GB2430020A

GB2430020A - Wellbore traction apparatus

Info

Publication number: GB2430020A
Application number: GB0617528A
Authority: GB
Inventors: Graeme Mcnay
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-09-13
Filing date: 2006-09-05
Publication date: 2007-03-14
Anticipated expiration: 2026-09-05
Also published as: GB0617528D0; GB2430020B; GB2430020C

Abstract

A wellbore traction apparatus 20 comprises traction elements, preferably wheels 14, for engagement with a wellbore wall 16, and drive means, preferably a motor 25. The apparatus 20 is selectably operable in a free-rolling mode in which the wheels 14 are configured to move freely of the motor 25; and a driven mode, in which operation of the motor 25 moves the apparatus 20 in relation to the wellbore. The apparatus is particularly suitable for deploying a tool string in a wellbore. The motor 25 may be coupled and decoupled with the wheels 14 via a clutch mechanism. The apparatus 20 preferably includes at least one magnet 18 to maintain contact of the wheels 14 with the (metallic) wellbore wall 16. The motor 25 may be engaged with the wheels 14 when there is insufficient gravitational force for the apparatus 20 to freely roll down the wellbore.

Description

1 We].lbore traction apparatus 3 The present invention relates to weilbore

traction 4 apparatus, and, in particular, to traction apparatus for assisting in the deployment of downhole tools in the oil 6 and gas industry.

8 In the oil and gas industry, deviated weilbores are 9 commonly drilled through the sub-surface. These deviated weilbores typically have high angles relative to the 11 surface near the top of the weilbore (around 900) and 12 shallow angles (for example around 10 ) toward the bottom 13 of the welibore.

Before production from the well, it is usual to conduct a 16 variety of downhole operations, such as logging the 17 physical piioperties of the weilbore. In order to conduct 18 such operations, different downhole tools are typically 19 deployed. These tools are often deployed in a string of tools for conducting a range of different measurements.

22 Such a tool string may for example be introduced to the 23 weilbore from the surface on a wireline or slickline, or 1 attached to coiled tubing. The operations are typically 2 carried out in a welibore that is cased or lined with a 3 metal tubular.

Such a tool string may be deployed from the surface under 6 the force of gravity. As the tool string progresses 7 through the weilbore toward the deployment locality, 8 frictional forces acting on the tool string will increase 9 as the well becomes increasingly deviated at depth.

11 In this situation, existing methods make use of a roller 12 device attached to the tool string. Such a roller device 13 includes a set of free rolling wheels that provide 14 discrete contact points with the weilbore wall and provide standoff of the tool string from the side of the 16 weilbore. This helps to reduce the friction acting on 17 the string and allows the deployment to progress more 18 efficiently.

As the deployment continues further, there typically 21 comes a point at which the tool string is prevented from 22 progressing further into the well where gravitational 23 components are no longer sufficient in the deployment 24 direction to overcome frictional forces (even when acting on roller wheels) due to contact with the welibore wall.

27 In order to deploy the tool string in the highly deviated 28 portion of the well, at shallow angles, it is typical to 29 use a rnotorised tractor tool to pull the tool string through the weilbore to the deployment locality. Such 31 tractors typically generate increased traction at the 32 weilbore wall in order to grip the wall and move the tool 33 string along.

1 There are a nuither of problems with existing methods.

2 High rental, installation and operational costs are 3 associated with using such tractors. In addition, where 4 deployment slows unexpectedly, and no tractor is pre- installed on the string, there may additionally be 6 significant operational downtime in sourcing and 7 installing a suitable tractor device.

9 It undesirable to use or even risk having to use separate roller and tractor devices/systems in deploying a tool 11 string. It is inconvenient and costly to install both 12 types of tool for a deployment operation, and to spend 13 time assessing the risk and need for using tractor and/or 14 roller systems for a particular deployment.

16 The tractors are often fitted with protruding mechanical 17 arms that actuate to exert force against the inner 18 surface of the welibore for generating traction. The 19 protruding mechanical arms are susceptible to damage and malfunctioning in use in a downhole environment.

22 Such arms are typically actuated by hydraulic fluid 23 supplied from the surface, and thus present tractor 24 systems may rely on a hydraulic fluid supply provided at the surface. It is often inconvenient and costly to 26 provide such a supply.

28 In addition, present tractor systems have demanding power 29 requirements, and rely on supply of power from the surface. Topside power and hydraulic equipment takes up 31 valuable work space and takes time to install.

1 Also, present tractor systems are limited to use with 2 tool strings deployed on a wirelirie or coiled tubing, and 3 are not suitable for use on slicklines.

It is an aim of the present invention to provide a 6 welibore traction device that obviates or at least 7 mitigates some of the drawbacks and deficiencies of the 8 existing techniques.

Other aims and objects of the invention will become

11 apparent from the description below.

13 According to a first aspect of the invention, there is 14 provided a weilbore traction apparatus for use in the deployment of a tool string in a welibore, the weilbore 16 traction apparatus comprising: 17 - drive means; 18 - traction means adapted to be driven by the drive 19 means; at least one magnet; 21 wherein the at least one magnet is arranged to bias the 22 traction means into frictional contact with a wall of the 23 weilbore.

Preferably, the weilbore traction apparatus comprises a 26 main body adapted to receive the at least one magnet.

27 More preferably, the at least one magnet is 28 interchangeably received in the main body. The at least 29 one magnet may be detachably received in the main body.

31 The main body may comprise at least one recess adapted to 32 receive the at least one magnet. The main body may 33 comprise a retaining element configured to keep the at 1 least one magnet in place in the main body. The main 2 body may comprise an access element providing a point of 3 access to the at least one magnet for locating and/or 4 removing the at least one magnet. The access element may comprise a hinged door.

