Abstract: A propulsion unit for a wellbore tool includes a tool body and at least one wheel section disposed along the tool body. The wheel section comprises a tractor pad movably coupled to a tractor housing coupled to the tool body. The tractor pad is movable only in a lateral direction with respect to the tool body. A wheel rotatably is supported in the tractor pad so as to contact a wall of a wellbore when the tractor pad is moved away from the tractor housing. An hydraulic motor is rotationally coupled to the wheel. The hydraulic motor comprises a displacement changing element operable to change displacement of the hydraulic motor. The unit comprises means for moving the tractor pad between an extended position and a retracted position.

Abstract: The disclosure provides a torque release tubing rotator comprising a rotator body and a split drive mandrel rotatably coupled to the rotator body. The split drive mandrel receives and engages at least a portion of a tubing hanger. The split drive mandrel comprises an outer driven portion, an inner mandrel portion, and a one-way locking mechanism coupling the outer driven portion and the inner mandrel portion. The disclosure also provides a torque release tubing hanger for a tubing rotator comprising an outer housing, a tubing mandrel suspended from the outer housing, and a locking swivel rotatably coupled to the outer housing. The locking swivel is movable between a locked configuration and an unlocked configuration. A bi-directional coupling is also provided. The disclosure also provides a torque release tubing rotator system comprising the tubing rotator and tubing hanger.

Abstract: A service tool that may be inserted into a tubular, the service tool includes an anchoring system. The anchoring system includes a body having a first end, a second end, and an opening extending along a portion of the body between the first end and the second end and a gripping assembly housed within and coupled to the body. The gripping assembly may anchor at least a portion of the service tool to the tubular, and the gripping assembly includes a plurality of anchor arms disposed within the opening and that may move relative to the body. The anchoring system also includes an actuator disposed within a central bore of the body and coupled to the gripping assembly.

Abstract: An autonomous tool includes a tool body and turbine wheels coupled to the tool body. Each turbine wheel is retractable into the tool body and extendable out of the tool body. When the turbine wheels are extended out of the tool body, the axial axes of the turbine wheels can be positioned parallel to the axial axis of the tool body, allowing generation of mechanical energy from a fluid stream moving along the tool body, or positioned perpendicular to the axial axis of tool body, allowing the turbine wheels to roll along a tubular wall. Electrical generators are mechanically coupled to the turbine wheels to convert the mechanical energy produced by the turbine wheels into electrical energy. An energy storage stores the electrical energy for use by components of the tool.

Abstract: A method of performing an annular cementing operation after setting an integrated hanger and seal includes introducing a tubular including a flow passage having an inlet and an outlet into a wellbore, positioning and setting the integrated hanger and seal in the tubular, flowing cement between the tubular and the integrated hanger and seal into the inlet of the flow passage, passing the cement through the flow passage to the outlet, flowing the cement from the outlet, and closing the outlet.

Abstract: A wellbore radial positioning apparatus includes a tool body and a motor that actuates a traction wheel. The tool body is configured to be positioned within a wellbore. The motor driving the traction wheel is connected to the tool body and is configured to rotate the tool body in the wellbore. The traction tool is configured to frictionally contact or attach to the wellbore. The tool body is rotated in the wellbore by the action of the motor actuating the traction wheel.

Abstract: A system and method of removing sand from a wellbore by mixing the sand with a liquid to form a slurry, and forcing the slurry through a discharge line to surface. The sand is separated from the production fluid within the wellbore by centrifugal action created using a specially design screen or tangential perforations, and directed into a portion of the wellbore that is sealed from the remainder of the wellbore. The liquid and sand are mixed together in the sealed portion of the wellbore, and the pressure of the fluid is sufficient to force the slurry uphole. Included in the sealed portion of the wellbore is a perturbation element for mixing the sand and liquid.

Abstract: Apparatus and method for drilling a wellbore using non-synchronous oscillators. An apparatus for drilling a wellbore includes a tubing string and a bottom hole assembly coupled to the tubing string. The bottom hole assembly includes a first oscillator and a second oscillator. The first oscillator is configured to restrict fluid flow and induce pressure pulses in the tubing string at a first frequency. The second oscillator is configured to restrict fluid flow and induce pressure pulses in the tubing string at a second frequency. The first frequency is different from the second frequency.

