GB2612995A

GB2612995A - Apparatus, systems and methods for conveying tools and equipment in a wellbore

Info

Publication number: GB2612995A
Application number: GB2116668.1A
Authority: GB
Inventors: Delavarmoghaddam Abbas
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-11-18
Filing date: 2021-11-18
Publication date: 2023-05-24
Anticipated expiration: 2041-11-18
Also published as: GB202116668D0; GB2612995B

Abstract

A first aspect relates to a traction apparatus (10, Fig 1) for conveying tools and equipment in a wellbore (12, Fig 1). The traction apparatus comprises a body; a shaft 16 extending in a longitudinal direction of the body; at least one drive member 44; and a means 16, 46 for converting linear motion of the shaft in a first longitudinal direction into rotation of the at least one drive member. This causes the drive member to apply a traction force to a surface of the wellbore to drive the traction apparatus in a downhole direction of the wellbore. The traction apparatus is configured to be attached to a wellbore conveyance means. Preferably the at least one drive member is a roller or wheel 44. Preferably, there is an anchor means that prevent motion of the traction apparatus and where the anchor means is an anchoring plate with a retracted position and an extended position. A second aspect relates to an assembly comprising the above traction apparatus and a wellbore conveyance means. A third aspect relates to a method of conveying tools and equipment using the above wellbore conveyance means and traction apparatus.

Description

I Apparatus, Systems and Methods for Conveying Tools and Equipment in a Wellbore 3 The present invention relates to apparatus, systems and methods for oil and gas 4 operations, in particular to apparatus, systems and methods for performing intervention operations in a wellbore. More specifically, the present invention relates to apparatus, 6 systems and methods for conveying tools and equipment within a wellbore. The invention 7 has particular application to highly deviated and horizontal wells.

9 Background to the invention

11 In the offshore oil and gas exploration and production industry it is common to drill 12 directional wells. Such wells are known as deviated, highly deviated (where the well 13 inclination exceeds a certain angle for a section of its length) and horizontal wells.

In vertical wells, tools and equipment can be run downhole in a straightforward manner, 16 using gravity to assist with downhole motion. However, in deviated, highly deviated and 17 horizontal wells, tools and equipment often require assistance in moving downhole to 18 prevent them from becoming stuck in the well.

Coiled tubing (CT) can be used to run tools and equipment in deviated, highly deviated 21 and horizontal wells. However, deploying tools and equipment on CT is expensive, time- 22 consuming, and logistically challenging given the amount and scale of the dedicated 23 equipment required. In particular, the requirement for a CT unit to be delivered to an 24 offshore facility and appropriately located to facilitate the deployment of tools and equipment in a wellbore -in an environment where the conditions are harsh and space on 26 the facility is constrained -is inconvenient and disruptive. The use of CT can also require 27 specialist operators and crew.

29 As an alternative to CT, tools and equipment can be deployed into deviated, highly deviated and horizontal wellbores using cables. To stop the tools and equipment from 31 becoming stuck during deployment, devices known as wellbore tractors must be utilised 32 which provide traction, when operated, to convey the cable and the associated tools down 33 the wellbore. Most wellbore tractors are electrically powered, and the cable which is used 34 to run the tractor and the tools and equipment downhole is an electric line (e-line) which supplies the required electrical power to the tractor.

1 Like CT, this method of deployment also has pitfalls: a power supply is required, and 2 electricity is consumed, increasing operational requirements and cost; the e-line must 3 comply with a complex combination of project, capacity, and load requirements; and 4 specialist personnel may be required to operate the e-line and wellbore tractor.

6 Summary of the invention

8 There is generally a need for apparatus, systems and methods for conveying tools and 9 equipment in a wellbore that address one or more deficiencies of current apparatus, systems and methods, and/or provide an alternative solution.

12 There is generally a need for a method and apparatus which addresses one or more of the 13 problems identified above.

It is amongst the aims and objects of the invention to provide apparatus, systems and 16 methods for conveying tools and equipment in a wellbore which do not require electrical or 17 hydraulic power, but which instead utilise mechanical relationships to produce traction.

19 According to a first aspect of the invention there is provided a traction apparatus for conveying tools and equipment in a wellbore, the traction apparatus comprising: 21 a body; 22 a shaft extending in a longitudinal direction of the body; 23 at least one drive member; and 24 a means for converting linear motion of the shaft in a first longitudinal direction of the body into rotation of the at least one drive member, to cause the at least one drive member to 26 apply a traction force to a surface of the wellbore to drive the traction apparatus in a 27 downhole direction of the wellbore; 28 wherein the traction apparatus is configured to be attached to a wellbore conveyance 29 means.

31 The body may be a substantially tubular body.

33 The body may comprise a bore and the shaft may extend through at least part of the bore 34 in the body.

1 Where the body is a substantially tubular body, the shaft may extend through at least a 2 portion of the substantially tubular body.

4 The first longitudinal direction may be a longitudinal direction in line with or parallel to a longitudinal axis of the body.

7 Linear motion of the shaft in a first longitudinal direction of the body may refer to linear 8 motion of the shaft in a first longitudinal direction of the body with respect to the body.

The wellbore may comprise deviated, highly deviated and/or horizontal sections.

12 The shaft of the traction apparatus may be configured to be attached to the wellbore 13 conveyance means.

The wellbore conveyance means may be a wellbore conveyance means selected from the 16 following group: slickline, cable, braided cable, wireline, a workstring, a tubular (including 17 pipes), cable line, coiled tubing (CT), electric line (e-line) or any other suitable a wellbore 18 conveyance means. Preferably, the wellbore conveyance means is a non-electric 19 deployment means. Preferably, the wellbore conveyance means is a flexible (non-rigid) wellbore conveyance means. More preferably, the wellbore conveyance means is slickline.

22 The traction apparatus may be formed by a plurality of modules which may be connected 23 to one another. The substantially tubular body of the traction apparatus may not be 24 continuous, but instead may be formed from an assembly of the plurality of modules, all or some of which may have a substantially tubular body. The shaft may extend through all or 26 some of the modules making up the traction apparatus. All or some of the modules may be 27 interchangeable.

29 The at least one drive member may be a roller or a wheel. The roller or wheel may have an outer surface which is configured to contact the surface of the wellbore to drive the 31 traction apparatus in the wellbore. The outer surface of the roller or wheel may be textured 32 or roughened to increase the friction between it and the surface of the wellbore.

34 The traction apparatus may comprise a plurality of drive members. Where the traction apparatus comprises a plurality of drive members, linear motion of the shaft in a first 1 longitudinal direction of the body may be converted into rotation of the plurality of drive 2 members. Some of the plurality of drive members may rotate in opposite directions to one 3 another and some may rotate in the same direction as one another. For example, where 4 there are two drive members positioned opposite one another with respect to the body, each of the two drive members may rotate in opposite directions (with one rotating in a 6 clockwise direction and the other in an anti-clockwise direction). It will be appreciated that, 7 although rotating in opposite directions, given their arrangement, the rotation of both drive 8 members is suitable for applying a traction force to the surface of the wellbore to drive the 9 traction apparatus in a downhole direction with respect to the wellbore.

11 The traction apparatus may comprise one or more pairs of rollers or wheels which may be 12 coupled together. Each pair of rollers or wheels may be coupled together by a joining 13 shaft, rod or member. The joining shaft, rod or member may form a rotation member (as 14 described below).

16 Linear motion of the shaft in a first longitudinal direction of the body may be converted into 17 rotation of a pair of wheels or rollers in the same direction as one another.

19 The means for converting linear motion of the shaft in a first direction into rotation of the at least one drive member may be located in a traction generation module.

22 The means for converting linear motion of the shaft in a first direction into rotation of the at 23 least one drive member may comprise a mechanical relationship between the shaft and 24 the at least one drive member. The mechanical relationship may require direct contact between the shaft and the at least one drive member. The mechanical relationship may 26 not require direct contact between the shaft and the at least one drive member. Instead, 27 there may be intermediate components located between the shaft and the at least one 28 drive member.

The mechanical relationship may be in the form of a worm and wheel geared arrangement.

