Raise boring tool with improved chip removal

Abstract

A reamer bit (10) for raise boring operations, comprising: a reamer body (16); a plurality of hobs (21) connected to the main body (16), each hob being connected to the main body (16) using a mounting plate (22); and an upper drill string connection portion (12) connected to the body (16), where the mounting plate (22) includes a cutout (26) in the form of a through hole for removing cuttings from the reamer bit (10).

Description

Technical Field

[0001] This invention relates to a reverse well boring tool, and more specifically to a reamer head for reverse well boring operations. The reamer head has improved chip removal. Background Technology

[0002] Reverse borehole tools have a reamer head used to drill a well by enlarging a pilot hole to the desired final diameter. The reamer head typically consists of multiple cutters arranged in a ring pattern on a body and rotate as the reamer head is fed upwards, thereby breaking up the rock around the pilot hole. During drilling, a drive rod or bull nose is positioned in the pilot hole. The pilot hole can be drilled simultaneously with (in the case of blind boreholes) or before drilling the well.

[0003] EP3916194 discloses a reamer tip with a wear-resistant pad, which improves stability and can be easily replaced after drilling. EP3916194's... Figure 3 The problem with the type of reamer head shown is that chips easily get stuck in the tool recess below the hob. This leads to increased wear on the cutting edge of the hob.

[0004] Therefore, it is necessary to improve the reamer head used for reverse boring operations so that the chips can be more effectively removed from the area below the cutter.

[0005] Therefore, one object of the present invention is to provide an improved reamer head for improving boring operations while reducing the risk of chip accumulation under the hob. Summary of the Invention

[0006] According to the present invention, the above objective is achieved by means of a reamer head for reverse well boring operation having the features defined in claim 1.

[0007] A reamer head for reverse boring operations according to the present invention comprises: a reamer body; a plurality of cutters connected to the body, each cutter being connected to the body using a mounting plate; and an upper drill string connection portion connected to the body. The mounting plate includes a through-hole for removing chips from the reamer head.

[0008] The present inventors have recognized that this configuration mitigates the problem of cuttings accumulating below the roller cutter. When the reamer head is used for drilling, the upper drill string connection or the nipple is the front end of the under-reamer cutter, or more specifically, the front end of the reamer head. In this application, the upper drill string connection or nipple will also be referred to as the front end. The opposite end of the reamer head will be referred to as the back end. Throughout the application, words such as "upper", "top", "above" and "upwardly" will be in the direction towards the front end. Words such as "lower", "bottom", "below" and "downwardly" refer to the direction towards the back end.

[0009] The upper drill string connection is typically connected to a drill pipe, which in turn is connected to a drill rig positioned at the top of the well to be reamed. The drill rig will then deliver rotational and pulling forces through the drill pipe to pull the under-reamer cutter through a pilot hole drilled beforehand to make the hole larger in diameter. Alternatively, the upper drill string connection is connected to a pilot bit that drills a well while the under-reamer cutter increases the diameter of the hole. In this case, the under-reamer cutter is additionally provided with a lower drill string connection to connect to a drill rig positioned below the under-reamer cutter. The drill rig will then provide rotational and pushing forces to push the under-reamer cutter and the pilot bit upwardly.

[0010] Cuttings produced during the drilling operation will fall from the roller cutter towards the back end due to gravity. Due to the cutout in the mounting plate, the cuttings will not accumulate below the roller cutter. Instead, the cuttings will pass through the cutout and escape from the drilled hole.

[0011] Accumulation of cuttings below the roller cutter can cause increased wear of the roller cutter and cutting inserts positioned on the roller cutter. The roller cutter can also stop rotating due to the accumulation of cuttings. The cutout in the form of a through hole in the mounting plate greatly reduces the wear of the roller cutter and the cutting inserts and reduces the risk of the roller cutter stopping rotation.

