Downhole tool

Abstract

The present invention relates to a downhole tool comprising a tool body having a tool axis and at least three arms movable between a retracted position and a projected position, each arm having a first arm part and a second arm part, where the second arm part is connected with the tool body, and the first arm part is projectable from the tool body, wherein the tool body comprises three actuator assemblies, each actuator assembly comprising a piston chamber and a piston unit, and each piston unit being connected with one of the second arm parts.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to European Patent Application No. 25167228.3 filed Mar. 28, 2025, the entire contents of which are hereby incorporated by reference.DESCRIPTION

[0002] The present invention relates to a downhole tool comprising a tool body having a tool axis and at least three arms movable between a retracted position and a projected position.

[0003] In a well, one casing may extend around another tubing, and it may happen that the tubing is not arranged to have a centre axis coinciding with that of the casing as the tubing is arranged offset and off-centre of the casing. Some wells may be designed with non-coinciding tubulars to make room for other equipment. On well intervention with a tool, the tool is introduced in the innermost tubing and then may have to perform an operation in the surrounding casing while being arranged off-centre. However, this is not possible with the known tools.

[0004] It is an object of the present invention to wholly or partly overcome the above disadvantages and drawbacks of the prior art. More specifically, it is an object to provide an improved downhole tool which is able to perform an operation in a casing while being partly arranged in an off-centre tubing.

[0005] The above objects, together with numerous other objects, advantages and features, which will become evident from the below description, are accomplished by a solution in accordance with the present invention by a downhole tool, comprising:

[0006] a tool body having a tool axis, and

[0007] at least three arms movable between a retracted position and a projected position, each arm having a first arm part and a second arm part, where the second arm part is connected with the tool body, and the first arm part is projectable from the tool body,

[0008] wherein the tool body comprises three actuator assemblies, each actuator assembly comprising a piston chamber and a piston unit, and each piston unit being connected with one of the second arm parts.

[0009] When each arm is activated by each respective actuator assembly, the arms are enabled to move individually but to apply an even force on the inner face of the casing so as to anchor the tool or machine, i.e. cut, in the casing. By having the actuator assembly with a piston unit moving in a chamber, it can be ensured that each arm has enough force to either anchor with sufficient force without making an indentation in the wall of the casing, or that, during the machining operation, the weight on bit, i.e. the force with which the cutting edge is pressed against the casing, is sufficient to cut or mill the casing without the risk of the tool stalling.

[0010] Moreover, the downhole tool may be a downhole tubing cutting tool for cutting a production tubing, a casing or similar tubing in a well from within a first casing at an off-centre location in a second casing.

[0011] Furthermore, the piston units may be allowed to move individually.

[0012] Also, each chamber may comprise a first hydraulic aperture and a second hydraulic aperture, wherein the first hydraulic apertures of the three chambers are fluidly connected, and the second hydraulic apertures of the three chambers are fluidly connected.

[0013] Because the first hydraulic apertures are hydraulically connected, the fluid from one chamber part to another runs quickly as the fluid does not flow back to the pump or a common chamber but flows from a decreasing first chamber part to an increasing first chamber part, and the same applies to the second hydraulic apertures and the second chamber parts.

[0014] In addition, the piston chamber may comprise a first chamber part and a second chamber part, and the first chamber part may be fluidly separated from the second chamber part.

[0015] Moreover, the piston chamber of the actuator assemblies may be fluidly connected to a common chamber.

[0016] Thus, the common chamber may function as an accumulating chamber, should the fluid from one chamber part not match the space created in another chamber part.

[0017] Further, the piston unit may comprise a piston rod mechanically connected with the second arm part.

[0018] By having a piston rod, the mechanical connection to the arm can be made the “dirty part”, i.e. the part surrounded by well fluid, which simplifies the design of the downhole tool.

[0019] Also, the piston rod may comprise a groove for receiving the second arm part and / or an engagement part of the arm.