Abstract: This invention relates to a hydrate plug remover for removal of a hydrate plug in a tube. The hydrate plug remover includes a collecting container provided with a valve in a lower end portion. The valve connects the collecting container to surroundings of the hydrate plug remover. The collecting container in an upper end portion is provided with a circulation gate connecting the collecting container to the surroundings of the hydrate plug remover.

Abstract: A rotatable downhole cutting tool configured for enhanced drive consistency in low power circumstances. The tool is equipped with a hydraulic axial drive actuator suitable for use in wireline deployment. The actuator itself includes a reciprocating piston with a ball screw that threadably interfaces a ball nut for dampening the axial drive imparted by the piston. As such, even though hydraulically driven at generally well under about 10 horsepower, bounce in the axial drive is substantially eliminated.

Abstract: A technique facilitates on-demand release of desired sections of a well string, e.g. sections of a perforating gun string, via at least one on-demand release tool. The on-demand release tool has an activation mechanism which may be selectively actuated to transition the on-demand release tool from a first loadbearing configuration to a second loadbearing configuration. The on-demand release tool may then be transitioned to a release stage which allows a first section of the on-demand release tool to be separated from a second section of the on-demand release tool by activating a release mechanism. In at least some applications, the on-demand release tool also comprises a ballistic transfer device to enable reliable ballistic transfer between sections of the perforating gun string.

Abstract: A drive module for a borehole or well tractor or runner comprises a drive module housing and a hydraulically actuated and pivoting drive arm comprising an arm housing and a drive wheel arranged thereto, wherein the drive wheel is driven by a motor mounted outside the drive arm housing and arranged along and parallel with the drive arm in resting position and onto or into the drive module wall for the cavity arranged or provided for the drive arm, and wherein the drive wheel is drivingly connected to the motor via a drive line arrangement, i.e. via a belt or chain drive arrangement and further via an angular gear or gearing arrangement mounted outside the drive arm housing. A borehole or well tractor or runner comprises at least one of said drive modules.

Abstract: A setting tool (10) for use in a downhole wellbore is described as having a hydraulic fluid pumping mechanism (78) for providing pressurized hydraulic fluid. A piston mechanism (116) is moveable by said pressurized hydraulic fluid acting upon a portion of the piston mechanism (116). A resetting mechanism (84) is provided which when operated releases the pressurized hydraulic fluid from acting upon said portion of the piston (116) and which results in the resetting of the setting tool (10). In addition, a method for resetting a setting tool (10) is described including the steps of: (i) running the setting tool (10) downhole; (ii) actuating the setting tool (10) and thereby deploying an apparatus (203) downhole; (iii) retrieving the setting tool (10) to surface; and (iv) bleeding off pressure to reset the setting tool (10).

Abstract: A downhole pumping system includes a motor, a pump driven by the motor and a seal section positioned between the pump and the motor. The seal section preferably includes a first seal bag assembly, a second seal bag assembly and an interconnect module connected between the first seal bag assembly and the second seal bag assembly. The interconnect module includes a plenum, at least one fluid exchange passage connected to the plenum, and a shaft seal assembly. The shaft seal assembly is configured to divert fluid from the plenum into the at least one fluid exchange passage. In another aspect, a first group of interconnect modules within the seal section each includes a shaft seal assembly oriented in a first direction and a second group of the interconnect modules each includes a shaft seal assembly oriented in a second direction to selectively apply an axial force on the shaft.

Abstract: A latching assembly has a tubular housing having an inner surface that defines an inner bore and an outer surface. A latch moves between a latch position that extends out from the outer surface and an unlatched position that is retracted from the latch position. A latching actuator moves between a first axial position that moves the latch to the latch position and a second axial position that moves the latch to the unlatched position. A manual release moves axially in response to a mechanical force to selectively move the latching actuator to the second axial position.

Abstract: A feeding device is for a rotatable downhole tool. The feeding device is provided with several feeding wheels lying in a plane which is slanted relative to a plane which is perpendicular to the center axis of the downhole tool. A method is for feeding a downhole tool axially by the use of the feeding device, when working a portion of a surrounding pipe body.

Abstract: A turbine drive may include a rotor that includes multiple turbine blades arranged in one or more turbine stages, as well as a stator cooperating with the rotor to direct fluid against the turbine blades and convert hydraulic, kinetic energy into rotational energy. The rotor may be fixed to the shaft to rotate synchronously therewith. The stator may be formed of multiple components that can be coupled together to define the stator and encompass the turbine blades of the turbine stages of the rotor. Two stator halves may each include vanes for positioning above and below a corresponding turbine stage, to direct fluid against the turbine blades. The stator may also be connected to a housing that encompasses the stator. Longitudinal slots and tabs on the stator and housing may hold the stator stationary relative to the housing.