31 The shaft may comprise one or more grooves, slots, recesses and/or projections which are 32 configured to engage with one or more corresponding grooves, slots, recesses and/or 33 projections of a rotation member, such that the shaft may be equivalent to the worm of a 34 worm and wheel gear arrangement and rotation member may be equivalent to the wheel in the worm and wheel gear arrangement. A longitudinal axis of the shaft may be 1 substantially perpendicular to a longitudinal axis of the rotation member. The rotation 2 member may be the at least one drive member or it may be a member coupled to the at 3 least one drive member. Where at least one pair of drive members are provided, the 4 rotation member may couple the pair of drive members together such that linear motion of the shaft in a first direction is converted into rotation of the pair of drive members. The 6 shaft may be a slotted shaft which may comprise a plurality of slots in one or more of its 7 surfaces which may or may not be uniformly distributed over the length of the shaft. The 8 rotation member may be a toothed shaft which may comprise a plurality of teeth or 9 projections which may be configured to engage with the plurality of slots of the slotted shaft. A longitudinal axis of the slotted shaft may be substantially perpendicular to a 11 longitudinal axis of the toothed shaft.

13 The mechanical relationship may comprise a geared arrangement.

The mechanical relationship may comprise a slider-crank mechanism or arrangement.

17 The mechanical relationship may comprise a cam mechanism and/or one or more cams.

19 The ability to cause the drive member to rotate as a result of linear motion of the shaft is advantageous, because it means that the traction apparatus is able to function without the 21 use of an external power source (whether electric, hydraulic or otherwise). In addition, it 22 enables the tractor to be used with a flexible (non-rigid) wellbore conveyance means such 23 as slickline or e-line, because the tractor does not require a pushing force to be applied to 24 it (which would require pipe, CT or some other kind of rigid conveyance means). Instead, the transmission of motion and force relies on mechanical relationships between the 26 components of the apparatus.

28 The means for converting linear motion of the shaft in a first direction into rotation of the at 29 least one drive member may only be operable to do so in a single direction. In short, movement of the shaft in one direction may result in rotating the drive member in one 31 direction of rotation, but moving the shaft in another direction may not result in rotation of 32 the drive member. That is, the means for converting linear motion of the shaft in a first 33 direction into rotation of the at least one drive member may only be able to convert linear 34 motion of the shaft in a single direction (the first direction) into a single direction of rotation of the at least one drive member. Linear motion of the shaft in a first direction may be 1 translated into rotation of the at least one drive member in a first direction of rotation, but 2 linear motion of the shaft in a second direction, opposite the first direction, may not be 3 translated into rotation of the at least one drive member in a second direction of rotation, 4 opposite the first direction of rotation.

6 The first longitudinal direction may be a downhole direction with respect to a wellbore and 7 the first direction of rotation may be suitable for applying a traction force to the surface of 8 the wellbore to drive the traction apparatus in a downhole direction with respect to the 9 wellbore.

11 Where the means for converting linear motion of the shaft in a first direction into rotation of 12 the at least one drive member comprises a mechanical relationship in the form of a worm 13 and wheel geared arrangement between a slotted shaft and a rotation member, the 14 rotation member may be coupled to the at least one drive member via a sprag clutch, to enable one-way transmission of motion.

17 Linear motion of the shaft in a first longitudinal direction of the body may be effected by an 18 expanding member moving the shaft. More specifically, linear motion of the shaft in a first 19 longitudinal direction of the body may be caused by the expanding member exerting a force on the shaft to move it in a first direction. The expanding member may be a 21 previously compressed member and it may exert a force on the shaft when it is caused to 22 expand from a compressed state (compressed length) to a natural state (equilibrium 23 length).

The traction apparatus may be configured to compress the expanding member. The 26 traction apparatus may be configured to compress the expanding member as a result of 27 the shaft being moved in a second longitudinal direction of the body.

29 The force required to initially move the shaft in a second longitudinal direction of the body may need to be greater than a threshold force. The shaft may be initially fixed to the 31 traction apparatus -more specifically, to the body of the traction apparatus -by a shear 32 pin, restricting movement in a longitudinal direction of the body. The force required to 33 move the shaft in a second longitudinal direction of the body may need to be greater than 34 the shear strength of the shear pin.

1 The shaft may comprise or may be connected to a projection, end or part which abuts an 2 end or a part of the expanding member such that movement of the shaft (and the 3 projection) in a second longitudinal direction of the body moves the end or a part of the 4 expanding member. The second direction may be a direction opposite the first direction.

The second direction may be an uphole direction with respect to a wellbore. Therefore, 6 linear motion of the shaft in a second, uphole direction in a longitudinal direction of the 7 body may compress the expanding member. The shaft may be configured to be moved in 8 the second direction when an uphole pulling force is applied to it which may be achieved 9 by pulling the wellbore conveyance means (which may be slickline) in an uphole direction or, in other words, tensioning the wellbore conveyance means. The expanding member 11 may be caused to expand from its compressed state (compressed length) to its natural 12 state (equilibrium length) when the uphole pulling force on the shaft is ceased and/or falls 13 below a certain force level. The expanding member and/or the projection on the shaft may 14 be located in a distinct module, which might be a power storage module.

16 The expanding member may be a drive spring. The drive spring may be a coiled spring.

18 The expanding member may be a gas chamber containing a compressible gas. The 19 volume/size of the gas chamber may be reduced when the shaft moves in a second longitudinal direction of the body. When the volume/size of the gas chamber increases it 21 may effect motion of the shaft in a first longitudinal direction of the body.

23 The expanding member may be formed from material, such as compressible foam.

The traction apparatus may comprise an anchor means for preventing motion of the 26 traction apparatus in at least one direction in the wellbore. The anchor means may be 27 located in or on an anchor module. The anchor means may be an anchor apparatus 28 according to a sixth aspect of the invention.

The traction apparatus may comprise a centraliser. The centraliser may be located in or on 31 a centraliser module.

33 According to a second aspect of the invention there is provided an assembly for conveying 34 tools and equipment in a wellbore, the assembly comprising: a wellbore conveyance means; and 1 a traction apparatus for conveying tools and equipment in a wellbore, the traction 2 apparatus comprising: 3 a body; 4 a shaft extending in a longitudinal direction of the body; at least one drive member; and 6 a means for converting linear motion of the shaft in a first longitudinal direction into rotation 7 of the at least one drive member, to cause the at least one drive member to apply a 8 traction force to a surface of the wellbore to drive the traction apparatus in a downhole 9 direction of the wellbore; wherein the traction apparatus is attached to the wellbore conveyance means.

12 The body may be a substantially tubular body.

14 The body may comprise a bore and the shaft may extend through at least part of the bore in the body.

17 Where the body is a substantially tubular body, the shaft may extend through at least a 18 portion of the substantially tubular body.

The first longitudinal direction may be a longitudinal direction in line with or parallel to a 21 longitudinal axis of the body.

23 Linear motion of the shaft in a first longitudinal direction of the body may refer to linear 24 motion of the shaft in a first longitudinal direction of the body with respect to the body.

26 The shaft of the traction apparatus may be configured to be attached to the wellbore 27 conveyance means.

29 The wellbore conveyance means may be a wellbore conveyance means selected from the following group: slickline, cable, braided cable, wireline, a workstring, a tubular (including 31 pipes), cable line, coiled tubing (CT), electric line (e-line) or any other suitable a wellbore 32 conveyance means. Preferably, the wellbore conveyance means is a non-electric 33 deployment means. More preferably, the wellbore conveyance means is slickline.

1 The wellbore conveyance means may support additional tools and/or equipment, including 2 tools and/or equipment for performing intervention operations in the wellbore.

4 The assembly may not require the provision of electric or hydraulic power.

6 The traction apparatus may be a traction apparatus according to a first aspect of the 7 invention.

9 An anchor apparatus according to a sixth aspect of the invention may be supported by the wellbore conveyance means. The anchor apparatus may be part of the traction apparatus.

12 Embodiments of the second aspect of the invention may include one or more features 13 according to the first aspect of the invention, or its embodiments, or vice versa.

According to a third aspect of the invention there is provided a method of conveying tools 16 and equipment in a wellbore, the method comprising: 17 providing a wellbore conveyance means and a traction apparatus for conveying tools and 18 equipment in a wellbore, the traction apparatus comprising: 19 a body; a shaft extending in a longitudinal direction of the body; 21 at least one drive member; and 22 a means for converting linear motion of the shaft in a first longitudinal direction of the body 23 into rotation of the at least one drive member; 24 wherein the traction apparatus is attached to the wellbore conveyance means; using the wellbore conveyance means, locating the traction apparatus in a wellbore; 26 causing the shaft to move in a first longitudinal direction of the body, thereby causing the 27 at least one drive member to rotate to apply a traction force to a surface of the wellbore to 28 drive the traction apparatus and the wellbore conveyance means in a downhole direction 29 of the wellbore.