[0020] Furthermore, the piston unit may comprise a first piston and a second piston connected by means of a piston connection part.

[0021] By having both a first and a second piston, one side of the first and second pistons faces a chamber having clean fluid, and the other side faces a space which is fluidly connected to the well, i.e. subjected to “dirty” fluid. This simplifies the design as no accumulating chamber is needed because the well is used as the accumulator.

[0022] In addition, each actuator assembly may comprise a spring biasing the arm from the projected position to the retracted position. The arms are thereby retracted as a failsafe function of the downhole tool if the downhole tool loses power or hydraulic pressure.

[0023] Moreover, the first arm part may have a terminal end comprising a cutting edge element, the cutting edge element having a cutting insert or an abrasive insert.

[0024] Further, each arm may have a pivot point connecting the arm with the tool body.

[0025] Also, each piston unit may have a longitudinal piston axis parallel to the tool axis and offset in a radial direction from the tool axis.

[0026] In addition, the piston chambers of the actuator assemblies may be connected to a common chamber.

[0027] Furthermore, the second arm part may have an arm engagement face abutting a piston engagement face for transferring a force from the piston unit to move the arm, and the piston engagement face may be arranged on the piston rod in an area positioned between the tool axis and the piston axis.

[0028] By having the piston engagement face arranged on the piston rod in an area positioned between the tool axis and the piston axis, the second arm part is made as long as possible, enabling it to transfer a higher force to the cutting operation.

[0029] Moreover, the pivot point may be arranged at a first distance from the outer face of the tool body, the first distance being less than 20% of a tool body diameter.

[0030] In addition, the tool body may have a pivot section engaging a pivot connecting the arm to the tool body, and the pivot section may be made of a first material having a higher hardness than a second material of the tool body surrounding the pivot section.

[0031] Also, the pivot section may have a hole through which the pivot extends to pivotally fasten the arm to the tool body.

[0032] Further, the first chamber part and the second chamber part may be separated by a partition.

[0033] Moreover, the arm may comprise an arm projection at an intermediate part between the first arm part and the second arm part.

[0034] In addition, the tool body may comprise an opening through which the arm extends.

[0035] Furthermore, the first hydraulic apertures may be fluidly connected by a first circular fluid channel, and the second hydraulic apertures may be fluidly connected by a second circular fluid channel.

[0036] Moreover, the arm may comprise an engagement part having an arm engagement face with a curvature, the curvature being shaped like the profile of half a tooth of an involute gear, a trochoid gear or a cycloidal gear. Further, the engagement part may be an involute tooth.

[0037] Finally, the downhole tool may further comprise a motor powered through a wireline connected to the tool and a pump driven by the motor.BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings, which for the purpose of illustration show some non-limiting embodiments and in which:

[0039] FIG. 1 shows a side view of a downhole tubing cutting tool for cutting a casing or similar tubing in a well from within a second tubing arranged off-centre from the casing to be machined in,

[0040] FIG. 2 shows a front perspective of a downhole tool with retracted arms,

[0041] FIG. 3 shows a front perspective of the downhole tool in FIG. 2 with individually projected arms,

[0042] FIG. 4 shows a front view of the downhole tool where the tool body is located in the previously cut tubing offset in a surrounding casing, and the arms are projected to an uneven extent in the surrounding casing for performing a second cut, and

[0043] FIG. 5 shows a cross-sectional view of part of the downhole tool with the arms in the retracted position.

[0044] All the figures are highly schematic and not necessarily to scale, and they show only those parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested.DETAILED DESCRIPTION

[0045] FIG. 1 shows a downhole tool 1 for performing an operation in a casing or similar tubing in a well from within a second tubing arranged off-centre from the casing. The downhole comprises a tool body 2 having a tool axis LT (shown in FIG. 5) and three arms 3 movable between a retracted position and a projected position as shown in FIG. 1. Each arm has a first arm part 4 and a second arm part 5, where the second arm part 5 is connected with the tool body 2, and the first arm part 4 is projectable from the tool body 2. The tool body 2 comprises three actuator assemblies 6 as shown in FIGS. 2 and 3. As shown in FIG. 5, each actuator assembly 6 comprises a piston chamber 7 and a piston unit 8, and each piston unit 8 is connected with one of the second arm parts 5 for moving the three arms 3 from the retracted position as shown in FIG. 2 to the projected position as shown in FIG. 3.