Abstract: A surface drivehead drives a downhole pump by rotating a rod string at the surface. The downhole pump can be connected downhole to the rod string via a downhole latching mechanism. The surface drivehead has an assembly that can move the rod string upwards or downwards along an axis to either increase or decrease rod string tension. During rod string rotation, rod tension is monitored. If rod string tension changes during rotation, the surface drivehead can automatically compensate by moving the rod string upwards or downwards along the axis to either recapture or eliminate tension. In this way, the surface drivehead can maintain a substantially constant rod string tension to drive the downhole pump at high speeds.

Abstract: An apparatus for mitigation of torsional noise effects on borehole measurements. The apparatus may include a conveyance device; a sleeve having a sensor section, the sleeve rotatably disposed on the conveyance device; a sensor having at least one component disposed on the sensor section; and a driver coupled to the conveyance device and configured to rotate at least the sleeve sensor section. The driver may rotate the sleeve sensor section independent of the conveyance device. The driver may rotate the sleeve sensor section at a preset substantially constant rotational speed. The sleeve may include at least one arm configured to selectively lock the sleeve to a surface in the borehole. The driver may rotate the sleeve sensor section during measurement by the sensor. The driver may selectively couple the sleeve.

Abstract: A downhole motor for drilling and servicing of wells has an elongated outer housing and an elongated mandrel rotatably disposed within the housing. A primary thrust bearing is disposed between the lower end of the housing and the mandrel, and transfers axial loads downward from the housing to the mandrel, and then to the drill bit or other tool mounted on the lowermost end of the mandrel. The placement of the primary thrust bearing permits it to extend radially to the outer diameter of the housing. One preferred embodiment of the primary thrust bearing comprises bearing surfaces of polycrystalline diamond compact (“PDC”) material.

Abstract: The present invention relates to a downhole driving unit (11) for insertion into a well, comprising a driving unit housing (51), a hydraulic motor (23) comprising a hydraulic motor housing (93), a wheel assembly (90) comprising a stationary part (91) and a rotational part (92), the stationary part being connected with the driving unit housing and being rotatably connected with a rotational part, the wheel assembly comprising a wheel ring (99) for contacting an inner wall in the well and connected with or forming part of the rotations part. The wheel assembly further comprises the hydraullic motor (23) so that the stationary part and the rotational part constitute the hydraulic motor housing, the hydraulic motor comprising a rotatable section (84) connected with the rotational part for rotating part of the wheel assembly.

Abstract: The present invention relates to a downhole tool, comprising a hydraulic assembly, an arm assembly, the arm assembly comprising a wheel, a hydraulic motor for rotating the wheel, thereby driving the downhole tool in a forward direction, and a hydraulic pump unit for simultaneous generation of a first and a second pressurised fluid, characterised in that the arm assembly is movable between a retracted position and a projecting position in relation to the tool housing, and the downhole tool furthermore comprises an arm activation assembly for moving the arm assembly between the retracted position and the projecting position, and the hydraulic motor drives the downhole tool in the forward direction when the arm assembly is in the projecting position, the arm activation assembly being in fluid connection with the first pressurised fluid and the hydraulic motor being in fluid connection with the second pressurised fluid, a hydraulic control block for controlling the pressure of the first pressurised fluid having a

Abstract: The present invention relates to a downhole driving unit (11) for insertion into a well, comprising a driving unit housing (51), a hydraulic motor (23) comprising a hydraulic motor housing (93), a wheel assembly (90) comprising a stationary part (91) and a rotational part (92), the stationary part being connected with the driving unit housing and being rotatably connected with the rotational part, the stationary part and the rotational part constituting the hydraulic motor housing, the rotational part comprising a wheel ring (99) closed from one end, wherein the wheel assembly comprises a spring member (113) assembling the hydraulic motor housing.

