Drill assembly for percussive drilling, a drill bit and a drill string element

Abstract

A drill assembly for percussive drilling, includes a drill bit having a downhole portion and an attachment portion having a cylindrical male coupling thread, and a drill string element for transferring impacts from a percussion device to the drill bit and having a female coupling thread for threadedly coupling with the male coupling thread. The drill bit includes a first annular impact surface arranged on an uphole-side end the downhole portion, the first annular impact surface surrounding the attachment portion, and the drill string element includes, at a downhole-side end thereof, a second annular impact surface. The first and second impact surfaces are inclined with respect to a plane perpendicular to the longitudinal direction. A drill bit and drill string element are also disclosed.

Claims

1. A drill assembly for percussive drilling, the drilling assembly comprising: a drill bit extending along a longitudinal direction and having: a downhole portion having a downhole end surface equipped with inserts configured for transferring percussive impacts to points of contact with a borehole, and an attachment portion extending from the downhole portion towards an uphole direction, the attachment portion having a cylindrical male coupling thread; and a cylindrical hollow drill string element configured for transferring at least percussive impacts from a percussion device to the drill bit, the drill string element extending along the longitudinal direction and having, on a downhole-side end thereof, a female coupling thread for threadedly coupling with the male coupling thread; wherein the drill bit includes a first annular impact surface arranged on an uphole-side end the downhole portion, the first annular impact surface surrounding the attachment portion; wherein the drill string element includes, at a downhole-side end thereof, a second annular impact surface; wherein the drill bit is configured to be threadedly coupled with the drill string element such that the first annular impact surface abuts the second annular impact surface so as to transfer percussive impact during operation from the drill string element to the drill bit through the first and second impact surfaces; and wherein the first annular impact surface, and respectively, the second annular impact surface are inclined with respect to a plane perpendicular to the longitudinal direction.

2. The drill assembly according to claim 1, wherein the first annular impact surface, and respectively, the second annular impact surface are inclined radially outwardly towards a downhole direction.

3. The drill assembly according to claim 1, wherein the first annular impact surface, and respectively, the second annular impact surface are inclined at an angle of between 3-20 deg.

4. The drill assembly according to claim 1, wherein the drill bit comprises: a cavity for conducting a flushing flow, the cavity being open towards an uphole-side end of the attachment portion; and a plurality of conduits extending between the cavity and the end surface of the drill bit for conducting the flushing flow to the end surface.

5. The drill assembly according to claim 4, wherein the cavity has a diameter of at least 2 times that of a conduit.

6. The drill assembly according to claim 4, wherein the cavity extends parallel to the longitudinal direction, and the plurality of conduits are inclined with respect to the longitudinal direction.

7. The drill assembly according to claim 4, wherein a volume defined by the cavity is at least 2 times of that defined by the plurality of conduits.

8. The drill bit according to claim 7, wherein the drill bit comprises: A cavity for conducting a flushing flow, the cavity being open towards an uphole-side end of the attachment portion; and a plurality of conduits extending between the cavity and the end surface of the drill bit for conducting the flushing flow to the end surface.

9. The drill bit according to claim 8, wherein the cavity has a diameter of at least 2 times that of a conduit.

10. The drill bit according to claim 8, wherein the cavity extends parallel to the longitudinal direction, whereas the plurality of conduits are inclined with respect to the longitudinal direction.

11. The drill bit according to claim 8, wherein a volume defined by the cavity is at least 2 times of that defined by the plurality of conduits.

12. The drill string assembly according to claim 1, wherein the cylindrical hollow drill string element is configured as an adaptor or a drill rod.

13. A drill bit for percussive drilling, the drill bit comprising: a downhole portion having a downhole end surface equipped with inserts configured for transferring percussive impacts to points of contact with a borehole, and an attachment portion extending from the downhole portion towards an uphole direction, the attachment portion having a cylindrical male coupling thread; a first annular impact surface arranged on an uphole-side end the downhole portion, the first annular impact surface surrounding the attachment portion; and wherein the drill bit is configured to be threadedly coupled to a drill string such that the first annular impact surface abuts a second annular impact surface of the drill string so as to transfer percussive impact during operation from the drill string element to the drill bit through the first and second annular impact surfaces, wherein the first annular impact surface is inclined with respect to a plane perpendicular to the longitudinal direction.

