A Downhole Tractor And Drive System

Field

This invention relates to a downhole tractor and drive system. More particularly the invention relates to a drive system which is suitable, for example, for use with types of downhole tractor used in well interventions and in well completions.

Background

A downhole tractor is used for propelling tools, such as well logging tools and other well intervention downhole tools. Well logging tools and well intervention downhole tools are deployed by the tractor generally in deviated or horizontal well bores in order to perform a number of essential downhole operations in the well bore.

These operations include removal of debris; retrieval of downhole tools from the well bore; and well logging. Well logging is usually performed to measure various properties of a hydrocarbon bearing rock formation in order to establish well flow potential. In addition downhole tools may be used to establish other downh ole conditions including: local temperature and local pressure under flowing and non- flowing conditions.

Conventional coiled tubing is restricted in the distance it can enter a deviated or horizontal oil or gas well due to a combination of friction, (against production tubing, casing or well bore), and the tendency for coil tubing to coil in the same manner as a spring under compression. This coiling of the tubing can limit the so-called intervention distance to which injected coiled tubing can travel in a well bore. This is known as coiling, coiled tubing bunching or 'bunching'.

One way of overcoming the problem of coiling or 'bunching', is to attach a tractor to one end of the coiled tubing in order to apply a force, so enabling the coiled tubing to remain straight and achieve much greater intervention distances into the well bore.

There are two main types of existing downhole tractors suited to coiled tubing deployment. The first type is an electrically driven tractor powered by one or more electric motors with an electrical supply provided by a conducting power cable that passes through a central bore of the coiled tubing. A drive force is applied to the well bore or casing through hydraulically or mechanically driven wheels that are attached to extending arms. The wheels apply traction to the wall of the production tubing, casing or well bore.

The second type of downhole tractor that is suited to coiled tubing deployment, is a hydraulically driven tractor which typically uses a series of sequentially phased hydraulic rams, with extending armatures that sequentially set against the tubing or well bore wall thereby drawing the tractor forwards, in a 'caterpillar' fashion.

Once a first set of extending armatures is set (thereby providing an anchor to the well bore or wall of the well tubing) hydraulic pressure is transferred to a hydraulic ram forward of the extending armatures. A second set of armatures is subsequently urged in a forward direction until the limit of their forward extension is reached. Hydraulic pressure then causes flow to pass to the second set of extending armatures which expand (under hydraulic pressure), anchoring the tractor against the well bore or tubing wall. When the extending armatures are fully set, the hydraulic ram is retracted pulling the coiled tubing forward in a 'caterpillar' type motion. Multiple tractor sections may be fitted to a single well intervention tractor tool string.

Both systems are effective but each suffers from inherent problems. Electrically powered systems suffer from problems associated with electrical motor burn out and/or time delays due to a need to stop the intervention process to allow the electric motor cool down. Wheel driven well intervention tractors are also restricted by the limited traction they can apply to the tubing wall or well bore, due to the small contact area ('foot print') between well bore or liner and the drive wheels. Such relatively small wheels can result in a loss of traction and 'wheel spin', frequently causing the electric motor to overheat or burn out.

Hydraulically driven tractors have tended to exhibit a jerking action which can badly affect quality of data collected by on-board logging tools that are being conveyed into the well bore. Consequently well logging interventions which use these types of tractor systems are usually only performed in a single direction (that is coming upwards out of the well bore) under surface overpull, so as to provide 'smooth' readings, when the tools are being withdrawn from a well bore.

As a consequence the mass of payload these hydraulic tractors can convey, and the amount of traction force they can exert, is limited.

Intervention distance is often limited by the overpull available at the surface , and the strength of the conduction electric line in the case of an electrically powered tractor. Another factor that affects intervention distance is the strength of the coil tubing and tool connections. In the case of a coiled tubing conveyed tractor, excessive overpull from the surface can also result in coiled tubing or electric line failure/parting, and/or the tractor, and/or logging tools becoming detached from the coiled tubing.

This problem is sometimes exacerbated by a tool snagging ('hanging up') against internal walls of the well bore. Under these circumstances such downhole tools require retrieval which is often referred to as 'fishing'. These types of well intervention are expensive due to lost production. There is also a risk of jeopardising the tool and a risk of damaging the well bore itself.

Both the aforementioned types of tractor system are therefore limited by the amount of effective drive power they can deliver.

Prior Art

European Patent EP-B1 -2 402 555 (Titan Specialities Limited) describes a tractor communication and control system which employs a method of switching between a safe mode for tractoring and a perforation mode for perforating in a tool string and includes a tractor that is capable of connecting and disconnecting electrical power below the tractor.

European Patent EP-B1 -2 232 083 (Welltec) discloses a sequence valve and a down hole tractor. The sequence valve includes a pressure controlled sliding portion with a return spring for controlling a down-hole tractor. United States Patent US 4 415 316 (Christensen Inc) discloses a fluid motor in which relatively rotatable elements are formed from a deformable material, and axial movement of tapered surfaces within the element, caused by variation in fluid pressure, causes adjustment of a sealing force in dependence upon fluid pressure.

United States Patent US 6 183 226 (Steven Wood) teaches a motor in which the stator, rotor and/or flex shaft of a progressive comprises composite materials in a variety of combinations with and without bonded resilient elastomer. The composite materials are formulated to provide resilience and non-resilience where needed.

United States Patent US 6 544 015 (Wilhelm Kaechele Elastomertechnik GmbH) discloses a rotor for an eccentric screw pump or a sub-surface drilling motor which consists of a straight cylindrical core element onto which a shell is forged. Forging instils a helical external form required for the eccentric screw pump.

The present invention arose in order to overcome problems associated with existing tractor drive systems.

An object of the invention is to provide an improved tractor, power delivery and drive for use in well bore interventions.

Another object is to provide a tractor whose speed is controllable remotely, such as from the well bore surface.

A further object is provide a tractor whose speed is in excess of 2 metres/minute, ideally a tractor whose speed is greater than 5 metres/minute and ideally a tractor whose speed is more than 10 metres/minute and most preferably a tractor whose speed is more than 50 metres/minute.

A further object of the present invention is to provide a tractor system that has improved traction to the well bore in combination with a more powerful and controllable drive so that heavier payloads - that is payloads in excess of 25 kg and preferably in excess of 50 kg - may be conveyed. This enables the conveyance of heavy tubulars, such as liners, during well construction activities without the need to use a drilling rig, thereby avoiding additional cost.

A yet further object of the present invention is to provide a tractor capable of providing improved and smooth logging motion, thereby enabling a well to be logged in two directions under surface controlled and regulated speed , so that logging can be performed whilst running into the well bore and coming out of the well bore under tractor power.

A further object of the present invention is to eliminate logging errors due to jerky logging tool motion caused by bunching, well bore friction and well bore/upper completion hang up on the coiled tubing during surface applied overpull whilst logging going up the well bore by providing a consistent, surface controlled powered force at the logging tool thus removing any jerking action against the tool that may be applied by stretch in the coiled tubing through the conditions described above.

Summary of the Invention

According to the present invention there is provided a downhole tractor comprising: a stator which is surrounded by a commutator, a drive system rotates the commutator with respect to the stator; and a well bore engagement means is connected to the commutator, the well bore engagement means engages with a well bore or well liner by way of a plurality of engagement devices supported thereon, the engagement devices, in use, traversing the well bore or liner thereby driving the tractor in a forwards or a reverse direction.

In a preferred embodiment the well bore engagement means engages the well bore or liner so as to traverse a helical pathway.

It is appreciated that the tractor is connected to a coil and/or wire and does not twist substantially with respect thereto; rather turning is achieved by the commutator which is decoupled from the coil or wire so that torque is not transmitted to the latter.

Preferably the drive system includes a stator which has a stator helical profile and connected to the commutator is a flexible jacket which has a helical profile of an opposite sense to the stator helical profile, a fluid pathway is defined between the stator helical profile and the helical profile of the flexible jacket, through which pathway a hydraulic fluid flows so as to cause the flexible jacket to deform and adopt the helical profile of the stator, thereby converting a force delivered by the fluid to a torsional force, so as to rotate the commutator with respect to the stator.

Optionally a second drive system is included, for purposes of additional motive power and in case of redundancy. The second drive system may be similar to the first drive system or it may have a different power supply.

In one embodiment the downhole tractor may include caterpillar tracks or belts, which may be toothed, and which act as engagement devices with the well bore or liner. Alternatively drive may be transmitted to engagement devices by way of belts, cranks or gears so that drive is transmitted to a plurality of wheels in contact with the well wall or liner in order to provide traction.

Ideally the wheels are in contact with the well bore or liner so as to traverse a helical pathway.

In the embodiment of the downhole tractor that employs wheels as engagement devices, the wheels are preferably disposed between the commutator and the well wall or liner on axles. The axes of the wheel axles are offset so that the wheels traverse a helical path along the well wall or liner. Likewise a similar offset may be achieved with tracks so that these traverse a helical pathway.

In an alternative system the engagement devices may include elastomer balls mounted fore and aft of the tractor body which are compressed and expanded to engage with the well bore or liner.

Preferably the drive system includes an internal combustion engine. In this embodiment a control means is also provided to control operation of the internal combustion engine. Optionally the control means is operated by a command signal transmitted via a downhole communication device. Preferably the control means includes a means for switching on and switching off the drive system; a means for changing the speed of the drive system and a means for changing the direction of travel of the tractor. Where an internal combustion engine is used as the drive system, preferably the engine includes a rotary engine block driving a crank. Alternatively the internal combustion engine includes at least one crank driven by a reciprocating piston.

Ideally a starter motor is adapted to engage the internal combustion engine by way of a ring gear and optionally a timer switch is connected to the starter motor. A flywheel may also be provided which may be driven by the starter motor. In this way a downhole tractor comprises: a stator which is surrounded by a commutator, the drive system rotates the commutator with respect to the stator; and the engagement means drives a plurality of engagement devices which, in use, traverse the well bore or pipe so as to propel the tractor along a helical pathway.

Logging, whilst deploying the tractor enables two datasets to be obtained. Previously an operator was only able to obtain readings when overpull was applied from the surface as a tractor withdrew from a well bore. Using the present invention a tractor may move in a controlled manner into and out of the well bore.

In the preferred embodiment, where the tractor is driven by an internal combustion engine, a rotating crank may be arranged to drives a planetary gear system which in turn drives the commutator.

Ideally a control means is provided and is operated by at least one of the following command signals from the group comprising: an overpull command signal on a connecting slickline; an overpull command signal, applied as tension from the surface, on a connecting wireline; and an overpull command signal on connecting coiled tubing. Alternatively firing of the internal combustion engine may be initiated by the tractor sensing a reduced overpull.

One or more supercharging system (s) may be provided to increase exhaust gas pressure which may be increased to pressures in excess of 5000 PSI (34474 kPa), more preferably in excess of 8000 psi (55158 kPa) and most preferably in excess of 15,000 psi (103421 kPa).

In this embodiment a fuel storage tank is sealed and adapted to contain a petroleum spirit mixture or ether and lubricating combustible oil, such as SAE30. Preferably a high pressure injector pump is provided for injecting fuel into the internal combustion engine cylinder via a plenum. Optionally a gas accumulator and regulator moderate oxygen flow to the internal combustion engine cylinder through an inlet manifold.

Ideally the internal combustion engine has an on board supply of oxygen or a dedicated oxygen generator. Advantages of the drive system are that: it is able to pull greater payloads; has greater forward and reverse speeds; and i s controllable in both forwards and backwards directions.

In an alternative embodiment the drive system comprises a pressurised hydraulic fluid, such as mud; a stator which has a stator helical profile, surrounding the stator is a commutator, connected to the commutator is a flexible jacket which has a helical profile of an opposite sense to the stator helical profile ; a fluid pathway is defined between the stator helical profile and the helical profile of the flexible jacket, through which pathway a hydraulic fluid flows so as to cause the flexible jacket to deform and adopt the helical profile of the stator, thereby converting a force delivered by the fluid to a torsional force, so as to rotate the commutator with respect to the stator.

Ideally the jacket also provides a flexible and extended barrier to a so-called partial bead, the barrier extending around the stator.

In a further alternative embodiment an electric motor may be used as a drive system.

An advantage of all the aforementioned On board' drive systems is that they all drive an external commutator which rotates about a relatively static stator. Engagement means that are connected to the commutator rotate and engage with a well bore or liner so as to propel the tractor.

Therefore in all the aforementioned embodiments the stator remains relatively stationary, with respect to a logging cable, and so does not exert a twisting moment against the logging cable. This ensures that a continuous electrical connection to the logging tool(s) is maintained with a surface operator. In addition, the connection between coil tubing and/or electrical connection and/or slickline and the tractor stator, does not rotate so that the body of the tractor resists rotational torque. This ensures that any wellbore influenced rotation or 'corkscrewing', against the logging tools, is resisted.

In a yet further embodiment the drive system includes a static turbine stator around which a turbine commutator is arranged to provide drive against a well bore or liner.

A further advantage of a relatively fixed, non-rotating stator is that rotational torque is directly transmitted to the well bore by engagement means, which are ideally supported by expanding drive bows (or drive arms) by the revolving commutator or tractor 'jacket'.

In a preferred embodiment the drive system may be used to propel well logging tools and other well intervention tools. Well logging tools and well intervention downho le tools are deployed by the tractor generally in highly deviated or horizontal well bores in order to perform a number of essential downhole operations in the well bore that can range from removal of debris and lost downhole tools from the well bore, to well logging which is performed to measure the various properties of the hydrocarbon bearing rock formation in order to establish the flow potential of the well as well establish other downhole conditions, including local temperature and pressure conditions under flowing and non-flowing conditions.

In the hydraulic drive system a central, circularly symmetric stator requires a pressurised hydraulic fluid to pass through one or more helical pathways so as to provide an axial force which is converted into a torsional force which rotates the external housing.

Preferably the pressurised hydraulic fluid urges the flexible jacket to adopt the profile of the surrounding rotor which is connected to the external housing or commutator. The pressurised fluid also acts on the jacket to marginally deflect the barrier formed by the jacket against the stator thus providing a clearance between the stator and the helical flexible barriers to the beads which provide both lubrication and cooling to the stator and a reduction in wear to the jacket helical flexible rotor barriers thus allowing a small degree of fluid bypass. The drive system includes a helical rotor (commutator) which surrounds the stator and is located thereon or machined therein, and has an elastomer jacket that surrounds the helical rotor communicator so as to transmit hydraulic pressure into rotational torque so as to provide a moment about the axis of the external housing or commutator.

The jacket defines one or more helical or spiral threads or bead barriers which engage with spiral grooves on the outer surface of a fixed stator so as to rotate the external housing or commutator with respect to the fixed stator.

It will be appreciated that in the alternative, spiral threads or beads may be provided on the inner surface of the housing or rotor so as to engage with spiral grooves formed or machined on the outer surface of the stator thereby achieving relative rotation of the external housing or commutator with respect to the stator.

Helical threads on the stator are disposed in clockwise and counter-clockwise senses so to balance the directional drive and eliminate rotational torque imbalance and transfer to the coiled tubing and in so doing reduces the chance of coiled tubing failure due to twist off. With these bidirectional helical threads bi-directional power delivery is possible and therefore permits forward and reverse movement.

The tractor overcomes the disadvantages of prior art tractor systems by providing: a reliable and effective means of traction to the well bore; by providing consistent and smooth motive power delivery in forwards and reverse directions.

Another advantage is that the tractor can move at low or high speeds and this enables powered logging operations under low or high power in real time, both on the way into a well and on the way out of the well ; and which also permits the operator at surface to reverse direction of the tractor and logging tools in order to re- survey a section of the well bore using surface control. This is useful should the real time logging read out on surface prove indistinct or corrupted; and importantly in a surveying can be performed in a smooth and predictable manner, thereby providing more reliable data.

Another object is to provide a flow responsive on/off drive switch within the tractor to initiate or cease drive in either forwards or rearwards directions.

A yet further object of the present invention is to provide a system which maintains pump pressure (and flow) to maintain hydrostatic circulation to maintain a hydrostatic head at surface to prevent well flow and/or well to prevent pressure build up.

An even further object of the present invention is to provide a remote controlled directional change which is repeatable.

In a particularly preferred embodiment a flow responsive on/off drive switch is provided. The switch uses pump rate and internal differential pressure within the tractor to initiate or cease drive in either forwards or rearwards directions.