Abstract: The present invention relates to a downhole driving unit (11) for insertion into a well, comprising a driving unit housing (51), a hydraulic motor comprising a hydraulic motor housing (93), the hydraulic motor comprising a cam ring (24), a wheel assembly (90) comprising a stationary part (91) and a rotational part, the stationary part (92) being connected with the driving unit housing and a rotatably connected with a rotational part, the stationary part and the rotational part constituting the hydraulic motor housing, said hydraulic motor comprising a rotatable section (84) connected with the rotational part, the cam ring being connected with or forming part of the stationary part of the wheel assembly, the rotational part comprising a wheel ring (99), where in a bearing (36) is arranged between the cam ring and the wheel ring. The present invention also relates to a downhole system comprising the driving unit and to use of such driving unit.

Abstract: The present invention relates to a downhole driving unit (11) (for insertion into a well, comprising a driving unit housing (51), an arm assembly (60) movable between a retracted position and a projecting position in relation to the driving unit housing, an arm activation assembly (41) arranged in the driving unit housing for moving the arm assembly between the retracted position and the projecting position and a wheel assembly (90) comprising a stationary part (91) and a rotational part (92), the stationary part being connected with or forming part of the arm assembly and being rotatably connected with a rotational part. The wheel assembly comprises a hydraulic motor comprising a hydraulic motor housing (93) and a rotatable section (84) connected with the rotational part for rotating part of the wheel assembly. Furthermore, the present invention relates to a downhole system comprising said driving unit and to use of such driving unit.

Abstract: A downhole positive displacement motor converts hydraulic fluid pressure into rotational torque. The motor includes a non-helical rotor and stator, and upper and lower valve assemblies each comprising cylindrical rotating and stationary elements which define longitudinal passages. The timing of alignment of the passages creates pressure in power pockets in the stator, rotating the rotor. The rotational torque can be used in any application that may require mechanical force to operate or drive a mechanism created for oil, gas, or water production in a down hole application.

Abstract: The motor of an electrical submersible pump generates a significant amount of heat that can be removed by transferring it to the well production fluid. The motor housing may have turbulators that increase the turbulence of the production fluid to increase the rate of heat transfer. The turbulators are designed for manufacturability and maintenance.

Abstract: A high efficiency fluid pumping apparatus and methods having of an electronic motor controller controlling at least one electric motor that is directly coupled to the input of a hollow helical mechanism. The output of the hollow helical mechanism is directly coupled to the shaft of a reciprocating piston pump. Each moving component of the apparatus is designed with a hollow central bore, so that the apparatus assembly will accept a continuous, stationary, hollow conduit containing electrical through wiring and or fiber optics for power and communication to devices physically positioned below the apparatus.

Abstract: A method of translating a member through a bore comprises moving fluid through a tubular member such as a drill string (2A), and generating impulses on the member by varying the passage of fluid through the member using a valve (60) which opens at a first rate and closes at a different second rate to urge the member to advance in a selected direction. The valve may close quickly and open slowly, or may close slowly and open quickly.

Abstract: A method for selecting a drilling motor for rotating a drill bit relative to a drill string made up of casing accounts for a tendency for the casing to elongate as the internal pressure increases. The increase in pressure in the casing string increases the weight on the drill bit, the amount of which may be calculated based on the size and type of the string of casing. The ratio of bit torque over the weight on the bit may be assumed to be a constant number based on empirical measurements or a theoretical model. The increase in the weight on the drill bit can be expressed in terms of the bit torque versus the casing pressure, which is a linear slope. This linear slope may be compared to the delivery torque of candidate motors.

Abstract: Apparatus and methods for establishing electrical communication between an instrument subsection disposed below a mud motor and an electronics sonde disposed above the mud motor in a drill string conveyed borehole logging system. Electrical communication is established via at least one conductor disposed within the mud motor and connecting the instrument sub section to a link disposed between the mud motor and the electronics sonde. The link can be embodied as a current coupling link, a magnetic coupling ling, an electromagnetic telemetry ling and a direct electrical contact link. Two way data transfer is established in all link embodiments. Power transfer is also established in all but the electromagnetic telemetry link.

Abstract: An electric submersible pump (ESP) assembly comprises an integrated sub-assembly encased within a shroud. The integrated sub-assembly comprises a well fluid intake having a shroud hanger formed in an upper portion thereof, a seal section having a motor head formed in a lower portion thereof, and an electrical conduit extending between the shroud hanger and the motor head. The intake has a plurality of fluid entry slots positioned a select distance from the shroud hanger in order to minimize the space for the accumulation of gas within the shroud. The electrical conduit sealingly extends through the shroud hanger to a receptacle located on an upper portion thereof. Conductors are encased within the conduit and are connected between the receptacle and the motor head. The conduit prevents the conductors from being affected by reservoir fluid and pressures.