14. The drill bit according to claim 13, wherein the first annular impact surface is inclined radially outwardly towards a downhole direction.

15. The drill bit according to claim 13, wherein the first annular impact surface is inclined at an angle of between 3-20 deg.

16. A drill string element for percussive drilling configured for transferring at least percussive impacts from a percussion device to a drill bit, the drill string element comprising: a cylindrical hollow body extending along a longitudinal direction and having, on a downhole-side end thereof, a female coupling thread configured for threadedly coupling with a male coupling thread of a drill bit; at a downhole-side end thereof, a second annular impact surface; wherein the cylindrical hollow body is configured to be threadedly coupled to a drill bit such that the second annular impact surface abuts a first annular impact surface of the drill bit so as to transfer percussive impacts from the drill string element to the drill bit through the first and second impact surfaces; and wherein the second annular impact surface is inclined with respect to a plane perpendicular to the longitudinal direction.

17. The drill string element according to claim 16, wherein the second annular impact surface is inclined radially outwardly towards a downhole direction.

18. The drill string element according to claim 16, wherein the second annular impact surface is inclined at an angle of between 3-20 deg.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following the disclosure will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which

(2) FIG. 1 illustrates a partially cut schematic representation of a drill bit according to an embodiment of the present disclosure, and

(3) FIG. 2 and FIG. 3 illustrate partially cut schematic representations of drill bit assemblies according to various embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

(4) FIG. 1 illustrates a longitudinally cut schematic representation of a drill bit according to an embodiment of the present disclosure.

(5) Particularly, the drill bit 1 extends longitudinally along its axial direction, such that a downhole portion is provided at a downhole end of the drill bit 1, whereas an attachment portion 3 is provided at an uphole end of the drill bit 1. The downhole portion 2a has a generally larger diameter than the attachment portion 3.

(6) The downhole portion 2 has a downhole end surface 2a. Although not illustrated in the FIG. 1 the end surface 2a is equipped with inserts.

(7) The attachment portion 3 extends from the downhole portion towards the uphole direction, and has cylindrical male coupling thread, denoted with reference numeral 3a.

(8) A first annular impact surface 4 is arranged on an uphole-side end of the downhole portion 2, such that it surrounds the attachment portion 3. In the configuration of FIG. 1, the first impact surface is inclined with respect to a plane perpendicular to the longitudinal direction.

(9) Particularly, the first impact surface 4 is inclined radially outwardly towards a downhole direction.

(10) Although not shown in FIG. 1, a second impact surface 9 of the drill string element 7, abuts the first impact surface 4, when the drill string element is coupled to the drill bit 1.

(11) Furthermore, the drill bit 1 comprises a cavity 5 open towards an uphole-side end of the attachment portion 3 and extending longitudinally through the attachment portion 3 for a distance into the downhole portion 2. In the configuration of FIG. 1, the cavity 6 is concentric with longitudinal axis of the drill bit. The conduits 6 illustrated in FIG. 1, in turn, are inclined with respect to the longitudinal direction.

(12) FIG. 2 illustrates a partially cut schematic representations of a drill bit assembly according an embodiment of the present disclosure. Particularly, FIG. 2 illustrates a drill bit 1 attached to a drill string element 7. The attachment portion 3 of the drill bit 1 is received within the drill string element 7, such that the male coupling thread 3a is engaged with the female coupling thread 8. Furthermore, the first annular impact surface 4 of the drill bit 1 abuts the second annular impact surface 9 of the drill string element 7. In the configuration of FIG. 2 the drill bit 1 corresponds to that illustrated in FIG. 1, whereas the drill string element 7 is provided as a drill tube.

(13) FIG. 3 illustrates a partially cut schematic representations of a drill bit assembly similar to that of FIG. 2, with the exception of the drill string element 7 being provided as an adapter coupling the drill bit 1 to a drill rod.