Underreamer with Radial Expandable Cutting Blocks

Abstract

A cutting tool (1) for widening the diameter of a borehole and method thereof is disclosed. The cutting tool (1) comprises a housing (2) having cavity (10) in which a moveable activation element (6) is arranged. The activation element (6) is moved in an axial direction and is connected to one or more cutting blocks via a mechanical coupling (15). The mechanical coupling (15) transfers the axial movement of the action element into a radial movement of the cutting blocks. An activation unit (24) pushes the activation element (6) towards a stopping position which in turn causes the cutting blocks (11) to move out of the housing. The activation unit (24) further pulls the activation element back towards its starting position which in turn causes the cutting blocks to move back into the housing. The cutting blocks (11) extend into one or more cavities formed in the activation element, thereby increasing the travel-to-expansion ratio. The cutting blocks can be replaced by stabiliser blades (20) which are used to stabilise the drilling in the expanded borehole.

Claims

1. A cutting tool for widening the diameter of a borehole, comprising: a housing having a top end, a bottom end and a first outer surface, wherein the housing defines a longitudinal direction and a transverse radial direction, at least one moveable cutting block having at least one cutting element, each cutting block being arranged in a first opening located in the first outer surface and configured to move in the radial direction between a retracted position and an expanded position relative to the housing, at least one moveable activation element arranged relative to the at least one cutting block and configured to move along the longitudinal direction relative to the housing for activation of the at least one cutting block wherein the housing comprises a cavity connected to the first opening in which the at least one cutting block and the at least one activation element are arranged, wherein the cavity is arranged between the first outer surface and an inner surface of the housing.

2. A cutting tool according to claim 1, wherein the activation element is further connected to an activation unit arranged in the cavity, wherein the activation unit is configured to drive the activation element.

3. A cutting tool according to claim 2, wherein the activation unit is arranged in a chamber inside the cavity, the chamber being sealed off from the rest of the cavity.

4. A cutting tool according to claim 2, wherein the activation unit comprises a linear actuator connected to a control unit configured to control the operation of the activation unit.

5. A cutting tool according to claim 1, further comprising a mechanical coupling comprising a first set of guiding elements, e.g. a pin, configured to engage a second set of guiding elements, e.g. through hole, wherein one of the first and second sets of guiding elements is arranged on a third surface of the at least one cutting block and the other set of the guiding elements is arranged on a fourth surface on the at least one activation element facing the third surface.

6. A cutting tool according to claim 1, wherein the at least one activation element comprises a cavity or through hole located on an outer surface, wherein at least a part of the at least one cutting block extends into the cavity or through hole.

7. A cutting tool according to claim 1, wherein the ratio between the relative axial movement of the at least one activation element and the relative radial movement of the at least one cutting block is between 1:1 and 1:100.

8. A cutting tool according to claim 1, wherein the cutting tool comprises a spring element configured to apply a spring force to the activation element, the spring element being arranged relative to the activation element inside the cavity.

9. A cutting tool according to claim 1, wherein the cutting tool further comprises at least one stabiliser blade arranged in at least one second opening located on the first outer surface, wherein the at least one stabiliser blade is moveably connected to the at least one activation element.

10. A method for operating a cutting tool according to claim 1, wherein the method comprises the steps of: moving the at least one activation element in the longitudinal direction relative to the housing, and further moving the at least one cutting block in the radial direction out of the housing towards an expanded position, wherein the at least one activation element is arranged in a cavity in the outer surface, wherein said at least one activation element is moved along the cavity by an activation unit further arranged in the cavity.

11. A method according to claim 10, wherein a linear actuator drives the at least one activation element, wherein the operation of the linear actuator is controlled by a control unit.

12. A method according to claim 10, wherein the longitudinal movement is transferred into the radial movement by using a mechanical coupling located between the at least one activation element and the at least one cutting block.

13. A method according to claim 11, wherein the method further comprises the step of: monitoring at least one parameter of the drilling fluid passing through the cutting tool via the control unit, and further detecting when the at least one parameter has reached a predetermined level within a predetermined time window, or communicating with a remote unit via the control unit, wherein the remote unit and the control unit control the operation of the cutting tool.

14. A method according to any claim 10, wherein one end of the at least one cutting block extends into an opening located on the at least one activation element, wherein the one end is at least moved further into the at least one activation element when the cutting block is moved towards the retracted position.

Description

DESCRIPTION OF THE DRAWING

[0089] The invention is described by example only and with reference to the drawings, wherein:

[0090] FIG. 1 shows a first exemplary embodiment of a cutting tool according to the invention in a retracted position,

[0091] FIG. 2 shows the cutting tool of FIG. 1 in an expanded position,

[0092] FIG. 3 shows a cross sectional view of the cutting tool of FIG. 1,

[0093] FIG. 4 shows a cross sectional view of a second exemplary embodiment of the cutting tool

[0094] FIG. 5 shows a third exemplary embodiment of the cutting tool in a retracted position,

[0095] FIG. 6 shows the cutting tool of FIG. 5 in an expanded position,

[0096] FIG. 7 shows the cutting tool of FIG. 5 seen in the radial direction, and

[0097] FIG. 8 shows a cross-section of the cutting tool of FIG. 5.