31 The body may be a substantially tubular body.

The traction apparatus may be attached to the wellbore conveyance means via the shaft 11 (i.e. the shaft of the traction apparatus may be attached to the wellbore conveyance 12 means) 14 The method may comprise applying a pulling force to the wellbore conveyance means from the surface to tension the wellbore conveyance means.

17 The shaft may be initially fixed to the traction apparatus (i.e. unable to move in a 18 longitudinal direction of the body) -more specifically, fixed to the body of the apparatus - 19 by a shear pin, restricting movement in a longitudinal direction of the body. The force required to move the shaft in a second longitudinal direction of the body may be greater 21 than the shear strength of the shear pin.

23 The method may comprise tensioning the wellbore conveyance means to shear the shear 24 pin and release the shaft, such that the shaft is able to move in a longitudinal direction of the body.

27 Continued tensioning of the wellbore conveyance means may cause the shaft to move in a 28 second longitudinal direction.

The first longitudinal direction may be a downhole direction and the second longitudinal 31 means may be an uphole direction.

33 The traction apparatus may comprise an anchor means for preventing motion of the 34 traction apparatus in at least one direction in the wellbore. The anchor means may be located in or on an anchor module. The anchor means may be an anchor apparatus 1 according to a sixth aspect of the invention. The method may comprise operating the 2 anchor means according to a seventh aspect of the invention.

4 The method may comprise using the anchor means to prevent the tractor apparatus from travelling in an uphole direction in the wellbore.

7 The method may comprise actuating the anchor means (i.e. causing an anchoring plate of 8 the anchoring apparatus to move into an extended position in which it contacts an inner 9 surface of the wellbore to prevent motion of the anchor apparatus in at least one direction in the wellbore) prior to causing the at least one drive member to rotate apply a traction 11 force to a surface of the wellbore to drive the traction apparatus and the wellbore 12 conveyance means in the wellbore.

14 Tensioning the wellbore conveyance means -which as described may cause the shaft to move in a second longitudinal direction -may cause the anchor apparatus to be actuated.

16 The method may comprise tensioning the wellbore conveyance means to actuate the 17 anchor apparatus. Following actuation of the anchor apparatus, continued tensioning of 18 the wellbore conveyance means may not result in uphole motion of the tractor apparatus.

Tensioning the wellbore conveyance means -which as described may cause the shaft to 21 move in a second longitudinal direction -may also cause an expanding member in the 22 traction apparatus to be compressed from an equilibrium length to a compressed length.

24 The method may comprise continuing to tension the wellbore conveyance means to compress the expanding member from a natural state (equilibrium length) to a 26 compressed state (compressed length). The expanding member may be a drive spring 27 and linear motion of the shaft in a first longitudinal direction of the body may be a result of 28 the drive spring moving the shaft.

The method may comprise releasing the tension applied to the wellbore conveyance 31 means to cause the shaft to move in the first longitudinal direction of the body. Movement 32 of the shaft in the first longitudinal direction may be a result of the expanding member 33 moving from its compressed state (compressed length) to its natural state (equilibrium 34 length) as a result of releasing the wellbore conveyance means. The expanding member 1 may act on / exert a force on the shaft to move it in the first longitudinal direction of the 2 body as it moves from its compressed length to its equilibrium length.

4 The means for converting linear motion of the shaft in a first longitudinal direction of the body into rotation of the at least one drive member may comprise a mechanical 6 relationship between the shaft and the at least one drive member such that movement of 7 the shaft in a first longitudinal direction of the body causes rotation of the at least one drive 8 member.

The method may comprise releasing the tension applied to the wellbore conveyance 11 means to cause the at least one drive member to rotate to apply a traction force to a 12 surface of the wellbore to drive the traction apparatus and the wellbore conveyance means 13 in a downhole direction of the wellbore After use of the traction apparatus, the method may comprise tensioning the wellbore 16 conveyance means to deactivate the anchor apparatus (i.e. causing an anchoring plate of 17 the anchoring apparatus to move into a retracted position in which it is substantially 18 retracted to the body). This may be done following use of the traction apparatus and/or use 19 of the tools and/or equipment in the wellbore. This may be done following an intervention operation. This may be done prior to (and to allow) the traction apparatus and the tools 21 and equipment to be pulled out of (i.e. removed from) the wellbore.

23 The method may include some or all of the steps or features according to the fifth and/or 24 sixth aspects of the invention.

26 Embodiments of the third aspect of the invention may include one or more features 27 according to the first or second aspects of the invention, or their embodiments, or vice 28 versa.

According to a fourth aspect of the invention there is provided a traction apparatus for 31 conveying tools and equipment in a wellbore, the traction apparatus comprising: 32 a body; 33 a shaft extending in a longitudinal direction of the body; 34 at least one drive member; 1 a means for converting linear motion of the shaft in a first longitudinal direction into rotation 2 of the at least one drive member, to cause the at least one drive member to apply a 3 traction force to a surface of the wellbore to drive the traction apparatus in a downhole 4 direction of the wellbore; and an anchor means for preventing motion of the traction apparatus in at least one direction in 6 the wellbore; 7 wherein the traction apparatus is configured to be attached to a wellbore conveyance 8 means.

The body may be a substantially tubular body.

12 The body may comprise a bore and the shaft may extend through at least part of the bore 13 in the body.

Where the body is a substantially tubular body, the shaft may extend through at least a 16 portion of the substantially tubular body.

18 The first longitudinal direction may be a longitudinal direction in line with or parallel to a 19 longitudinal axis of the body.

21 Linear motion of the shaft in a first longitudinal direction of the body may refer to linear 22 motion of the shaft in a first longitudinal direction of the body with respect to the body.

24 The anchor means may be configured to prevent motion of the traction apparatus in an uphole direction of the wellbore. The anchor means may permit motion of the traction 26 apparatus in a downhole direction of the wellbore.

28 Embodiments of the fourth aspect of the invention may include one or more features 29 according to the first to third aspects of the invention, or their embodiments, or vice versa.

31 According to a fifth aspect of the invention there is provided a method of conveying tools 32 and equipment in a wellbore, the method comprising: 33 providing a wellbore conveyance means and a traction apparatus for conveying tools and 34 equipment in a wellbore, the traction apparatus comprising: a body; 1 a shaft extending in a longitudinal direction of the body; 2 at least one drive member; 3 a means for converting linear motion of the shaft in a first longitudinal direction of the body 4 into rotation of the at least one drive member; and an anchor means; 6 wherein the traction apparatus is attached to the wellbore conveyance means; 7 using the wellbore conveyance means, locating the traction apparatus in a wellbore; 8 actuating the anchor means to prevent motion of the traction apparatus in an uphole 9 direction of the wellbore; causing the shaft to move in a first longitudinal direction of the body, thereby causing the 11 at least one drive member to rotate apply a traction force to a surface of the wellbore to 12 drive the traction apparatus and the wellbore conveyance means in a downhole direction 13 of the wellbore.

The body may be a substantially tubular body.

17 The body may comprise a bore and the shaft may extend through at least part of the bore 18 in the body.

Where the body is a substantially tubular body, the shaft may extend through at least a 21 portion of the substantially tubular body.

23 The shaft of the traction apparatus may be configured to be attached to the wellbore 24 conveyance means.

26 The first longitudinal direction may be a longitudinal direction in line with or parallel to a 27 longitudinal axis of the body.

29 Linear motion of the shaft in a first longitudinal direction of the body may refer to linear motion of the shaft in a first longitudinal direction of the body with respect to the body.

32 Prior to causing the shaft to move in a first longitudinal direction of the body, the method 33 may comprise causing the shaft to move in a second longitudinal of the body. Movement 34 of the shaft in the second longitudinal of the body may actuate the anchor means.

1 The method may include some or all of the steps or features according to the third and/or 2 sixth aspects of the invention.

4 Embodiments of the fifth aspect of the invention may include one or more features according to the first to fourth aspects of the invention, or their embodiments, or vice 6 versa.

8 According to a sixth aspect of the invention there is provided an anchor apparatus for 9 preventing motion of tools and/or equipment in at least one direction in a wellbore, the anchor apparatus comprising: 11 a body; 12 a shaft extending in a longitudinal direction of the body; 13 an anchoring plate attached to the body having a first, retracted position in which it is 14 substantially retracted to the body and a second, extended position in which it is extended outwardly from the body and configured to contact an inner surface of a wellbore to 16 prevent motion of the anchor apparatus in at least one longitudinal direction in the 17 wellbore; 18 an outward biasing means biasing the anchoring plate towards the second, extended 19 position; and a retaining means operable to retain the anchoring plate in its first, retracted position, 21 against a force of the outward biasing means, the retaining means being operable to 22 release the anchoring plate as a result of linear motion of the shaft in a longitudinal 23 direction of the body.