Abstract: A drive mechanism is described for moving/controlling objects/mechanisms/systems coupled with a drillstring and/or pipe. The drive mechanism may be axially arranged on a drillstring or pipe, compact, capable of fine control and delivering high torque or the like and may be electrically and/or hydraulically powered. The drive mechanism may comprising a driving member comprising a plurality of drivers linearly translatable with respect to the driving member, each driving member having at their ends a male engaging portion and an associated driven member, comprising a plurality of female receiving portions adapted to receive a male engaging portion, the arrangement being such that linear translation of a driver causes its engaging portion to engage with a female receiving portion and the action of the engaging portion produces a reaction in the receiving portion causing displacement of the driven member in a direction other than that of the translatable driver.

Abstract: The present invention relates to a drilling tool (1) for drilling downhole, comprising a drilling head (2) in connection with a first portion (18) of the drilling tool, a driving unit (9) for driving the drilling head and the first portion forward in a longitudinal movement while drilling, and a feed control (19) for controlling the longitudinal movement of the drilling head.

Abstract: A back-off tool for use in breaking a joint of a tubular disposed in a well. The tool is dual anchoring in nature such that breaking of the joint may be achieved with a degree of precision heretofore unavailable. Additionally, the dual anchoring nature of the tool at both sides of the joint allows for power requirements to be met through use of a dowhole power source incorporated into the tool. As a result, the use of heavier power carrying cables and equipment may be avoided as well as explosives or similarly hazardous and/or imprecise measures.

Abstract: A drive assembly for powering a rotating rod string (14) passing through a surface wellhead (18) includes a torque conveying housing (32) containing a radially outer member supporting a plurality of outer member magnets and rotated by a motor. A radially inner member (48) supports a plurality of inner member magnets and is rotatable within the outer member, with magnetic forces between the plurality of outer member magnets and the plurality of inner member magnets rotating the inner member magnets and thus the radially inner member.

Abstract: A Seismic source comprising an actuator having a rotary part (104) and a reciprocative part (105), conversion means (109) in the form of corrugated surfaces to convert a rotation of the rotary part (104) into a reciprocal movement of the reciprocative part (105), and a vibrator body (106) that is connected to the reciprocative part (105) of the actuator by means of a spring (107).

Abstract: An electric submersible pump (ESP) assembly comprises an integrated sub-assembly encased within a shroud. The integrated sub-assembly comprises a downhole monitoring gauge, a motor, a well fluid intake, a seal section, a mounting member, and an electrical conduit extending between the mounting member and the motor. The intake has a plurality of intake slots positioned a select distance from the mounting member in order to minimize the space for the accumulation of gas within the shroud. The electrical conduit sealingly extends through the mounting member to a receptacle located on an upper portion thereof. Conductors are encased within the conduit and are connected between the receptacle and the motor. The conduit prevents the conductors from being affected by reservoir fluid and pressures.

Abstract: An inlet apparatus for a well pump.

Abstract: A pipe gripping assembly having a quill, an actuator and a drive assembly mounts to a top drive of a drilling rig. The quill is connected to a mandrel in the drive assembly. The drive assembly has a tapered mandrel and a set of slips that move along the taper into and out of engagement with the pipe. The actuator is connected to both the quill and a portion of the drive assembly. The actuator includes a motor and at least two sleeves that are threaded together. One sleeve has a spline on its outside diameter that mates to the motor and a gear. Power applied to the motor causes the actuator to move slips in the drive assembly into an engagement position that grips the pipe for lifting and rotating the pipe.

Abstract: In accordance with the teachings of the present invention, a method is provided for preventing formation of sludge in a subsurface cavity having particulate laden fluid disposed therein. The method includes positioning a downhole device having a fluid agitator into the fluid of the subsurface cavity and agitating the fluid using the fluid agitator.

Abstract: Apparatuses and methods for generating fluid pressure pulses are disclosed. An example apparatus may include a chamber that can collect fluid and an upstream ported disc coupled to a downstream end of the chamber. The upstream ported disc may rotate about a central axis. The upstream ported disc includes an upstream eccentric port that rotates about the central axis as the upstream ported disc rotates. The example apparatus may include a downstream ported disc coupled to a downstream end of the upstream ported disc such that the downstream ported disc remains substantially rotationally fixed relative to the upstream ported disc. The downstream ported disc includes a downstream eccentric port that may align with the upstream eccentric port to form a passageway for fluid to exit from the chamber to outside of the apparatus, at some time in a rotation cycle of the upstream ported disc.