A further object of the present invention is to provide a system where the direction of the tractor may be changed without significant distance overrun to enable the tractor to change direction at or very close to the point initiated by the operator at surface, so that critical points in the well might be established and/or verified for depth tagging purposes; and/or the tractor may be reversed to revalidate the data logged on the way in or out of the well bore data. Accordingly a section may be re-logged and data captured without the need for a second intervention run.

A further object of the present invention is to provide a means of accurately positioning the tractor at critical points in the well bore which may need to be marked using logging tool radio-active markers or a point downhole tools such as whipstocks and plugs may need to be accurately set.

In a particularly preferred embodiment there is provided a remote controlled directional change by applying surface overpull (or surface applied tension force) which is sensed at the tractor and which causes the tractor unit to change direction.

Preferably a means for remote controlled directional includes: a hydraulic flow diverter valve which in a first position diverts hydraulic flow to a well bore and in a second position diverts hydraulic flow to an overpull direction control valve.

Ideally the overpull direction control valve acts to direct hydraulic fluid through an upper (rearward) upper and a lower (forward) positive cavity motor which is returned to the direction control valve through a flow path defined in the stator body, flow being directed to at least two ports in the direction control valve to ensure minimal backpressure.

Direction change is therefore achieved by applying a measured surface overpull, otherwise described as a surface applied tension force, which is sensed at the tractor and which causes the tractor unit to change direction.

Preferably a means is included for accurately positioning the tractor at critical locations in the well bore which may need to be marked using logging tool radioactive markers or a point downhole tools such as whipstocks or plugs which may need to be set accurately.

The tractor may be deployed in deviated and horizontal oil and gas wells; using coiled tubing; and (due to the nature of its well traction engagement system and hydraulic power unit) the tractor may also be deployed for well construction purposes as a means of high power downhole motive drive.

Ideally a means is provided to control the tractor drive speed at surface by controlling hydraulic pump rate accordingly controlling flow delivery and hence power and speed applied to the hydraulic motor.

Ideally using surface controlled pump rate and overpull on the coiled tubing surface the direction and speed of the tractor allows ingress and egress into and out of the well bore and is exactly controlled. In a preferred system the means to control the tractor drive is a pressure head created by the pump at surface.

In a particularly preferred embodiment there is provided a hydraulic fluid power supply including: an anti-rotational power delivery system which inhibits coiling of the fluid delivery path.

An anti-rotational power delivery path prevents coil tubing twist-off and leakage. Tubing 'twist-off' initially causes the loss of hydraulic flow to the tool below through leakage to the well bore and consequently the loss of hydraulic power delivery to the tractor and is to be avoided at all times. Continued rotation causes coiled tubing to narrow to a neck which can be seen at the surface as a sudden pressure increase before the coiled tubing parts where the pressure reduces at surface. This twist off requires the coil tubing to be withdrawn from the well bore prior to a re-intervention into the well bore with a coiled tubing fishing bottom hole assembly to 'fish' parted coiled tubing and any attached tools. This can be a difficult, time consuming and consequently expensive exercise costing rig time and lost production as well as specialist service costs from a specialist 'fishing' service company.

Ideally by providing a fluid exhaust porting capability the drive arrangement and introduction of turbulent fluid movement, allows good fluid bypass with a washing action assisting well solids to be circulated away from the tractor assembly by nature of its dual directional rotation and jetting action.

Hydraulic fluid exhausting from the direction control valve in its relaxed state flows between an upper (rearward) stator and a jacket of a downhole tractor, so as to drive the rotor in a clockwise (forwards) direction; and hydraulic fluid exhausts to flow through ports in the planetary drive housing to flow to a lower (forward) stator and a jacket of a downhole tractor, so as to drive the lower rotor in an anticlockwise direction. This configuration ensures that balanced clockwise and counter-clockwise forces (torques) are applied to the well bore by the driving the tractor due to the reverse orientation of the engagement slip assembly.

As in the abovementioned aspect, the stator and the jacket are connected to an external housing, and the jacket is flexible so that it conforms to an external helical profile of the stator, thereby defining at least one fluid pathway, whereby in use, a hydraulic medium acts as a power supply and flows along the at least one fluid pathway between the stator and the jacket, such that dynamic fluid pressure urges the jacket into a corresponding helical pathway in the external housing, thereby causing the external housing to rotate with respect to the stator.

Ideally the jacket includes an aerated elastomer, such as molybdenum filled poly- tetra-fluoroethylene (PTFE). Ideally a reinforcing fibre mesh, such as nylon, carbon fibre, steel, Kevlar (Trade Mark) is also included so as to improve strength and durability of the jacket.

Optionally a wear resistant material, such as molybdenum, may also be incorporated into a mesh or other forms of reinforcement within the jacket.

In another particularly preferred embodiment there is provided a downhole tractor having a profiled stator with a rotating drive element (hereinafter referred to as an outer housing or a rotor) and an elastomer jacket arranged around the exterior of the stator, whereby distortion of an elastomer bead seals against a varying profile of the fixed stator powered by the circulated hydraulic medium to rotate the drive element with respect to the stator.

Usually in all coiled tubing well interventions the hydraulic medium is drilling mud which is used to maintain a hydrostatic head to prevent ingress of hydrocarbons from the pressured formation/zone which can result in a loss of pressure control also known as a blowout. Apart from providing a hydrostatic barrier to well flow, the drilling mud has a cooling and lubricating effect between jacket, elastomeric and stator profile by acting as a lubricant to prevent friction and consequential wear to both the stator and the elastomer jacket whilst also providing a dense flowing hydraulic power source. The elastomer jacket helical flexible rotor bead barriers deform to conform to the varying profile of the helical stator.

Ideally an overpull direction control valve is also provided which is switched from a first position to a second position using surface overpull on the coil tubing in order to reverse the drive direction. This enables remote control of the forwards and reverse direction of the tractor.

Ideally two opposing helices are eccentric helical coil drive profiles machined to the exterior of the stator with jackets over fitted and are linked by a planetary gear system.

It is appreciated that the invention may be incorporated in a tractor system assembly including a motorhead that is used to connect the motorhead to coiled tubing as well as to downhole tools.

Ideally expandable and driven drive bows or drive arms fitted to the exterior of the upper (rearwards) and lower (forwards) rotors which are expanded and retracted by dual or multiple drive bow or drive arms expanders and followers arranged to deflect drive bows or drive arms outwards against the well bore.

Advantageously upper and lower drive bows, or optionally drive arms, are fitted with engagement slips with opposing directional drive serrations orientations to upper (rearward) and lower (forward) drives. These are mounted at the mid -point of the exterior of the drive bows or drive arms such that when the drive bows or drive arms are expanded by the dual or multiple drive bow or drive arm expanders the engagement slips are pressed hard against the well bore and when rotated by the action of the upper and lower drive rotors through the drive bow or drive arms enables transmission of rotational torque and therefore directional motion.

As the engagement slips are pressed and rotated against the well bore, a slight groove is cut into the well bore by the serrated drive profiles machined in the engagement slip face meeting the well bore. This is in a similar manner to how a threading tap, engaging with a drilled hole, creates a threaded groove that so that a screw thread may engage to propel the screw in and out of the tapped treaded hole by clockwise and anti-clockwise rotation of the screw.

The engagement slips therefore engage against the well bore such that traction is applied when the engagement slips are rotated so achieving simultaneous cutting of a thread profile in the well bore and the engagement slips riding and engaging in this threaded groove.

Accordingly strong traction forces may be applied in both forwards (into the well) and backwards (out of the well) is applied through a larger and stronger traction footprint provided by a rotating engagement slip than a wheeled drive could possibly apply.

The direction of the drive is dictated by the position of an overpull direction control valve whose flow path is controlled from surface to provide a means of traction forwards and backwards by clockwise and anti -clockwise rotations of the drive bows or drive arms acting through engagement slips enabling drive in and out of the well bore. Preferably a pair of drive systems is provided: one at a forward position lower and one at a rearward upper position. Advantageously the stator extends between the two drive systems (rearward and forward) so as to provide a continuous driver which may extend along substantially the entire length of a downhole tool.

Optionally a pair of drive bow units is provided on each of the rearward and forward drive systems so that each drive system has at least two and preferably three or most preferably four expanding bow springs. This configuration has the advantageous effect that, in the event that the tool encounters a restriction in the well bore, the drive system that first encounters the restriction is adapted to reduce its diameter so that it may pass therethrough by take up on the drive bow expander through take up splines in the upper (rearwards) and lower (forwards) rotor drive bodies. This is achieved as the drive bow units are arranged to retract so as to pass through the restriction.

The drive bow units enable the reduced diameter drive system to progress through the restriction whilst both drive systems continue to engage with the well bore so as to provide continuous and rotationally balanced forward drive to drive the tool. Once the drive system is clear of any restriction, the drive bow units attached thereto expand and continue to engage with the well bore.

Drive bow expanders and carriers are provided to ensure that each drive bow opens/closes in unison.

Opening and closing the drive bow units is ideally achieved by winding them about a clockwise or anti-clockwise helical thread: that is around oppositely spiralling helices. An advantage with this configuration of drive bows is that each drive bow acts as a return spring to retract or collapse, as the resistance to rotation of the rotor housing changes. This in turn acts as self-adjusting expandable drive in the same manner as leaf springs. Similarly where drive arms are used in place of drive bows, leaf return springs are fitted to an underside of the drive arms which act against the drive arms to positively retract the drive arms when the expanders retract. Both drive bows and drive arm expanders as described above, are reactive to both rotational directions and expand the drive bows when rotational force is applied in either clockwise or anti-clockwise senses.

Torque is further transmitted through the rotor by mating splined sections in the upper and lower rotors which accommodate torque transmission through the rotors and also the expansion and collapse of the drive bows and drive arms along the length of the drive rotors.

Preferably a straight bar is included to add mass to the bottom hole assembly and also to act as a spacer between a motor head and tractor assembly and connects a tool head to the tractor assembly.

Preferably a hydraulic flow diverter valve operates in the open position which diverts flow from the coiled tubing and upper assembly to the well bore and in the closed position activates a piston and shuttle sleeve to divert hydraulic media flow through an overpull direction control valve to the tractor positive cavity rotors.

An overpull direction control valve controls the flow path of hydraulic medium (mud) through tractor positive cavity motors which in the open (relaxed) position (where no surface overpull is being applied) diverts flow to an upper (rearwards) positive cavity drive motor in the tractor assembly. This flow of hydraulic medium drives the tractor forwards with hydraulic flow circulating through the upper (rearward) drive rotor assembly through ports in a planetary gear system to the lower (forward) drive rotor and returns hydraulic media flow back through a gun drilled duct or via machined in the centre of the upper and lower sections of the fixed stator to ports in the overpull direction control valve which exhausts this hydraulic media flow to the well bore annulus.

As mentioned earlier, hydraulic drive medium flow through the tractor rotors not only cools and lubricates the action of the jacket and stator within the tractor but also, it assists in the removal of solids from the well bore by means of circulation whilst maintaining hydrostatic pressure on the oil and gas bearing pressurised formation (zone). Ideally in order to keep unhindered the retracting action of the drive bows and drive arms into the body of the tractor, which importantly allows the tool to pass through upper well bore completion restrictions such as nipples, flow ports may be included in the rotors and jackets allowing the flow and consequently a jetting action of hydraulic media into the recesses into which the drive bows or drive arms retract to ensure the removal of any solid debris which may interfere with this action.

Return of hydraulic flow from the lower (forward) drive system to the overpull direction control valve is via a duct which is gun drilled and through the stator in which a cable may pass. Hydraulic fluid exhausts via a hydraulic flow exhaust port in the overpull direction control valve to the well bore. In the closed position the valve diverts hydraulic flow in the opposite direction through the duct via an aperture in the overpull direction control valve from the fixed positive cavity motor stator.

The action of this reversal of flow is to reverse the direction of the drive rotors with hydraulic media flow exhausting through the same integral hydraulic flow exhaust ports positioned within the overpull direction control valve. The exhaust ports are used to exhaust media in the opposing flow direction due to a change of porting caused by the relative change in position of a segmented flow control plug thereby providing a drive which can travel forwards or backwards.

Integral pressure retaining thrust bearings enable the rotation of the jackets and rotor housings. The pressure retaining thrust bearings are located at each end of the positive cavity drives, and ideally also at the mid-point of the tractor where the rotors act against the planetary gear system.

At the lower (forwards) section of the tractor an end cap is fitted which not only seals around the logging cable but also provides a flow path between the lower forwards rotor and the gun drilled cable duct (via) in the fixed stator permitting flow in either direction.

Preferred embodiments of the invention will now be described, by way of examples only, and with reference to the drawings in which:

Brief Description of the Figures

Figure 1 a is a block diagram showing the relationship between coiled tubing to key components of: hydraulic medium, coiled tubing to surface, anti -rotational dimple connector; heavy duty anti-rotational motorhead, a straight bar and a tractor; Figure 1 b shows a diagrammatic overview of a drive section and shows the location of key components within the tractor assembly and their relationship to drive system;

Figure 1 c shows an extended heavy duty anti-rotational dimple connector;

Figure 1 d shows an overview of a dimple hammer used to fit and remove extended heavy duty anti-rotational dimple connector to a coiled tubing;

Figure 1 e shows a part sectional view through an example of a straight bar;

Figure 2a is a block diagram of components and their arrangement within a heavy duty anti-rotational motorhead with a cable bypass;

Figure 2b is a schematic block diagram showing motorhead components and their arrangement within a heavy duty anti-rotational motorhead without cable bypass;

Figure 3a shows sectional views through a tractor top sub-assembly incorporating a hydraulic flow diverter valve, shown in an open position;

Figure 3b below shows hydraulic flow diverter valve in the part closed position with the exhaust port closed to circulation to the annulus;

Figure 3c below shows hydraulic flow diverter valve in the closed position conducting flow to the tractor below;

Figure 4a shows a sectional view through an overpull direction control valve in a forward primary drive position with flow returning through an inner chamber and exhausting through an exhaust port;

Figure 4b shows a sectional view through an overpull direction control valve in the overpull secondary position with flow directed to a lower rotor into inner chamber, returning through an outer chamber and exhausting through an exhaust port;

Figure 4c shows a general view of a segmented control valve plug;

Figure 4d shows a part sectional view of a control valve plug and illustrates profile and segment flow ports;

Figure 4e shows a part sectional view of a control valve seat and locking grub screws;

Figures 5 to 8 show views of key components of a motor assembly drive system in different states in order illustrate its operation;

Figure 5 shows a sectional view of an upper (rearwards) section of a fixed positive displacement motor stator;

Figure 6 shows a part sectional view of the upper (rearwards) section of the fixed positive displacement rotor assembly and motor assembly drive system;

Figure 7 shows a sectional view of the motor assembly drive system with an elastomer drive sleeve in an outer casing expanded by the stator so as to form helical flexible rotor bead barriers; Figure 8 shows a sectional view of the upper rotor assembly drive system, including the stator and elastomer drive sleeve forming a series of helical flexible rotor bead barriers in helical pathways, depicting in detail a helical drive system ;

Figure 9a shows upper drive bow expander sub-assembly;

Figure 9b shows lower drive bow expander sub-assembly;

Figure 10 shows a half sectional view of exterior of upper rotor section in a relaxed position showing bi-directional splined expander assembly acting through thrust bearing on a drive bow assembly;

Figure 1 1 is an alternative drive expander unit arrangement and shows rotor assembly drives arranged against a planet gear system;

Figure 12a shows upper (rearward) drive bow assembly in relaxed position with attached engagement slip collapsed into an upper drive rotor casing;

Figure 12b shows a sectional view of Figure 12a including a planetary gear system with upper (rearward) drive bow assembly in a relaxed position and attached drive engagement slips collapsed into upper drive rotor casing;

Figure 13a shows lower (forward) drive bow assembly in a relaxed position with attached drive engagement slips collapsed into lower drive rotor casing;

Figure 13b shows a sectional view of Figure 13a including planetary gear system with lower (forward) drive bow assembly in a relaxed position and attached drive engagement slips;

Figure 14 shows an end cap in place with a drive bow expander and one of three drive bows;

Figure 15a shows drive arms in the relaxed position and fully retracted;

Figure 15b shows the drive arms with engagement slips in the expanded position;

Figure 16a shows a sectional view of an upper tractor section with a flow diverter valve, overpull direction control valve, stator and rearwards rotor assembly with an integral drive bow expander;

Figure 16b shows a diagrammatic continuation of Figure 16a with upper rearwards rotor section engaged with a planetary gear system which is connected to lower forwards rotor section and a splined section;

Figure 16c shows a further diagrammatic continuation of Figures 16a and 16b with lower forwards rotor section and drive bows (and engagement slips in place), splined section connected to drive bow expander assembly and lower rotor section with end cap assembly;

Figure 16d shows an overall (un-annotated) view of a complete tractor shown in separate Figures 16a, 16b and 16c; Figures 17a and 17b are schematic of a typical surface coiled tubing unit with blow out preventer hydraulic circuitry and coiled tubing injector pressure control equipment detail;

Figure 18 shows a schematic of a coiled tubing unit with an injector on a wellhead showing a typical hydraulic media (mud) system; and

Figure 19 shows a sectional diagrammatic view of a coiled tubing reel and injector with coiled tubing and tractor assembly in a well bore, in operation and shows hydraulic media (mud) flow and return from well bore.

