Abstract:
A torque anchor for anchoring well equipment in a well conduit to arrest movement in both longitudinal directions and rotation in a first direction, but not rotation in an opposed second direction. A mandrel connected to the equipment has L-shaped grooves for slideably receiving respective pins from a drag body on the mandrel. A slip retainer on the mandrel houses slips for selectively engaging and disengaging the conduit. An initial pull of the mandrel causes the pins to move the drag body toward the slip retainer driving the slips outward to grip the conduit, and rotation of the mandrel in the first direction sets the anchor to arrest movement. Further pulling maintains the set position. The anchor is unset by releasing pull, rotating the mandrel in the second direction, and pushing the mandrel to disengage the slips. Alternate unsetting requires increased pull beyond the shear resistance of the slip retainer.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to tools for oil and gas wells generally, including wells accessing heavy crude, and in particular relates to a torque anchor for anchoring well equipment, such as a progressive cavity pump, and related tubing string in a well conduit from rotation in a given direction and from movement in both linear directions along the well conduit. 
       BACKGROUND OF THE INVENTION 
       [0002]    Known torque anchors, also referred to as anchor catchers, use either a combination of right and left hand threads, or are limited to one thread orientation. Examples of such torque anchors are shown in U.S. Pat. No. 3,077,933 to Bigelow and in Canadian patent no. 933,089 to Conrad. Disadvantages of such torque anchors include the expense of manufacturing the threaded portions, and the stop pins are vulnerable to breakage during use. 
         [0003]    Another type of torque anchor shown in U.S. Pat. No. 5,771,969 and corresponding Canadian patent no. 2,160,647 to Garay avoids the aforementioned threads and instead uses a helical bearing to transform rotational movement into linear movement for setting and unsetting the torque anchor. The helical bearing also accommodates shear pins for secondary unsetting if required. The use of one component, namely the helical bearing, to perform several functions has the advantage over the previous prior art of being less expensive to manufacture and less susceptible to breakage. 
         [0004]    However, there is a need for a torque anchor that further improves on these prior designs. In particular, there is a need for a torque anchor that avoids the prior art threads and helical bearings that require multiple full (i.e. 360 degree) rotations of the torque anchor&#39;s mandrel to either set or unset the torque anchor. The torque anchor should not need to translate rotational movement into linear movement to engage the anchor slips with the well conduit, but rather should directly transfer a short longitudinal movement of the mandrel to extend the slips into gripping engagement with the well conduit. The torque anchor should require only a limited rotation, such as a quarter turn, of the mandrel in a first direction to set the torque anchor, and to help maintain the anchor in the set position by merely pulling tension on the mandrel via the tubing string. One or more tracks in the mandrel, each formed by a groove having joined longitudinal and transverse arms, should guide a corresponding drive pin to achieve the desired longitudinal and rotational movements. The groove&#39;s arms should be relatively short to reduce both manufacturing costs and the risk of debris entering the groove to interfere with proper operation. The torque anchor should have a secondary unsetting capability where release is achieved by merely pulling the mandrel at a predetermined force to sever certain fasteners mounted to the mandrel, rather than shearing the drive pins in the grooves. 
       SUMMARY OF THE PRESENT INVENTION 
       [0005]    According to the present invention, there is provided a torque anchor for anchoring well equipment in a well conduit to arrest movement in both longitudinal directions and rotation in a first direction comprising: 
         [0006]    a mandrel connected to said well equipment; 
         [0007]    a cone element mounted to said mandrel and having a first conical surface; 
         [0008]    a drag body mounted on said mandrel, housing a drag means for contacting said well conduit, and having a second conical surface; 
         [0009]    a slip retainer mounted on said mandrel housing a plurality of slips, each of said slips having an inner surface, and an opposed outer surface for gripping said well conduit, and biasing means for urging said slip inwardly toward said mandrel and away from said well conduit; 
         [0010]    at least one pin connected to said drag body and a portion of said pin protruding toward said mandrel; and, 
         [0011]    said mandrel having at least one L-shaped groove for slideably receiving said protruding portion of said pin; 
         [0012]    wherein an initial pulling of said mandrel causes said pin, and in turn said drag body, to move toward said cone element so that said second conical surface of said drag body contacts said inner surface of said slips and urges said inner surface to contact said first conical surface of said cone element to drive said slips outward so that said outer surfaces of said slips grip said well conduit, and a further rotation of said mandrel in said first direction sets said torque anchor. 