7 Preferably, the apparatus comprises a longitudinal axis 8 in the direction of deployment of the apparatus in the 9 welibore. More preferably, the at least one magnet is a magnet polarised along an axis substantially normal to 11 the longitunial axis of the apparatus. The at least one 12 magnet may be a tabular magnet.

14 The at least one magnet may comprise a rare earth magnet.

The at least one magnet may have a characteristic 16 magnetic field property. The characteristic magnetic 17 field property may comprise one or more of the following:

18 - field strength

19 - magnetic flux - polarity 22 The apparatus may be adapted to operate in a first 23 operational mode with the drive means decoupled from the 24 engagement means.

26 In this first mode, when the drive means are decoupled, 27 the engagement means are free to respond passively and 28 independently of the drive means. At steep welibore 29 angles, in the first mode, the apparatus acts substantially as a roller device for friction reduction.

32 Preferably, the apparatus is adapted to operate in a 33 second operational mode with the drive means activated to 1 drive the engagement means. The apparatus may be adapted 2 to control operation in the second operational mode 3 according to a property of the weilbore. The apparatus 4 may comprise at least one sensor operable to measure the property of the weilbore. The property of the weilbore 6 may comprise any number of the following: 7 - temperature 8 - pressure 9 - angle of inclination 11 More preferably, the apparatus is selectably operable in 12 the first or second operational modes. The apparatus may 13 comprise control unit operable to selectively control 14 operation in the first or second modes. The control unit may be programmed to control operation according to at 16 least one pre-determined condition.

18 The drive means may comprise a motor. Further, the drive 19 means may comprise a gearbox system operable to couple the motor to the engagement means for driving the 21 engagement means. Alternatively or in addition, the 22 drive means may comprise a clutch mechanism. The drive 23 means may be adapted to drive the engagement means in a 24 forward direction. The drive means may be further adapted to drive the engagement means in a reverse 26 direction.

28 The engagement means may comprise a wheel. Alternatively 29 or in addition, the engagement means may comprise a track. The at least one magnet may be received in the 31 wheels. The track may comprise the at least one magnet.

1 Preferably, the apparatus is adapted to self-orientate in 2 the weilbore. The apparatus may comprise a surface for 3 orienting the apparatus in the weilbore. The surface may 4 be formed to initiate rotation of the apparatus from a non-operational position into an operational position in 6 which the apparatus and the wall of the welibore 7 experience an attractional force. The surface may 8 comprise a profiled surface for initiating rotation of 9 the apparatus.

11 According to a second aspect of the invention, there is 12 provided a method of deploying a downhole string in a 13 weilbore, the method comprising the steps of: 14 - attaching a weilbore traction apparatus to a string, the weilbore traction apparatus comprising a drive 16 means and a traction means; 17 - inserting the tool string in the welibore; and 18 magnetically biasing the welibore traction apparatus 19 toward a wall of the weilbore.

21 Preferably, the step of magnetically biasing the weilbore 22 traction apparatus comprises the step of biasing the 23 traction means into frictional contact with the wall of 24 the welibore.

26 The step of magnetically biasing the traction means may 27 include the step of producing an attractional magnetic 28 force between the apparatus and the wall of the weilbore.

The step of magnetically biasing the apparatus may 31 include the step of using at least one magnet to attract 32 the apparatus toward the weilbore wall.

1 The step of magnetically biasing the apparatus may 2 include the step of locating the at least one magnet on a 3 body of the apparatus to attract the apparatus toward the 4 welibore wall.

6 The weilbore traction apparatus may be a weilbore 7 traction apparatus according to the first aspect of the 8 invention.

The method may comprise the step of running the welibore 11 traction apparatus in a free-rolling mode with the 12 traction means freely decoupled from the drive means; 14 The method may comprise the further step of selectably driving the traction means in a driven mode to move the 16 string through the wellbore using the drive means.

18 The method may comprise the step of determining the 19 timing of driving the traction means.

21 The method may comprise the further step of selecting the 22 at least one magnet according to a traction required to 23 drive the apparatus through the weilbore; Preferably the method includes the step of calculating 26 the traction required.

28 According to a third aspect of the invention, there is 29 provided a welibore traction apparatus for use in deployment of a tool string in a welibore, the welibore 31 traction apparatus comprising: 1 - traction means configured for engagement with a wall 2 of the welibore such that movement of the traction means 3 moves the apparatus along the welibore; 4 - drive means operable to drive the traction means; wherein 6 the apparatus is selectably operable in: a free-rolling 7 mode, in which the traction means is configured to move 8 freely of the drive means; and a driven mode, in which 9 operation of the drive means causes movement of the apparatus along the weilbore.

12 In the free-rolling mode the traction means may be 13 decoupled from the drive means, and in the driven mode, 14 the drive means may be coupled to the traction means.

The drive means may be coupled to the traction means to 16 drive the apparatus along the welibore.

18 Preferably, the apparatus comprises at least one magnet 19 arranged to bias the traction means into frictional contact with the wall of the weilbore. The at least one 21 magnet may be interchangeably received by the apparatus.

22 The wellbore wall may comprise metallic material.

24 Preferably, the apparatus is configured to operate in the free-rolling mode in regions of the welibore in which 26 gravitational force acting on the apparatus is sufficient 27 to move the apparatus in the direction of deployment.

29 Preferably, the apparatus is configured to operate in the driven mode in regions of the welibore in which 31 gravitational force acting on the apparatus is 32 insufficient to move the apparatus in the direction of 33 deployment.