[0098] In the following text, the figures will be described one by one and the different parts and positions seen in the figures will be numbered with the same numbers in the different figures. Not all parts and positions indicated in a specific figure will necessarily be discussed together with that figure.

REFERENCE LIST

[0099] 1 Cutting tool [0100] 2 Housing [0101] 3 Top end [0102] 4 Bottom end [0103] 5 Side wall [0104] 6 Activation element [0105] 7 Sealing element [0106] 8 Pressure regulating unit [0107] 9 Spring element [0108] 10 Cavity [0109] 11 Cutting block [0110] 12 Opening [0111] 13 Outer surface [0112] 14 Cutting elements [0113] 15 Mechanical coupling [0114] 16 Longitudinal direction, axial movement [0115] 17 Transverse direction, radial movement [0116] 18 Fluid path, through hole [0117] 19 Annular space [0118] 20 Stabiliser blade [0119] 21 Inner wall [0120] 22 Cutting tool [0121] 23 Cavity [0122] 24 Actuator unit [0123] 25 Wall [0124] 26 Shaft [0125] 27 Linear actuator [0126] 28 Control unit

DETAILED DESCRIPTION OF THE INVENTION

[0127] FIG. 1 shows a first exemplary embodiment of a cutting tool 1 in the form of an underreamer seen from the side. The cutting tool comprises a housing 2 having a longitudinal direction and a transverse radial direction adapted to be placed in a borehole. The housing 2 comprises a top end 3 connected to a bottom end 4 via a cylindrical shaped side wall 5. Part of the housing 2 is cut away for illustrative purposes. The housing 2 is made of high strength material, such as steel. The longitudinal direction extends through the top and bottom ends 3, 4 while the radial direction extends through the side wall 5.

[0128] The housing 2 forms an internal chamber in which a moveable activation element 6 is arranged. The activation element 6 in the form of a box is configured to be moved axially along the longitudinal direction when activated. One or more sealing elements 7 are arranged on the inner surface of the housing 2 and/or on the outer surface of the activation element 6. The sealing element 7 forms a fluid tight seal which separates the drilling fluid passing into the fluid path (shown in FIGS. 3-4).

[0129] The activation element 6 is at a top end connected to a pressure regulating unit 8 which is configured to regulate the different pressure across the cutting tool 1. The pressure regulating unit 8 may comprise fixed regulating elements or adjustable regulating elements for diverting a drilling fluid into one or more fluid paths (shown in FIGS. 3 and 4) located in the housing 2 or the activation element 6. The fluid paths may be through holes which at the other end are connected to an outlet (not shown). If the cutting tool 1 comprises active regulating elements, an actuator element (not shown) may be connected to the regulating elements for adjusting their position. The actuator element may be controlled by a control unit (shown in FIG. 5).

[0130] The activation element 6 is at a bottom end connected to a spring element 9, e.g. a compression spring, arranged inside the chamber. The spring element 9 is further connected to the bottom end 4 of the housing 2. The spring element 9 is configured to generate a spring force when it is deformed which is used to bias the differential pressure of the drilling fluid.

[0131] The activation element 6 comprises a cavity 10 (not shown in FIGS. 1 and 2) configured to receive and hold at least a part of a moveable cutting block 11. The cavity 10 is connected to at least one opening located in the outer surface 6a of the activation element 6. The opening faces an opening 12, e.g. a through hole, located in the outer surface 13 of the housing 2. The cutting block 11 comprises a longitudinal direction parallel to the radial direction of the housing 2. The cutting block 11 comprises a plurality of cutting elements 14 at one end configured to perform an underreaming process when brought into contact with the inner surface of the borehole. The other end is configured to extend into the cavity 10 of the activation element 6. For illustrative purposes, only one cutting block 11 is shown.

[0132] A mechanical coupling 15 is arranged between the cutting block 11 and the activation element 6 for transferring the axial movement of the activation element 6 into a radial movement of the cutting blocks 11. The mechanical coupling 15 comprises a first set of coupling elements (not shown) arranged on a side surface of the activation element 6 and a second set of coupling elements (not shown) arranged on a side surface of the cutting block 11. The first coupling elements are grooves configured to engage complementary tracks defining the second set of coupling elements. The track and grooves are placed in an inclined angle, e.g. 45 degrees, relative to the respective longitudinal directions of the elements 6, 11, or any other angle capable of providing a radial expansion rate (travel-to-expansion ratio) from 1:1 and 1:100.

[0133] The method of operation will now be described in reference to FIGS. 1 and 2. FIG. 2 shows the cutting tool 1 in an expanded position while FIG. 1 shows the cutting tool in a retracted position. The cutting tool 1 is mounted to a drill string or bottom hole assembly and located into position in the borehole. The pressure in the drilling fluid is increased. As the differential pressure exceeds the activation level of the activation element 6, e.g. the spring force, the activation element 6 is moved/pushed axially downwards (marked with arrow 16) towards a stopping position, thereby compressing the spring element 9. The second coupling elements then slide along the first coupling elements in the mechanical coupling 15 which in turn cause the cutting block 11 to move radially outwards (marked with arrow 17) of the housing 2 and the cavity 10.