The anchor apparatus may be configured to be attached to a wellbore conveyance means.

26 In particular, the shaft of the traction apparatus may be configured to be attached to the 27 wellbore conveyance means.

29 The body may be a substantially tubular body.

31 The body may comprise a bore and the shaft may extend through at least part of the bore 32 in the body.

34 Where the body is a substantially tubular body, the shaft may extend through at least a portion of the substantially tubular body.

1 Linear motion of the shaft in a longitudinal direction of the body may refer to linear motion 2 of the shaft in a longitudinal direction of the body with respect to the body.

4 The retaining means may be operable to release the anchoring plate as a result of linear motion of the shaft in a second longitudinal direction of the body, where the second 6 longitudinal direction may be an uphole direction with respect to a wellbore. When the 7 retaining means releases the anchoring plate the anchor apparatus is actuated.

9 The anchor apparatus may be located in an anchoring module which may be assembled with other functional modules to integrate the anchoring apparatus into a larger functional 11 tool.

13 The shaft may not be unique to the anchor apparatus. Instead, it may additionally extend 14 through or into other modules or apparatus.

16 The anchoring plate may be located in a groove or a slot in the tubular body.

18 An outer surface of the anchoring plate may be configured to contact an inner surface of a 19 wellbore to prevent motion of the anchor apparatus in at least one direction in the wellbore.

The outer surface of the anchoring plate may be textured or roughened, to increase the 21 friction between it and a surface of the wellbore, in use. The outer surface of the anchoring 22 plate may be curved.

24 When the anchoring plate is in its retracted position, the curved outer surface of the anchoring plate may be substantially continuous with the outer surface of the tubular body.

27 The retaining means may comprise a first member which may engage with a second 28 member. The first member may be located on the shaft. The first member may be 29 removably and/or temporarily connected to the shaft. The first member may be held against the shaft when the retaining means retains the anchoring plate in its first, retracted 31 position and may no longer be held against the shaft when the shaft undergoes linear 32 motion in a longitudinal direction of the body to release the anchoring plate. The first 33 member may be held against the shaft and/or temporarily coupled to the shaft by a 34 bushing. The second member may be located on a surface of the anchoring plate. The second member may be located on the underside of the anchoring plate (i.e. on the 1 surface which faces a bore of the substantially tubular body). The first member may be a 2 hook. The second member may be a pin. The hook on the shaft may engage with the pin 3 on the surface of the anchoring plate in a first position of the shaft. Linear motion of the 4 shaft in a longitudinal direction of the body may cause the hook to release the pin, thereby releasing the anchoring plate and allowing it to move from its first, retracted position into its 6 second, extended position under the influence of the outward biasing means. Tensioning 7 the wellbore conveyance means -which as described may cause the shaft to move in a 8 second longitudinal direction (which may be an uphole direction) -may cause the retaining 9 means to release the anchoring plate and actuate the anchor apparatus.

11 The outward biasing means may comprise one or more springs. The one or more springs 12 may be one or more wireframe springs.

14 The anchor apparatus may further comprise an inward biasing means. The inward biasing means may bias the anchoring plate towards the first, retracted position. The inward 16 biasing means may comprise one or more springs. The one or more springs may be one 17 or more wireframe springs.

19 The outward biasing means may be stronger than the inward biasing means. Where the outward and inward biasing means each comprise one or more springs, the overall spring 21 constant of the one or more outward biasing springs may be greater than the overall spring 22 constant of the one or more inward biasing springs.

24 The anchoring plate may be attached to the body by one or more pivoting arms. The one or more pivoting arms may comprise one or more pairs of pivoting arms. Preferably, the 26 anchoring plate is attached to the body by two pairs of pivoting arms. The two pairs of 27 pivoting arms may comprise a first pair and a second pair. The outward biasing means 28 may be located in or on or integrated into the first pair of pivoting arms. The inward biasing 29 means may be located in or on or integrated into the second pair of pivoting arms.

31 The anchoring plate may be substantially parallel to a longitudinal axis of the body at all 32 times: that is, in its first, retracted and second, extended positions. The pivoting arms may 33 hold the anchoring plate substantially parallel to a longitudinal axis of the body at all times.

1 Embodiments of the sixth aspect of the invention may include one or more features 2 according to the first to fifth aspects of the invention, or their embodiments, or vice versa.

4 According to a seventh aspect of the invention there is provided a method of preventing motion of an anchor apparatus in at least one direction in a wellbore, the method 6 comprising: 7 providing a wellbore conveyance means and an anchor apparatus, the anchor apparatus 8 comprising: 9 a body; a shaft extending in a longitudinal direction of the body 11 an anchoring plate attached to the body having a first, retracted position in which it is 12 substantially retracted to the main body and a second, extended position in which it is 13 extended outwardly from the main body; 14 an outward biasing means biasing the anchoring plate towards the second, extended position; and 16 a retaining means retaining the anchoring plate in its first, retracted position, against a 17 force of the outward biasing means; 18 wherein the anchor apparatus is attached to the wellbore conveyance means 19 using the wellbore conveyance means, locating the anchor apparatus in a wellbore; causing the shaft to move in a longitudinal direction of the body, thereby causing the 21 retaining means to release the anchoring plate such that the anchoring plate moves into its 22 second, expanded position in which it contacts an inner surface of the wellbore to prevent 23 motion of the anchor apparatus in at least one direction in the wellbore.

The body may be a substantially tubular body.

27 The body may comprise a bore and the shaft may extend through at least part of the bore 28 in the body.

Where the body is a substantially tubular body, the shaft may extend through at least a 31 portion of the substantially tubular body.

33 The shaft of the anchor apparatus may be attached to the wellbore conveyance means.

4 The retaining means being operable to release the anchoring plate as a result of linear motion of the shaft in a longitudinal direction of the body, where the longitudinal direction 6 may be an uphole direction with respect to a wellbore. When the retaining means releases 7 the anchoring plate the anchor apparatus is actuated.

9 The anchoring apparatus may prevent motion of the anchor apparatus in an uphole direction in the wellbore.

12 The method may comprise applying a pulling force to the wellbore conveyance means 13 from the surface to tension the wellbore conveyance means.

The method may comprise using an anchor apparatus to prevent movement in an uphole 16 direction in the wellbore.

18 Tensioning the wellbore conveyance means -which as described may cause the shaft to 19 move in a second longitudinal direction -may cause the anchor apparatus to be actuated.

The method may comprise tensioning the wellbore conveyance means to cause the 21 retaining means to release the anchoring plate and actuate the anchor apparatus.

23 The method may comprise tensioning the wellbore conveyance means to deactivate the 24 anchor apparatus (i.e. causing an anchoring plate of the anchoring apparatus to move into a retracted position in which it is substantially retracted to the body). This may be done 26 following use of the anchor apparatus and/or use of associated or linked tools and/or 27 equipment in the wellbore. This may be done following an intervention operation. This may 28 be done prior to (and to allow) the anchor apparatus and the associated or linked tools and 29 equipment to be pulled out of (i.e. removed from) the wellbore.

31 The method may include some or all of the steps or features according to the third and/or 32 fifth aspects of the invention.

34 Embodiments of the seventh aspect of the invention may include one or more features according to the first to sixth aspects of the invention, or their embodiments, or vice versa.

1 According to an eighth aspect of the invention there is provided a traction apparatus for 2 conveying tools and equipment in a wellbore, the traction apparatus comprising: 3 a body; 4 a shaft extending in a longitudinal direction of the body; and at least one drive member; 6 wherein a mechanical relationship exists between the shaft and the at least one drive 7 member which converts linear motion of the shaft in a first longitudinal direction of the 8 body into rotation of the at least one drive member, such that the at least one drive 9 member applies a traction force to a surface of the wellbore to drive the traction apparatus in a downhole direction of the wellbore; 11 wherein the traction apparatus is configured to be attached to a wellbore conveyance 12 means.

14 Embodiments of the eighth aspect of the invention may include one or more features according to the first to seventh aspects of the invention, or their embodiments, or vice 16 versa.