         [0013]    In another aspect the invention provides a method of anchoring well equipment in a well conduit to arrest movement in both longitudinal directions and rotation in a first direction, and to allow rotation in an opposite second direction, using a torque anchor having: 
         [0014]    a mandrel connected to said well equipment; 
         [0015]    a cone element mounted to said mandrel with fasteners; 
         [0016]    a drag body mounted on said mandrel, housing a drag means for contacting said well conduit; 
         [0017]    a slip retainer mounted on said mandrel housing a plurality of slips for moving into and out of gripping engagement with said well conduit; 
         [0018]    at least one pin operatively engaging said drag body to said mandrel; and, 
         [0019]    said mandrel having at least one groove with a first longitudinal arm and a second circumferential arm, for slideably receiving said pin; 
         [0000]    wherein said method comprises: 
         [0020]    exerting an initial pull on said mandrel to move said pin along said first leg of said groove to extend said slips to grip said well conduit; and, 
         [0021]    then rotating said mandrel in said first direction to move said pin along said second leg of said groove to set said torque anchor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         [0022]    Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: 
           [0023]      FIG. 1  is a side view of a torque anchor according to a preferred embodiment of the present invention, shown in a run (unset) orientation; 
           [0024]      FIG. 2  is a perspective view, in isolation, of a mandrel of the torque anchor of  FIG. 1 ; 
           [0025]      FIG. 3  shows the torque anchor of  FIG. 1  in a run position within a segment of well conduit shown in transparent view; 
           [0026]      FIG. 3   a  is a cross-sectional view of the torque anchor and well conduit along line  3   a - 3   a  of  FIG. 3 ; 
           [0027]      FIG. 4  shows the torque anchor and well conduit of  FIG. 3  with a partially transparent view of a drag body housing; 
           [0028]      FIG. 4   a  is a close up view of the circled area  4   a  of  FIG. 4 ; 
           [0029]      FIG. 5  is a longitudinal section through the torque anchor and well conduit of  FIG. 3 , generally along the line  5 - 5 ; 
           [0030]      FIG. 6  shows a set position of the torque anchor of  FIG. 3  in the conduit; 
           [0031]      FIG. 6   a  is a cross-sectional view of the torque anchor and well conduit along line  6   a - 6   a  of  FIG. 6 ; and, 
           [0032]      FIG. 7  is a longitudinal section through the torque anchor and well conduit of  FIG. 6 , generally along the line  7 - 7 . 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0033]    Referring first to  FIGS. 1 to 5 , a preferred embodiment of a torque anchor, generally indicated by reference numeral  10 , is shown inserted within a well conduit  12 , such as a wellbore casing. The torque anchor is shown in an unset, or “run-in”, orientation in which it can be run inside the well conduit on a tubing string, along with other well equipment  14 , such as a safety sub, attached above and below. In particular, the well equipment is attached to a cylindrical mandrel  20  having attachment means, such as an inner threaded lower end  22  and an outer threaded upper end  24 . In this embodiment, the torque anchor is run down the well conduit on the tubing string in the direction indicated by arrow  16 . It is noted, however, that terms such as “up”, “down”, “forward”, “backward” and the like used to identify certain features of the torque anchor when placed in a well conduit is not intended to limit the torque anchor&#39;s use or orientation. Further, when describing the invention, all terms not defined herein have their common art-recognized meaning. 