[0046] In FIG. 1, the downhole tool 1 is a downhole tubing cutting tool 1 for cutting in and from within and separating in two a production tubing, a casing or similar tubing, where the downhole tool 1 is arranged in an offset casing 32 and is to cut into a surrounding casing 31 so that the downhole tubing cutting tool 1 is arranged with its tool axis LT displaced from the longitudinal axis LC of the casing 31. When engaging such surrounding casing 31, the arms 3 of the tool body 2 must extend to a varying extent in order for each arm 3 to be able to abut the inner face of the surrounding casing 31 in which the cutting operation is to be performed. When performing an operation such as milling or drilling in a valve, such as a ball valve, situated in front of the tool 1, the tool 1 needs to anchor up in the casing 31 so that the machining bit, e.g. a milling bit or a drilling bit, does not just slide on the curvature of the ball valve. In order to anchor the downhole tubing cutting tool 1 up this must be done inside the offset casing 32, then the arms 3 need to be able to extend at different lengths so that one arm 3 is projected to a larger extent than a neighbouring arm 3 in order to reach and cut or mill in the surrounding casing 31. When performing such operation such as separating a tubing in two in order to release and pull the upper part of the casing 31 out of the well, a first tool part 51 in the form of a cutting head is rotated in relation to a second tool part 52, and the arms 3 have cutting edge elements 17 need to project to a different extent in order to machine, such as mill or cut, in the wall of the casing 31. Thus, the arms 3 are rotated, and then the arms 3 move between varying degrees of projection as can be seen in FIG. 4, where a first arm 3a is extended more than a second arm 3b, which again is projected more than a third arm 3c.

[0047] The downhole tool 1 in FIG. 1 comprises a nose 40 indicated by dotted lines for guiding the downhole tool 1 in the well without damaging the arms 3 and the cutting edge elements 17. Prior to the position disclosed, the downhole tool 1 shown in FIG. 1 has made a cut 41 in the off-centre and offset the casing 32 in order to separate the offset casing 32 in two sections, and in the situation shown in FIG. 1 the second part of the offset casing 32 has fallen further down the well and is therefore not shown. When the next surrounding casing 31 must be cut, the tool part 51 projects at least partly out of the offset casing 32, the tool part 51 is rotated, and the arms 3 move individually and are pressed radially outwards. While rotated, the most projected arm 3, being the first arm 3a in FIG. 4, is pressed radially inwards towards the retracted position by the wall of the casing 31 during rotations, while the other two arms 3, being the second and third arms 3b, 3c, are allowed to project further outwards as these two arms are given more space to extend due to the offset position of the tool in the surrounding casing 31.