Detailed Description of Preferred Embodiments of the Invention

Various aspects of the invention will now be described with reference to the Figures.

Figures 1 to 16 illustrate an embodiment of a tractor that has an hydraulic drive system. It will be appreciated that many aspects of the engagement means and devices; the direction and speed control and other preferred features are interchangeable from one drive system to another, as demanded by circumstances and the requirements of the tractor. Therefore it is understood that many of the features shown in Figures 8 to 16, and described in detail with respect to the hydraulic drive system may be included in the tractor that has an internal combustion engine as a drive system.

Referring to Figure 1 a, there is shown a block diagram showing the relationship between coiled tubing 2 to key components of: hydraulic medium 1 (not shown), coiled tubing to surface 2, anti-rotational dimple connector 3; heavy duty anti- rotational motorhead 4 or 8, a straight bar 5 and a tractor assembly 6.

Figure 1 b shows a diagrammatic overview of a drive section of the tractor assembly 6 and shows the location of key components within the tractor assembly 6 and their relationship to drive system and indicate that part 60 is a fixed positive displacement motor stator.

Referring to the Figures generally and in particular to Figures 1 a and 1 b, Figure 1 a is a block diagram which depicts the relationship between coiled tubing 2, which delivers hydraulic drive medium to key components of a tractor assembly 6.

The tractor bottom hole assembly includes a heavy duty anti-rotational dimple connector 3 (shown in detail in Figure 1 c) which is connected to the coiled tubing 2 and which further connects to a heavy duty anti rotational motorhead 4 or 8. In turn motorhead 4 or 8 connects to a straight bar 5 (shown in detail in Figure 1 e). Figure 1 e shows an example of a straight bar 5, which is a standard piece of equipment that adds weight to a bottom hole assembly and may be varied in length to suit specific deployment needs.

Straight bar 5 also acts as a spacer and connector and is a standard piece of equipment. Straight bar 5 connects motorhead 4 or 8 to tractor assembly 6 as shown in Figures 1 a and in detail in Figure 1 e. It should also be noted that both forms of motorhead 4 and 8 hereindescribed is a standard piece of equipment manufactured by a number of specialist manufacturers. The specification of the motorhead may change between manufacturers and its operational requirements may be determined by the operator. Accordingly the means of achieving circulation to a well bore annulus and detachment may vary from using drop balls, jarring impacts or overpressure of hydraulic medium 1 . Detachment functions may differ as may surface applied overpressure of hydraulic drive medium 1 and/or surface applied overpull or jarring to shear out shears screws or shear pins. A drop ball may be used to either detach or circulate hydraulic drive medium 1 to the well bore 99.

Referring now to Figure 1 b schematic tractor assembly shows fixed positive displacement motor stator 60 surrounded and enveloped by rotor sections 67 and 68 and are connected by planetary drive 65. Upper rotor section 67 and lower rotor section 68 are attached to drive bow expander assemblies 63 and 69 and drive bow carrier assemblies 64 and 70. Optionally rotor section 67 and lower rotor section 68 are connected to secondary expander assemblies 61 and 62 which are in turn connected to and operate to expand drive bows 71 and 72. Engagement slips 73 and 74 are connected to drive arms assemblies 75, 76, 77 and 78.

Figure 1 b also shows diagrammatically the position of a hydraulic flow diverter valve 30, shown in detail in Figures 3a, 3b and 3c, which is connected to an overpull direction control valve 50, which is shown in greater detail in Figures 4a and 4b. An upper drive bow expander 63 incorporates a thrust bearing 635 (Figure 9a) where it acts against drive bow assembly 71 and optionally against drive arm assemblies 75 and 76. A lower drive bow expander 69 incorporates thrust bearing 696 (Figure 9b) which acts against drive bow assembly 72 and optionally against drive arm assemblies 77 and 78.

Upper rotor section 67 incorporates flow retaining thrust bearings 673 (Figures 4a and 4b) and 674 (Figure 12b). Lower rotor section 68 incorporates flow retaining thrust bearings 684 and 661 (Figures 13b and 14). The tractor 6 may be used for well interventions which do not require power or signal cable conveyance. In these interventions the same tractor assembly is run on heavy duty anti-rotational motorhead without cable bypass as shown, for example in Figure 2b where drop balls, surface pump overpressure (Figure 18) and surface applied overpull operation may be used to effect detachment of the coiled tubing 2 from the tractor assembly 6 or open a circulation path for hydraulic media 1 to well bore 99.

The heavy duty anti-rotational dimple connector 3 is fitted to the coiled tubing 2 by means of a dimple hammer 10 and shown in Figure 1 d. The dimple hammer 10 shown in Figure 1 d is a modification of a standard tool permitting a longer connector body with more dimples in the coiled tubing 2 may be created and more dimple screws 106 may be fitted and therefore a strong bind with the coiled tubing 2 than the standard connector. Dimple hammer 10 is used to create dimples in the coiled tubing 2 to match heavy duty anti-rotational dimple connector 3 where the connector body has been extended to accommodate additional seals 33, 34 and additional grub screws 36 (whose number and position may change due to individual operational requirements).

Operational pressure and overpull requirements need to be calculated and sufficient overpull tension and over-pressure delivery at the tool needs to be carefully established so as not to detach or circulate mud during high flow/pressure operating conditions or momentary pressure spikes as many occur, such as in tractor reversing operations, and are used as an indicator (tattle-tail or tell-tale) of a change of state within the tool and seen at surface.

Referring to Figure 1 b, a planetary gear system 65 is shown in association and connected to upper rearward 67 and lower forward 68 rotor sections and end cap 66. Upper rearward 67 and lower forward 68 rotor sections connect respectively to drive bows 71 and 72 which are connected to drive engagement slips 73 and 74 or optionally to drive arms 75, 76, 77 and 78 and engagement slip assemblies 763, 764 and 765 and 783, 784 and 785 respectively.

Figure 1 c shows an extended heavy duty anti-rotational dimple connector; where: the coiled tubing 2 connects to surface heavy duty anti -rotational dimple connector body 31 . A threaded hole 32 is formed to accommodate locking grub screws 36 (not shown). O-ring seals 33 and 34 are located between coiled tubing 2 and dimple connector body 31 in order to prevent fluid bypass and pressure loss to the well bore 99.

Figure 1 c shows a dimpled connector 3 fitted over coiled tubing 2. Coil tubing has dimples 35 formed thereon by dimple forming set screw 102. The dimples receive grub screws 36 with a domed nose which screw into threaded holes 32 around the circumference of a heavy duty anti-rotational dimple connector body 31 in order to engage dimpled sections 35 of coiled tubing 2. This connection ensures securing the heavy duty anti-rotational dimple connector body 31 to the coiled tubing 2. A connecting thread 37 connects the connector 3 to motorhead 4 or 8.

Figure 1 d shows a dimple hammer assembly 10 which is used to fit and remove extended heavy duty anti-rotational dimple connector 3 to coiled tubing 2. Coiled tubing 2 is inserted into drive-over dimple mandrel 101 by hammer action. Dimple forming set screws 102 are hardened and have an extended round nosed and hex- drive. A slide hammer 104 runs on a sliding hammer core 103.

Figure 1 e shows a part sectional view through an example of a straight bar 5 and a straight bar body 51 and O-rings 52.

Figure 2a is a block diagram of the components and their arrangement within a heavy duty anti-rotational motorhead 4 with a cable bypass 407. A top subassembly 401 provides a connection to heavy duty anti rotational dimple connector 3 and to a straight bar 5 at the bottom sub 406. A dual check valve assembly 402 provides a double barrier preventing back flow from a well to coiled tubing 2. A circulation sub-assembly 403 opens a circulation path through the motorhead 4 to a well bore annulus 99. This may be operated by from the surface by surface applied overpressure. A release joint 404 allows detachment of upper section of the motorhead 4 to expose an internal fishing neck profile 405 which may be operated from the surface by surface applied overpull or optionally by fluid overpressure.

An up-facing internal fishing neck 405 may be latched by a suitable fishing/pulling tool not shown to recover the motorhead 4 and any attachments to the surface in the event of a detachment and is described in detail below. Bottom sub-assembly 406 provides a connection to straight bar 5 and/or tools and/or a tractor 6 allowing the connection of logging tool cable 7 from surface to logging tool 9 shown in Figure 19. A cable bypass 407 with seals not shown provides a means of passage for a logging tool cable 7, power and a signal cable connection to a logging tool 9 payload shown in Figure 19 below the tractor assembly.

It should further be noted that a logging cable 7 may be fitted with an overpull electrical disconnect socket 48 (not shown) which allows the separation of the cable in the event that release joint sub-assembly 404 is operated. Overpull electrical disconnect socket 48 and logging cable 7 is ideally positioned so as not to interfere with latching of the fishing tool in 405.

Referring now to Figure 2b there is shown a schematic diagram of motorhead components and their arrangement within an embodiment of a heavy duty anti - rotational motorhead without a cable bypass 8. A top sub-assembly 401 provides a connection to heavy duty anti-rotational dimple connector 3. A dual check valve 402 assembly provides a double barrier preventing back flow from well bore 99 to coiled tubing 2. A circulation sub-assembly 403 opens a circulation path through the motorhead 8 to the well bore annulus 99 and may be operated by drop ball from surface or by surface applied overpressure.

Release joint 404 allows detachment of upper section of the motorhead 8 to expose a fishing neck profile at 405 which may be operated by drop ball from surface or by surface applied overpull. Up-facing internal fishing neck profile in 405 may be latched by a suitable fishing tool (not shown) to recover the motorhead and attachments to surface in the event a detachment. Bottom sub-assembly 406 provides a connection to straight bar 5 and/or tools and/or a tractor 6.

Figure 3a shows sectional views through a tractor top sub-assembly incorporating a hydraulic flow diverter valve part 30, shown in its open position circulating flow to the well bore 99. Figure 3b shows hydraulic flow diverter valve 30 in the part closed position with an exhaust port 302 closed to circulation to the well bore 99. Figure 3c shows hydraulic flow diverter valve 30 in the closed position so as to divert flow to overpull direction control valve 50.

Referring to Figures 3a, 3b and 3c a hydraulic flow diverter valve body 301 is shown. There is a circulation port 302 in hydraulic flow diverter valve body 301 and in a shuttle sleeve 303. O-ring seals 304, 305 and 323 act with piston 306 to initially compress disc spring stack 309 as shown in Figure 3b. Also shown are O-ring seals 307, 308 and 315 which prevent fluid bypass between piston 306 and cable conductor tube 317 to prevent pressure loss. A disc spring stack 309 is arranged to collapse under the action of hydraulic medium 1 flow against the piston areas in shuttle sleeve 303. A piston stop collar 310 limits travel of piston 306. Disc spring stack calibration shims 31 1 are arranged to adjust the resistive force of the disc spring stack 309 ported piston and disc spring support ring 312 acts to support disc spring stack calibration shims 31 1 and piston stop collar 310 whilst also providing a support housing for piston 306 to travel along cable conductor tube 317.

Also shown are O-ring seals 307, 308 and 31 5 sealing between piston 306 and cable conductor tube 317. Piston return coil spring 314 ensures piston sealing flange maintains contact with shuttle sleeve 303 in open and part closed operation shown in figures 3a and 3b. Piston return spring adjuster ring 316 is arranged to adjust and set the resistive force of piston return coil spring 314. A cable conductor tube 317 shown in Figures 3a 3b and 3c, attaches to the cable conductor tube 542 shown in Figures 4a and 4b. Logging tool cable 7 is listed as cable section 318 in Figures 3a, 3b and 3c and centred in cable conductor tube 317 which is held in place by ported cable conductor support ring 319 with conductor tube seal 322 and ported piston and disc spring support ring 312. Locking grub screw 320 connects ported cable conductor support ring 319 to hydraulic flow diverter valve body 301 . Within ported cable conductor support ring 319 is a splined travel joint outer with a stop ring profile 325 whose internal splines mate with external splines on 317 cable conductor tube. Cable conductor tube 317 has threaded lock ring 324 attached to the threaded section of 317 to act as a stop ring against the stop ring profile on the splined travel joint with stop ring profile 325. Also, within ported cable conductor support ring 319, is a conductor tube seal 322 sealing against cable conductor tube 317 and logging cable 7 shown as logging cable section 318 in figures 3a and 3c.

Figures 4a and 4b show an example of an overpull direction control valve 50. Figure 4a shows a sectional view through the overpull direction control valve 50 when in a forward primary drive position, with flow directed to an outer flow chamber 547 via ports in ported support ring 1 522 through segmented flow control valve seat 530, segmented flow control valve plug 525 and ports in second ported support ring 537 to upper rotor section 67. Flow returns through the annulus between logging cable section 543 (7) and cable conductor tube 542 entering an inner chamber 548 through flow port 551 in cable conductor tube 542 and exhausts therefrom via exhaust ports 533

Figure 4b shows a sectional view through an overpull direction control valve 50 in an overpull secondary position with flow directed to the lower rotor 68 through port 532 into inner chamber 548 and into the annulus between cable 543 and cable conductor tube 542 through port 551 returning through outer chamber 547 and exhausting through exhaust ports 533.

Top sub-assembly 521 spline with a stop profile 521 A is formed in the top subassembly 521 . A ported support ring 522 has locking grub screws 523 which lock it in place with respect to top sub 521 . A circlip 524 ensures that segmented flow control valve plug 525 does not over travel under the resistive force of coil spring 544 and ensures flow between segmented flow control valve plug 525 and segmented flow control valve seat 530 to upper chamber 547 in the open position as shown in Figure 4a to drive tractor in the forwards direction into the well bore 99.

The segmented flow control valve plug 525 is arranged to close against segmented flow control valve seat 530 when overpull is experienced from surface . A disc spring stack 527 is compressed under surface overpull by tension taken through top sub assembly 521 which is transmitted to disc spring retainer sleeve 528 through ported support ring 522 so as to initially compress coil spring 558 and when in full compression acts upon spring trust ring/shim to compress disc spring stack 527 and move segmented flow control valve plug 525 to close off the flow path through segmented flow control valve seat 530. O-rings 529, 534 and 546 are shown and prevent flow between sleeve 535 and segmented flow control valve plug 525 as explained in detail below.

Locking grub screws 531 secures segmented flow control valve seat 530 to bottom sub 536, locking grub screw 559 secures stop profiled slotted spline ring 536a to bottom sub 536. When overpull is applied from surface, top sub 521 with spline 521 a extends against stop profile slotted spline ring 536a to a point where travel is limited by closing stop profile 521 a and stop profile on 536a. In so doing this overpull also acts upon hydraulic flow diverter body 301 (as shown in Figures 3a, 3b and 3c) which being attached to ported cable support ring 319 (by locking grub screws 320) transfers the surface applied overpull tension to the splined travel joint outer with stop ring profile 325, such that it similarly travels on the splined section of cable conduction tube 317.

Travel of the stop ring profile 325 is restricted by contact with threaded lock ring 324, so that overpull is transferred to overpull control valve 50 and not to the fixed stator assembly 60, by tension on conductor tube sections 317 and 542. Segmented flow control valve plug 525 operates so as to close flow to multiple exhaust ports 533 to close flow from inner chamber 548 and opens flow to multiple exhaust port 533 to exhaust flow from outer chamber 547.

Bottom sub-assembly 536 is attached to stop profiled slotted spline ring 536a which is secured to bottom sub body 536 by a threaded connecting body joint and multiple locking grub screws 559. A stop profile on stop profiled slotted spline ring 536a is arranged to engage and stop against stop profile 521 a. Ported support ring 537 is arranged to support and fix sleeve 535. A locking grub screw 538 ensures O-rings 539, 540, seal between ported support ring 522 and cable conductor tube 542, O- ring 541 seals between disc spring retainer sleeve 528 and cable conductor tube

542, O-rings 529, 534 and 546 seals between sleeve 535 and segmented flow control valve plug 525. Cable conductor tube 542 receives logging section cable

543. A coil spring 544 is arranged to act between ported support ring 522 and segmented flow control valve plug 525.

Multiple ports are located in ported support ring 522 to provide a flow path to outer flow chamber 547 in the open position through the open segmented control valve plug 525. Figure 4b shows segmented control valve seat 530 and inner flow chamber 548 in the closed position when segmented flow control valve plug 525 closes flow through segmented control valve seat 530. Overpull direction control valve 50 operates by applying a tension to the coil tubing 2 and this results in a direction change of the tractor 6 as described below.