[0134] When the reaming process is completed, the pressure in the drilling fluid is reduced. The spring force causes the activation element 6 to move axially upwards (marked with arrow 16) towards its starting position as the differential pressure drops below the activation level of the activation element 6. The first coupling elements are then slid along the second coupling elements which in turn cause the cutting block 11 to move back into the housing 2 and further into the cavity 10. The cutting tool 1 may then be raised to the ground level or moved to a new position.

[0135] FIG. 3 shows a cross sectional view of the cutting tool 1 where the cutting block 11 is placed in its retracted position. The outer surface of the activation element 6 is shaped to substantially match the inner contour of the housing 2 so they form a more or less tight fit. One or more optional guiding elements configured to limit the movement of the activation element 6 to an axial movement may be arranged between the inner surface of the housing 2 and the outer surface of the activation element 6. The sealing element (shown in FIGS. 1-2) forms a fluid tight seal which separates the drilling fluid passing into the fluid path 18 from the drilling fluid passing through the annular space 19. The fluid path 18 is formed by a central through hole in the activation element 6 in fluid connection with an inlet and outlet (not shown) located at the ends 3, 4 respectively.

[0136] The cavity 10 extends in a longitudinal direction parallel to the longitudinal direction of the activation element. The mechanical coupling 15 is arranged in the cavity 10 between two opposite facing surfaces of the two elements 6, 11. The cutting elements 14 are in the retracted position flushed with or placed in a retracted position relative to the outer surface 13 of the housing 2.

[0137] One or more stabiliser blades 20 are arranged in a second opening located on the outer surface 13 of the tool 1. The stabiliser blade 20 extends into the housing 2 and into a second cavity in the activation element 6, as shown in FIG. 3. The stabiliser blade 20 is moveable connected to the activation element 6 by a second mechanical coupling 15. Instead of cutting elements, the stabiliser blade 20 comprises a curved guiding surface 20a or a plurality of rollers for contacting the inner wall 21 of the borehole (marked with a dotted line). The stabiliser blade 20 is expanded and retracted in the same manner as the cutting blocks 11. This stabilises the tool 1 during movement in the expanded borehole.

[0138] FIG. 4 shows a cross sectional view of a second exemplary embodiment of the cutting tool 1. In this embodiment the tool 1 comprises two or more cutting blocks 11a, 11b, 11c, here three blocks are shown, each of which is arranged in an individual opening 12a, 12b, 12c and cavity 10a, 10b, 10c. The cutting blocks 11 are angled relative to each other, e.g. in 120 degrees intervals and are simultaneously activated, e.g. moved radially, when the activation element 6 is moved axially downwards as described above.

[0139] FIG. 5 shows a third exemplary embodiment of the cutting tool 22 in a retracted position where FIG. 6 shows the cutting tool 22 in an expanded position. The cutting tool 22 has a cavity 23 formed in the outer surface 13 of the housing 2 in which the activation element 6 and the cutting block 11 are arranged. An activation unit 24 is further arranged in the cavity 23 and connected to the activation element 6 via a shaft 25. An inner wall 26 separates the cavity 23 into a first chamber and a second chamber, wherein the shaft 25 extends through the inner wall 26.

[0140] The activation unit 24 comprises a linear actuator 27 connected to a control unit 28 which controls the operation of the cutting tool 22. The activation unit 24 is accessible via a cover removable connected to the housing 2. The control unit 28 communicates with a remote unit (dotted lines) via a communications module arranged in the cavity 23.

[0141] When activated, the control unit 28 send a control signal to the linear actuator 27 which in turn moves the activation element 6 and the cutting block to their expanded position as described in FIGS. 1 and 2. After completing the underreamer process, the control unit 28 then sends another control signal to the linear actuator 27 which moves the activation element 6 and the cutting block to their retracted position as described in FIGS. 1 and 2.

[0142] In this configuration, the drilling fluid is able to pass freely through the cutting tool 22 as the central trough hole of the housing 2 acts as the fluid passageway 18.

[0143] FIG. 7 shows the cutting tool 22 seen in the radial direction where the housing 2 is omitted for illustrative purposes. As illustrated, the cavity 23 is connected to three openings which can be closed off by a cover or hatch (not shown). The coupling elements 15 are here shown as a through hole in the cutting block 11 and a pin extending through the hole. The pin is connected to two opposite facing surfaces on the activation element 6.

[0144] The cavity 10 of the activation element 6 is an elongated cavity which at least corresponds to the axial movement of the activation element 6.

[0145] FIG. 8 shows a cross-section of the cutting tool 22 and the cavity 23 in which the activation element 6 and the cutting block 11 are arranged. The inner diameter of the through hole 18 is greater than the inner diameter of the through hole 18 shown in FIGS. 3 and 4. Thus, more drilling fluid may be led through the cutting tool 22 without any significant loss of pressure.

[0146] The invention is not limited to the embodiments described herein, and may be modified or adapted without departing from the scope of the present invention as described in the patent claims below.