18 Brief description of the drawings

There will now be described, by way of example only, various embodiments of the 21 invention with reference to the drawings, of which: 23 Figure 1 is a perspective view of a wellbore tractor according to an embodiment of the 24 invention, in a wellbore; 26 Figures 2A and 2B are perspective view of a power storage module of the wellbore tractor 27 of Figure 1; 29 Figure 3 is a side view of a traction generation module of the wellbore tractor of Figure 1; 31 Figure 4A is a perspective view of an anchor module of the wellbore tractor of Figure 1, in 32 a retracted position; 34 Figure 4B is a side view of the anchor module of the wellbore tractor of Figure 1, in a retracted position; Figure 4C is a perspective view of the anchor module of the wellbore tractor of Figure 1, in 2 an extended position; 4 Figures 4D and 4E are schematic side views of the opening and closing springs of the anchor module of the wellbore tractor of Figure 1; 7 Figures 4F and 40 are detailed perspective views of a part of the anchor module of the 8 wellbore tractor of Figure 1, in retracted and extended positions, respectively; Figures 5A to 5F are perspective views of a wellbore tractor in operation; and 12 Figured 50 to 51 are side views of the wellbore tractor of Figures 5A to 5F in operation.

14 Detailed description of preferred embodiments

16 The terms "upper", "lower", "above", "below", "up" and "down" are used herein to indicate 17 relative positions in the wellbore. The invention also has applications in wells that are 18 deviated or horizontal, and when these terms are applied to such wells they may indicate 19 "let, "right" or other relative positions in the context of the orientation of the well. Similarly, the terms "uphole and "downhole" are used herein to indicate relative directions in a 21 wellbore, including deviated or horizontal wellbores, with "uphole" being taken to mean in a 22 direction towards the wellbore opening and "downhole" being taken to mean in a direction 23 away from the wellbore opening (in other words, deeper or further into the wellbore).

24 Uphole and downhole are generally opposite directions.

26 Although the term wellbore is used throughout the following description, with no reference 27 to linings, casings or internal tubular structures within the wellbore, it will be appreciated 28 that the downhole tractor can be used in wellbores which generally include wellbore 29 tubulars, such as in cased and/or lined wellbores, either partially or entirely.

31 Referring firstly to Figure 1 there is shown, generally at 10, a downhole tractor according to 32 an embodiment of the invention. For illustrative purposes, the tractor 10 is shown within a 33 horizontal section of a wellbore 12. The orientation of the wellbore 12 -together with 34 gravity -causes the tractor 10 and the other slickline, tools and equipment (not shown) to sit eccentrically within the wellbore 12. The arrow A indicates an uphole direction, towards 1 the top (or start) of the wellbore and the arrow B indicates a downhole direction, towards 2 the bottom (or end) of the wellbore. Although not shown, the tractor has been run into the 3 wellbore using slickline. The purpose of the tractor is to convey tools and equipment (also 4 not shown) which are similarly run on the slickline downhole in the wellbore, to perform tasks, such as intervention operations. Typically, the tractor is located on the slickline, 6 above (or uphole) of the tools and equipment to be moved, such that operation of the 7 tractor pushes the tools and equipment downhole in the wellbore.

9 A key feature of the tractor of the present invention is its ability to provide the traction required to draw or pull itself and the slickline assembly in a downhole direction without the 11 use of an electrical power source, or any other kind of energy source used by alternative 12 tractors (such as hydraulics). Instead, the tractor utilises mechanical relationships to 13 convert linear force/motion into rotation, to produce the tractional forces required to drive 14 the tractor (and the associated equipment and tools) in the wellbore. The ability to function without the use of electrics or hydraulics means that the tractor can be run on simple 16 slickline; electric cables, such as e-line are not required. This not only reduces the 17 logistical strain and complexity of an intervention operation, but also the equipment 18 required, the cost (because the cost of slickline use is significantly lower than e-line and 19 slickline is more readily available) and the crew and specialists required for set-up and operation. Slickline is not a rigid conveyance means (like pipe). Instead, it is flexible and 21 therefore cannot generally be used to push items (such as tools and equipment) down a 22 wellbore or similarly to apply compression. Not only does the wellbore tractor disclosed 23 herein not require the use of an electrical or hydraulic power source, it is also able to be 24 operated with a flexible conveyance means (such as slickline) without the need for a push force to be applied to it.

27 The tractor 10 comprises a number of interconnected modules, including: a power storage 28 module 20 (shown as transparent in Figure 1 for clarity), a primary traction generation 29 module 40, a back-up traction generation module 40', an anchor module 60 and a centraliser module 90. Each module is described in more detail below. A slotted shaft 16 31 (shown in the power storage module 20) extends through at least the back-up traction 32 generation module 40', the power storage module 20, the primary traction generation 33 module 40, and the anchor module 60. The centraliser module 90 is provided on the 34 downhole end of the tractor and comprises freely movable wheels. The centraliser module 90 prevents the anchor module -and generally the bottom end of the tractor -from 1 contacting the inner wall of the wellbore and reduces friction between the tractor and the 2 wellbore wall.

4 Referring now to Figures 2A and 2B, the power storage module 20 is shown in more detail.

The power storage module 20 comprises a tubular housing 22 and a spring 24 located 6 within the housing 22. As previously described, the slotted shaft 16 extends through the 7 power storage module 20. The slotted shaft 16 has slots (or other recess types) on its 8 surfaces which are configured to cooperate with other components of the tractor 10 during 9 its operation. In the embodiment shown, the shaft 16 has a substantially square cross section and comprises cylindrical slots in each of its four surfaces, which are not 11 continuous along its entire length and instead provided only in the areas where they are 12 required. It will be appreciated that the exact form and arrangement of the shaft can vary in 13 alternative embodiments of the invention.

Rigidly coupled to the slotted shaft 16, within the power storage module 20, there is a 16 spring header block 26. The spring header block 26 acts on the spring 24 to compress it 17 when the shaft is moved in an uphole direction (arrow A). With particular reference to 13 Figure 2B, it can be seen that the spring header block 26 is rigidly connected to the 19 housing 22 of the power storage module 20 by a shear pin 28. Whilst intact, the shear pin 28 therefore prohibits the shaft 16 and consequently the spring header module 26 from 21 being moved in an axial direction of the tractor. Only when an uphole pulling force large 22 enough to overcome the shear strength of the shear pin 28 is applied, will the shaft 16 be 23 able to move in an uphole direction to compress the spring 24.

Figure 3 shows the traction generation module 40 in more detail. The module 40 26 comprises a tubular housing 42 (shown as partially transparent, for clarity) with four pairs 27 of drive wheels 44a, 44b, 44c and 44d located in respective apertures in the wall of the 28 housing 42. The pairs of drive wheels 44a, 44b, 44c and 44d are arranged in such a way 29 that they provide contact surfaces (for contact with a wall of the wellbore) offset at 90 degrees to one another around the longitudinal axis of the tractor to ensure that the tractor 31 can present at least one pair of contact wheels to a surface of the wellbore, regardless of 32 its orientation within the well. Two of the pairs 44a and 44d comprise wheels which are 33 arranged in planes perpendicular to the planes of the wheels of the other two pairs 44b 34 and 44c. All of the wheels have a roughened outer surface 45 to maximise the friction between the tractor and the walls of the wellbore, improving traction.

1 Each pair of wheels 44a, 44b, 44c and 44d comprises two wheels connected by a toothed 2 shaft 46a, 46b, 46c and 46d. Each toothed shaft 46a, 46b, 46c and 46d comprises teeth or 3 projections which engage with slots in the slotted shaft 16, causing the toothed shafts 46a, 4 46b, 46c and 46d to rotate when the slotted shaft is moved in the axial direction of the tractor, in either an uphole or a downhole direction. The slotted shaft 16 and the toothed 6 shafts 46a, 46b, 46c and 46d form a worm and wheel gear arrangement. The relationship 7 between the slotted shaft 16 and the toothed shafts 46a, 46b, 46c and 46d converts linear 8 motion of the slotted shaft 16 into rotation of the pairs of wheels 44a, 44b, 44c and 44d.

With reference to a single pair of wheels for clarity -pair 44a -it can be seen that the 11 toothed shaft 46a is connected at either end to each wheel via a sprag clutch 50a and 12 50a': a device which only engages with the wheels to transmit motion in a single direction 13 of rotation. Each sprag clutch comprises an inner race and an outer race. In this 14 embodiment of the invention, the inner race is the input member. In one direction of rotation, the inner race engages the outer race to drive the outer race and rotate it in the 16 same direction. In the opposite direction of rotation, the inner race does not engage the 17 outer race and instead is able to freely rotate with respect to the outer race, exhibiting no 18 drive force on the outer race.