[0012] According to one embodiment, the reamer head comprises a cutter pocket below each respective roller cutter, the cutter pocket having a cutter pocket floor, wherein the cutter pocket floor comprises an exit having a lowest point positioned level with or up to 30 mm above the bottom of the entrance of the cutout. More preferably, the lowest point of the exit of the cutter pocket floor is up to 20 mm above the entrance of the cutout, and most preferably up to 10 mm above.

[0013] The tool pocket floor has a longitudinal axis which is substantially parallel to the surface of the housing of the corresponding roller cutter. Due to gravity, the chips will generally flow in the direction of the longitudinal axis of the tool pocket floor. In a direction perpendicular to the longitudinal axis, the tool pocket floor is limited by a convex edge.

[0014] The outlet is defined as the cross section of the tool pocket floor which is perpendicular to the longitudinal axis of the tool pocket floor at the rear end of the tool pocket floor. The outlet is thus the part of the tool pocket floor which is closest to the mounting plate. The lowest point of the outlet of the tool pocket floor is the most rearward point of the outlet.

[0015] The inlet of the cut-out is the opening of the cut-out which faces the tool pocket floor. The bottom of the inlet is the rear end of the inlet.

[0016] The technical effect of having the lowest point of the outlet of the tool pocket floor level with or at most 30 mm above the bottom of the inlet of the cut-out is that the chips will then flow smoothly from the tool pocket floor to the cut-out and away from the reamer head. If the lowest point of the outlet of the tool pocket floor is below the bottom of the inlet of the cut-out, a step will be formed where chips can accumulate.

[0017] According to one embodiment, the tool pocket floor has a substantially concave shape in a direction perpendicular to the longitudinal direction of the tool pocket to direct the chips to the center of the cut-out.

[0018] Here substantially concave means that most of the tool pocket floor has a concave shape in a direction perpendicular to the longitudinal direction of the tool pocket floor, but some parts can have a flat bottom. The central part closest to the longitudinal axis of the tool pocket floor can have a flat bottom, and the area closer to the convex edge is convex.

[0019] The technical effect of this embodiment is that the chips will flow towards the central part closest to the longitudinal axis of the tool pocket floor and thus reach the inlet of the cut-out at a more central position. With this arrangement, the width X of the cut-out can be reduced and more material can be kept in the mounting plate, resulting in a higher strength of the mounting plate.

[0020] According to one embodiment, the tool pocket comprises a chute centrally positioned in the area adjoining the mounting plate.

[0021] There is a chute positioned from the outlet of the tool pocket floor and upwards along the longitudinal axis of the tool pocket floor.

[0022] The technical effect of this embodiment is that most of the chips will flow along the chute to a specific location at the outlet of the tool pocket floor. With this arrangement, the width X of the cutout can be reduced and more material can be kept in the mounting plate, resulting in a higher strength of the mounting plate.

[0023] According to one embodiment, the chute has a concave shape in a direction perpendicular to the longitudinal direction of the tool pocket.

[0024] With this arrangement, the chips will flow towards the longitudinal center line of the chute and thus the width X of the cutout can be made smaller than the width of the chute. With the reduced width X of the cutout, more material can be kept in the mounting plate, resulting in a higher strength of the mounting plate.

[0025] According to one embodiment, the chute has a flat bottom in a direction perpendicular to the longitudinal direction of the tool pocket.

[0026] With this arrangement, the chips will flow evenly along the width of the chute towards the outlet of the tool pocket floor. Since the chips will be distributed evenly along the width X of the cutout, the height Y of the cutout can be reduced. With the reduced height Y of the cutout, more material can be kept in the mounting plate, resulting in a higher strength of the mounting plate.

[0027] According to one embodiment, the width X of the cutout is at least 30% of the width W of the outlet of the tool pocket floor. More preferably, the width X is at least 40% of the width W of the outlet of the tool pocket floor. Even more preferably, the width X is at least 50% of the width W of the outlet of the tool pocket floor. Most preferably, the width X is at least 70% of the width W of the outlet of the tool pocket floor.

[0028] With this arrangement, the chips are less likely to accumulate at the edges of the cutout.

[0029] According to one embodiment, the cutout has a width X and a height Y, and the ratio X / Y is between 1 and 5.