Overpull direction control Thrust bearing housing 549 is locked by locking grub screws 550, 551 is a flow port in cable conductor tube 542, 552 is the inner flow segregating toroid 552 for ported support ring 537. O-ring 553 seals between cable conductor tube 542 and inner flow segregating toroid 552, locking circlip snap ring 554 prevents movement of inner flow segregating toroid 552 against cable conductor tube 542. Locking circlip snap ring 555 prevents movement of inner flow segregating toroid 552 against sleeve 535 and O-ring 556 seals between inner flow segregating toroid 552 and sleeve 535. Inner flow segregating toroid 552 prevents flow between outer flow chamber 547 and inner flow chamber 548. It should be noted that the combined fixing of inner flow segregating toroid 552 to cable conductor tube 542, is by way of a locking circlip snap ring 554 and fixing to sleeve 535 by locking circlip snap ring 555. The connection of sleeve 535, to ported support ring 537 is attached to bottom sub assembly 537 by locking grub screw 538 so as to hold fixed stator 60 in place. In the open position flow of hydraulic media 1 exhausts from inner chamber 548 to well bore 99. In the closed position flow ports 557 in sleeve 535 and flow port 533 in body 536 are no longer in alignment with segmented control valve plug 525 and so prevent flow of hydraulic media 1 to the well bore 99. In the closed position hydraulic media is exhausted through ports 533 which are now exposed to flow from outer chamber 547.

Referring now to Figure 16b an overview through one embodiment of a tractor assembly 6 is shown, including a planetary gear system 65 connecting upper (rearwards) rotor assembly 67 to lower (forwards) rotor assembly 68 in a position over a fixed static stator 60 which is attached to a planetary gear plate 653.

Upper rotor jacket 672 and lower (forwards) rotor jacket 682 are shown and planetary gear flow ports 650 are located between upper (rearwards) rotor 67 and lower (forwards) rotor 68 with upper (rearwards) rotor flow retaining thrust bearing 674 and lower (forwards) flow retaining thrust bearings 684 sealing against the planetary gear plate 653.

Figure 16b shows planetary gear 651 supported by a planetary gear axle 652 in place in planetary gear plate 653 and upper (rearwards) drive bows 716, 717 and 718 and lower (forwards) drive bows 726 and 728 secured by upper (rearwards) drive bow axle 715 and lower (forwards) drive bow axle 723 in upper (rearwards) rotor assembly 67 and lower forwards rotor section 68, both having drive bow carrier profiles machined into the upper (rearwards) rotor casing 671 and lower forward rotor casing 681 .

The aforementioned drive bow arrangement also allows the drive bows or drive arms to retract in the event of the tractor assembly encountering a variation in well bore diameter whilst still applying maximum traction against the well bore. This is achieved by means of the action in opposing spiralling helices in upper rearward drive bow expander assembly 63 and in lower forwards drive bow expander assembly 69 which assist the drive bows assemblies 71 and 72 or drive arms 75, 76, 77 and 78 to collapse and re-expand them to engage with the well bore when hydraulic flow through the rotors 67 and 68 is changed due to sensed surface overpull and accordingly a change of flow direction through the rotors ensues, as is explained below.

It should be noted that in an alternative drive system dual arms are attached at top and bottom locations to engagement slips 763, 764 and 765 in upper rearward rotor 67 and engagement slips 783, 784 and 785 in the lower forward rotor 68 by axles 753, 755, in upper rotor 67 and 773 and 775 in the lower rotor 68 in a similar manner as the drive bows. These dual arms 75, 76 and 77, 78 have further axles 760 and 762, connecting the drive arms 756 and 757 to the upper rearward drive engagement slips 763, 764, 765, as shown in Figures 15a and 15b and have further axles 780 and 782 connecting the drive arms 776 and 777 to the lower forwards drive engagement slips 783, 784 and 785.

Optionally drive arms are inter-changeable with drive bows because of common axle ports, axle sizes and drive bow and drive arm assembly lengths. Additionally the drive arms are retracted by upper drive arm leaf springs 758 and lower drive arm leaf springs 778 mounted under upper rearwards engagement slips 763, 764, 765 and lower forwards drive engagement slips 783, 784 and 785 respectively and acting upon the upper rearwards drive arms 756 and 757 and lower forwards drive arms 776 and 777. These leaf springs 758 and 778 may be formed from a spring steel alloy such as Inconel (Trade Mark) or another spring like material to suit well conditions and drive arm engagement action.

As with the drive bow systems (such as assemblies 71 and 72) these drive arms may be connected to both the drive carrier sub-assemblies and drive expander subassemblies by axles.

A further drive arm return means interposes an elastomer material, such as Viton 90 (Trade Mark) between drive arms 756, 776 and 777 and expander assemblies 61 , 62, 63 and 69, so as to form a fixed cylindrical trunnion, such that when torque is removed the cylindrical trunnion acts upon the drive arms to retract them to the body of the drive assemblies in the same manner as a trunnion type suspension unit. As mentioned above, in the relaxed position, the upper forwards drive engagement slips 763, 764 and 765 retract back into recesses 679a, 679b and 679c defined in the drive upper rearward drive bow body 675 and lower forwards drive engagement slips 783, 774 and 785 retract back into recesses 689a, 689b and 689c defined in the drive lower forwards drive bow body 685

Referring to Figure 12a there is shown drive bows 716, 717, 718 (supported on upper rearwards drive bow assembly 71 ) and in Figure 13a drive bows 726, 727, 728 (supported on lower forwards drive bow assembly 72). The drive bows may be replaced by dual pivoted upper rearwards and lower forwards drive arms assemblies 75/76 and 77/78. Upper rearwards drive arm assembly 75 includes drive arms 756a and 756b and 756c, 757a, 757b and 757c and leaf return springs 758a, 758b and 758c.

Additionally in completions where either the well bore is larger, and thus where a greater expansion is required to set the drive engagement slips against the well bore or where required expansion would exceed a safe bending limits of a drive bow, an additional set of expander mandrels may be used in place of carrier sub-assemblies to double the expansion of the drive engagement slips. Expander mandrels are located as shown in Figure 1 1 so that two drive arm expander mandrels act upon each end of the drive arms or drive bows. In this configuration a total of four expander mandrels are provided. A further advantage of using this dual expander mandrel approach is that the drive slip automatically levels against the well bore with any variation taken up by movement within expander helices.

Figure 16d shows an overall view of an example of a tractor assembled in three sections (Figures 16a, 16b and 16c) with drive bows 71 located at the upper (rearwards) and 72 lower (forwards) in position on drive rotors 67 and 68. This arrangement uses single forwards 69 and rearwards 63 drive bow expanders with drive bow carrier sub-assemblies forwards 70 and rearwards 64 located at the centre of a tractor by planet gear system 65 as shown in Figure 16b.

In some applications it may be desirable to replace drive bow carriers with dual expander mandrels as shown in Figure 1 1 and to replace the drive bows with drive arms as described in Figure 15.

Figures 17a and 17b are schematic views of a coiled tubing unit surface rig up and depicts in diagrammatical form a coiled tubing unit surface rig up of a system including coil tubing unit, injector head, control cabin, hydraulic lines, pumps and tanks. A typical blow out preventer hydraulic supply and return hose cluster 120 is shown together with an operator control cabin 87 and a blow out preventer stack 21 . Figure 18 shows a schematic diagram of typical surface layout of a mud circulation system and a schematic of coiled tubing key components. Figure 19 shows coil tubing in the well bore and a tractor assembly in situ in a well bore under drive.

The following is a description of how dimples are created in the coiled tubing. Dimples in the coiled tubing 2 are made by fitting drive-over dimple mandrel 101 over coiled tubing 2 and using the slide hammer action using slide hammer 104 riding on 103 is the slide hammer core to impart impacts to seat the drive-over dimple mandrel 101 to the end of the coiled tubing 2 .

Dimple forming hardened set screws 102 are then tightened in pre-drilled and threaded holes to make a dimple 35 in the coiled tubing 2 at predetermined positions to align with the grub screws 106 to fit the dimple connector 3 to the coiled tubing 2. Once the dimples 35 are made in coiled tubing 2 the dimple forming hardened set screws 102 are removed and the dimple hammer 10 removed from the coiled tubing 2 by reversing the slide hammer action.

Heavy duty anti-rotational coiled tubing connector 3 may then be fitted to the dimple connector receptacle 105 on the drive over dimple hammer 10 which may then be aligned with the dimples 35 in coiled tubing 2 and fitted to the coiled tubing 2 by slide hammer action. The dimple hammer 10 is then removed and heavy duty dimple connector 3 and dimple connector grub screws 106 tightened into threaded holes 32, in heavy duty anti rotational dimple connector body 3, to secure it to coiled tubing 2 securing with grub screws 106 to lock to coiled tubing 2. The heavy duty anti - rotational coiled tubing connector 3 is then attached to motorhead 4 or 8.

It should be noted overpull direction control valve 50 is set to 'snap action' due to the inclusion and action of disc springs stack 527. A degree of proportional control of forward drive to overcome variations in overpull tensile on the coiled tubing from surface or drag caused by coiled tubing friction against the well bore, may be desirable to control the amount of 'pull' delivered by the tractor 6 which could possibly exceed the safe working tensile limits of the coiled tubing 2 and bottom hole assembly 2-6 and optionally 8 as shown in Figure 1 a.

Accordingly a degree of proportional control may be achieved by adding a coil spring 558 and spring thrust ring/shim 561 to disc spring stack 527 such that when overpull is applied through the coiled tubing 2 this firstly compresses the coil spring 558 which acts as load compensator, where the coil spring 558 at maximum compression is set below the disc spring collapse load and therefore compensates for load peaks due to well bore friction, before collapsing on full surface overpull and so that the tensile load is transferred directly onto disc spring stack 527 through spring trust ring/shim 561 .

When the transmitted load exceeds the collapse load, the disc spring stack 527 moves with a snap action, a segmented control valve plug 525 engages against a segmented flow control valve seat 530 and which also similarly opens segmented control valve port 532 with a snap action to reverse the flow path of an hydraulic medium 1 effectively allowing hydraulic flow at full flow and pressure through the segmented control valve port 532 to inner chamber 548, through port 551 in to the bore of the cable conductor tube 542 and so delivering hydraulic medium 1 to the lower forwards rotor assembly 68 to apply the drive in a reverse direction to travel up the well bore 99 towards surface.

To provide an increased degree of proportional control, the spring ranges of both disc springs stack 527 and coil springs 544 and 558 may be varied in order to proportionally control the drive power delivered. Also the thickness of spring thrust ring/shim may be varied to calibrate and pre-load the amount of resistive compression force applied by the disc spring stack 527 and by coil spring 558. Likewise port flow areas may need to be varied in order to control drive power delivered.

The hydraulic medium 1 acts as a power supply and flows along a fluid pathway, such as the coiled tubing 2. Hydraulic drive medium 1 is diverted along helical pathways 12 (as shown in detail in Figures 6 to 9) between stator sections 601 and jacket 672 in upper rearward rotor assembly 67; and stator 602 and jacket 682 in lower forward rotor assembly 68. This results in dynamic fluid pressure urging the stator jacket 672 into a corresponding helical pathway 12 following external helical profile 24 in an external wall of the stator sections 601 (60) and 602 (60) causing a trunnion or helical flexible bead barrier 20 to form in the internal stator jacket of rotor housing 672 and 682 as part of rotor assembly 67 and 68. The force exerted by the drive medium 1 causes the external rotor assembly 67 and 68 to rotate with respect to the stator 60.

Referring to Figures 5 to 8 generally and in particular to Figure 7 there is now shown in greater detail a sectional view of a rotor drive system 67 with a stator jacket 672 and 682 flexing and distorting as it passes over a helical pathway 12 formed against external profile on stator section 24. The stator jacket 672 and 682 are formed from an elastomer drive sleeves, which are attached to external rotor casing 671 and 681 forming rotor sections 67 and 68, are expanded by the stator 60 so as to form a rotating helical flexible rotor bead 20. The stator jackets 672 and 682 are flexible so that it conforms to an external helical profile 24 of the stator 60 thereby defining at least one fluid pathway for the drive medium 1 , which may be saline, diesel, water or drilling/chemical mud.

The hydraulic drive medium 1 acts as a power supply and flows along a delivery channel, such as coiled tubing 2. Hydraulic drive medium 1 is diverted along helical pathway 12 (Figure 6) between the stator 60 and the stator jacket 672 and 682 (Figure 16) acting against helical flexible rotor bead barriers 20 causing the upper rotor housings 67 and 68 to rotate and engage with a well bore 99 (not shown) by way of engagement slips 73 and 74 mounted on drive bow assemblies 71 and 72.

Drive bow assemblies 71 and 72 are operated by upper drive bow expander units 63 and lower drive bow expander unit 69. Upper rearward drive bow expander unit 63 and lower forward drive bow expander unit 69 operate against drive bow carriers 64 and 70 that are fixed to their respective upper 67 and lower 68 rotor sections as described in greater detail below with reference to Figures 1 2a and 13a. Operation of the stator 60 is also described below.

Referring again to Figure 2a which is a block diagram showing the location and relationship between key components of a typical motorhead 4 with cable bypass; and Figure 2b which shows the key components of a motorhead 8 without cable bypass. In both instances a motorhead 4 or 8 as described in this specification is a standard piece of equipment manufactured by a number of specialist manufacturers. The specification of the motorhead may therefore change between these manufacturers. Accordingly the means of achieving circulation to the well bore annulus and initiating detachment may vary from using drop balls or darts launched from surface through the coiled tubing 2 in motorhead 8 without cable bypass to initiate circulation and detachment functions.

Referring to motorhead 4 with cable bypass, it should be noted that logging tool cable 7 in the bore of coiled tubing 2 may cause a potential obstruction to drop balls or darts. It is more usual to use surface applied overpressure of hydraulic drive medium 1 or surface applied overpull to shear out shear screws or shear pins may be used to either detach the rest of the motorhead assembly or to circulate hydraulic drive medium 1 as an alternative to drop ball operation. Accordingly operational pressure and overpull requirements need to the calculated and sufficient overpull tension and over-pressure delivery at the tool needs to be carefully established so as not to detach or circulate during high flow/pressure operating conditions or momentary pressure spikes, as many occur such as in tractor reversing operations and are used as an indicator (tattle-tail or tell-tale) of a change of state within the tool and seen at surface.

Likewise in the case of motorhead 4 (with cable bypass) an overpull electrical cable disconnect socket 48 (not shown) should be fitted to the logging cable 7 to act as a detachment feature to disconnect electric current and signal from logging cable 7 from the payload, such as a logging tool 7 (not shown). This overpull electrical cable disconnect socket 48 should be so positioned in the cable bypass duct so that it does not interfere with the latching of a pulling or fishing tool during retrieval (fishing) of the motorhead and any attached tools to surface. Conveyance of a standard tractor bi-directional tool string to pull downhole devices avoids excessive overpull in jarring operations.

Hydraulic media 1 is conveyed through the coiled tubing 2, dimple connector 3, and motorhead 4 or 8 and straight bar 5 to the tractor top sub-assembly and thence to hydraulic flow diverter valve 30, shown in detail in Figures 3a, 3b and 3c. The operation of the hydraulic flow diverter switch 30 is important and is described in detail below.

Hydraulic drive medium 1 (mud) is pumped from a remote surface station (not shown) and enters the tractor assembly 6 via coiled tubing 2, anti -rotational dimple connector 3, heavy duty anti-rotational motorhead 4 or 8, straight bar 5 to the hydraulic flow diverter valve 30. Depending upon the differential pressure acting on piston 306 within hydraulic flow diverter valve 30, hydraulic drive medium 1 is either ported to the well bore 99 through ports 302 when in the relaxed open position or forced through the body of the hydraulic flow diverter valve 301 when in the closed position where differential pressure acts upon piston 306, moving the shuttle sleeve 303 back against spring disc spring stack 309. At this position piston 306 flange lands on and shifts shuttle sleeve 303 so acting to close port 302 and thereby stops circulation to the well bore 99 (Figure 3b).