Each end of the toothed shaft 46a is attached to the respective inner race of sprag 21 clutches 50a and 50a' to provide an input force. The outer races of the sprag clutches 50a 22 and 50a' are attached to each of the wheels to provide an output force. When the slotted 23 shaft 16 is pushed in a downhole direction, it causes the toothed shaft 46a, and 24 consequently the inner races of the sprag clutches 50a and 50a' to rotate in a first direction. In this direction, the inner races engage with the outer races to rotate the pair of 26 wheels 44a, producing traction to drive the tools and equipment in a downhole direction.

27 When the slotted shaft 16 is moved in an opposite direction (uphole), the toothed shaft 28 46a, and consequently the inner races of the sprag clutches 50a and 50a' are caused to 29 rotate in a second direction. In the second direction, the inner races do not engage with the outer races; instead, they are able to rotate freely with respect to the outer races, and 31 no rotation is applied to the wheels. Each pair of wheels 44b, 44c and 44d operates in the 32 same way. In summary, the sprag clutches allow the wheels to convey the tractor in a 33 downhole direction only when the slotted shaft 16 is moved downhole, but when the 34 slotted shaft 16 is moved in an uphole direction, the wheels of the traction generation module 40 are not driven.

1 In this embodiment of the invention, the back-up traction generation module 40' is identical 2 to the traction generation module 40 shown in Figure 3 and operates in the same way.

3 However, in alternative embodiments the arrangement of the back-up traction generation 4 module can differ or, alternatively, it can be omitted altogether. In further alternative tractor configurations, more than one back-up traction generation module can be provided. The 6 main purpose of the back-up traction generation module is to provide the required traction 7 for moving the tractor if the wheels of the main traction generation module 40 fail to 8 sufficiently contact the inner wall of the wellbore or which otherwise become stuck, 9 damaged or defective.

11 Referring now to Figures 4A to 40, the anchor module 60 and its components are shown 12 in more detail. With reference to Figure 4A, the anchor module 60 generally comprises a 13 substantially tubular body 62 and an anchor plate 66 having a curved outer surface 14 positioned in a cut-out of the body 62 such that, in the retracted position shown in Figure 4A, the curved outer surface of the anchor plate 66 is substantially continuous with the 16 outer surface of the tubular body 62. In an extended position, shown and described below, 17 the anchor plate 66 is moved radially outwards from the body 62 to contact the inner 18 surface of the wellbore, anchoring the tractor in place and preventing it from moving in an 19 uphole direction. The anchor plate 66 has a textured, roughened outer surface to increase the friction, and therefore the grip, between it and the wellbore when the anchor is 21 extended. Due to the nature of the arrangement of the anchor plate and the pivoting arms 22 which attach it to the body (which will be described in more detail below), the anchor is a 23 one-way anchor, in that it prevents motion in one direction but allows motion in the other.

24 Namely, the anchor module prevents motion in an uphole direction but allows motion in a downhole direction. This is because the pivoting arms do not cause the anchor plate to 26 engage with the wellbore wall when the anchor module moves in a downhole direction 27 (when the tractor operates), because the pivoting arms are inclined with respect to the 28 longitudinal axis of the tool in the direction of movement (i.e. downhole) by an angle 29 greater than 90 degrees. This arrangement allows the anchor to permit downhole movement, even when the anchor is in an extended position. Conversely, when an uphole 31 force is applied to the anchor module, the pivoting arms tend to rigidly lock (or lock out) to 32 resist uphole motion.

34 Opposite the cut out which accommodates the anchor plate 66, the tubular body 62 of the anchor module comprises a weighted section 64. The weighted section 64 causes gravity 1 to orient the anchor module in such a way that the weighted section 64 is substantially 2 below the anchor plate 66 when the tractor 10 is located in a deviated or horizontal 3 wellbore. This allows the anchor plate 66 to more freely open when actuated, because it 4 not restricted by -and therefore does not have to push against -the body 62 of the anchor module 60. Swivel joints (not shown) between the anchor module and the other tractor 6 modules -the traction generation module and the centraliser module -allow the anchor 7 module to rotate with respect to the other modules, such that the weighted section 64 of 8 the anchor module does not cause the entire tractor (and other interconnected tools and 9 equipment) to reorient in the wellbore.

11 The slotted shaft 16 continues to extend through the anchor module 60. A pin 72-shown 12 in more detail in Figure 4B -is provided on the underside of the anchor plate 66.

13 Releasably located on the shaft 16 within the anchor module 60 is a hook 68. The hook 68 14 comprises a portion (not shown) which is slidably placed in a slot of the slotted shaft 16. A bushing 70 fixed inside the body 62 of the anchor module surrounds an elongate potion of 16 the hook 68-including the portion which is located in a slot of the slotted shaft 16-when 17 the anchor plate 66 is held in the retracted position and the hook 68 is engaged with the 18 pin 72 in a locked position, to hold the hook 68 against the shaft 16 and prevent the hook 19 68 from being pulled radially outward by the anchor plate.

21 Whilst the hook 68 engages the pin 72, as shown in Figure 4B, the anchor plate 66 is 22 unable to move from the retracted position as shown into an extended position. The pin 23 72, hook 68 and bushing 70 together form a retaining mechanism that locks the anchor 24 module 60 in a retracted position. The retaining mechanism is required because, as will be explained below, the anchor plate is naturally urged into its extended position.

27 By virtue of the releasable connection between the hook 68 and the shaft 16, movement of 28 the shaft 16 in an uphole direction, indicated by arrow A, results in similar uphole 29 movement of the hook, thereby releasing the pin 72 from the hook 68 and causing the anchor plate 66 to be moved into an extended position. As a consequence of no longer 31 being held against the shaft 16 by the stationary busing 70 after being moved in an uphole 32 direction, the hook 68 is able to freely detach from the shaft 16.

34 Figure 4C shows the anchor module 60 in an extended position, in which the anchor plate 66 is positioned radially outwardly from the body 62. In this Figure, additional details of the 1 anchor module are shown (however, the slotted shaft 16 has been omitted for clarity). In 2 particular, it can be seen that the anchor plate 66 is coupled to the body 62 by two pairs of 3 spring biased, pivoting arms 74 and 76. The first pair 74 are opening arms, which help to 4 move the anchor plate 66 into an extended position and the second pair 76 are closing arms, which help to move the anchor plate 66 into the retracted position, described in 6 more detail below with reference to Figures 4D, 4E, 4F and 4G.

8 Each pair of arms 74 and 76 is pivotally connected at one end to the body 62 by a pin 78.

9 At this end, the ends of the arms 74 and 76 are located in grooves cut in the body 62 (not shown). At the other end, the arms within in each pair 74 and 76 are located in grooves cut 11 in the underside of the anchor plate 66 and are connected to each other by a pin 80. A rod 12 82 extends between the two pins 80, rigidly connecting them together, to make sure that 13 both pairs of arms 74 and 76 move together when moving the anchor plate 66 between the 14 retracted position and an extended position. By linking their movement, the rod 82 also ensures that the two pairs of arms 74 and 76 hold the anchor plate 66 parallel to the body 16 62 of the anchor module 60 at all times. Finally, two elongated plates 84 are rigidly 17 connected at each of their ends to the underside of the anchor plate 66, to slidably couple 18 the rod 82 to the anchor plate 66.

Figures 4D and 4E show, schematically, the springs which are provided for each of the 21 pairs of arms 74 and 76, respectively, for biasing the anchor plate 66 towards the 22 extended and retracted positions. The springs are shown in their natural (equilibrium) 23 states, before they have been assembled into the anchor module. The spring 86 shown in 24 Figure 4D is the opening spring which is provide for the first pair of arms 74, the opening arms. The spring 86 is generally U-shaped and comprises a first pair of legs 86a and a 26 second pair of legs 86b, joined at one end by a straight portion 87. The spring shown in 27 Figure 4E is the closing spring -two of which are provided for the second pair of arms 76, 28 the closing arms. The spring 88 is generally U-shaped and comprises a single first leg 88a 29 and a single second leg 88b.

31 The biasing force provided by the opening spring 86 for the pair of opening legs 74 is 32 greater than the biasing force provided by the two closing springs 88 for the pair of closing 33 legs 76.