2 In addition, the apparatus may be configured to operate 3 in the driven mode in regions of the welibore in which 4 gravitational force acting on the apparatus is S insufficient to move the apparatus in the direction of 6 deployment above a pre-determined threshold value. The 7 threshold value may be a speed.

9 The apparatus may be configured to operate in the driven mode according to a property of the weilbore.

12 The property of the welibore may comprise one or more of: 13 - welibore temperature; 14 - weilbore pressure; - angle of the weilbore.

17 Alternatively, or in addition, the apparatus may operate 18 in the driven according to a property of deployment of 19 the apparatus.

21 The property of deployment may comprise one or more of: 22 - a deployment speed; 23 - a capacity of the drive means; 24 - a time period.

26 The apparatus may be adapted to operate in the free 27 rolling or driven mode in response to a received signal.

28 The signal is received according to a property of 29 deployment, property of the wellbore, and/or progress of deployment.

32 The apparatus may be adapted to be run on a slickline.

33 Alternatively, or in addition, the welibore traction 1 apparatus may be adapted to be run on a wireline and/or 2 coiled tubing.

4 The apparatus may comprise a downhole power source.

6 The apparatus may comprise control unit operable to 7 selectively control operation in the free-rolling or 8 driven modes. The control unit may be programmed to 9 control operation according to a property of the welibore. The control unit may be programmed to control 11 operation according to a property of the deployment.

13 The drive means may comprise a motor. Further, the drive 14 means may comprise a gearbox system operable to couple the motor to the engagement means for driving the 16 engagement means. Alternatively or in addition, the 17 drive means may comprise a clutch mechanism. The drive 18 means may be adapted to drive the engagement means in a 19 forward direction. The drive means may be further adapted to drive the engagement means in a reverse 21 direction.

23 The gearbox system may be adapted to provide a gearbox 24 ratio for driving the apparatus, in the driven mode, at a torque and/or speed for facilitating in the deployment of 26 the tool string.

28 The engagement means may comprise wheels. Alternatively, 29 or in addition, the engagement means may comprise a track. The at least one magnet may be received in the 31 wheels. The track may comprise the at least one magnet.

1 According to a fourth aspect of the invention, there is 2 provided a method of deploying a string in a weilbore, 3 the metho comprising the steps of: 4 - locating a string in the weilbore, the string comprising a welibore traction apparatus comprising 6 traction means, and drive means operable to drive the 7 traction means; and 8 - selecting between operation of the apparatus in a free- 9 rolling mode, in which the traction means is configured to move freely of the drive means, and a 11 driven mode, in which the apparatus operates to move 12 the traction means along the weilbore.

14 The step of driving the traction means may comprise the step of coupling the drive means to the traction means.

16 The step of driving the traction means may comprise the 17 step of powering the drive means.

19 The string may comprise a plurality of weilbore traction apparatus'. The welibore traction apparatus may be an 21 apparatus in accordance with the first and third aspects 22 of the invention. The apparatus may be connected to the 23 tooi.string via a sucker rod or QLS connection.

The method may comprise the step of driving the apparatus 26 in the driven mode to optimise the duration of deployment 27 of the string.

29 The method may include the step of measuring a property of the deployment. The step of measuring a property of 31 the deployment may include measuring speed of the string 32 moving through the welibore. The step of measuring a 33 property of the deployment may include measuring angle of 1 inclination of the welibore traction apparatus.

2 Alternatively or in addition, the method may include the 3 step of measuring a property of the welibore. The step 4 of measuring a property of the welibore may comprise measuring pressure of the welibore. Alternatively or in 6 addition, the step of measuring a property of the 7 welibore may include measuring temperature of the 8 welibore.

The method may comprise the step of producing a signal 11 for providing to the drive means according to the 12 measured property.

14 Preferably, the method comprises the step of running the welibore traction apparatus in a free-rolling mode for 16 frictional contact of the traction means with the 17 weilbore wall.

19 The method may comprise the step of selecting to operate the weilbore traction apparatus in the driven or free- 21 rolling modes.

23 The method may comprise the step of switching between the 24 driven mode and the free-rolling mode.

26 The method may include the further step of controlling 27 operation of the welibore traction apparatus in the 28 driven or free-rolling modes.

The method may include the step of controlling operation 31 of the apparatus in the free-rolling or driven modes 32 according to a measured property.

1 The method may include the step of determining the timing 2 of driving the traction means in the driven mode.

4 Preferably, the method includes the step of magnetically biasing the traction means into frictional contact with a 6 wall of the welibore.

8 Preferably, the step of magnetically biasing the traction 9 means includes the step of producing an attractional magnetic force between the apparatus and the wall of the 11 welibore.

13 The method may comprise the step of inserting a magnet 14 into the welibore traction apparatus to produce an attractional magnetic force biasing the weilbore traction 16 apparatus toward the wall of the weilbore.

18 The method may include the step of calculating a required 19 traction.

21 The step of producing an attractional magnetic force may 22 comprise the step of selecting at least one magnet 23 according to the traction required.

According to a fifth aspect of the invention, there is 26 provided a method of deploying a string in a welibore, 27 the method comprising the steps of: 28 - locating a string in the weilbore, the string 29 comprising a welibore traction apparatus comprising a drive means and a traction means configured to be 31 in frictional contact with a wall of the weilbore; 32 - selectably running the wellbore traction apparatus 33 in a free-rolling mode for providing low-friction 1 stand-off of the string from the welibore wall, and 2 in a driven mode, wherein the drive means are 3 coupled to the traction means for driving the string 4 through the weilbore.