These actions in turn open a new flow path through the tool as hydraulic media 1 flow acts upon the shuttle sleeve 303 flange forcing it back against disc spring stack 309 and opening a flow path between piston 306 and shuttle sleeve 303, as shown in Figure 3c. This delivers hydraulic media 1 to the overpull flow diverter valve 50. The direction of flow of the hydraulic drive medium 1 , through the overpull flow diverter valve 50 (as seen in Figures 4a and 4b) determines whether the tractor assembly 6 travels forwards or backwards along a well bore 99 (not shown).

The operation of the overpull direction control valve 50 is therefore important and will be described in detail below.

The overpull direction control valve 50 is set to 'snap action' due to the inclusion and action of disc springs stack 527. A degree of proportional control of forward drive to overcome variations in overpull tensile on the coiled tubing 2 from surface or drag caused by coiled tubing friction against the well bore may be desirable to control the amount of 'pull' delivered by the tractor 6 which could possibly exceed a safe working tensile limits of the coiled tubing 2 and bottom hole assembly.

Proportional control may be achieved by adding a coil spring 558 and spring thrust ring/shim 561 to the disc spring stack 527 such that when overpull is applied, through the coiled tubing 2, this firstly compresses the coil spring 558 before the overpull tensile of coiled tubing or drag overcomes the disc spring collapse resistance and moves segmented flow control valve plug 525 in a snap action towards the segmented flow control valve seat 530 and which immediately opens segmented control valve port 532 in segmented control valve 530, effectively allowing maximised hydraulic flow to bleed through the segmented control valve port 532 so changing the direction of flow to the rotor sections and changing direction of flow delivery and accordingly the direction of drive of tractor 6.

To provide an increased degree of proportional control the spring ranges of both disc spring stack 527 and coil springs 544 and optionally 558 and port flow areas may need to be varied in order to proportionally control the drive power delivered. In certain downhole intervention operations where a consistent pull, rather than a consistent speed is required, it may be necessary to increase the degree of proportional control and change the action of overpull direction control valve 50 to a fully overpull operated proportional control.

Where disc spring stack 527 is replaced longer coil spring 558 , which progressively collapses against surface applied overpull or drags with moves segmented flow control valve plug 525 in a progressive manner towards the segmented flow control valve seat 530 and which also progressively opens segmented control valve port 532. This effectively allows flow to bleed through the port 532 to circulation to well bore 99 and thus reduces the power delivery to the rotor sections 67 and 68. In the relaxed position hydraulic media 1 flows to the upper (rearward) drive bow rotor assembly 67.

Interposed between upper (rearward) drive bow rotor assembly 67 and lower (forward) motor drive assembly 68 there is a planet and gear drive system 65 and an example of this is shown in Figure 16b. The planet gear drive system 65 has a planet gear plate 653 that connects upper rearward drive rotor assembly 67 to a lower forward rotor assembly 68 through a series of planet gears 651 .

The planet gears 651 are centred and held in a planet gear plate 653 by planet gear axles 652 thereby transmitting regulated drive in both (clockwise and anticlockwise) senses from upper drive rotor assembly 67 and lower drive rotor assembly 68, so that the upper rotor assembly 67 and lower rotor assembly 68 rotate in opposing senses when flow acts from either the upper drive rotor assembly 67 or the lower drive rotor assembly 68. The result is that the planet gear drive system provides a power balanced and connected drive in opposing senses.

By way of this connected drive, the planet gear drive system 65 also regulates the speed of rotation of both upper 67 and lower 68 rotors assemblies. Also the planet and gear drive system 65 helps to compensate for any power or speed variation between upper 67 and lower 68 rotors.

When a change in the direction of travel of the tractor 6 is required, tension is applied to the coiled tubing 2, by not paying out any additional tubing whilst continuing to supply hydraulic drive medium 1 through coiled tubing 2 so that an overpull state is reached. This operates the overpull direction control valve 50 reversing flow through the upper and lower positive cavity rotors 67 and 68 and accordingly reverses the direction of the tractor 6.

In the event that hydraulic power, controlled by surface pump 152 to hydraulic drive medium 1 , is reduced hydraulic flow diverter valve 30 opens and diverts flow from a rotor sections 67 and 68 to the well bore 99. The drive bows 71 and 72 are retracted and drive arm assemblies 75, 76, 77 and 78 and engagement slips 73 and 74 are retracted from bearing against the well bore.

As a result surface overpull returns tractor 6 and any attached tools, to the surface whilst providing circulation to the well bore 99 through hydraulic flow diverter valve 30 via circulation port 302. It is appreciated that this drive arrangement will fail safe in the event of hydraulic power supply ceasing. The failsafe process is described in greater detail below with reference to Figures 3a and 3b.

A hydraulic flow diverter valve 30 which, in its open position, diverts flow to well bore 99 and in the closed position diverts flow of hydraulic drive medium 1 to a overpull direction control valve 50 operates using overpull, as described below and shown in Figures 4a and 4b. Hydraulic flow diverter valve 30 is shown in detail in Figures 3a, 3b and 3c. The hydraulic flow diverter valve 30 is triggered by over pressuring piston 306 which slides on a conductor tube 317 and acts to compress shuttle sleeve return disc spring stack 309 and thus moves shuttle sleeve 303 to close flow to well bore 99 via circulation port 302.

The piston 306 seats against piston stop collar 310 and shuttle sleeve 303. When the flow path to well bore 99 through circulation port 302 is closed, flow and pressure exerted by hydraulic drive medium 1 acts against the shuttle sleeve 303 to fully collapse shuttle sleeve return disc spring stack 309 opening a flow path through the hydraulic flow diverter valve body 301 to an overpull direction control valve 50 which in its open state permits flow through the tool thereby allowing the hydraulic medium 1 to act upon the upper positive cavity drive rotor 67 and through the planet gear system 65 to the lower rotor assembly 68.

Figure 16b shows an overview through tractor 6 showing positioning and relationship of the sections of the drive system of the tractor 6 showing upper rotor assembly 67 connected to lower rotor assembly 68 positioned over fixed positive displacement motor stator 60. Opposed helical profiles of the fixed positive displacement motor stator 601 and 602 are shown in position sealing against upper (rearwards) rotor jacket 672 and lower (forwards) rotor jacket 682. Upper rotor assembly 67 and lower rotor assembly 68 are connected by planetary gear system 65 which regulates rotational speed between both rotors and shows upper rotor flow retaining thrust bearing 673 and 674 sealing against planetary gear plate 653 and upper rotor casing

671 and lower rotor flow retaining thrust bearings 684 and 661 sealing against planetary gear plate 653 and lower rotor casing 681 .

Referring to Figures 4a and 12b the flow retaining thrust bearings 673 and 674 and 684 and 661 permit relative rotation of upper 67 and lower 68 rotors and with thrust bearings 684 and 674 permitting relative rotation of upper rotor 67 and lower rotor 68 against planetary gears 65. Flow retaining thrust bearings 673 and 661 permit relative rotation of upper rotor 67 with respect to overpull direction control valve 50 and lower rotor 68 with respect to end cap 66. In the case of the lower rotor 68 the flow retaining thrust bearings 661 permit relative rotation of the upper drive rotor 67 and lower drive rotor 68 with respect to an end cap 66.

Figure 5 shows a sectional view through another embodiment of a stator 60. Figure 5 shows a (fixed) stator 60 with a single helical or corkscrew drive profile machined to the exterior surface of the stator 60. Referring to Figures 4a, 4b, and 14 a logging tool cable 7, providing power supply and signal to the logging tool 9, passes through a cable via 14 in the stator 60. This cable via 14 also enables flow of hydraulic drive medium 1 in both directions through the tractor.

A logging tool signal is sent from a remote logging tool 9 (not shown) to the surface. The tractor 6 is also capable of well construction operations and accordingly a logging tool power supply and signal cable may not be required where an electrical or signal setting system is not required. In this type of well construction operation a standard motorhead without power cable bypass 8 would be used.

Flow retaining thrust bearings 673 and 674 are mounted at upper and lower regions of upper (rearwards) rotor assembly 67 and similar flow retaining thrust bearings 684 and 661 are mounted at the upper and lower regions of the lower (forwards) rotor assembly 68 to provide a low friction rotation capacity. Located against the flow retaining thrust bearings 673 and 674, sits a commutator or outer external rotor casing 671 .

Referring to Figure 10 outer external rotor housing 671 consists of steel outer cylinder into which is fitted an aerated elastomer stator jacket 672. Stator jacket 672 has a single and opposing helical flexible rotor bead or rotor bead barrier 20 which opposes the stator profile 24 in fixed positive displacement motor stator section 601 (60) such that the jacket 672 internal helical bead barrier 20 sits across the stator profile 24 contracting against raised portions of the profile 24 in stator 60 and relaxing to mainly fill lower or trough portions of helical pathway in fixed tractor stator 12 of the stator profile 24 in stator 60 as shown in Figure 8.

Figure 6 shows a next stage in the sequence rotor with jacket 672 in place over stator 60 showing helical flow pathway 1 2 where jacket helical flexible rotor beads 20 have deformed over stator profile 24 in stator 60 to become a barrier and with jacket

672 encased by rotor casing 671 . Figure 7 shows a part sectional view of motor assembly and shows rotor helical flexible bead 20 able to deliver rotation using hydraulic flow from either direction. Figure 8 depicts a rotor section which when hydraulic flow is applied from either end of the rotor section deflects opposing helical flexible rotor beads 20 in the jacket 672 to form as a rotating barrier to flow such that the rotor casing 671 is caused to turn following the track of helical pathways 12 in the tractor fixed stator 60 so as to produce a net forward (or rearwards) drive force.

The hydraulic flow creates a bypass between the helical flexible rotor bead 20 in jacket 672 and the stator external helical profile 24 in stator 60. This serves to lubricate and cool the elastomer jacket 672 and stator 60 thereby improving efficiency and providing for longer service whilst still containing enough positive hydraulic force to apply a strong rotation to the rotor casing 671 .

Referring to Figures 9a, 9b and 10 there is shown examples of twin bi -directional rotational expander sub-assemblies 63 and 69. Figure 9a shows upper drive bow expander assembly 63 and Figure 9b shows lower drive bow expander assembly 69. Upper drive bow expander assembly 63 and lower drive bow expander assembly 69 have one or more fixed internal expander helical profile which is/are machined into rotor casings 671 and 681 . Expander helical profiles may alternatively be manufactured in two half sections and attached to the rotor casings 671 and 681 by grub screws (not shown).

Grub screws may be located in upper rotor assembly 67 in Figure 9a and at the lower rotor section 68 (not shown) in Figure 9b. Bow spring drive unit assemblies 71 and 72 or drive arm assemblies 75, 76, 77 and 78 are attached to top and bottom portions of the positive cavity drive rotors 67 and 68 respectively by drive bow expander units 63 and 69 and drive bow carriers 64 and 70. In some configurations using secondary expander assemblies, drive bow carriers 64 and 70 are replaced by secondary expander assemblies 61 and 62.

Bow spring drive unit assemblies 71 and 72 are fitted with serrated well bore engagement slip sets 73 and 74 which are mounted at the mid-point of bow spring drive units 71 and 72 such that the bow spring drive units 71 and 72, in their relaxed state, collapse into recesses in 679 and 689 the body of the rotor assemblies 67 and 68 respectively. This ensures that when collapsed the drive unit assemblies 71 and 72 and engagement slip sets 73 and 74 sit within the overall outside diameter of the tractor 6 assembly and are held in position by drive bows which act as leaf springs and positively retract the engagement slips when any compression force is removed.

Drive arm assemblies 75, 76, 77 and 78 are mounted to engagement slips 763, 764, 765, 783, 784, and 785 with leaf return springs 758a, 758b and 758c and 778a, 778b and 778c as shown in Figures 15a and 15b such that with the drive arm assemblies 75, 76, 77 and 78 in their expanded state force the leaf return spring 758a, 758b and 758c and 778a, 778b and 778c to act as a reflex force such that when compressive force is removed the by expander assemblies 63, 69 and optionally 61 and 62 secondary expander assemblies, drive arm assemblies 75, 76, 77 and 78 retract and the assembly collapses into recesses in 679 the body of the rotor assemblies 67 and recesses 689 the body of the rotor assembly 68 within the overall outside diameter of the tractor assembly 6. Ideally there are three serrated well bore engagement slips 731 , 732 and 733 each attached to three drive bows 716, 717 and 718 in the upper (rearwards) drive bow assembly 71 and similarly three serrated well bore engagement slips 741 , 742 and 743 each attached to three drive bows 726, 727 and 728 in the lower (forwards) rotor assembly 72. Where drive arms are used, drive arms 756a, 756b and 756c and 757c, 757b and 757c are attached to the three serrated well bore engagement slips 763, 764 and 765. Engagement slips 763, 764 and 765 in the upper rearward drive arm assembly 75, 76 and in the lower (forward) drive arm assembly 77, 78 are attached to three drive arms 776a, 776b and 776c and 777a, 777b and 777c are attached to three serrated well bore engagement slips 783, 784 and 785 in the lower rotor assembly 72.

The well bore engagement slips are located at 120 ^Q one to another, so as to provide balanced rotational alignment and in order to minimise the total external diameter of the tractor assembly 6 (outer diameter) but maximise engagement slip area.

In the expanded state the serrated well bore engagement slips 763, 764 and 765 in the upper rearward drive bow assembly 71 and serrated well bore engagement slips 783, 784 and 785 in the lower drive bow assembly 72 are expanded to engage against the well bore 99 when the drive bow spring expander sub-assemblies 63 and 69 and in some configurations with assemblies 61 and 62 operate to expand their respective engagement slips due to rotational force exerted by the upper rotor 67 and lower rotor 68 which then proceeds to rotate the drive bows 71 and 72 or optionally drive arms 75, 76, 77, 78 driving the tractor forwards or backwards.

A self compensating feature of the drive bow is that the drive bows assemblies 71 and 72 retracts when presented with excess reactive force such as a restriction in the internal surface of a well bore 99 - for example when well bore narrows - so as to retract the drive bow units 71 and 72 by winding them down the helical spline in expander units 63 and 69 whilst still permitting transmission of full drive. Optionally the serrated engagement slips assemblies 73 and 74 include or be made from tungsten carbide or a tungsten alloy or similar hardened steel. Optionally the slips assemblies 73 and 74 may be coated with a low friction high wear material such as poly-tetra-fluoroethylene (PTFE).

Speed of the tractor assembly 6 in the well bore 99 is also determined by the pitch of the serrations on the serrated well bore engagement slips 731 , 732 and 733 in the upper (rearwards) drive bow assembly 71 and 741 , 742 and 743 in the lower (forwards) drive bow and drive arm supported engagement slips 763, 764 and 765 in the upper rearward drive arm assemblies 75 and 76 and serrated engagement slips 783, 784 and 785 in the lower drive arm assemblies 77 and 78 and the angle at which they engage with the well bore 99.

A range of serrated well bore engagement slips 731 , 732 and 733 in the upper (rearwards) rotor assembly 67 and 741 , 742 and 743 in the lower (forwards) rotor assembly in the upper rotor assembly 68 and drive arm supported engagement slips 763, 764 and 765 in the upper rearward rotor assembly 67 and serrated engagement slips 783, 784 and 785 in the lower rotor assembly 68, may be machined with differing serration attack angles and may be used to address the requirements of different well intervention applications. Where applied traction and power delivery might be a priority there would be an increased number of serrations per linear length in comparison where speed of ingress or egress from the well bore is a not a priority over the delivery of applied power and traction. Where speed of ingress or egress from the well bore 99 is a priority, the profile machined into the engagement slip will have fewer number of serrations per linear length and a greater angle of attack.

In the event that the requirement is to reach to total depth (TD) quickly, for example so as to perform a logging activity in one direction (usually under overpull from the surface on the way out of the well bore), the serrated well bore drive slips have a high angle of attack and accordingly are able to drive the tractor 6 and its payload forwards or backwards at a greater distance per revolution and so at a higher speed. This serrated engagement slip profile is shown in engagement slips 763, 764 and 765 in Figures 15a and 15b.

However, in an extended reach or long lateral well logging intervention, where the conveyance of heavy and long well logging tools is required and in well construction interventions where heavy tubulars made need to be deployed, the tractor assembly 6 is ideally fitted with serrated well bore engagement slips 731 , 732 and 733 shown in Figures 12a and 12b and 741 , 742 and 743 in Figures 13a and 13b which have a profile machined into the well bore engagement slip surface to provide effectively a lower gearing with respect to the rotational speed of the drive bows or drive arms, hence travelling at a slower speed in the well bore 99 but capable of pulling a greater payload. These same reduced attack angle serrated well bore engagement slips may be used when actively logging long sections of the well in either direction where a slow, powerful and smooth transit up and down the well bore 99 is desired.