[0048] In order to move the arms 3 individually, the tool body 2 comprises the three actuator assemblies 6 shown in FIG. 5, and each actuator assembly 6 comprises the piston chamber 7 and the piston unit 8, where each piston unit 8 is connected with one of the second arm parts 5 for moving the three arms 3 from the retracted position as shown in FIG. 2 to the projected position as shown in FIG. 3. The piston chamber 7 comprises a first chamber part 11 and a second chamber part 12, and the first chamber part 11 is fluidly separated from the second chamber part 12. The piston unit 8 has a longitudinal piston axis LP that is parallel to the tool axis LT and is offset in a radial direction R1 from the tool axis LT. The piston unit 8 comprises a piston rod 14 mechanically connected with the second arm part 5. The piston rod 14 has a groove 39 (also shown in FIG. 4) into which an engagement part 26 of the second arm part 5 extends. By having a piston rod 14, the mechanical connection to the arm 3 can be made the “dirty part”, i.e. the part surrounded by well fluid, which simplifies the design of the downhole tool 1. The engagement part 26 has an arm engagement face 21 abutting a piston engagement face 22 of the groove of the piston rod 14 for transferring a force from the piston unit 8 to move the arm 3. The piston engagement face 22 is arranged on the piston rod 14 in an area 23 positioned between the tool axis LT and the piston axis LP and thus at a position that is closer to the centre of the tool body 2 than the centre of the piston unit 8. By having the piston engagement face 22 arranged on the piston rod 14 in an area 23 positioned between the tool axis LT and the piston axis LP, the second arm part 5 is made as long as possible, enabling it to transfer a higher force to the cutting operation. The engagement part 26 has a curvature so that the arm engagement face 21 is in the form of a curvature shaped like the profile of half a tooth of an involute gear, a trochoid gear or a cycloidal gear. With such curvature, the engagement part 26 is rolling along the piston engagement face 22 in the groove, which is a more efficient way of transferring force than a solution where the faces are sliding in relation to each other. As can be seen, the engagement part 26 is formed as a tooth so that one half has a first curved arm engagement face 21 rolling against one edge of the groove, and the other half of the engagement part 26 has a second curved arm engagement face 21 rolling on the other edge of the groove, resulting in a very efficient transfer of force between the piston unit 8 and the arm 3.

[0049] The piston unit 8 comprises a first piston 43a connected to a second piston 43b by means of a piston connection part 44. The first piston 43a is arranged in the first chamber part 11, and the second piston 43b is arranged in the second chamber part 12. The first chamber part 11 and the second chamber part 12 are fluidly separated by a partition 28 and a sealing element 33 abutting the piston connection part 44. The actuator assembly 6 further comprises a spring 15 arranged in the second chamber part 12, and as fluid is pumped into the first chamber part 11 for moving the piston unit 8 to force the arm 3 to project, the spring 15 is compressed as the arm 3 moves from the retracted position to the projected position, and the arm 3 is thus biased as it moves from the projected position to the retracted position. So, if the pressure is lost, the arm 3 is retracted by the compressed spring 15 as a failsafe function of the tool 1. By having both a first and a second piston 43a, 43b, one side of the first and second pistons 43a, 43b faces a chamber having clean fluid, and the other side faces a space which is fluidly connected to the well, i.e. subjected to “dirty” fluid. This simplifies the design as no accumulating chamber is needed because the well is used as the accumulator.

[0050] Each chamber 7 of the actuator assemblies 6 comprises a first hydraulic aperture 9 and a second hydraulic aperture 10. The first hydraulic apertures 9 of the three chambers 7 are fluidly connected, and the second hydraulic apertures 10 of the three chambers 7 are fluidly connected. In this way, when a second arm 3b, as shown in FIG. 4, is moved towards the position of the first arm 3a, fluid in the second chamber part 12 related to the second arm 3b is leaving the second chamber part 12 and entering the second chamber part 12 related to the first arm 3a since the first arm 3a is forced by the wall of the casing 31 to move the piston unit 8 backwards, pressing fluid out of the first chamber part 11 related to the first arm 3a. The fluid pressed out of the first chamber part 11 related to the first arm 3a is then transferred into the other first chamber parts 11 of the second and third arms 3. In order to quickly move fluid between the chamber parts 11, 12, the first hydraulic apertures 9 are fluidly connected by a first circular fluid channel 37, and the second hydraulic apertures 10 are fluidly connected by a second circular fluid channel 38. Thus, the piston units 8 are allowed to move individually, and thereby the arms 3 are enabled to move individually. The first chamber parts 11 of the actuator assemblies 6 are fluidly connected to a common chamber 34 so that all first chamber parts 11 are pressurised with the same fluid pressure. Thus, the common chamber 34 may function as an accumulating chamber, should the fluid from one chamber part 11, 12 not match the space created in another chamber part 11, 12.