1 Figure 4F shows the springs 86 and 88 in more detail, when the anchor plate is in its 2 retracted position. The body and the anchor plate have been omitted for clarity, with only 3 the shaft 16, the first and second pairs of arms 74, 76 and their corresponding joining 4 components being shown. Each leg of the first pair of legs 86a of the first spring 86 is located in a grove in one of the arms of the pair of opening arms 74. The straight portion 6 87 joining the second pair of legs 86b abuts the slotted shaft 16. Two springs 88 are 7 provided for the pair of closing arms 76, the first leg 88a of each spring being located in a 8 groove in one of the arms 76. The second legs 88b of the springs 88 abut a pin 89 which is 9 fixed inside the anchor module body 62 (not shown).

11 The anchor plate is held into the retracted position, as shown, by virtue of the retaining 12 mechanism described above with particular reference to Figure 4B. In this position, the 13 pairs of legs 86a and 86b of the opening spring are pulled apart. When the retaining 14 mechanism is released (i.e. when the slotted shaft 16 is moved in an uphole direction such that the hook 68 releases the pin 72 on the underside of the anchor plate 66) the legs 86a 16 and 86b of the opening spring 86 are no longer pulled apart to the same extent and are 17 able to spring towards one another, urging the anchor plate 66 into an extended position, 18 as seen in Figure 40. In an extended position, the legs 88a and 88b of each of the closing 19 springs 88 are pulled apart by virtue of the anchor plate's movement. However, the combined biasing forces of the closing springs 88 cannot overcome the biasing force of 21 the opening spring 86 and thus the anchor plate remains extended at this stage.

23 Operation of the tractor 10 will now be described with reference to Figures 5A to 51. The 24 slickline and other tools and equipment have been omitted from these Figures for clarity. In use, when the slickline (supporting tools and/or equipment, including the tractor) enters a 26 deviated or horizontal section of the well and is unable to continue effective downhole 27 movement using gravity alone, the downhole tractor can be employed to provide the 28 necessary traction to continue moving the slickline, tools and equipment downhole. Before 29 it is actuated, the tractor is inactive and presents a substantially smooth, cylindrical outer profile to the wellbore, with the exception of the wheels of the traction generation module 31 40, the back-up traction generation module 40', and the centraliser module 90.

32 As described above, the tractor (on the slickline) continues to travel downhole under its 33 own weight until the friction between the tractor and the wellbore wall prevents it from 34 freely travelling any further. The tractor 10 is actuated in a number of steps.

1 To begin actuation, the shear pin which rigidly connects the spring header block to the 2 housing 22 of the power storage module, and therefore restricts movement of the slotted 3 shaft in an axial direction of the tractor, must be broken. To shear the pin, a sharp uphole 4 pulling force is applied to the slotted shaft 16, as shown in Figure 5A. This is achieved by tensioning the slickline (not shown), causing the pin 28 to shear and detaching the spring 6 header block 26 and the slotted shaft 16 from the tractor housing in the power storage 7 module 20, as shown in Figure 5B. The slotted shaft 16 can now move freely in an axial 8 direction of the tractor.

With reference now to Figure 5C, it can be seen that initial uphole movement of the slotted 11 shaft 16 causes the retaining mechanism of the anchor module 60 to release the anchor 12 plate 66 by moving the hook 68 in an uphole direction to disengage the pin 72. The anchor 13 plate 66 moves radially outward to engage the inner wall of the wellbore and prevent 14 uphole movement of the tractor, as shown in Figure 5D, whilst the uphole pulling force applied to the slotted shaft 16 indicated by arrow A continues.

17 With the anchor preventing uphole movement of the tractor, continued uphole motion of 18 the slotted shaft 16 causes the spring header block 26 to also move in an uphole direction 19 and compress the spring 24, as shown in Figures 5E and 5F. Compressing the spring 24 stores the energy required to produce the traction for moving the tractor downhole, when 21 the spring is later released. The spring 24 has a high spring constant. In this example, the 22 spring constant is greater than 500 N/m.

24 Finally, to transmit the stored energy and power to the traction generation module 40, the tension / pulling force on the slotted shaft 16 is ceased, and the shaft 16 is released. No 26 longer held in compression, the spring in the power storage module moves back into its 27 normal state, pushing the spring header block and, consequently, the slotted shaft 16 in 28 the downhole direction indicated by the arrow B in Figures 50 and 5H. With reference to a 29 single pair of wheels only, as the slotted shaft 16 moves downhole, the toothed shaft 46a coupling the wheels in pair 44a is rotated, by virtue of its teeth engaging with the slots in 31 the shaft 16. The rotating toothed shaft 46a rotates the inner race of the sprag clutches 32 50a and 50a, which engage with the outer races to rotate them and consequently rotate 33 each of the wheels. As such, in the traction generation module 40 the linear motion of the 34 slotted shaft 16 is converted into rotation of the wheels. Each pair of wheels in the traction generation module 40 functions in the same way. In this example, the pair 44b are in 1 contact with the inner bore of the wellbore and move the tractor in a downhole direction 2 whilst they rotate.

4 When it is desirable to pull the slickline out of the wellbore (for example, after an intervention operation has concluded), the anchor mechanism of the tractor must be 6 collapsed to allow the tractor and the rest of the slickline, tools and equipment to be moved 7 in an uphole direction. To do this, a pulling force is once again applied to the slotted shaft 8 16 to move it in an uphole direction, as indicated by the arrow A in Figure 51. When the 9 lowermost end 16a of the shaft 16 moves away from the opening spring 86 the, the second pair of legs 86b and the straight portion 87 of the spring 86 no longer abut the 11 shaft 16 and there is no longer any force or obstacle holding the legs 86a and 86b of the 12 spring 86 apart. With the spring 86 released in this way, the legs 86a and 86b move 13 towards one another, causing the opening pivot arms 74 to move freely. As a 14 consequence of the opening spring 86 moving in this way, each of the closing springs are similarly moved, to retract the anchor plate. The first legs 88a of the closing springs 88 are 16 permitted to move towards the second legs 88b of the closing springs 88, fixed in place by 17 the pin 89. This causes the closing pivot arms 76 to rotate. Rotation of the arms 74 and 76, 18 effected by the closing springs 88 (as the slotted shaft 16 is moved in an uphole direction 19 in this phase) results in the anchor plate 66 moving to its retracted position.

21 The wellbore tractor described in the foregoing description is beneficial because it 22 facilitates the conveyance of well intervention tools through horizontal or highly deviated 23 sections of the well, where gravitational forces are not sufficient to pull the tool forward, 24 without requiring the use of electrical or hydraulic power sources to function.

Consequently, the tractor can be deployed using a non-electric deployment means -such 26 as slickline -which is operationally less demanding and complex to utilise when compared 27 with conventional electric lines (i.e. e-line), cheaper, more readily available and requires 28 less auxiliary equipment, components and connections. At the surface, operators are able 29 to operate the tractor disclosed herein by simply applying a pulling force to the slickline, to tension the line and initiate the tractors operation.

32 It will be appreciated that although the tractor described above comprises an anchor 33 module, the type and configuration of the anchor module used may vary and is not limited 34 to the type and configuration expressly described. The tractor may be provided without an anchor module, for example where a stand-alone anchor module (not integrated into the 1 tractor) is provided in addition to the tractor. The anchor module described can be 2 provided as a stand-alone module or integrated into alternative downhole tools and/or 3 equipment.

Throughout the foregoing description, the tractor is described as being used to provide 6 traction for travelling in a downhole direction of a well (that is, further into a wellbore); 7 however, it will be appreciated that the tractor technology may be employed in alternative 8 scenarios and applications to provide traction for travelling in alternative directions.

The invention provides a traction apparatus, assembly and method for conveying tools and 11 equipment in a wellbore. The traction apparatus is configured to be attached to a wellbore 12 conveyance means. It comprises a body, a shaft extending in a longitudinal direction of the 13 body and at least one drive member. The traction apparatus further comprises a means for 14 converting linear motion of the shaft in a first longitudinal direction of the body into rotation of the at least one drive member. Rotation of the at least one drive member causes it to 16 apply a traction force to a surface of the wellbore to drive the traction apparatus in a 17 downhole direction of the wellbore.

19 Various modifications to the above-described embodiments may be made within the scope of the invention, and the invention extends to combinations of features other than those 21 expressly claimed herein.