An alternative expander sub-assemblies 61 and 62 shown in Figure 1 1 may be used to replace existing drive bow carrier subs 64 and 70 in applications using drive arms. This is beneficial where drive arms with expanded outside diameter capacity are required. Sub-assemblies 61 and 62 may also be used in conjunction with subassemblies 63 and 64 giving four expanders units in total. These expander subassemblies 61 , 62, 63 and 69 in this configuration may have the internal expander helical profile machined into the rotor casings 671 and 681 or they may be machined in two half sections which are placed over rotor casings 671 and 681 and are attached to the rotor casing by locking grub screws (not shown).

Figures 9a and 9b and Figure 10 show one type of bi-directional rotationally operated helically splined type expander sub-assembly 63 (Figure 9a), and a second bi-directional rotationally operated helically splined type expander sub-assembly 69 (Figure 9b). These are fitted to the positive cavity drive rotor casings 671 and 681 respectively. The first and second helically splined type expander sub-assemblies now fixed to cavity drive rotor casings 671 and 681 rotate to expand drive bow units 71 and 72 or drive arms assemblies 75, 76 and 77, 78 so as to engage walls of the well bore 99 using the serrated well bore engagement slips 731 , 732 and 733; in the upper (rearwards) rotor assembly 67 the engagement slips are 741 , 742 and 743 in the lower (forwards) rotor assembly 68, the engagement slips are fitted to drive arms assemblies 75 , 76, 77 and 78 are drive arm supported engagement slips 763, 764 and 765 driven by upper rearward rotor 67 and 783, 784 and 785 driven by lower forward rotor 68 The serrated well bore engagement slips as listed above are mounted at the midpoint of the drive bow units 71 and 72 and may be replaced with modified serrated well bore engagement slips depending upon the nature of surrounding rock or other conditions.

Serrated well bore engagement slips are typically manufactured from a single billet (not shown) of steel which is turned to size with a large progressive thread machined on its outer diameter. The billet is then bored and profiled on its internal diameter so as to accommodate a fixture means to the drive bow units 71 and 72 and optionally drive arm assembles 75, 76 and 77, 78. The billet is milled into three segments which provide the three serrated well bore engagement slips 731 , 732 and 733 in the upper (rearwards) rotor assembly 67 and as in engagement slips 741 , 742 and 743 in the lower (forwards) rotor assembly 68 and for use with drive bows assemblies 71 and 72. Drive arm supported engagement slips 763, 764 and 765 in the upper (rearward) rotor assembly 67 and engagement slips 783, 784 and 785 in the lower rotor assembly 68 are manufactured in a similar way but have a different attachment profile.

The engagement slips as given previously are then hardened by heat treatment and may be finished in low friction coatings. Optionally engagement slips as given previously they may also be manufactured in tungsten or include elements made of tungsten such as the well bore engagement section of the engagement slip assembly (not shown) is replaceable and held in place to the engagement slips body by locking grub screws and fixture profile. It should be appreciated that as the engagement slips are sized to fit within the outside diameter of the tractor 6, when expanded against the well bore 99, the leading edges of the engagement slips stand off the wall of well bore 99 due to their smaller radii enabling the drive engagement slips leading edges to ride over rocks irregularities without hanging up.

Referring to Figures 1 1 , 12b, 13b and 16b a planet and gear drive system 65 is used to reverse the drive direction of a first drive bow assembly 71 and a second drive bow assembly 72. The planet and gear drive system 65 connects the first and second drive bow assemblies and assists in the regulation of the speed of the two drive bow assemblies 71 and 72 coupling torque between rotor casings of upper (rearward) rotor section 67 and lower (forwards) rotor section 68.

The drive system of tractor 6 will now be described in operational mode with reference to all the Figures and specifically Figure 16a, 16b and 16c. The tractor 6 operates when a hydraulic media 1 (normally drilling mud) supplied at by a surface controlled fluid pump 152, as shown in Figure 18, is delivered to the tractor 6 at a controlled flow rate and pressure. An increase in pressure causes a differential pressure in a hydraulic flow diverter valve assembly 30 which is shown in detail in Figures 3a, 3b and 3c in varying states of operation.

Figure 3a shows the hydraulic flow diverter valve assembly 30 in a relaxed open position circulating hydraulic medium 1 from the hydraulic flow diverter valve 30 to annulus between tractor 6 and well bore 99. Figure 3b shows the hydraulic flow diverter valve 30 in the primary stage of operation where a differe ntial pressure has moved piston 306 back to an end stop position at stop collar 310. As this occurs disc spring stack 309 is compressed and piston 306 moves a shuttle sleeve 303 thereby closing circulation to the well bore 99 between tractor 6 and well bore 99 through circulation port 302.

This action causes a sharp pressure build up against the piston flange section of shuttle sleeve 303, which in turn applies force against disc spring stack 309 which eventually collapses with a snap action allowing hydraulic medium 1 to pass between piston 306 and shuttle sleeve 303, as shown in Figure 3c. This snap action causes overpull direction control valve assembly 50 to receive flow of hydraulic medium 1 which in its open state diverts flow to upper rotor assembly 67 and in its closed (over-pulled) state to divert hydraulic medium 1 along a different pathway and consequently to reverse the drive of the tractor.

Figure 4a shows hydraulic flow control valve 50 in the open (non over-pulled) position receiving flow through ported support ring 522 and to an open flow path between segmented flow control plug 525 and segmented flow control valve seat 530 to outer flow chamber 547 and on through ported support ring 2 (537) to upper rearwards rotor section 67.

Figure 4b shows overpull direction control valve in its closed (operated) position where overpull (that is with excess tension applied from the surface) has closed overpull direction control valve 50 where segmented flow control plug 525 has closed against segmented flow control valve seat 530 and which switches hydraulic medium 1 to flow through ports 532 in segmented flow control plug 525 and exit to inner chamber 548 and into the bore of cable conductor tube 542 via ports 551 thence to end cap 66 and finally exhausting through outer flow chamber 547 and to well bore 99 by ports 533 in bottom sub body 536. Once hydraulic media 1 has passed through outer flow chamber 547 in overpull direction control valve 50 pressure increases on flow retaining thrust bearing housing 549 and flow retaining thrust bearing 673 to upper (rearwards) rotor section 67.

Hydraulic medium 1 flow rate is controlled at the surface by varying the pump rate and accordingly pump pressure. Hydrostatic forces are transmitted to upper (rearwards) rotor section 67 and mud is trapped between the rotor elastomer jacket 672 and upper fixed helical stator profile 601 . Fixed stator profile 24 is fixed with respect to drive stator 60, as shown in Figure 5. This causes elastomer stator jacket 672 to distort in the form of a travelling helical flexible rotor bead barrier 20 and to deflect against a raised part of external helical profile 24 whilst maintaining a partial seal against lower (trough) portions of fixed stator 60 and causing an axial force (from the hydraulic fluid) to be converted to a rotational torque by way of a reactive component of the axial force acting against the helices.

The hydraulic force of hydraulic medium 1 acts against the elastomer stator jacket 672 and forces the rotor casing 671 to rotate in the direction of the helical coil spiral profile 24 that is machined into the relatively fixed stator 601 , in a manner analogous to how a toy spinning top rotates when an axial force is applied via a central spindle.

Hydraulic medium 1 flows through the upper positive cavity drive rotor 67 and exits at an aft region and enters a forward drive bow section of lower (forwards) positive cavity drive rotor assembly 68 via flow retaining thrust bearings 674 and ports 650a, 650b, 650c and 650d in planetary gear plate 653. After passing planetary gear plate 653 mud passes through flow retaining thrust bearings 684 shown in greater detail in Figures 12b and 13b. After hydraulic medium (mud) 1 flows through the planet and gear drive system 65 (shown in detail in Figures 12b, 13b and 16b) it enters the lower positive cavity drive rotor 68 and meets lower forwards positive displacement motor stator 602 which ideally has a similar spiral profile machined in its fixed positive cavity drive stator but in an opposing direction to that in the upper (rearwards) fixed positive displacement stator section 601 to that of fixed positive displacement stator 61 .

As a result of this switch in mud flow lower positive cavity drive rotor assem bly 68 is driven in the opposite sense to upper positive cavity drive rotor assembly 67. On exiting lower positive cavity drive rotor assembly 68 the hydraulic flow 1 is returned to an overpull direction control valve 50 through cable via/duct 14 in fixed stator 60 and exhausts to well bore 99 through port 533 in bottom sub casing 536. Tractor 6 direction change is controlled by way of an overpull from surface. That is hydraulic flow is diverted through cable via 14 and is exhausted to well bore 99 through integral hydraulic flow ports 533 in the direction control valve bottom sub-assembly with spline 536 of overpull direction control valve 50.

Typically an initial rotational 'kick' of the positive cavity drive rotors 67 and 68 activate bow spring expander units 63 and 69 so as to cause them to extend and in so doing expand drive bows 71 and 72 outwards and rotate drive rotors 67 and 68 Serrated well bore engagement slips 73 and 74 are rotated, expanded and act against the well bore 99 or well bore casing 17 to drive tractor 6 forwards into the well bore 99 or backwards towards surface 56. Due to the flow direction of the hydraulic medium 1 , the relationship of the upper (rearward) 67 and lower (forward) 68 positive cavity drive rotors a contra-directional and fully power transmitting drive is achieved in the opposite drive direction.

When hydraulic pressure from a pump 152 , as shown in Figure 18 reduces delivery of hydraulic medium 1 to the tractor 6 to a point where the compressive action of stored kinetic energy in disc spring stack 309. This results in hydraulic flow diverter valve 30 overcoming the hydraulic force exerted by hydraulic medium 1 on shuttle sleeve 303 as shown in Figure 3a. Hydraulic flow diverter valve 30 opens firstly with shuttle sleeve 303 moving back to its position as shown in Figure 3b and then to fully relaxed and open position as shown in Figure 3a. At this instant hydraulic medium 1 is circulated to well bore 99 through port 302.

This series of actions causes upper and lower rotor sections 67 and 68 to cease rotation which causes the drive bow expander units 63 and 69 to 'unwind' against the spring action of the drive bow assemblies 71 and 72 so causes drive bow units 71 and 72 to return to their relaxed or collapsed state.

It should be noted that drive bow units 71 and 72 are expanded and rotated under the influence of drive bow spring resistance which causes the drive bow 71 and 72 to rotate and thereby engage the serrated well bore engagement slips 73 and 74 with well bore 99 in with a controlled engagement force moderated by the resistive action of the drive bows 71 and 72.

The drive bow units 71 and 72 rotate in opposing senses and balance out rotati onal torque on the coiled tubing 2 thereby avoiding 'twist off' and failure of the coiled tubing 2 at extended reach from the surface, due to so-called developed tractor torque against the coiled tubing 2. Likewise each drive bow unit 71 and 72 is offset so that they are fixed by drive bow axles 713, 714 and 715 and 723, 724 and 725 to respective drive bow unit sub-assemblies 71 and 72, so that a leading edge of a serrated well bore engagement slips 73 and 74 is angled into the direction of the drive bow rotation to reduce torque being applied laterally across drive bows 716,717, 718, 726, 727 and 728 and drive bow axles 713 and 715 and 723 and 725.

A benefit of the aforementioned ability to collapse back drive bows and drive arms with their respective engagement slips into recesses 679 and 689 the body of the tractor 6 is that in the event of failure of the hydraulic supply the rotors drive bows or drive arms cease to rotate and the drive bows and drive arms retract thereby reducing the tractor assembly 6 to its minimum external diameter allowing the tractor assembly 6 to be recovered to surface in its fully retracted position and allowing the tractor 6 to pass through upper tubing restrictions using coiled tubing unit overpull.

Figures 12b and 13b show integral pressure retaining thrust bearings 674 and 684 located at ends of each of the upper 67 and lower 68 rotor assemblies end subassemblies. These integral pressure retaining thrust bearings 674 and 684 serve to permit the rotation of upper rotor assembly 67 and lower rotor assembly 68 which act on the planet gear system 65 and serves seal flow hydraulic medium 1 though planetary gear system 65 via port 650a, 650b, 650c and 650d between upper 67 and lower 68 rotor assemblies.

Referring to Figures 9a and 9b and Figure 1 1 show drive bow expander assemblies 63 and 69 and 61 and 62 may be manufactured in two halves where the helical expander spline followers 632, 633, in assembly 63, 693 and 694 in assembly 69, 612 and 613 in assembly 61 and 622 and 623 in assembly 62 may be clamped over a matching male expander spline profile as in 630 and 631 in assembly 63 and 691 and 692 in assembly 69 which is machined into exterior of a positive cavity drive rotor casing 671 and 681 respectively.

The drive bow units 71 and 72 may also be clamped over the positive cavity drive rotor casing 671 and 681 and secured by grub screws (not shown).

Alternatively drive bow units 71 and 72 may also be fitted as a separate assembly to a front part of the top of upper (rearwards) rotor section 67 and lower (forwards) rotor section 68. Referring again to Figures 9a, 9b and 1 1 , drive bow expander assemblies 63 (upper rearwards drive bow) and 69 lower (rearwards drive bow) and 61 (upper rearwards drive arms) and 62 lower (rearwards drive arms) have clockwise helically splined type expander spline sub-assembly 630 and 631 ; 691 and 692; 610 and 61 1 ; 620 and 621 (male) is made in two halves and clamped around the exterior of rotor casings 671 and 681 rotor casings and locked into the housing with locking grub screws (not shown).

Figures 9a and 9b show both clockwise and anti-clockwise helically splined type expander sub-assembly which runs on the mating male expander sub-assembly and expands in a uniform way and in a singular motion when turned anti-clockwise or clockwise. Accordingly the expander sub-assemblies 63, 69, 61 and 62 uniformly extend when turned in either clockwise or anti clockwise directions and having travelled to the extent of expansion locks and transmits rotation and rotational torque.

The tractor 6 will now be described in one mode of operation with reference to the Figures, tractor 6 operates when a hydraulic media 1 (normally drilling mud) at a surface controlled fluid pump rate and pressure increase causes a differential pressure in the hydraulic flow diverter 30 which switches to transmits hydraulic flow and pressure from well bore circulation to the tractor 6 drive. Hydraulic flow at the surface is controlled by varying pressure using pump 152 which transmits pressure initially to the upper rearward rotor section assembly 67.

Following an initial kick and initial rotation of the rotors 67 and 68 and initial take up of expander units 63 and 69, and optionally 63, 69, 61 and 62, the serrated well bore engagement slips 73 and 74 are firmly engaged against walls of the well bore 99, and any take up on the helical drive expander sub-assembly 63, 69, 61 and 62 at its fullest extent, the bow spring drive units 71 and 72 begin rotating in opposite directions and drive the tractor 6 forwards transmitting drive through the serrated well bore engagement slips 73 and 74 which cut a 'thread' of small grooves into the rock or casing scale as a means of rotational hold, in a same way as a self-tapping screw engages with a hole into which it is being rotated.

Due to the flow direction of the upper (rearwards) rotor section 67 and lower (forwards) rotor section 68 (which are connected by the planet drive 65 to regulate the speed and balance power delivery of both drives), a contra-directional drive is achieved through engagement of both rotor sections. It should be noted that where traction may be reduced at one or other of the two drives due to the tractor 6 crossing an open section of casing or well bore (not shown) such as a lateral junction, drive is maintained due to engagement slip traction by the engagement slips which remain in contact with the well bore. It should further be noted that the overall diameter of the drive bows and drive arms is maintained whilst passing such Open' sections due to the uniformly controlled expansion of drive bow expanders and carriers, thus avoiding rotating and an expanded engagement slips hanging up in the Open' section.

When hydraulic drive from the pump 152 ceases the drive bow 71 and 72 and drive arm units 75, 76 and 77, 78 return to their collapsed position under the influence of the drive bow spring resistance and in the case of drive arms units 75, 76 and 77, 78 by an integral leaf spring 758 and 778 acting between the drive arms. As stated above forward and aft drive bow assemblies 71 and 72, and drive arm assemblies 75, 76 and 77, 78, deliver balanced rotational torque to the well bore 99. In so doing rotational torque applied to the coiled tubing 2 is reduced and this avoids 'twist off and failure of the coiled tubing 2.