6 Preferably, the method may comprise the step of switching 7 between the free-rolling mode and the driven mode.

9 According to a sixth aspect of the invention, there is provided a weilbore traction apparatus for use in 11 deployment of a tool string in a welibore, the weilbore 12 traction apparatus comprising: 23 - drive means for driving the traction means; 14 - traction means for frictional contact with a wall of the welibore; 16 wherein 1? the apparatus is selectably operable in a free rolling 18 mode, wherein the drive means is decoupled from the 19 traction means, and in a driven mode, wherein the drive means is coupled to drive the traction means.

22 According to a seventh aspect of the invention, there is 23 provided a method of deploying a string in a welibore, 24 the method comprising the steps of: - locating a string in the weilbore, the string 26 comprising a welibore traction apparatus comprising 27 a drive means and a traction means configured to be 28 in frictional contact with a wall of the weilbore; 29 - providing a signal to the drive means; and - driving the traction means in a driven mode in 31 response to the signal received by the drive means.

1 There will now be described by way of example only, 2 embodiments of the invention with reference to the 3 following drawings, of which: Figure 1 is a cross-sectional line representation of 6 a wellbore traction device according to an embodiment 7 of the invention; 9 Figure 2 is a schematic cross-sectional line representation of a weilbore traction device 11 according to a further embodiment of the invention; 13 Figure 3A is a bottom view of a welibore traction 14 device according to a further embodiment of the invention; 17 Figure 33 is a side view of the traction device of 18 Figure 3A; Figure 3C is a top view representation of a welibore 21 traction device according to the embodiment of Figure 22 3A; 24 Figure 4 is a schematic line representation of welibore traction device according to a further 26 embodiment of the invention; 28 Figure 5 is a schematic representation of a drive 29 component for a welibore traction device in accordance with an embodiment of the invention; 32 Figure 6A is a schematic drawing of the welibore 33 traction apparatus of Figure 2 incorporated in 1 toolstring during deployment in an upper section of a 2 deviated welbore, according to an embodiment of the 3 invention; and Figure 6B is a schematic drawing of the welibore 6 traction apparatus of Figure 2 incorporated in 7 toolstring during deployment in a lower section of a 8 deviated welbore, according to the embodiment of 9 Figure 6A.

11 With reference firstly to Figure 1, there is generally 12 shown at numeral 10 a welibore traction apparatus 13 comprising a body 12 and wheels 14 located on a wall 16 14 of a welibore 15. The body 12 further comprises magnets 18 received by the body 12. The magnets 18 are located 16 toward a side of the body 12 and are oriented to produce 17 a high density magnetic field in the welibore 15 and in a 18 region between the body 12 and the welibore wall 16. The 19 weilbore wall 16 is formed from a magnetic material and experiences an attractional force due to the magnetic 21 field causing the traction device to be drawn toward the 22 weilbore wall 16.

24 The magnets function to force the wheels 14 into contact with the wall 16. The wheels exert a force against the 26 pipe wall at the contact point due to the magnetic 27 attraction. This increases the frictional force 28 experienced by the wheels in contact with the welibore 29 wall 16. Strong magnetic fields and attractional forces provide a strong corresponding frictional force exerted 31 on the wheels.

1 In a deviated welibore, a component of gravitational 2 force may also act on the body of the apparatus in the 3 travel direction through the welibore. This force may 4 assist in the movement of the device through the welibore at the same time as the magnets 18 keep the wheels 14 in 6 contact with the welibore wall.

8 This apparatus 10 is generally configured for attachment 9 to a tool string for deployment in a welibore.

11 With reference to Figure 2, a welibore traction apparatus 12 20 comprises a main body 12 with wheels 14 located at 13 first and second ends of the body 12 according to a 14 further embodiment of the invention.

16 A number of magnets 18 are attached to the main body 12 17 for producing an attractional force for drawing the 18 device toward the wall of a weilbore 16 as described 19 above.

21 In this embodiment, the welibore traction apparatus 20 22 also comprises an auxiliary body 22 physically connected 23 to the main body 12. The auxiliary body 22 houses a 24 power supply 24 for powering a motor 25 and a programmable electronics unit 27 also housed in the 26 auxiliary body 22.

28 The motor 25 can function to drive the wheels 14. The 29 frictional force acting on the wheels provides traction for the wheels 14 to grip the surface when being driven 31 by the motor. Thus, magnets 18 providing increased 32 frictional force against the welibore wall enhances 1 traction available for the motor to drive the wheels in 2 order to push a tool string through a welibore.

4 The motor 25 can be switched on or off by breaking the power circuit supplying the motor 25 from the power 6 supply 24.

8 In the "on" position, the motor 25 can couple to the 9 wheels to drive and turn them. The motor couples via a gearbox system. The gearbox system acts to provide a 11 gearbox ratio that is optimised for torque and speed of 12 deployment. The optimum ratio is set according to the 13 number of magnets and/or level of attraction generated by 14 the magnets. The gearbox coupling allows the wheels to be turned clockwise or anticlockwise direction allowing 16 two-way motion of the device through a welibore. Thus, 17 the wellbore traction device 20 can therefore function to 18 pull or push welibore tools connected to the device into 19 or out of the welibore.

21 In embodiments of the invention, the motor may couple to 22 the wheels via a spring-loaded clutch mechanism, which 23 allows operation of the apparatus with the wheels free 24 rolling against the weilbore wall and operation with the motor coupled to drive the wheels.

27 Also in the "on" position, it is possible to decouple the 28 wheels 14 from the motor 25 allowing the wheels to rotate 29 freely. Decoupling of the motor in the on position may be controlled by the programmable electronics unit 27.

32 In the "off" position, the motor 25 may similarly be 33 decoupled from the wheels 14 as controlled by the 1 programmable electronics unit 27. When decoupled, the 2 motor 25 is not able to engage to drive the wheels 14 and 3 the wheels are free to rotate or spin.