Claims

1 Claims: 3 1. A traction apparatus for conveying tools and equipment in a wellbore, the traction 4 apparatus comprising: a body; 6 a shaft extending in a longitudinal direction of the body; 7 at least one drive member; and 8 a means for converting linear motion of the shaft in a first longitudinal direction of the 9 body into rotation of the at least one drive member, to cause the at least one drive member to apply a traction force to a surface of the wellbore to drive the traction 11 apparatus in a downhole direction of the wellbore; 12 wherein the traction apparatus is configured to be attached to a wellbore conveyance 13 means.

2. The traction apparatus according to claim 1, wherein the body is a substantially 16 tubular body and the shaft extends through at least a portion of the substantially 17 tubular body.19

3. The traction apparatus according to claim 1 or claim 2, wherein the traction apparatus is configured to be attached to the wellbore conveyance means via the 21 shaft.23

4. The traction apparatus according to any of claims 1 to 3, wherein the at least one 24 drive member is a roller or a wheel which has an outer surface configured to contact the surface of the wellbore to drive the traction apparatus in a downhole direction of 26 the wellbore.28

5. The traction apparatus according to any preceding claim, wherein the means for 29 converting linear motion of the shaft in the first longitudinal direction of the body into rotation of the at least one drive member comprises a mechanical relationship 31 between the shaft and the at least one drive member.33

6. The traction apparatus according to claim 5, wherein the mechanical relationship is 34 in the form of a worm and wheel geared arrangement.1

7 The traction apparatus according to claim 6, wherein the shaft comprises one or 2 more grooves, slots, recesses and/or projections which are configured to engage 3 with one or more corresponding grooves, slots, recesses and/or projections of a 4 rotation member, such that the shaft is equivalent to a worm of the worm and wheel gear arrangement and rotation member is equivalent to a wheel of the worm and 6 wheel gear arrangement, and wherein the rotation member is the at least one drive 7 member or is coupled to the at least one drive member.9

8. The traction apparatus according to claim 7, wherein the traction apparatus comprises a plurality of drive members arranged in drive member pairs, wherein 11 each of the drive members in a drive member pair are coupled together by the 12 rotation member such that linear motion of the shaft in the first longitudinal direction 13 of the body is converted into rotation of each of the plurality of drive members 14 arranged in drive member pairs.16

9. The traction apparatus according to claim 7 or claim 8, wherein the shaft is a slotted 17 shaft comprising a plurality of slots and the rotation member is a toothed shaft 18 comprising a plurality of teeth configured to engage with the plurality of slots of the 19 slotted shaft, and wherein a longitudinal axis of the slotted shaft is substantially perpendicular to a longitudinal axis of the toothed shaft such that linear motion of the 21 slotted shaft in a longitudinal direction effects rotation of the rotation member.23

10 The traction apparatus according to any preceding claim, wherein the means for 24 converting linear motion of the shaft in the first longitudinal direction of the body into rotation of the at least one drive member is only operable to do so in a single 26 direction, such linear motion of the shaft in the first longitudinal direction of the body 27 is translated into rotation of the at least one drive member in a first direction of 28 rotation and linear motion of the shaft in a second longitudinal direction of the body, 29 opposite the first longitudinal direction of the body, is not translated into rotation of the at least one drive member in a second direction of rotation, opposite the first 31 direction of rotation.33

11 The traction apparatus according to any preceding claim, further comprising an 34 expanding member configured to effect the linear motion of the shaft in the first longitudinal direction of the body by exerting a force on the shaft when it expands 36 from a compressed length to an equilibrium length.2

12. The traction apparatus according to claim 11, wherein the shaft or a component 3 coupled to the shaft is configured to contact the expanding member to compress the 4 expanding member from its equilibrium length to its compressed length when the shaft is moved in a second longitudinal direction of the body.7

13. The traction apparatus according to any preceding claim, further comprising an 8 anchor means for preventing motion of the traction apparatus in an uphole direction 9 of a wellbore.11

14. The traction apparatus according to claim 13, wherein the anchor means comprises: 12 an anchoring plate attached to the body having a first, retracted position in which it is 13 substantially retracted to the body and a second, extended position in which it is 14 extended outwardly from the body and configured to contact an inner surface of the wellbore to prevent motion of the traction apparatus in at least one longitudinal 16 direction in the wellbore; 17 an outward biasing means biasing the anchoring plate towards the second, extended 18 position; and 19 a retaining means operable to retain the anchoring plate in its first, retracted position, against a force of the outward biasing means, the retaining means being operable to 21 release the anchoring plate as a result of linear motion of the shaft in a second 22 longitudinal direction of the body.24

15. An assembly for conveying tools and equipment in a wellbore, the assembly comprising: 26 a wellbore conveyance means; and 27 a traction apparatus for conveying tools and equipment in a wellbore, the traction 28 apparatus comprising: 29 a body; a shaft extending in a longitudinal direction of the body; 31 at least one drive member; and 32 a means for converting linear motion of the shaft in a first longitudinal direction into 33 rotation of the at least one drive member, to cause the at least one drive member to 34 apply a traction force to a surface of the wellbore to drive the traction apparatus in a downhole direction of the wellbore; 1 wherein the traction apparatus is attached to the wellbore conveyance means.3

16. The assembly according to claim 15, wherein the wellbore conveyance means is 4 slickline or braided cable.6

17. A method of conveying tools and equipment in a wellbore, the method comprising: 7 providing a wellbore conveyance means and a traction apparatus for conveying tools 8 and equipment in a wellbore, the traction apparatus comprising: 9 a body; a shaft extending in a longitudinal direction of the body; 11 at least one drive member; and 12 a means for converting linear motion of the shaft in a first longitudinal 13 direction of the body into rotation of the at least one drive member; 14 wherein the traction apparatus is attached to the wellbore conveyance means; using the wellbore conveyance means, locating the traction apparatus in a wellbore; 16 causing the shaft to move in a first longitudinal direction of the body, thereby causing 17 the at least one drive member to rotate to apply a traction force to a surface of the 18 wellbore to drive the traction apparatus and the wellbore conveyance means in a 19 downhole direction of the wellbore.21

18. The method according to claim 17, wherein the first longitudinal direction of the body 22 is a downhole direction with respect to the wellbore and wherein a second 23 longitudinal direction of the body is an uphole direction with respect to the wellbore.

19. The method according to claim 17 or 18, wherein the traction apparatus is attached 26 to the wellbore conveyance means via the shaft such that linear motion of the shaft 27 in a longitudinal direction of the body can be effected by applying a force to the 28 wellbore conveyance means, and wherein the method comprises tensioning the 29 wellbore conveyance means to cause the shaft to move in a second longitudinal direction of the body.32

20. The method according to any of claims 17 to 19, wherein the shaft is initially fixed to 33 the body of the traction apparatus by a shear pin, such that its motion in a 34 longitudinal direction of the body is restricted, and wherein the method comprises tensioning the wellbore conveyance means to exert a force on the shaft sufficient to shear the shear pin and release the shaft to permit it to move in a longitudinal 2 direction of the body.4

21. The method according to any of claims 17 to 19, wherein the traction apparatus comprises an anchor means for preventing motion of the traction apparatus in an 6 uphole direction of the wellbore, and wherein the method comprises actuating the 7 anchor means prior to causing the at least one drive member to rotate by tensioning 8 the wellbore conveyance means to cause the shaft to move in a second longitudinal 9 direction of the body.11

22. The method according to any of claims 17 to 21, wherein the traction apparatus 12 comprises an expanding member configured to effect the linear motion of the shaft in 13 the first longitudinal direction of the body by exerting a force on the shaft when it 14 expands from a compressed length to an equilibrium length, and wherein the shaft or a component coupled to the shaft is configured to contact the expanding member to 16 compress the expanding member from the equilibrium length to the compressed 17 length when the shaft is moved in a second longitudinal direction of the body.

23. The method according to claim 22, comprising tensioning the wellbore conveyance 21 means to cause the shaft to move in a second longitudinal direction of the body to 22 compress the expanding member from the equilibrium length to the compressed 23 length.26

24. The method according to claim 23, comprising releasing the tension on the wellbore 27 conveyance means to allow the expanding member to expand from the compressed 28 length to the equilibrium length to exert a force on the shaft and move it in the first 29 longitudinal direction of the body, thereby causing the at least one drive member to rotate and apply a traction force to a surface of the wellbore to drive the traction 31 apparatus and the wellbore conveyance means in a downhole direction of the 32 wellbore.34

25. The method according to any of claims 22 to 24, when dependent upon claim 21, comprising tensioning the wellbore conveyance means to cause the shaft to move in 36 a second longitudinal direction of the body to deactivate the anchor apparatus.