[0030] More preferably, the ratio X / Y is between 1.3 and 4, and most preferably between 1.5 and 3.

[0031] With this arrangement, a stable flow of chips is achieved while still keeping enough strength in the mounting plate.

[0032] According to one embodiment, the cut-out is limited by two parallel side walls, a top wall and a bottom wall, and the radius Rl between the bottom wall and the respective side wall is smaller than the radius R2 between the top wall and the respective side wall.

[0033] With this arrangement, the bottom of the cut-out has a large surface to effectively remove swarf, while the large radius between the top wall and the respective side wall ensures that more material can be kept in the mounting plate, resulting in a higher strength of the mounting plate.

[0034] According to one embodiment, the cut-out has a substantially rectangular cross-sectional area.

[0035] According to one embodiment, the cut-out has a substantially trapezoidal cross-sectional area.

[0036] According to one embodiment, the cut-out has a substantially circular cross-sectional area.

[0037] According to one embodiment, the reamer head comprises exactly two hobs.

[0038] This arrangement results in a well-balanced counter-boring tool and is cost-effective compared to having more than two hobs.

[0039] Further advantages of the invention will appear from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0040] Embodiments of the invention will now be described in detail with reference to the accompanying drawings, in which:

[0041] Figure 1 is a perspective view of a reamer head according to a first embodiment of the invention.

[0042] Figure 2 is a perspective view of a reamer head according to a second embodiment of the invention, with the hobs and the mounting plate removed.

[0043] Figure 3 is a perspective view of a reamer head according to a first embodiment of the invention, with the hobs and the mounting plate removed.

[0044] Figure 4 is a cross-sectional view through the centre line CL and through the centre of a hob according to a second embodiment of the invention.

[0045] Figure 5 is a front view of a mounting plate with a first embodiment of a cut-out.

[0046] Figure 6 is a front view of a mounting plate with a second embodiment of a cut-out.

[0047] Figure 7is a front view of a mounting plate of a third embodiment with a cutout.

[0048] Figure 8 is a front view of a mounting plate of a fourth embodiment with a cutout. DETAILED DESCRIPTION

[0049] REFERENCE Figure 1 which shows a reaming tool 8 with a reamer head 10. The reamer head 10 comprises a reamer body 16 having a substantially cylindrical shape. This cylindrical shape is interrupted by a tool recess 17, wherein a hob 21 is rotatably mounted on the reamer body 16 using a mounting plate 22, also referred to as a fastener, a holder or a saddle.

[0050] The reaming tool 8 further has an upper drill string connection or a box 12 with a threaded connection for attachment to a drill pipe and / or a pilot bit (not shown). The upper drill string connection 12 is connected to a drill pipe, which is connected to a drilling rig, which is preferably positioned at ground level. This drilling rig will then deliver a rotational force and a pulling force through the drill pipe to pull the reaming tool 8 through a pilot hole that has been pre-drilled to make the hole larger in diameter. Alternatively, the upper drill string connection 12 is connected to a pilot bit, which drills a well while the reaming tool increases the hole in diameter. In this case, the reaming tool 8 has a lower drill string connection 14 for connection to a drilling rig, which is positioned below the reaming tool 8. This drilling rig will then provide a rotational force and a pushing force to push the reaming tool 8 and the pilot bit upwards.

[0051] The reaming tool 8 has a centre line CL, around which the reaming tool rotates during use.

[0052] The wear pad 28 is attached to the reamer body 16 by conventional attachment means such as, for example, a bolted connection, a threaded connection or welding. The wear pad 28 provides stability and wear protection during drilling and is easily replaceable when worn.

[0053] The hob 21 comprises cutting inserts (not shown). The cutting inserts are preferably made of a hard material such as, for example, cemented carbide. The hob 21 rotates around a shaft 23 attached to two saddles 24. One saddle 24 is part of the reamer body 16 and the other saddle is part of the mounting plate 22.