When the wheels are decoupled from the motor 25, the 6 wheels are free to rotate and the weilbore traction 7 device 20 functions passively as a roller device in the 8 welibore. This is useful at particular locations, for 9 example, in upper sections of the weilbore where the wheels provide a low/minimal friction against steep 11 weilbore sides. In these locations, gravity is the 12 dominant force acting to move the apparatus through the 13 welibore.

In lower sections of the weilbore, the motor 25 can 16 couple to the wheels to actively drive the apparatus 17 through the welibore using the added wheel traction 18 available due to force produced the magnets 18.

The welibore traction device 20 includes a male and 21 female connector 26A, 26B for incorporation into a tool 22 string. The connectors 26A, 26B are threaded connectors 23 for engaging with complimentary connection sections on 24 adjacent sections.

26 Programmable electronics unit 27 in the auxiliary body 12 27 is used in controlling the motor. In embodiments of the 28 invention, the programmable unit 27 can be programmed to 29 switch the motor 25 on or off and couple or de-couple the motor to the wheels 14.

32 The programmable electronics unit 27 controls the motor 33 according a measured state of the weilbore environment or 1 other criteria. For example, the apparatus 20 may be 2 fitted with sensors to measure well pressure or 3 temperature data or inclination angle of the apparatus, 4 and the programmable electronics unit 27 uses the measurements to determine when to switch on the motor and 6 when to couple or decouple the motor to the wheels.

8 In alternative embodiments, the motor can be triggered to 9 switch on via a mechanical motion or jarring of the tool, or in response to provision of a signal from the ii. electronics unit as pre- set time, pressure, or depth 12 criteria are met.

14 In a further embodiment, a weilbore traction apparatus 30 is shown generally in Figures 3A, 3B and 3C. This 16 apparatus 30 has an elongate main body 32 comprising 17 recesses 34 for housing magnets 18 as describedwith 18 reference to the above embodiments. The slots or 19 recesses are located between wheels 40 coupled to the elongate main body 32. The recesses have hinged lids 36 21 for accessing the space accommodating the magnets. The 22 hinged lids 36 close and retain the magnets in place 23 toward an underside 50 of the device.

Rare earth magnets are inserted into the recesses as 26 required for the particular deployment. The magnets are 27 therefore interchangeable and may be selected according 28 to requirements for traction. In another embodiment, the 29 magnets could be electromagnets that are electronically selected and activated to produce a magnetic force as 31 required.

1 The device 30 comprises an auxiliary body 38 housing a 2 programmable electronics unit for controlling and driving 3 wheels 40. The electronics package includes a motor with 4 gearbox system, programmable unit, and a power supply operable as described above. In this case, the power 6 supply is a battery.

8 In Figure 3B, the wheels 40 can be seen side-on. The 9 wheels 40 are located in a wheel housing 42 connected to the main body 32. The wheel housing is provided with a 11 profiled surface 44 toward a topside 52 of the apparatus 12 30.

14 An outer hemispherical surface 48 of the wheels is exposed through the wheel housing 42 for engaging with a 16 weilbore wall when deployed. The hemispherical surface 17 48 provides a relatively large contact area when the 18 apparatus is biased against a weilbore wall. The 19 hemispherical surface 48 also has grooves 40 machined into the surface. The large contact area and grooves act 21 to provide traction when the wheels are in contact with 22 the weilbore wall and driven by the motor.

24 In general, the wheels are optinüsed according to the internal bore sizes of the welibore. For example, where 26 the welibore wall comprises casing of different 27 diameters, wheel size and shape may be chosen to enable 28 effective operation of the apparatus in all Sections of 29 the weilbore.

31 This configuration of the wheels 40 also allows the outer 32 wheel surfaces 48 to contact a circumferentially curved 33 weilbore surface around the underside 50 of the apparatus 1 and enables the underside 50 to come into close proximity 2 to the welibore wall. With the underside in close 3 proximity to the wall, the magnets 18 housed in the slots 4 of the body 32 are able to generate a strong magnetic field and to exert a strong attractional force on the 6 welibore wall.

8 The profiled surface 44 of the wheel housings 42 9 functions such that when the profiled surface contacts a weilbore the apparatus tends to tip to a side, thereby 11 rotating the apparatus around longitudinal axis 70 of the 12 apparatus. Thus, when the apparatus contacts the 13 weilbore wall in a "wrong" or non-operative position, for 14 example where the magnets are not in the correct orientation to attract the apparatus toward the weilbore 16 wall, the apparatus is unstably located on the profiled 17 surface 44 and thus the surface 44 acts to rotate the 18 apparatus into the correct orientation for the tool to 19 function as a magnetic traction apparatus. The weilbore traction apparatus is therefore a self-righting 21 apparatus.

23 In addition, the wheels 40 are fitted to the apparatus a 24 certain radial distance either side of the central longitudinal axis 70. In this off-axis position, the 26 wheels assist in initiating rotation of the apparatus 27 around the longitudinal axis into the operational 28 position.

In this embodiment, the profiled surface 44 comprises a 31 central region 45 extending outwardly beyond the outer 32 surface 60 of the body 32. The profiled surface 44 is 33 also convex in the direction of first radial axis 90 1 perpendicular to the longitudinal axis 70. This surface 2 44 may contact a welibore wall and cause the the traction 3 apparatus 30 to "rotate" around the longitudinal axis 4 into an orientation with the underside 38 of the apparatus facing the weilbore wall for operation. For 6 example, if the surfaces contact a portion of the 7 weilbore wall the apparatus responds by rolling into the 8 correct operational orientation.

The apparatus 30 is provided with connector 72 for 11 attaching the apparatus to an adjacent string section.

