Abstract:
An actuator device for moving a tool within a borehole in the ground, the actuator being positioned between a coiled tubing and a tool, and the actuator being arranged to move the tool at a substantially constant axial speed and the actuator including a motor-operated mandrel which is moved outwards in the actuator by means of a releasable nut, the nut being locked in its active position by means of a hydraulically operated locking piston.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a national phase application of international application no. PCT/NO2008/000283, filed on Aug. 6, 2008, which claims the benefit of and priority to Norwegian application no. 20074140, filed on Aug. 9, 2007. The disclosures of the above-referenced applications are incorporated herein by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to an actuator. More particularly, it relates to an actuator for moving a tool within a borehole in the ground, the actuator being positioned between a coiled tubing and a tool, and the actuator being arranged to move the tool at a substantially constant axial speed. The actuator includes an actuator housing with an internal cylinder jacket and an end wall, there being arranged at the end wall a releasable nut which engages, in its active position, a threaded, axially bored-through mandrel, the mandrel projecting, axially movable, through an opening in the end wall. A motor is arranged to rotate the mandrel about its longitudinal axis via a non-circular, axially bored-through shaft. A locking piston, which is movable within the cylinder jacket, surrounds the mandrel, the locking piston being arranged to lock, when it is in its end position nearest to the end wall, the nut in its active position. An inner through opening in the wall of the shaft communicates with a first space in the actuator housing upstream relative to the locking piston when the mandrel is in its retracted position within the actuator housing, whereas an outer through opening in the wall of the mandrel communicates with a second space between the locking piston and the end wall when the mandrel is in its extended end position. 
       BACKGROUND 
       [0003]    During work in a borehole, for example, the cleaning of a pipe, which is in the borehole, by means of a pressure-fluid tool which is on the end portion of a coiled tubing, it is well known that the feeding rate of the tool into the borehole may be irregular even though the coiled tubing is fed into the borehole at a regular rate. 
         [0004]    The reason for this irregular rate of conveyance may be friction between the coiled tubing and borehole wall, obstructions in the borehole or curved boreholes, in which the coiled tubing changes the radius of curvature as it is being fed in. These conditions may result in a so-called “stick slip” effect, in which the tool stops, only to be moved, next, at a relatively high speed. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art. 
         [0006]    The object is achieved in accordance with the invention through the features which are specified in the description below and in the claims that follow. 
         [0007]    An actuator in accordance with the invention for moving a tool within a borehole in the ground, the actuator being positioned between a coiled tubing and a tool, and the actuator being arranged to move the tool at a substantially constant axial speed, is characterized by the actuator including an actuator housing with an internal cylinder jacket and an end wall, a releasable nut being arranged at the end wall, engaging, in its active position, a threaded, axially bored-through mandrel, the mandrel projecting, axially movable, through an opening in the end wall, and a motor being arranged to rotate the mandrel about its longitudinal axis via a non-circular, axially bored-through shaft, and a locking piston, movable in the cylinder jacket, surrounding the mandrel, the locking piston being arranged to lock, when it is in its end position nearest to the end wall, the nut in its active position, and an inner through opening in the wall of the shaft communicating with a first space in the actuator housing upstream relative to the locking piston when the mandrel is in its retracted position within the actuator housing, and an outer through opening in the wall of the mandrel communicating with a second space between the locking piston and the end wall when the mandrel is in its extended end position. 
         [0008]    In its initial position the mandrel is in its retracted position, the locking piston is in an intermediate position between the piston and the nut, whereas the motor rotates the mandrel and thereby the tool about the longitudinal axis of the mandrel. Pressurized fluid flows through the axial bores of the shaft and mandrel. 
         [0009]    Pressurized fluid flows via the inner opening into the first space, moving the locking piston up to the nut, where the locking piston causes the nut to be moved from its inactive position into its active position, engaging the threads of the mandrel. 
         [0010]    The motor thereby feeds the mandrel out of its retracted position, whereby the liquid flow via the inner opening is shut off. 
         [0011]    As the mandrel takes its projecting end position, the outer opening is uncovered, whereby pressurized fluid may flow into the second space. The locking piston is moved away from the nut which is thereby moved back into its inactive position. 
