12, wherein the protrusion is surrounded by threads of the threaded pin.

14. The downhole drilling assembly of claim 12, wherein an exposed portion of the protrusion comprises a generally circular exposed surface.

15. The downhole drilling assembly of claim 1, wherein an exposed portion of the protrusion comprises a noncircular exposed surface.

16. The downhole drilling assembly of claim 15, wherein the protrusion comprises a periphery surface extending from a boundary of the noncircular exposed surface parallel with a central axis of the bottom hole assembly.

17. The downhole drilling assembly of claim 15, wherein the working face comprises a cutter comprising superhard material disposed on the working face and encroaching on a boundary of the noncircular exposed surface.

18. The downhole drilling assembly of claim 1, further comprising a removable retainer holding the protrusion on the end of the bottom hole assembly.

19. The downhole drilling assembly of claim 18, wherein the removable retainer comprises a snap ring.

20. The downhole drilling assembly of claim 1, wherein the protrusion is attached to the bottom hole assembly by a spider allowing drilling fluid passing through the bottom hole assembly to pass the protrusion.