         [0034]    The torque anchor has a tubular drag body  40  mounted over the mandrel  20  to house a drag means in the form of multiple drag blocks  42  for spacing the torque anchor away from the inner wall  13  of the conduit  12 . In the preferred embodiment four drag blocks  42  are generally evenly spaced circumferentially about the torque anchor. Each drag block  42  has a drag spring  44  to urge the outer surface  46  of the drag block against the conduit&#39;s inner wall  13 . Upper and lower drag retaining rings  48 ,  50  keep the drag blocks  42  removably mounted within the drag body  40 . At least one lower cap screw  52  attaches the lower retaining ring  50  to the drag body  40 . For illustrative purposes,  FIG. 3   a  shows the use of three circumferentially staggered cap screws  52 . In addition to keeping the torque anchor spaced from the conduit, the contact of the drag block surface  46  with the conduit&#39;s inner wall  13  causes friction that urges the drag body  40  to remain stationary while the mandrel  20  moves within. 
         [0035]    A tubular slip retainer  60 , or slip cage, mounted on the mandrel  20  adjacent the drag body  40  houses a plurality of radially movable slips  62 . In the drawings three slips  62  are shown generally evenly spaced about the drag body. Each slip has an outer surface  63  with teeth for gripping the conduit wall  13  upon contact, and an inner surface with opposed outwardly inclined edges  64 . A fastener in the form of a socket head cap screw  65  is fastened to the drag body  40  and is located within each of a plurality of elongate slots  66  spaced circumferentially about the slip retainer, preferably between each slip. The cap screw  65  is adapted to contact the upper and lower shoulders  68   a ,  68   b  at the ends of the slot, which form stop means to prevent the slip retainer  60 , and the drag body  40 , from moving off the mandrel  20 . 
         [0036]    A cone element  70  at an upper end of the slip retainer is mounted to the mandrel  20  by a plurality of circumferentially spaced fasteners in the form of set screws  72 . These set screws also act as shear pins to release the torque anchor from a set position upon exertion of sufficient tension on the well equipment, as will be discussed later. The edge of the cone  70  opposite the set screws  72  forms a first conical surface  74  whose inclined surface wedges under the slips  62  when the torque anchor is moved into a set position. Likewise, an upper edge of the drag body  40  forms a second conical surface  54  whose inclined surface concurrently wedges under the slips  62  when the torque anchor is moved into a set position. However, the first and second conical surfaces  74 ,  54  should not actively contact the slips in the unset position, as shown in  FIG. 5 . A biaser in the form of a slip spring  76  urges each slip  62  radially inwardly into the slip retainer and away from the well conduit  12  in the unset position ( FIG. 5 ). 
         [0037]    An important aspect of this torque anchor is the configuration of the at least one groove  80  formed in the mandrel&#39;s outer cylindrical surface  26 , best seen in  FIG. 2 . The L-shaped groove has a first or upper arm  82  extending longitudinally with a shoulder  83  at its upper end forming a stop and an elbow  81  at its lower end. A second or lower arm  84  extends circumferentially from the elbow  81  at a generally right angle to the upper arm  82 . A terminal end  86  of the lower arm forms another stop and has opposed indents  86   a ,  86   b  extending longitudinally upwardly and downwardly therefrom. The groove  80  is dimensioned (width, depth) to slidingly accommodate a portion of a drive pin  88  extending therein threaded through a hole  56  in an lower part of the drag body  40  ( FIG. 5 ). The lower retaining ring  50  keeps the drive pin  88  within the drag body  40  and engaged within the groove  80 . In the  FIG. 3   a  embodiment three sets of grooves  80  and drive pins  88  are shown generally evenly spaced about the mandrel. 