[0054] Figure 1 The shown embodiment comprises two hobs 21. This is the most common number of hobs 21 for this type of tool, but more than two hobs can also be used.

[0055] The mounting plate 22 is preferably attached to the reamer body by conventional attachment means such as, for example, bolting or screwing. Alternatively, the mounting plate 22 can be integrally formed with the reamer body 16. The mounting plate 22 forms an acute angle with the centre line CL.

[0056] The mounting plate 22 includes a cut-out 26 in the form of a through hole. If the cut-out is not present, cuttings will be formed during drilling and these cuttings will accumulate in the cutter pocket 17 below the roller cutter 21. Accumulation of cuttings in the cutter pocket 17 results in increased wear of the cutting inserts and increased loading on the bearings in the roller cutter 21. Due to gravity, the cuttings will fall downwards in a direction away from the upper drill string connection 12 and then the cuttings can easily pass through the cut-out 26 and escape the cutter pocket 17 away from the under-reaming cutter 8.

[0057] Figure 2 The under-reaming cutter 8 is shown with the roller cutter 21 and mounting plate 22 removed. The cutter pocket 17 includes a cutter pocket floor 18. The cutter pocket floor 18 has a generally concave shape in its width direction (i.e. the direction perpendicular to the longitudinal axis of the cutter pocket floor 18). That is, the cross-section parallel to the width of the mounting plate 22. By generally concave shape, it is meant that the overall appearance of the cutter pocket floor 18 is concave, but parts of the cutter pocket floor 18 can deviate from the concave shape. As shown, the central portion of the cutter pocket floor 18 has a straight shape. The cutter pocket floor 18 has a convex shape in the direction perpendicular to the longitudinal axis of the cutter pocket floor as limited by the convex edge 20. Figure 2

[0058] The outlet 19 of the cutter pocket floor is defined as the cross-section perpendicular to the longitudinal axis of the cutter pocket floor 18 at the trailing end of the cutter pocket floor 18. Thus, the outlet 19 is the portion of the cutter pocket floor 18 closest to the mounting plate 22. The outlet 19 of the cutter pocket floor 18 has a width W.

[0059] Figure 3 A second embodiment of the invention is shown having an alternative design for the cutter pocket 17. The cutter pocket floor 18 has an additional chute 18c at the outlet 19c of the cutter pocket floor 18. The shape of the chute 18c in cross-section perpendicular to the longitudinal axis of the cutter pocket floor 18 is generally straight in the embodiment shown, but in alternative designs can have a generally concave shape. For this embodiment, the width of the outlet 19c of the cutter pocket floor 18 is equal to the width of the chute Wc.

[0060] Figure 4 ​A cross-section through the centre line CL and through the centre of the roller cutter 21 is disclosed. The outlet 19c of the chute 18c abuts the bottom of the inlet 27 of the cut-out 26. The outlet 19c is here positioned to be approximately flush with the bottom of the inlet 27 of the cut-out 26. In other embodiments, the outlet 19c can be positioned up to a maximum of 10mm above the bottom of the inlet 27 of the cut-out 26. The inlet of the cut-out 26 is the side of the cut-out facing the cutter pocket 17. The reason for having the outlet 19c flush with or up to a maximum of 10mm above the bottom of the inlet 27 of the cut-out 26 is to reduce the risk of chip jamming between the chute 18c and the mounting plate 22.

[0061] In embodiments without a chute 18c, the outlet 19 of the cutter pocket floor 18 is flush with or up to a maximum of 10mm above the bottom of the inlet 27 of the cut-out 26 in the mounting plate 22.

[0062] Figure 5 An embodiment of the mounting plate 22 is shown in a front view. The cut-out 26 in the form of a through hole has the form of being limited by two parallel side walls 30, a top wall 28 and a bottom wall 29. The respective walls are connected to each other by a rounded corner. The radius R1 between the bottom 29 and the respective side wall 30 is smaller than the radius R2 between the top 28 and the respective side wall 30. The radius R1 is between 1mm and 250mm and the radius R2 is between 2mm and 300mm. The radii depend on the type of rock being drilled and the size of the counter bore cutter 8. Preferably, R1 is smaller than R2.