         [0012]    With advantage, the mandrel is provided with a piston which is sealingly movable within the cylinder jacket. The fluid pressure moves the locking piston and the piston together with the mandrel in the direction of their initial positions. The further movement of the mandrel into its initial position may take place by means of, for example, a force directed at the actuator from the tool. 
         [0013]    In an alternative embodiment the mandrel may be connected to a spring or gas spring which is arranged to move the mandrel in an inward direction within the actuator housing. 
         [0014]    In a further embodiment the mandrel is moved inwards within the actuator housing by means of an external displacing force. 
         [0015]    With advantage, the locking piston is provided with releasable locking dogs fitting complementarily into a locking groove in the cylinder jacket, the piston being provided with a releaser which is arranged to release the locking dogs when the piston is near the locking piston. 
         [0016]    The motor is typically driven by means of pressurized fluid, but electric operation may also be applicable under certain conditions. It is advantageous that the motor is in the actuator housing, but the motor may also project, at least partially, from the actuator housing. 
         [0017]    By the motor feeding the mandrel in a direction out of the actuator housing by means of a thread-nut-connection, a steady feeding rate is achieved, even if the axial force on the mandrel should vary somewhat. The device according to the invention provides a relatively simple actuator, in which the mandrel is moved automatically outwards at a constant rate, subsequently returning at a relatively high speed before the feeding out of the mandrel is repeated again. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    In what follows, is described an example of a preferred embodiment which is visualized in the accompanying drawings, in which: 
           [0019]      FIG. 1  shows, partially in section, an actuator in accordance with the invention which is connected between a coiled tubing and a tool coupling; 
           [0020]      FIG. 2  shows, on a somewhat larger scale, the actuator in its initial position; 
           [0021]      FIG. 3  shows the same as  FIG. 2 , but here a locking piston is moving within the actuator; 
           [0022]      FIG. 4  shows the actuator after the locking piston has moved the nut of the actuator into its active position; 
           [0023]      FIG. 5  shows the mandrel of the actuator as it is being fed out; 
           [0024]      FIG. 6  shows the actuator as the mandrel is in its projecting position; 
           [0025]      FIG. 7  shows the actuator after the locking piston has been moved from its locking position relative to the nut; and 
           [0026]      FIG. 8  shows a section III-III of  FIG. 3 . 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0027]    In the drawings the reference numeral  1  indicates an actuator which is fitted between a coiled tubing  2  and a tool, not shown, by means of a tool holder  4 . 
         [0028]    The actuator  1  includes an actuator housing  6  which is provided with an internal cylinder jacket  8  and an end wall  10  at its end portion facing away from the coiled tubing  2 . The end wall  10  is formed with a centric through opening  12 . A pressure-fluid-operated motor  14  with a through centre opening  16  is connected to the actuator housing  6  and the coiled tubing  2  by means of an adapter  18 . 
         [0029]    Just inside the end wall  10  is arranged a nut housing  20  including a number of nut segments  22  pivotal in the nut housing  20 . Each nut segment  22  is pivotal about a nut axle  24  between a passive position, see  FIG. 2 , and an active position, see  FIG. 4 . The nut segments  22  are held in their passive positions by an annular spring  26 . Together the nut segments  22  constitute a nut  28 . 
         [0030]    In its active position the nut  28  is in engagement with a threaded, axially bored-through mandrel  30 . The mandrel  30  projects, axially movable, through the opening  12  in the end wall  10 , the mandrel  30  being connected to the tool holder  4 . 
         [0031]    At its opposite end portion, extending inwards, the mandrel  30  is provided with a piston  32  which is sealingly movable within the cylinder jacket  8 . A through opening  34  of the mandrel  30 , see  FIG. 2 , is along a portion of the opening  34  given a hexagonal shape, see  FIG. 8 , complementarily matching an axially bored-through shaft  36 . 
         [0032]    The shaft  36  is rotated about its longitudinal axis by the motor  14 . An inner opening  40  through the wall of the shaft  36  corresponds with a bore  42  in the piston  32  when the mandrel  30  is in its retracted position, see  FIG. 2 . The mouth of the bore  42  is on the side of the piston  32  facing the nut  28 . 
         [0033]    A valve sleeve  44  is moved sealingly in over the inner opening  40  by means of a spring  46  as the mandrel  30  is moved away from its retracted position, see  FIG. 5 . 