Abstract: A method and apparatus for managing power demand of a motor in a cyclic load system having a rotational mass is provided. Flat power draw is achieved through continuous manipulation of the motor torque as a function of feedback velocity while using the rotational mass of the cyclic load as a means to store/retrieve energy. Alternatively, reduced variation of power draw is accomplished through continuous manipulation of motor velocity as a function of feedback torque. The methods and apparatus are used in systems where zero or reduced power demand variation is either required or desired, such as in generator powered applications.

Abstract: Apparatus and methods for establishing electrical communication between an instrument subsection disposed below a mud motor and an electronics sonde disposed above the mud motor in a drill string conveyed borehole logging system. Electrical communication is established via at least one conductor disposed within the mud motor and connecting the instrument sub section to a link disposed between the mud motor and the electronics sonde. The link can be embodied as a current coupling link, a magnetic coupling ling, an electromagnetic telemetry ling and a direct electrical contact link. Two way data transfer is established in all link embodiments. Power transfer is also established in all but the electromagnetic telemetry link.

Abstract: The present invention generally provides apparatus and methods of operating a pumping system. The pump control apparatus includes a first sensor for measuring strain on a structure of the well pumping system and a second sensor for measuring a position of the structure. The apparatus also has a controller configured to control the well unit by receiving output signals from the first and second sensors and generating control signals according to a motor control sequence. This controller may be mounted to the structure of the pumping system to measure the strain experienced by the structure. The control signals may be transmitted to a motor control panel using a cable-less communications system. Preferably, the first sensor, the second sensor, and the controller are integrated into a single unit. In another embodiment, the pump control apparatus may be self-powered.

Abstract: In accordance with the teachings of the present invention, a method is provided for preventing formation of sludge in a subsurface cavity having particulate laden fluid disposed therein. The method includes positioning a downhole device having a fluid agitator into the fluid of the subsurface cavity and agitating the fluid using the fluid agitator.

Abstract: A gerotor and bearing apparatus for a whirling mass orbital vibrator which generates vibration in a borehole. The apparatus includes a gerotor with an inner gear rotated by a shaft having one less lobe than an outer gear. A whirling mass is attached to the shaft. At least one bearing is attached to the shaft so that the bearing engages at least one sleeve. A mechanism is provided to rotate the inner gear, the mass and the bearing in a selected rotational direction in order to cause the mass, the inner gear, and the bearing to backwards whirl in an opposite rotational direction. The backwards whirling mass creates seismic vibrations.

Abstract: The present invention generally provides apparatus and methods of operating a pumping system. The pump control apparatus includes a first sensor for measuring strain on a structure of the well pumping system and a second sensor for measuring a position of the structure. The apparatus also has a controller configured to control the well unit by receiving output signals from the first and second sensors and generating control signals according to a motor control sequence. This controller may be mounted to the structure of the pumping system to measure the strain experienced by the structure. The control signals may be transmitted to a motor control panel using a cable-less communications system. Preferably, the first sensor, the second sensor, and the controller are integrated into a single unit. In another embodiment, the pump control apparatus may be self-powered.

Abstract: A method and apparatus for advancing a rotating motorized downhole tool for operations in oil/gas wells. The apparatus is adapted for drilling and milling away of casing sections in the wells, as preparation for plugging the same. The apparatus includes a rotating tool and a driving motor indirectly suspended on coiled tubing. The apparatus also includes a carriage connected to the motor adapted to absorb torques that occur during use. The carriage is connected to the coiled tubing via a swivel coupling such that a tensile force on the coiled tubing provides an advancing force for the tool and motor.

Abstract: A traction apparatus (1) for propulsion along a bore comprises first and second traction members (6) having outwardly extending legs (14). A propulsion system for operating the traction members (6) comprises a turbine-driven shaft (7) which drives the traction members (6) by way of bearing members (15). In a first phase, one of the legs of the first traction member is moved in one direction whilst in contact with the traction surface to impart the propulsion force at the same time as one of the legs of the second traction member is moved in opposite direction whilst out of contact. In a second phase one of the legs of the second traction member is moved in said one direction whilst in contact with the traction surface to impart the propulsion force at the same time as one of the legs of the first traction member is moved in opposite direction whilst out of contact.