Likewise the drive bow assemblies 71 and 72 and drive arm assemblies 75, 76 and 77, 78 are offset where they are fixed by axles 713, 715, 723 and 725 and 753, 755, 760 and 762 and 773, 775, 780 and 782 so that the leading edge of the drive bow or drive arm is angled into the direction of rotation to reduce torque being applied across the drive bows, drive arms and their associated axles.

Figures 2a and 2b show a schematic diagram of the components in typical motorheads 4 (with cable bypass) and 8 (without cable bypass) which incorporate a top sub-assembly with upper connection 401 , twin check valves 402, circulation subassembly 403 and a release joint 404 with an integral internal fishing neck 405 forming a bottom sub-assembly with a connection 406 is shown in Figure 2a with a motorhead 4 and a cable bypass 407. The embodiment shown in Figure 2a may be varied in line with operational requirements. Also an overpull electrical disconnect 48 is adapted to disconnect when the motorhead 4 is disconnected from the tractor assembly 6. This is a standard piece of equipment which is usually supplied by a logging tool manufacturer and is mentioned to illustrate the fact that the invention allows for a cable disconnect, in conjunction with a motorhead disconnect capability.

Motorheads 4 and 8 are standard pieces of equipment and are mentioned in order to illustrate a means of attachment to tractor assembly 6. Straight bar 5 which is also a standard piece of equipment, adds mass to the bottom hole assembly and acts as a spacer between heavy duty anti-rotational motorhead 4 or 8 and tractor assembly 6. Straight bar 5 connects to tractor hydraulic flow diverter body 301 (shown in detail in Figures 3a, 3b and 3c).

The tractor assembly 6 incorporates the hydraulic flow diverter valve 30, which in the open position diverts mud flow (hydraulic media flow) 1 to the well bore 99 and in the closed position diverts mud flow to the overpull direction control valve 50, which in the embodiment shown in Figure 16a, is configured to be an overpull direction control valve 50 with a hydraulic flow diverter valve 30.

Hydraulic flow diverter valve 30 will now be described in detail and with reference to Figure 3a which shows the diverter valve 30 in the open position in which hydraulic flow diverter valve body 301 is in alignment with shuttle sleeve 303 to allow flow through multiple integral hydraulic flow ports 302, so as to divert the flow of hydraulic medium 1 to well bore 99.

Figure 3b shows the hydraulic flow diverter valve 30 in the semi closed position where flow of hydraulic medium 1 is closed to circulation to the well bore 99 and shows piston 306 in a fully retracted position, having shifted the shuttle sleeve 303 to close a flow path to well bore 99, by closing the flow path through multiple integral flow ports 302. Figure 3c shows hydraulic flow diverter valve 30 in the fully closed position so as to divert hydraulic medium 1 to flow to the top of upper (rearward) rotor section 67 in the tractor assembly 6 and then to lower (forward) rotor section 68 When overpull causes the overpull direction control valve 50 to actuate disc spring stack 527 to collapse, segmented flow control plug 525 moves backwards closing flow through a segmented flow control seat 530 and opening a flow path to an inner flow chamber 548 from the bore of top sub 521 and bottom sub 536 through multiple ports 532 that are formed in the segmented flow control plug 525. Segmented flow control plug 525 diverts flow to a bottom region of lower rotor section 68 via flow port 551 in cable conductor tube 542 and gun drilled cable duct via 14 in fixed stator 60.

Resistance to overpull, and therefore the amount of overpull required to operate the overpull direction control valve 50, is adjusted by the resistive strength of disc springs 527 and coil spring 558 which balances against opposing kinetic forces of coil spring 544, by the spring range and number of disc springs in disc spring stack 527, as well the orientation of the disc springs used. That is the disc springs either oppose one another or act in the same orientation in a cumulative manner.

As a consequence of this ability to reverse flow of the hydraulic medium 1 , the direction of movement of the tractor assembly 6 is controlled, resulting in hydraulic medium flow 1 exhausting through multiple integral hydraulic flow ports 533 from the overpull direction control valve 50 to the well bore 99. Referring now to Figures 12b and 13b, Figure 12b shows upper drive bow assembly 71 and upper rotor section 67 including an upper fixed stator 601 having a single corkscrew drive profile 24 machined to an exterior of the stator 601 . A gun drilled cable via 14 is shown as flow path 668, through which a logging tool signal and power cable 7 (not shown) may pass and hydraulic medium 1 (mud) is able to flow in both directions.

Flow retaining thrust bearings 673 and 674 in the upper rotor section 67 and flow retaining thrust bearings 661 and 684 in lower rotor section 68 are fitted to the out facing flanges of the rotor casing 671 and 681 which are mounted at the top and bottom regions of upper rotor casing 671 and lower rotor casi ng 681 .

The rotor assembly consists of a flanged steel outer rotor casing 671 and 681 with flow retaining thrust bearings 673, 674, 661 and 684 fitted to an outfacing flange of the rotor casings 671 and 681 into which is fitted a rotor jackets 672 and 682 respectively. Upper rotor jacket 672 and lower rotor jacket 682 are formed from a molybdenum loaded aerated elastomer. Stator jackets 672 and 682 have single and opposing helical profiles which form helical flexible rotor bead 20 or barrier which oppose the sense of the stator profile such that the jackets 672 and 682 sit snugly across the helical profile 24 of stator 60. Jackets 672 and 682 contract against raised helical regions and relax into helical troughs as shown in Figures 6, 7 and 8.

Figures 1 1 , 12b, 13b, 14 and 16a to 16c show rotor sections 67 and 68 in place over stator 60 which deflects opposing helical flexible rotor bead 20. A bypass channel or helical pathway 12 is defined between the lower relaxed section of the rotor bead 20 and stator 60. This serves to deliver lubricant and cool the elastomer jackets and the stator 60 thereby improving power delivery and ensures longer service periods for the tractor 6.

The invention overcomes a number of factors which limit the range, quality of data recovery and the maximum deployment depth during well interventions.

The invention has been described by way of examples only and it will be appreciated that variation may be made to the above mentioned embodiments without departing from the scope of the claims. Variation to the invention may be made for example it may be used as a hydraulic drive power take off in electricity generation. Variations of this invention might include a similar tractor powered by surface supplied electrical power as a replacement to the hydraulic positive cavity drive with an electrical drive system for electric line (E-line/wireline) well interventions in that the hydraulic positive cavity drive units can be replaced by an electric motor drive powered through the logging power and signal cable from surface coiled and with the same drive delivery system using drive bows and drive arms and drive arm/bow expanders.

Electrical drive motors include a fixed static stators (with a cable via/duct through the core) upper rearwards fixed stator section 791 and lower forwards fixed stator section 801 around which rotate electrical field coils (upper rearwards electrical field coils 792 and lower forwards electrical field coils 802) attached to the upper and rearwards rotor casing 793 and lower and forwards rotor casing 803 with electrical current being supplied through slip rings 794 upper and rearwards slip rings and 804 lower and forwards slip rings to the rotating field coils 792 upper and rearwards and 802 lower and forwards. Both upper 792 and lower 802 rotating field coil rotors assemblies 79 and 80 are similarly connected by a similar planetary gear system 806 as discussed above with direction and speed controlled by control box 805. Power is delivered to engagement slips driven by either drive bows 71 and 72 or drive arms 75, 76 and 77, 78 as described above and includes bi -directional helical expanders 63 and 69 or 61 and 62.

The invention is of particular benefit in extended range real time well logging as well as memory gauge tool conveyance in high deviation and/or horizontal well bores.

Open hole fishing operations and the conveyance of a variety of mechanical or electro-mechanical tools, including fishing spears, fishing over-shots and augers is achievable with the invention in a controlled manner due to its enhanced power delivery and traction enabling heavy duty bi-directional jarring in fishing and well interventions such as setting mechanical bridge plugs operations.

Deployment of electrically set bridge plugs and other downhole devices requiring electric power deliver to operate may be transmitted in open hole due to the ability of the tractor 6 to propel payloads into extended highly deviated or horizontal wells and conduct signal and power cable to the payload.

Assuming good traction against casing 17 the conveyance of perforating guns in long cased laterals is also achievable because of ability of the tractor 6 to propel extended heavy perforating gun string payloads into extended highly deviated or horizontal wells and conduct signal and power cable to a gun string payload (not shown). Likewise the invention is capable of conveying advanced electro hydraulic mechanical tools and downhole real time cameras and recording cameras.

This surface powered electrical tractor may be operated using an electric conductor cable on a standard electric line tool string including: an electric (conductor) cable to surface, a conductor rope socket, a conductor stem, a conductor mechanical jar, a conductor overpull to release slip type rope socket.

Other variants to the invention include right hand and left hand threaded drive systems. It will also be appreciated that the invention may be modified for use with drilling casing and liner location in well construction, downhole real time measurements using logging tools seismic and other surveys; and the provision of downhole services.

Although reference has been made throughout to downhole applications of the drive system and motor, the system may be used in tunnelling, pipeline laying, cable laying, drain construction and construction and piling. Parts List

1 hydraulic medium

2 coiled tubing

3 heavy duty anti-rotational dimple connector

4 motorhead

5 straight bar

6 tractor assembly

7 logging tool cable

8 heavy duty anti-rotational motorhead without cable bypass

9 logging tool

10 dimple hammer assembly

1 1 coiled tubing reel pack

12 helical flow pathway in tractor stator

13 coiled tubing counter head

14 cable duct or via through fixed positive displacement motor stator

15 surface mud system

16 upper casing

17 inner casing

18 packer

19 production tubing

20 internal helical bead profile in rotor jacket

21 blow out preventer stack

22 blind ram

23 shear ram

24 external helical profile of the stator

25 slip ram

26 pipe ram

27 goose neck (coiled tubing guide arch)

28 hydraulically driven coiled tubing injector

29 coiled tubing stripper assembly

30 hydraulic flow diverter valve assembly

31 heavy duty anti-rotational dimple connector body

32 threaded hole in 31 accommodates locking grub screws

33 O-ring seal

34 O-ring seal

35 dimpled section of coiled tubing

36 grub screw with a domed nose

37 tool connecting thread

38 O-ring seal

39 coiled tubing injector support frame

40 heavy duty anti-rotational motorhead with cable bypass

41 top sub-assembly provides a connection to upper bottom hole assembly

42 dual check valve assembly provides double barrier preventing back flow from well to coiled tubing

43 circulation sub-assembly to open a circulation path through the motorhead

44 release joint allowing detachment of the upper section of the motorhead to expose a fishing profile at 405 which may be operated by drop ball from surface or by surface applied overpressure 45 up-facing internal fishing neck which may be latched by a suitable tool

46 bottom sub-assembly providing a connection to the lower bottom hole assembly

47 cable bypass port with seals

48 overpull electrical cable disconnect socket

50 overpull direction control valve

51 straight bar body

52 O-rings

53 flow tee

54 swab valve

55 master or crown valve

56 Z-sol (surface)

60 fixed positive displacement motor stator

61 upper (rearwards) secondary expander assembly used with drive arms

62 lower (forwards) secondary expander assembly used with drive arms

63 upper (rearward) drive bow expander assembly which attaches to exterior of upper (rearward) rotor

64 upper (rearward) drive bow carrier sub-assembly incorporates flow retaining thrust bearings

65 planetary gear system (F)

66 end cap assembly

67 upper (rearward) rotor section incorporates flow retaining thrust bearings

68 lower (forward) rotor section incorporates flow retaining thrust bearings

69 lower (forward) drive bow expander assembly located and attached to exterior of lower (forward) rotor

70 lower drive bow carrier sub-assembly

71 upper (rearward) drive bow

72 lower (forward) drive bow

73 upper bow (rearward) drive engagement slip assemblies

74 lower bow (forward) drive engagement slip assemblies

75 upper (rearward) drive arm assembly

76 upper (rearward) drive arm assembly

77 lower (forward) drive arm assembly

78 lower (forward) drive arm assembly

79 upper rotor electrical power drive option

80 lower rotor electrical power drive option

81 top sub-assembly providing a connection to the upper bottom hole assembly

82 dual check valve assembly provides a double barrier preventing back flow from well to coiled tubing

83 circulation sub-assembly opens a circulation path through the motorhead to the well bore annulus and which may be operated by drop ball from surface or by surface applied overpressure

84 release joint allowing detachment of upper section of motorhead to expose a fishing profile which may be operated by drop ball from surface or by surface applied overpressure

85 up-facing internal fishing neck which may be latched by a suitable fishing/pulling tool to recover the motorhead in the event a detachment

86 bottom sub-assembly provides a connection to the lower bottom hole assembly or tools

87 operators control cabin 88 hydraulic power pack

89 hydraulic power pack hydraulic flow supply line

90 hydraulic power pack hydraulic flow return line

91 hydraulic flow supply/return line from control panel to coiled tubing reel pack drive motor

92 hydraulic flow supply/return line to control panel to coiled tubing reel pack drive motor

93 hydraulic flow supply/return line from control panel to hydraulically driven coiled tubing injector drive motors/

94 hydraulic flow supply/return line control panel to hydraulically driven coiled tubing injector drive motor

99 well bore

101 drive over dimple mandrel

102 hardened extended round nosed hex-drive dimple forming set screw

103 slide hammer core

104 sliding hammer

105 dimple connector receptacle

106 dimple grub screw

120 blow out preventer hydraulic supply/return hose cluster from control panel in operators control cabin to blow out preventer rams

121 blind ram with hydraulic hose open

122 blind ram with hydraulic hose closed

123 shear ram with hydraulic hose open

124 shear ram with hydraulic hose closed

125 slip ram with hydraulic hose open

126 slip ram with hydraulic hose closed

127 pipe ram with hydraulic hose open

128 pipe ram with hydraulic hose closed

150 surface mud system

151 mud return tank and gas buster

152 triplex mud pump

153 mud supply tank

154 centrifugal transfer pump

155 choke manifold

156 pump discharge T-piece

157 shut off valve to pump discharge T-piece and well kill valve

158 shut off valve between pump discharge T-piece and coiled tubing reel

159 kill valve

160 wing valve returns mud to choke manifold

161 shut off valve between mud return tank/gas buster to centrifugal transfer pump

162 flow line triplex mud pump discharge to T-piece

163 well kill flow line

164 flow line between wing valve 160 and choke manifold 155

165 flow line between choke manifold 155 and mud return tank 151

166 flow line between mud return tank to centrifugal transfer pump

167 flow line between centrifugal transfer pump 154 to mud supply tank 153

168 flow line between mud supply tank 153 to triplex mud pump 152

169 flow line between pump discharge T-piece 156 and coiled tubing reel 1 1

170 shut off valve for mud tank 153 from centrifugal transfer pump 154 supply side 171 shut off valve between mud tank discharge 153 to triplex mud pump 152

172 positive choke

173 adjustable choke

301 hydraulic flow diverter valve body

302 circulation port

303 shuttle sleeve

304 O-ring seal

305 O-ring seal

306 piston

307 O-ring seal

308 O-ring seal

309 disc spring stack

310 piston stop collar

31 1 disc spring stack calibration shims

312 ported piston and disc spring support ring

313 O-ring seal

314 Piston return coil spring

315 O-ring seal

316 piston return spring adjuster ring

317 cable conductor tube (attaches to stator)

318 logging cable section

319 ported cable conductor support ring

320 locking grub screw

321 conductor tube seal expander ring profile in 319

322 conductor tube seal

323 0-ring

324 threaded lock ring attaches to 317

325 splined travel joint outer with stop ring profile attached to 319

401 is a top sub-assembly providing a connection to the upper bottom hole assembly/straight bar

402 dual check valve assembly provides a double barrier preventing back flow from well to coiled tubing

403 is a circulation sub-assembly to open a circulation path through the motorhead to the well bore annulus and which may be operated by drop ball from surface or by surface applied overpressure

404 release joint allows detachment of upper section of motorhead to expose a fishing profile

405 up-facing internal fishing neck which may be latched by a suitable fishing tool

406 bottom sub-assembly provides a connection to the lower bottom hole assembly

407 cable bypass

521 top sub-assembly with spline

521 a stop profile on top sub-assembly spline

522 ported support ring

523 locking grub screw

524 circlip

525 segmented flow control valve plug

526 splines

527 disc spring stack

528 disc spring retainer sleeve 529 O-ring

530 segmented flow control valve seat

531 locking grub screw

532 port in segmented flow control valve

533 multiple exhaust ports

534 O-ring

535 sleeve

536 bottom sub-assembly

536a stop profiled slotted spline ring

537 ported support ring 2

538 locking grub screw

539 O-ring

540 O-ring

541 O-ring

542 cable conductor tube

543 logging cable section (7)