[0063] The purpose of having a small radius R1 between the bottom 29 and the respective side wall 30 is to have as large an opening as possible at the bottom of the cut-out 26 to effectively let the chips through. The radius R2 at the top 30 of the cut-out 26 is larger to increase the strength of the mounting plate 22 at a part where chips are less likely to pass through.

[0064] The cut-out 26 has a width X and a height Y. The width X is between 50 and 400mm and the height Y is between 30 and 200mm. Preferably, the ratio between X and Y is between 1 and 5, more preferably between 1.3 and 4 and most preferably between 1.5 and 3. This provides a good balance between the strength of the mounting plate 22 and the ability of the cut-out 26 to let chips through.

[0065] Preferably, the width X of the cut-out 26 should be at least 30% of the width W of the outlet 19 of the cutter pocket floor or of the outlet 19c of the chute. The purpose of having a cut-out at least this wide is to reduce the risk of chip jamming between the cutter pocket 17 and the mounting plate 22.

[0066] Figure 6 An alternative embodiment of the cut-out 26 is shown. Here, the cut-out 26 has a rectangular form.

[0067] Figure 7 An alternative embodiment of the cutout 26 is shown. The cutout 26 here has a trapezoidal shape.

[0068] Figure 8 An alternative embodiment of the cutout 26 is shown. The cutout 26 here has a circular form.

Claims

1. A reamer head (10) for reverse well boring operations, comprising: A reamer body (16); a plurality of hobs (21) connected to the body (16), each hob being connected to the body (16) using a mounting plate (22); and an upper drill string connector (12) connected to the body (16); The mounting plate (22) is characterized by having a through-hole (26) for removing chips from the reamer head (10).

2. The reamer head (10) according to claim 1, characterized in that, The reamer head (10) includes a tool recess (17) below each corresponding hob (21), the tool recess (17) having a tool recess base plate (18) including an outlet (19, 19c) having a lowest point positioned flush with or no more than 30 mm above the bottom of the inlet (27) of the cut (26).

3. The reamer head (10) according to claim 1 or 2, characterized in that, The tool recess base plate (18) has a generally concave shape in a direction perpendicular to the longitudinal direction of the tool recess (17) to guide the chips toward the center of the cut (26).

4. The reamer head (10) according to any one of the preceding claims, characterized in that, The tool recess base plate (18) includes a groove (18c) centrally located in the area adjacent to the mounting plate (22).

5. The reamer head (10) according to claim 4, characterized in that, The groove (18c) has a concave shape in a direction perpendicular to the longitudinal direction of the tool recess (17).

6. The reamer head (10) according to any one of claims 1 to 4, characterized in that, The groove (18c) has a flat bottom in a direction perpendicular to the longitudinal direction of the tool recess (17).

7. The reamer head (10) according to any one of claims 4 to 6, characterized in that, The width X of the cut (26) is at least 30% of the width W of the exit of the tool recess base plate (18).

8. The reamer head (10) according to any one of the preceding claims, characterized in that, The cut has a width X and a height Y, and the ratio X / Y is between 1 and 5.

9. The reamer head (10) according to any one of the preceding claims, characterized in that, The cut (26) is limited by two parallel sidewalls (30), a top wall (28) and a bottom wall (29), and the radius R1 between the bottom wall (29) and the corresponding sidewall (30) is smaller than the radius R2 between the top wall (28) and the corresponding sidewall (30).

10. The reamer head (10) according to any one of claims 1 to 8, characterized in that, The cut (26a) has a generally rectangular cross-sectional area.

11. The reamer head (10) according to any one of claims 1 to 8, characterized in that, The cut (26b) has a generally trapezoidal cross-sectional area.

12. The reamer head (10) according to any one of claims 1 to 7, characterized in that, The cut (26c) has a generally circular cross-sectional area.

13. The reamer head (10) according to any one of the preceding claims, characterized in that, The reamer head (10) includes exactly two hobs (21).

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