[0051] In another solution, the piston unit 8 comprises only one piston moving in the chamber 7, dividing the chamber 7 into the first chamber part 11 and the second chamber part 12, and the spring 15 is arranged in the second chamber part 12 and compressed as fluid is injected into the first chamber part 11, moving the piston unit 8 to project the arm 3.

[0052] As shown in FIG. 1, the first arm part 4 has a terminal end 16 comprising a cutting edge element 17 having a cutting edge 45, and the cutting edge element 17 comprises a cutting insert 18 or an abrasive insert. Each arm 3, 3a, 3b, 3c has a pivot point 19 connecting the arm 3 with the tool body 2. The tool body 2 has a pivot section 24 having a hole 27 receiving and engaging a pivot 25 in the form of a pin connecting the arm 3 to the tool body 2, and in order to strengthen this connection so that it is not so easily worn, the pivot section 24 is made of a first material having a higher hardness than a second material of the tool body 2 surrounding the pivot section 24.

[0053] As shown in FIG. 5, the pivot point 19 is arranged at a first distance D1 from the outer face of the tool body 2, the first distance being less than 20% of a tool body diameter DT, preferably less than 15%. Having the pivot point 19 so close to the outer face enables a longer distance between the pivot point 19 and the arm engagement face 21 of the engagement part 26 so as to generate more torque and thus more force on the arm 3 in the projected position.

[0054] As shown in FIGS. 1-3, the tool body 2 comprises three openings 30 through which the arm 3 extends in and out. Each arm 3 has an arm projection 29 at an intermediate part of the arm 3 between the first arm part 4 and the second arm part 5 so that when the arm 3 projects through the opening 30, the sides of the opening 30 support both sides of the arm projection 29, creating a much stronger force transfer as the arm 3 is strengthened and supported over a greater area than without the arm projections.

[0055] The downhole tool 1 may be a wireline downhole tool and thus be connected to and powered solely through a wireline, and it may further comprise a motor 36, as shown in FIG. 5, powered through the wireline and a pump 35 driven by the motor 36. The pump 35 generates the pressurised fluid into the first chamber parts 11 to force the arms 3 towards their projected positions, and the motor 36 rotates the first tool part 51 in order to rotate the arms 3 to cut or grind into the wall of the casing 31 to separate the casing 31 in two. A gear unit is arranged between the motor and the first tool part 51 in order to rotate the arms 3 at a lower rotational speed than the motor speed.

[0056] In another solution, the downhole tool 1 may also be a coiled tubing downhole tool and thus be connected to coiled tubing extending from surface and conducting pressurised fluid down to rotate the first tool part 51 while providing fluid into the first chamber parts 11 to force the arms 3 towards their projected positions.

[0057] The use of the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary”, etc., does not imply any particular order, but are included to identify individual elements. Moreover, the use of the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary”, etc., does not denote any order or importance, but rather the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary”, etc., are used to distinguish one element from another. Note that the words “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary”, etc., are used here and elsewhere for labelling purposes only and are not intended to denote any specific spatial or temporal ordering.

[0058] Furthermore, the labelling of a first element does not imply the presence of a second element and vice versa.

[0059] It is to be noted that the word “comprising” does not necessarily exclude the presence of other elements or steps than those listed.

[0060] It is also to be noted that the words “a” or “an” preceding an element do not exclude the presence of a plurality of such elements.

[0061] It should further be noted that any reference signs do not limit the scope of the claims.

[0062] In order to provide weight on bit for drilling or milling a stuck valve in front of the tool, a stroking tool may be used. A stroking tool is a tool providing an axial force. The stroking tool comprises an electric motor for driving a pump. The pump pumps fluid into a piston housing to move a piston acting therein. The piston is arranged on the stroker shaft. The pump may pump fluid out of the piston housing on one side and simultaneously suck fluid in on the other side of the piston.