12 The apparatus is rotatable relative to other string 13 sections. In general, the string to which the apparatus 14 may be attached may include a swivel allowing the apparatus to rotate relative to other string sections.

16 The device further includes a conical nose 74 for 17 assisting to penetrate and deflect debris in the welibore 18 during deployment.

With reference now to Figure 4, there is depicted at 100 21 a weilbore traction apparatus according to an alternative 22 embodiment, comprising a main body 102. Rotatable drive 23 wheels 104 are coupled to the main body 102 and are 24 generally configured to be driven by a motor, for example, housed in an auxiliary body as described in 26 reference to the above embodiments.

28 In this case, the device 100 further comprises a track 29 106 that engages with the drive wheels 104. The drive wheels 104 are located at first and second ends of the 31 main body 102 such that the track 106 contacts the outer 32 portions 108A,B of the drive wheels 104A,B, which turn to 33 rotate the track 106 around the body 102.

2 The track 106 comprises magnets 110 that serve to produce 3 an attractional force to the welibore wall so that the 4 device 100 is drawn against the wall 112 with the magnets 110 of the track 106 contacting the inner surface of the 6 wall.

8 With reference now to Figure 5, there is depicted 9 generally at 120 a wheel configuration 120 for a weilbore traction device in a further embodiment comprising a 1]. wheel 124 that may be coupled to a body of a welibore 12 traction device as described in above embodiments.

14 The wheel 124 comprises a ring magnet 122. The wheel 124 comprises a wheel core 126, a ring magnet 122 and an 16 outer shell 128 respectively going outwards in a radial 17 direction from the centre of the wheel. The ring magnet 18 may be magnetised radially to provide a magnetic field 19 suitable to attract the wheel toward the welibore wall.

21 Figure 5 shows the wheel 124 in contact with a welibore 22 wall 130. At the point of contact 132, the magnet causes 23 a magnetic force attracting the wheel 124 toward the 24 welibore wall 130 in a direction substantially normal to the wall 130. This serves to increase the apparent 26 weight of the apparatus to which the wheel may be coupled 27 increasing friction and traction.

29 In use, a weilbore traction apparatus 20 as described with reference to the embodiment of Figure 2, is 31 incorporated into, a downhole tool string on a slickline 32 for deployment in a deviated welibore. The string during 33 deployment in a deviated welibore is generally viewed 1 with reference to Figure 6A and 6B at 600. The deviated 2 weilbore 601 comprises magnetic material, which may be 3 for example the material of a metallic liner or casing.

The apparatus includes a motor 25 for driving the wheels 6 14 and this motor is switched off upon deployment. The 7 device includes a battery for supplying power to the 8 motor and electronics for controlling initiation of and 9 behaviour of the motor. The tool string is deployed with the motor switched off and wheels are free to rotate.

12 Magnets 18 are inserted into slots on the underside of 13 the device. These magnets produce a magnetic field that 14 serves to generate a magnetic force 605 that acts on the weilbore wall and functions to draw the body of the 16 apparatus comprising the magnets toward the wall of the 17 weilbore. Wheels 604 of the apparatus are forced against 18 the wall due to the magnetic force to produce a 19 frictional force acting on the wheels at the contact points 607. Different strength magnets may be inserted 21 for different operations. Magnets 18 may be inserted 22 into some or all of the slots in the body.

24 Magnets 18 are selected according to the requirements of operation. Selection depends on factors such as the 26 weight of the tool string and angle of the welibore, 27 thickness of casing of the welibore wall, together with 28 the drive capabilities of the motor. In general, magnets 29 will be chosen to produce traction as required to allow the downhole tool string to be deployed quickly and 31 efficiently with or without using the motor to drive the 32 apparatus.

1 Gravitational force 608 and magnetic force 605 act on the 2 apparatus.

4 The magnets are selected such that upon deployment in upper portions of the welibore as generally shown in 6 Figure 6A where the welibore is at a steep angle, 7 gravitational forces acting on the apparatus dominate, 8 the magnetic forces being near perpendicular to the 9 welibore wall and the gravitational force. In this section of the weilbore, gravity acts on the tool string 11 allows deployment to progress quickly.

13 The motor being switched off with the wheels decoupled 14 from the motor and free to rotate allows the device to act as a roller with the wheels providing stand off for 16 the tool string and low friction.

18 As deployment progresses, the angle of the well becomes 19 shallower as depicted in Figure 6B, and the component of gravitational force along the well reduces slows down 21 deployment. Sensors located on the tool function to 22 measure a property of the weilbore. The measurement is 23 used to initiate the motor, which drives the wheels and 24 moves the string through the welibore according to arrow 609.

27 The magnetic force 605 acts on the device perpendicular 28 to the wall providing a frictional force against the 29 wheels at the contact points 607. This provides traction for the wheels and the motor to drive the wheels and 31 progress deployment efficiently.

1 Selection of the magnets also takes into account the 2 power range of the motor.

4 If many magnets are chosen producing a strong attractive force and high magnetic traction, the apparatus can 6 engage with the welibore at steep angles and the motor 7 can be activated to pull the toolstring at an early stage 8 to speed up deployment.

In general, it will be appreciated that there will be a 11 region of the weilbore where the motor can be used to 12 drive the apparatus and move the tool string. Within 13 this region, it is possible to choose or select when to 14 engage the motor. Engagement of the motor may be determined according to a pre-determined condition. For 16 example, the motor may be engaged when the speed of 17 deployment dips below a threshold value. In this way, it 18 is possible to select operation of the apparatus in a 19 driven or free-rolling mode.