544 coil spring

546 O-ring

547 outer flow chamber

548 inner flow chamber

549 overpull direction control valve thrust bearing housing

550 locking grub screw

551 flow port in cable conductor tube to stator

552 inner flow segregating toroid for ported support ring 2

553 O-ring inner flow segregating toroid

554 locking circlip snap ring inner flow segregating toroid

555 locking circlip snap ring inner flow segregating toroid

556 O-ring inner flow segregating toroid

557 flow port in sleeve 535

558 coil spring

559 locking grub screw

560 locking circlip snap ring

561 spring thrust ring or shim

601 upper (rearwards) section of fixed positive displacement motor stator showing clockwise helical profile

602 lower (forwards) section of fixed positive displacement motor stator showing anti clockwise helical profile

610 top helical expander spline (senses and expands against clockwise rotation) upper drive bow expander

61 1 bottom helical expander spline (senses and expands against anti clockwise rotation) upper drive bow expander

612 top helical expander spline follower (senses and expands against clockwise rotation) upper drive bow expander

613 bottom helical expander spline follower (senses and expands against anti clockwise rotation) upper drive bow expander

614 upper rearwards drive bow expander stop ring upper drive bow expander

615 flow retaining thrust bearing upper drive bow expander

616 drive bow expander mandrel upper drive bow expander

617 thrust bearing upper drive bow expander 620 top helical expander spline (senses and expands against clockwise rotation) lower drive bow expander

621 bottom helical expander spline (senses and expands against anti clockwise rotation) lower drive bow expander

622 top helical expander spline follower (senses and expands against clockwise rotation) lower drive bow expander

623 bottom helical expander spline follower (senses and expands against anticlockwise rotation) lower drive bow expander

624 lower (forwards) drive bow expander stop ring lower drive bow expander

625 flow retaining thrust bearing lower drive bow expander

626 drive bow expander mandrel lower drive bow expander

627 thrust bearing lower drive bow expander

630 top helical expander spline (senses and expands against clockwise rotation)

631 bottom helical expander spline (senses and expands against anti clockwise rotation)

632 top helical expander spline follower (senses and expands against clockwise rotation)

633 bottom helical expander spline follower (senses and expands against anti clockwise rotation)

634 lower (forwards) drive bow expander stop ring

635 thrust bearing

636 drive bow expander mandrel

640 upper (rearwards) drive bow carrier sub-assembly

650a planetary gear flow port 0° clockwise

650b planetary gear flow port 90° clockwise

650c planetary gear flow port 180° clockwise

650d planetary gear flow port 270° clockwise

651 a planetary gears 0° clockwise

651 b planetary gears 90° clockwise

651 c planetary gears 180° clockwise

651 d planetary gears 270° clockwise

652a planetary gear axle 0° clockwise

652b planetary gear axle 90° clockwise

652c planetary gear axle 180° clockwise

652d planetary gear axle 270° clockwise

653 planet gear plate (attached to and part of fixed stator 60)

661 lower rotor flow retaining bearing

662 lower rotor flow retaining bearing housing

663 ported stator support ring

664 logging cable seal

665 logging tool connector sub

666 flow port to ported stator support ring

667 flow path between bore of lower (forwards) section of fixed positive displacement motor stator showing anti clockwise helical profile

668 flow path between bore of upper (rearwards) section of fixed positive displacement motor stator

669 locking grub screws (4 off located every 90°) around body of upper (rearward) drive bow body

670 locking nut

671 upper rotor casing 672 upper rotor jacket

673 upper rotor flow retaining thrust bearing seals between overpull direction control valve thrust bearing housing and upper rotor top flange

674 upper rotor flow retaining thrust bearing seals against planetary gear plate and upper rotor casing

675 upper (rearward) drive bow body

676 upper (rearward) spline connector located between drive bow body and drive bow expander mandrel

677 sealing flange for upper rotor casing

678 Locking grub screws (4 off located every 90°) around body of upper (rearward) drive bow body

679a machined recesses in upper (rearward) drive bow expander mandrel to accept collapsed drive bows and engagement slips

679b machined recesses in upper (rearward) drive bow body to accept collapsed drive bow

679c machined recesses in upper (rearward) drive bow body to accept collapsed drive bow

681 lower rotor casing

682 lower rotor jacket

684 lower rotor flow retaining thrust bearing seals against planetary gear plate and lower rotor casing

685 lower (forward) drive bow body with spline

686 lower (forward) spline connector between drive bow body and drive bow expander mandrel

687 sealing flange of lower rotor casing

688 locking grub screws (4 off located every 90°) around body of lower (forward) drive bow body 681

689a machined recesses in lower (forward) drive bow expander mandrel to accept collapsed drive bows and engagement slips

689b machined recesses in lower (forward) drive bow body with spline to accept collapsed drive bows and engagement slips

689c machined recesses in lower (forward) drive bow body with spline to accept collapsed drive bows and engagement slips

691 top helical expander spline (senses and expands against anti clockwise rotation)

692 bottom helical expander spline (senses and expands against clockwise rotation)

693 helical expander spline follower (senses and expands against anti clockwise rotation)

694 bottom helical expander spline follower (senses and expands against clockwise rotation)

695 lower (forwards) drive bow expander stop ring

696 thrust bearing

697 drive bow expander mandrel

701 lower drive bow carrier sub-assembly

71 1 upper (rearward) drive bow casing

712a upper (rearward) drive bow axle fixing port top 0°-120° clockwise

712b upper (rearward) drive bow axle fixing port top 121 °-240° clockwise

712c upper (rearward) drive bow axle fixing port top 241 °-360° clockwise

713a upper (rearward) drive bow axle top 0°-120° clockwise 713b upper (rearward) drive bow axle top 121 °-240° clockwise

713c upper (rearward) drive bow axle top 241 °-360° clockwise

714a upper (rearward) drive bow axle fixing port bottom 0°-120° clockwise

714b upper (rearward) drive bow axle fixing port bottom 121 °-240° clockwise

714c upper (rearward) drive bow axle fixing port bottom 241 °-360° clockwise

715a upper (rearward) drive bow axle bottom 0°-120° clockwise

715b upper (rearward) drive bow axle bottom 121 °-240° clockwise

715c upper (rearward) drive bow axle bottom 241 °-360° clockwise

716 upper (rearward) drive bow 0 -120° clockwise

717 upper (rearward) drive bow 121 °-240° clockwise

718 upper (rearward) drive bow 241 °-360° clockwise

721 lower (forward) drive bow casing

722a lower (forward) drive bow axle fixing port top 0°-120° clockwise

722b lower (forward) drive bow axle fixing port top 121 °-240° clockwise

722c lower (forward) drive bow axle fixing port top 241 °-360° clockwise

723a lower (forward) drive bow axle top 0°-120° clockwise

723b lower (forward) drive bow axle top 121 °-240° clockwise

723c lower (forward) drive bow axle top 241 °-360° clockwise

724a lower (forward) drive bow axle fixing port bottom 0°-120° clockwise

724b lower (forward) drive bow axle fixing port bottom top 121 °-240° clockwise

724c lower (forward) drive bow axle fixing port bottom 241 °-360° clockwise

725a lower (forward) drive bow axle bottom 0°-120° clockwise

725b lower (forward) drive bow axle bottom 121 °-240° clockwise

725c lower (forward) drive bow axle bottom 241 °-360° clockwise

726 lower (forward) drive bow 0 -120° clockwise attaches to engagement slip 741

727 lower (forward) drive bow 121 °-240° clockwise attaches to engagement slip 742

728 lower (forward) drive bow 241 -360° clockwise attaches to engagement slip 743

731 upper bow (rearward) drive engagement slip attaches to upper (rearward) drive bow 0°-120° clockwise

732 upper bow (rearward) drive engagement slip attaches to upper (rearward) drive bow 121 °-240° clockwise

733 upper bow (rearward) drive engagements slip attaches to upper (rearward) drive bow 241 °-360° clockwise.

734 retaining pin attaches upper bow (rearward) drive engagement slip 0-120°

735 retaining pin attaches upper bow (rearward) drive engagement slip 0-120°

736 retaining pin attaches upper bow (rearward) drive engagement slip 121 °-240°

737 retaining pin attaches upper bow (rearward) drive engagement slip to upper (rearward) drive bow 121 °-240° clockwise to drive bow

738 retaining pin attaches upper bow (rearward) drive engagement slip to upper (rearward) drive bow 241 °-360° clockwise to drive bow

739 retaining pin attaches upper bow (rearward) drive engagement slip to upper (rearward) drive bow 241 °-360° clockwise to drive bow

741 lower (forward) drive engagement slip located at 0°-120° clockwise to drive bow

742 lower (forward) drive engagement slip located at 121 °-240° clockwise to drive bow

743 lower (forward) drive engagements slip located at 241 °-360° clockwise to drive bow 744 retaining pin attaches lower (forward) drive engagement slip to lower forward drive bow 0°-120° clockwise to drive bow

745 retaining pin attaches lower (forward) drive engagement slip to lower forward drive bow 0°-120° clockwise

746 retaining pin attaches lower (forward) drive engagement slip to lower forward drive bow 121 °-240° clockwise

747 retaining pin attaches lower (forward) drive engagement slip to lower forward drive bow 121 °-240° clockwise

748 retaining pin attaches lower (forward) drive engagement slip to lower (forward) drive bow 241 °-360° clockwise

749 retaining pin attaches lower (forward) drive engagement slip to lower (forward) drive bow 241 °-360° clockwise

751 upper rearward drive arm casing

752a upper (rearward) drive arm axle fixing port top 0°-120° clockwise

752b upper (rearward) drive arm axle fixing port top axle fixing port top 121 °-240°

752c upper (rearward) drive arm axle fixing port top 241 °-360° clockwise

753a upper (rearward) drive arm axle top 0°-120° clockwise

753b upper (rearward) drive arm axle top 121 °-240° clockwise

753c upper (rearward) drive arm axle top 241 °-360° clockwise

754a upper (rearward) drive arm axle fixing port bottom 0°-120° clockwise

754b upper (rearward) drive arm axle fixing port bottom 121 °-240° clockwise

754c upper (rearward) drive arm axle fixing port bottom 241 -360 ° clockwise

755a upper (rearward) drive arm axle bottom 0°-120° clockwise

755b upper (rearward) drive arm axle bottom 121 °-240° clockwise

755c upper (rearward) drive arm axle bottom 241 °-360° clockwise

756a upper (rearward) top drive arm 0 -120° clockwise

756b upper (rearward) top drive arm 121 °-240° clockwise

756c upper (rearward) top drive arm 241 °-360° clockwise

757a upper (rearward) drive arm bottom 0 -120° clockwise

757b upper (rearward) drive arm bottom 121 °-240° clockwise

757c upper (rearward) drive arm bottom 241 °-360° clockwise

758a return leaf spring

758b return leaf spring

758c return leaf spring

759a upper (rearward) drive arm axle fixing port Top 0°-120° clockwise

759b upper (rearward) drive arm axle fixing port Top 121 °-240° clockwise

759c upper (rearward) drive arm axle fixing port top 241 -360 ° clockwise

760a upper (rearward) drive arm axle Top 0°-120° clockwise

760b upper (rearward) drive arm axle top 121 °-240° clockwise

760c upper (rearward) drive arm axle top 241 -360° clockwise

761 a upper (rearward) drive arm axle fixing port bottom 0°-120° clockwise

761 b upper (rearward) drive arm axle fixing port bottom 121 °-240° clockwise

761 c upper (rearward) drive arm axle fixing port bottom 241 °-360° clockwise

762a upper (rearward) drive arm axle bottom 0°-120° clockwise

762b upper (rearward) drive arm axle bottom 121 °-240° clockwise

762c upper (rearward) drive arm axle bottom 241 °-360° clockwise

763 upper drive bow (rearward) engagement slip 0°-120° clockwise

764 upper drive bow (rearward) drive engagement slip 121 °-240° clockwise

765 upper drive bow (rearward) drive engagement slip 241 -360° clockwise

766 locking grub screw attaches leaf type return spring to drive arms 771 lower (forward) drive arm casing

772a lower (forward) drive arm axle fixing port top 0°-120° clockwise - fixes axle to top expander mandrel assembly

772b lower (forward) drive arm axle fixing port top 121 °-240° clockwise - fixes axle to top expander assembly

772c lower (forward) drive arm axle fixing port top 241 °-360° clockwise - fixes axle to top expander assembly 62

773a lower (forward) drive arm axle top 0°-120° clockwise - fixes top drive arm to top expander assembly

773b lower (forward) drive arm axle top 121 °-240° clockwise - fixes top drive arm to top expander assembly

773c lower (forward) drive arm axle top 241 °-360° clockwise - fixes top drive arm to top expander assembly

774a lower (forward) drive arm axle fixing port bottom 0°-120° clockwise - fixes axle in bottom expander assembly to bottom drive arm

774b lower (forward) drive arm axle fixing port bottom 121 °-240° clockwise - fixes axle in bottom expander assembly to bottom drive arm

774c lower (forward) drive arm axle fixing port bottom 241 °-360° clockwise - fixes axle in bottom expander assembly to bottom drive arm

775a lower (forward) drive arm axle bottom 0°-120° clockwise - fixes bottom drive arm to bottom expander assembly

775b lower (forward) drive arm axle bottom 121 °-240° clockwise - fixes bottom drive arm to bottom expander assembly

775c lower (forward) drive arm axle bottom 241 °-360° clockwise - fixes bottom drive arm to bottom expander assembly

776a lower (forward) top drive arm 0°-120° clockwise - fixes top expander assembly and top of engagement slip

776b lower (forward) top drive arm 121 °-240° clockwise - fixes to top expander assembly and top of engagement slip

776c lower (forward) top drive arm 241 °-360° clockwise - fixes to top expander assembly and top of engagement slip

777a lower (forward) bottom drive arm 0°-120° clockwise - fixes bottom expander assembly and bottom of engagement slip

777b lower (forward) bottom drive arm 121 °-240° clockwise - fixes bottom expander assembly and bottom of engagement slip

777c lower (forward) bottom drive arm 241 °-360° clockwise - fixes to bottom expander assembly and bottom of engagement slip

778a return leaf spring for lower (forward) drive acts on top drive arm and bottom drive arm - upper (rearward) drive arms 0°-120° clockwise and is attached to engagement slip

778b return leaf spring for lower (forward) drive acts on top drive arm and bottom drive arm - upper (rearward) drive arms 121 °-240° clockwise and is attached to drive engagement slip

778c return leaf spring for lower (forward) drive acts on top drive arm and bottom drive arm - upper (rearward) drive arms 241 °-360° clockwise and is attached to drive engagement slip

779a lower (forward) drive arm axle fixing port top 0°-120° clockwise - fixes axle to top drive arm in top of engagement slip

779b lower (forward) drive arm axle fixing port top 121 °-240° clockwise - fixes axle to top drive arm in top of engagement slip 779c lower (forward) drive arm axle fixing port top 241 °-360° clockwise - fixes axle to top drive arm 776c in top of drive engagement slip

780a lower (forward) drive arm axle top 0°-120° clockwise - fixes top drive arm 776a to top of drive engagement slip 1 (783)

780b lower (forward) drive arm axle top 121 °-240° clockwise - fixes top drive arm 776b to top of drive engagement slip

780c lower (forward) drive arm axle top 241 °-360° clockwise - fixes top drive arm to top of engagement slip

781 a lower (forward) drive arm axle fixing port bottom 0°-120° clockwise - fixes axle 782a in bottom drive engagement slip)

781 b lower (forward) drive arm axle fixing port bottom 121 °-240° clockwise - fixes axle 782b in bottom of drive engagement slip (784)

781 c lower (forward) drive arm axle fixing port bottom 241 °-360° clockwise - fixes axle 782c in bottom of drive engagement slip (785)

782a lower (forward) drive arm axle bottom 0°-120° clockwise - fixes bottom drive arm 777a to drive engagement slip 1 (783)

782b lower (forward) drive arm axle bottom fixes bottom drive arm to drive engagement slip

782c lower (forward) drive arm axle bottom fixes bottom drive arm to drive engagement slip

783 lower (forward) drive engagement slip attaches to lower (forward) drive arms

784 lower (forward) drive engagement slip attaches to lower (forward) drive arms

785 lower (forward) drive engagement slip attaches to lower (forward) drive arms

791 electrical power upper fixed stator with cable via/duct through core

792 upper field coil assembly

793 upper rotor casing

794 upper slip ring assembly

801 electrical power lower fixed stator with cable via/duct through core

802 lower field coil assembly

803 lower rotor casing

804 lower slip ring assembly

805 control box

806 planetary gear system

807 wiring loom