[0063] By “fluid” or “well fluid” is meant any kind of fluid that may be present in oil or gas wells downhole, such as natural gas, oil, oil mud, crude oil, water, etc. By “gas” is meant any kind of gas composition present in a well, completion or open hole, and by “oil” is meant any kind of oil composition, such as crude oil, an oil-containing fluid, etc. Gas, oil and water fluids may thus all comprise other elements or substances than gas, oil and / or water, respectively.

[0064] By “casing” or “well tubular metal structure” is meant any kind of pipe, tubing, tubular, liner, string, etc., used downhole in relation to oil or natural gas production.

[0065] In the event that the tool is not submergible all the way into the casing, a downhole tractor can be used to push the tool all the way into position in the well. The downhole tractor may have projectable arms having wheels, wherein the wheels contact the inner surface of the casing for propelling the tractor and the tool forward in the casing. A downhole tractor is any kind of driving tool capable of pushing or pulling tools in a well downhole, such as a Well Tractor®.

[0066] Although the invention has been described above in connection with preferred embodiments of the invention, it will be evident to a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.

Claims

1. A downhole tool, comprising: a tool body having a tool axis, andat least three arms movable between a retracted position and a projected position, each arm having a first arm part and a second arm part, where the second arm part is connected with the tool body, and the first arm part is projectable from the tool body,wherein the tool body comprises three actuator assemblies, each actuator assembly comprising a piston chamber and a piston unit, and each piston unit being connected with one of the second arm parts, wherein each piston unit has a longitudinal piston axis that is parallel to the tool axis and is offset in a radial direction from the tool axis.

2. A downhole tool according to claim 1, wherein the piston units are allowed to move individually.

3. A downhole tool according to claim 1, wherein each piston chamber comprises a first hydraulic aperture and a second hydraulic aperture, wherein the first hydraulic apertures of the three piston chambers are fluidly connected, and the second hydraulic apertures of the three piston chambers are fluidly connected.

4. A downhole tool according to claim 1, wherein the piston chamber comprises a first chamber part and a second chamber part, and the first chamber part is fluidly separated from the second chamber part.

5. A downhole tool according to claim 1, wherein the piston unit comprises a piston rod mechanically connected with the second arm part.

6. A downhole tool according to claim 1, wherein each actuator assembly comprises a spring biasing the arm from the projected position to the retracted position.

7. A downhole tool according to claim 1, wherein the first arm part has a terminal end comprising a cutting edge element, the cutting edge element having a cutting insert or an abrasive insert.

8. A downhole tool according to claim 1, wherein each arm has a pivot point connecting the arm with the tool body.

9. A downhole tool according to claim 1, wherein the piston chambers of the actuator assemblies are connected to a common chamber.

10. A downhole tool according to claim 1, wherein the second arm part has an arm engagement face abutting a piston engagement face for transferring a force from the piston unit to move the arm, the piston engagement face being arranged on the piston rod in an area positioned between the tool axis and the piston axis.

11. A downhole tool according to claim 8, wherein the pivot point is arranged at a first distance from the outer face of the tool body, the first distance being less than 20% of a tool body diameter.

12. A downhole tool according to claim 1, wherein the tool body has a pivot section having a hole receiving and engaging a pivot connecting the arm to the tool body, the pivot section being made of a first material having a higher hardness than a second material of the tool body surrounding the pivot section.

13. A downhole tool according to claim 3, wherein the first hydraulic apertures are fluidly connected by a first circular fluid channel, and the second hydraulic apertures are fluidly connected by a second circular fluid channel.

14. A downhole tool according to claim 1, wherein the arm comprises an engagement part having an arm engagement face with a curvature, and the curvature being shaped like the profile of half a tooth of an involute gear, a trochoid gear or a cycloidal gear.

15. A downhole tool according to claim 1, further comprising a motor powered through a wireline connected to the tool and a pump driven by the motor.

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