21 Further, it will be appreciated that the extent of this 22 region will in general vary between different welibores 23 and operations. Moreover, the extent of the 24 abovementioned region of the weilbore is dependent on friction between the apparatus and the welibore wall.

26 The apparatus of the present invention functions to 27 control friction by using magnets that magnetically 28 attract the apparatus wheels into contact with the 29 weilbore wall.

31 The magnets may be selected to ensure that the motor can 32 drive the apparatus where gravity can no longer drive 33 deployment of the tool string. In other cases, the 1 magnets may be selected for the motor to drive the 2 apparatus in locations where gravity could drive 3 deployment, but where, for example, gravity alone does 4 not provide the required deployment speed.

6 In addition, it will be appreciated that in other 7 embodiments the magnets could be selected to satisfy 8 other requirements, such as a required operational range 9 of well angles.

11 It will be appreciated that in deployment of a tool 12 string, one or more weilbore traction devices as 13 described herein may be incorporated into the tool 14 string.

16 The apparatus and method of the present invention may be 17 applied in gauge runs, perforating runs, camera runs, 18 bailer runs, calliper runs, seismic runs and/or other 19 slickline operations.

21 The interchangeable magnets 18 allow the traction device 22 to be optimised for deployment in any given operation.

23 In particular, magnets can be selected to optimise 24 deployment speed. This helps to save costs.

The present invention provides further benefits. The 26 apparatus is self-sufficient in that it does not require 27 topside control. This enables the device to be installed 28 quickly and efficiently in a tool string for deployment, 29 thus saving cost. Furthermore, the device is compact and and self- contained unit making it easily transportable.

32 In addition, the apparatus can be readily used on 33 slicklines, and does not require deployment of the 1 toolstring using coiled tubing or wireline. However, it 2 will be appreciated that it may, in other embodiments, be 3 adapted within the scope of the invention to be powered 4 from a surface power source.

S

6 The present device advantageously has a dual function as 7 a substantially passive roller at the top of the deviated 8 well bore and a traction device at shallower angles of 9 the welibore. This removes the need to provide separate rollers and tractors in the tool string. 1].

12 Various modifications and improvements may be made within 13 the scope of the invention described herein.

Claims

1 CLAIMS 3 1. A welibore traction apparatus for use in deployment 4 of a

tool string in a welibore, the weilbore traction apparatus comprising: 6 traction means configured for engagement with 7 a wall of the wellbore such that movement of 8 the traction means moves the apparatus along 9 the weilbore; - drive means operable to drive the traction 11 means; 12 wherein 13 the apparatus is selectably operable in: a free- 14 rolling mode, in which the traction means is configured to move freely of the drive means, and; a 16 driven mode, in which operation of the drive means 17 causes movement of the apparatus along the weilbore.

19 2. A welibore traction apparatus as claimed in Claim 1, wherein the apparatus is configured to operate in 21 the free-rolling mode in regions of the weilbore in 22 which gravitational force acting on the apparatus is 23 sufficient to move the apparatus in the direction of 24 deployment.

26 3. A welibore traction apparatus as claimed in Claim 1 27 or Claim 2, wherein the apparatus is configured to 28 operate in the driven mode in regions of the 29 welibore in which gravitational force acting on the apparatus is insufficient to move the apparatus in 31 the direction of deployment.

1 4. A welibore traction apparatus as claimed in any one 2 of Claims 1 to 3, wherein the apparatus is 3 configured to operate in the driven mode in regions 4 of the weilbore in which gravitational force acting on the apparatus is insufficient to move the 6 apparatus in the direction of deployment above a 7 pre-determined threshold value.

9 5. A welibore traction apparatus as claimed in any one of the preceding claims, wherein the apparatus is 11 configured to operate in the driven mode according 12 to a property of the wellbore, wherein the property 13 of the weilbore comprises one or more of 14 - weilbore temperature; welibore pressure; and/or 16 - angle of the weilbore.

18 6. A weilbore traction apparatus as claimed in any one 19 of the preceding claims, wherein the apparatus is configured to operate in the driven mode according 21 to a property of deployment of the apparatus, 22 wherein the property of deployment comprise one or 23 more of: 24 - a deployment speed; - a capacity of the drive means; and/or 26 - a time period.

28 7. A welibore traction apparatus as claimed in any one 29 of the preceding claims, wherein the apparatus is adapted to operate in the free-rolling or driven 31 mode in response to a received signal.

1 8. A welibore traction apparatus as claimed in Claim 7, 2 wherein the signal is received according to a 3 property of deployment, property of the weilbore, 4 and/or progress of deployment.

6 9. A weilbore traction apparatus as claimed in any one 7 of the preceding claims, wherein the apparatus is 8 adapted to be run on a slickline.

10. A welibore traction apparatus as claimed in any one 11 of the preceding claims, wherein the apparatus is 12 adapted to be run on a wireline and/or coiled 13 tubing.

11. A weilbore traction apparatus as claimed in any one 16 of the preceding claims, wherein the apparatus 17 comprises a downhole power source.

19 12. A welibore traction apparatus as claimed in any one of the preceding claims, wherein the apparatus 21 comprises a control unit operable to selectively 22 control operation in the free-rolling or driven 23 modes.

13. The control unit may be programmed to control 26 operation according to a property of the weilbore, a 27 property of the deployment and/or progress of the 28 deployment.

14. A welibore traction apparatus as claimed in any one 31 of the preceding claims, wherein the drive means 32 comprises a motor.

1 15. A welibore traction apparatus as claimed in any one 2 of the preceding claims, wherein the apparatus 3 comprises a gearbox system operable to couple the 4 drive means to the engagement means for driving the engagement means.