         [0034]    A locking piston  48  which is movable within the cylinder jacket  8  surrounds the mandrel  30 . On its side facing the nut  28 , the locking piston  48  is provided with an externally conical sleeve projection  50  which is arranged to be moved in under the portions  51  of the nut segments  22  facing the locking piston  48 , the locking piston  48  thereby being arranged, when it is in its end position nearest to the end wall  10 , to lock the nut  28  in its active position, in which the nut  28  is in engagement with the mandrel  30 , see  FIG. 4 . 
         [0035]    When the mandrel is in its projecting position, an outer opening  52  in the wall of the mandrel  30  is uncovered, the outer opening  52  then having its mouth between the end wall  10  and the locking piston  48 . 
         [0036]    In this preferred embodiment, the locking piston  48  is provided with a number of locking dogs  54  which are arranged to engage a locking groove  56  in the cylinder jacket  8 , see  FIG. 4 . The piston  32  is provided with an axially movable, spring-biased release sleeve  58  which is biased in the direction of the end wall  10  by a spring  60 . The release sleeve  58  is arranged to move the locking dogs  54  out of their respective engagements in the locking groove  56  when the piston  32  is at the locking piston  48 , see  FIG. 6 . 
         [0037]    In its initial position the mandrel  30  is in its retracted position, the locking piston  48  is in its intermediate position between the piston  32  and the nut  28 . The motor  14  rotates the shaft  36 , the mandrel  30  and thereby the tool, not shown, about the longitudinal axis  62  of the mandrel  30 . Pressurized fluid from the coiled tubing  2  flows via the adapter  18 , centre bore  16  of the motor  14 , shaft  36  and mandrel  30  to the tool holder  4 . At the same time, pressurized fluid is flowing via the inner opening  40  and the bore  42  of the piston  32  into a first space  64  between the piston  32  and the locking piston  48 . 
         [0038]    The locking piston  48  is moved in the direction of the nut  28  by the fluid pressure, see  FIG. 3 , until the locking piston  48  hits the nut  28 , the sleeve projection  50  of the locking piston  48  being underneath the projecting portions  51  of the nut segments  22 , whereby the nut segments  22  have been moved into their respective active positions, in which they are in engagement with the mandrel  30 , see  FIG. 4 . At the same time, the locking dogs  54  engage the locking groove  56 , thereby preventing the nut  28  from being movable inwards within the actuator housing  6 . 
         [0039]    The rotating mandrel  30 , which is rotated by the motor  14 , is screwed outwards within the actuator housing  16  by means of the nut  28 , see  FIG. 5 . The spring  46  in the shaft  36  thereby moves the valve sleeve  44  closingly in over the second opening  40 . Fluid from the first space  64  is evacuated via the bore  42  in the piston  32 . Moreover, the actuator housing  6  can be replenished with fluid from the outside of the actuator  1  via an opening  66  in the actuator housing  6 . 
         [0040]    When the motor  14  has fed the mandrel  30  out into its projecting end position, see  FIG. 6 , the release sleeve  58  is underneath the locking dogs  54 , whereby the locking dogs  54  have been pivoted out of their engagement with the locking groove  56 . At the same time, the outer opening  52  communicates with a second space  68  located between the end wall  10  and the locking piston  48 . In this preferred embodiment the nut  28  has been fed out of engagement from the mandrel  30  as well. 
         [0041]    The pressure from the pressurized fluid flowing into the second space  68  works against the locking piston  48  and the force overcomes the force from the spring  60 , whereby the release sleeve  50  is moved sufficiently far back relative to the piston  32  for the sleeve projection  50  of the locking piston  48  to be disengaged from the nut segments  22 , see  FIG. 7 . The annular spring  26  moves the nut segments  22  into their respective inactive positions, whereby the mandrel  30  can be moved back into its retracted initial position. 
         [0042]    In the figures are shown a number of seals which have generally been assigned the reference numeral  70 . The purpose and operation of the seals  70  are well known and not described any further. Because of the relatively great flow rate of pressurized fluid prevailing, no great demands are made on the seals  70 . For example, it has turned out to be unnecessary to place a seal between the end wall  10  and the mandrel  30 .