7 16. A welibore traction apparatus as claimed in any one 8 of the preceding claims, wherein the gearbox system 9 is adapted to provide a gearbox ratio for driving the apparatus, in the driven mode, at a torque 11 and/or speed for facilitating in the deployment of 12 the tool string.

14 17. A weilbore traction apparatus as claimed in any one of the preceding claims, wherein the drive means 16 comprises a clutch mechanism.

18 18. A welibore traction apparatus as claimed in any one 19 of the preceding claims, wherein the drive means is adapted to drive the engagement means in a forward 21 direction.

23 19. A weilbore traction apparatus as claimed in any one 24 of the preceding claims, wherein the drive means is adapted to drive the engagement means in a reverse 26 direction.

28 20. A weilbore traction apparatus as claimed in any one 29 of the preceding claims, wherein the engagement means comprises wheels.

1 21. A welibore traction apparatus as claimed in any one 2 of the preceding claims, wherein the engagement 3 means comprises a track.

22. A wellbore traction apparatus as claimed in any one 6 of the preceding claims, wherein the apparatus 7 comprises at least one magnet arranged to bias the 8 traction means into frictional contact with the wall 9 of the welibore, the welibore wall comprising metallic material.

12 23. A weilbore traction apparatus as claimed in any one 13 of the preceding claims, wherein the at least one 14 magnet is interchangeably received by the apparatus.

16 24. A weilbore traction apparatus as claimed in any one 17 of the preceding claims, wherein the at least one 18 magnet may be received in the drive means.

25. A method of deploying a string in a welibore, the 21 method comprising the steps of: 22 - locating a string in the welibore, the string 23 comprising a weilbore traction apparatus 24 comprising traction means, and drive means operable to drive the traction means; and 26 - selecting between operation of the apparatus in 27 a free-rolling mode, in which the traction 28 means is configured to move freely of the drive 29 means, and a driven mode, in which the apparatus operates to move the traction means 31 along the weilbore.

1 26. A method as claimed in Claim 25, wherein the method 2 comprises the step of coupling the drive means to 3 the traction means.

27. A method as claimed in Claim 25 or Claim 26, wherein 6 the method comprises the step of powering the drive 7 means.

9 28. A method as claimed in any one of Claims 25 to 27, wherein the method comprises the step of driving the 11 apparatus in the driven mode to optimise the 12 duration of deployment of the string.

14 29. A method as claimed in any one of Claims 25 to 28, wherein the method comprises the step of measuring a 16 property of the deployment.

18 30. A method as claimed in any one of Claims 25 to 29, 19 wherein the step of measuring a property of the deployment comprises measuring speed of the string 21 moving through the weilbore.

23 31. A method as claimed in any one of Claims 25 to 30, 24 wherein the step of measuring a property of the deployment comprises measuring angle of inclination 26 of the welibore traction apparatus.

28 32. A method as claimed in any one of Claims 25 to 31, 29 wherein the method comprises the step of measuring a property of the welibore, wherein the property of 31 the weilbore is pressure and or temperature of the 32 welibore.

1 33. A method as claimed in any one of Claims 25 to 32, 2 wherein the method comprises the step of producing a 3 signal for providing to the drive means according to 4 the measured property.

6 34. A method as claimed in any one of Claims 25 to 33, 7 wherein the method comprises the step of running the 8 welJ.bore traction apparatus in a free-rolling mode 9 for frictional contact of the traction means with the weilbore wall.

12 35. A method as claimed in Claim 34, wherein the method 13 comprises the step of selecting to operate the 14 welibore traction apparatus in the driven or free- rolling modes.

17 36. A method as claimed in Claim 34 or claim 35, wherein 18 the method comprises the step of switching between 19 the driven mode and the free-rolling mode.

21 37. A method as claimed in any one of Claims 34 to 36, 22 wherein the method comprises the further step of 23 controlling operation of the weilbore traction 24 apparatus in the driven or free-rolling modes.

26 38. A method as claimed in any one of Claims 34 to 37, 27 wherein the method comprises the step of controlling 28 operation of the apparatus in the free-rolling or 29 driven modes according to a measured property.

31 39. A method as claimed in any one of Claims 25 to 38, 32 wherein the method comprises the step of determining 1 the timing of driving the traction means in the 2 driven mode.

4 40. A method as claimed in any one of Claims 25 to 39, wherein the method comprises the step of 6 magnetically biasing the traction means into 7 frictional contact with a wall of the weilbore.

9 41. A method as claimed in Claim 40, wherein the step of magnetically biasing the traction means includes the 11 step of producing an attractional magnetic force 12 between the apparatus and the wall of the welibore.

14 42. A method as claimed in any one of Claims 25 to 41, wherein the method comprises the step of inserting a 16 magnet into the welibore traction apparatus to 17 produce an attractional magnetic force biasing the 18 wellbore traction apparatus toward the wall of the 19 welibore.

21 43. A method as claimed in any one of Claims 25 to 42, 22 wherein method comprises the steps of: 23 - calculating a required traction; and 24 - driving the drive means according to the required traction.

27 44. A method as claimed in Claim 43, wherein the method 28 includes the step of producing a signal according to 29 the required traction.

31 45. A method as claimed in Claim 43 or Claim 44, when 32 dependent on Claim 41 or 42, wherein the method 33 comprises the step of selecting at least one magnet 1 for biasing the traction means according to the 2 traction required.

4 46. A method of deploying a string in a welibore, the method comprising the steps of: 6 - locating a string in the welibore, the string 7 comprising a welibore traction apparatus 8 comprising a drive means and a traction means 9 configured to be in frictional contact with a wall of the welibore; 11 - providing a signal to the drive means; and 12 - driving the traction means in a driven mode in 13 response to the signal received by the drive 14 means.