         [0038]    The operation of the torque anchor may now be described with reference to all figures, including  FIGS. 6 to 7  showing the torque anchor in the set position in the well conduit  12 . There are generally two steps for moving the mandrel  20  in a “setting direction” to the set position, and a third step to help fix or maintain that set position. The first step is to initially pull the mandrel upwardly by lifting the tubing string  14  in the direction of arrow  17 , so that each drive pin  88  travels downwardly along the first arm  82  of the respective groove to the elbow  81  ( FIG. 2 ). In this embodiment that travel is relatively short, approximately 2.5 mm (about 1.0 inch). The pull on the mandrel forces the drive pins  88  to push the drag body&#39;s second conical surface  54  toward the first conical surface  74  of the cone element  70 . As these two components converge, the conical surfaces contact the inner edges  64  of each slip  62  to drive the slips outwards, so that the slip&#39;s outer surface  63  contacts and bites into the well&#39;s inner wall  13 . As a result, the mandrel  20  and the attached well equipment are fixed such that they can not move longitudinally in the well either up or down. At this point the second step is to turn the tubing string to the right (i.e. clockwise when looking down the tubing string in the direction of arrow  16 , in this embodiment) approximately “a quarter turn” (i.e. about 90 degrees) so that each drive pin  88  travels along the lower arm  84  from the elbow  81  to the stop  86 . At this point the mandrel and tubing string should be rotationally fixed in this first, or clockwise, setting direction. And finally the third step is to maintain the torque anchor in this set orientation by continuing to pull tension on the tubing string straight up, which should also engage the drive pin  88  with the lower indent  86   b  which “stores” the pin upon entry to aid in maintaining the set position. The drill string should be kept in tension as long as the set position is desired. 
         [0039]    The torque anchor is released, or unset, by reversing the above described setting procedure. The first unsetting step requires release of tension by moving the tubing string, and hence the mandrel  20 , down somewhat, which should move the drive pins  88  out of the corresponding lower indents  86   b  to the upper indents  86   a  which temporarily “store” the pins on exit. The second step requires rotating the tubing string and mandrel in a second direction opposite to the setting rotation, namely turning to the left (i.e. counter-clockwise when looking down the tubing string in the direction of arrow  16 , in this embodiment) approximately “a quarter turn” so that each drive pin  88  travels from the upper indents  86   a  along the lower arm  84  to the elbow  81 . Finally, in a third step, the mandrel should be moved further down relative to the drag body so that the drive pin  88  travels up the upper arm  82  from the elbow  81  toward the stop  83 . After the pin reaches this stop, continuing this mandrel movement causes the drag body  40  to move downwards, and thereby the second conical surface  54  to move away from the inner edge  64  of each slip  62 . The springs  76  urge the respective slips  62  inwardly away from the well&#39;s inner wall  13 , thus releasing the torque anchor for movement longitudinally (both up and down the well) and rotationally (in the unsetting direction). This allows the torque anchor to be moved to a different position in the well conduit  12  and be set again, or to lift the torque anchor and remove it from the well conduit. 
         [0040]    An alternate method of unsetting the torque anchor is to pull tension on the tubing string to exert sufficient upward force on the mandrel  20  to shear the set screws  72  by exceeding their maximum shear resistance. Once the sets screws are sheared, the cone element  80  becomes detached from the mandrel  20  and is free to move away, namely upward, from the slips  62 , allowing the springs  76  to retract the slips away from the inner surface  13  of the conduit. The torque anchor is therefore freed for removal from the well conduit  12 . The maximum shear resistance may be “adjusted” by either changing the set screws  72  to ones with a different shear value, or by altering the number of set screws inserted into the cone element  80 . For instance, in one version of the torque anchor, twelve brass screws  72  can be employed each with about 5000 pounds (2273 kg) resistance, and their maximum shear resistance does not exceed that of the drive pins  88  to avoid damaging the pins during such secondary release of the torque anchor. 
         [0041]    Some of the many advantages of the present invention may now be better appreciated. The torque anchor  10  is designed to anchor the tubing string from movement longitudinally along the well (in both directions, up and down the well) and from rotation (in the setting direction). The anchoring is achieved by simple setting and release procedures with relatively little movement of the tubing string. In this instance, setting is achieved by a small pull of the mandrel (via the tubing string) that is adequate for the drive pin  88  to travel the short distance along the longitudinal arm  82  to reach the elbow  81 , and then by a small “quarter” turn of the mandrel that is adequate for the drive pin  88  to travel the short distance along the circumferential arm  82  to reach the toe  85 , and finally by further pulling to engage the drive pin  88  with the lower indent  86   b . The torque anchor  10  avoids the more labourious and time consuming multiple full rotations of the mandrel that are currently required to set a torque anchor. The relatively short L-shaped groove  80 , in comparison to the multiple twists of the long threads or helical groove of other mandrels, reduces the risk of foreign objects obstructing the drive pin&#39;s travel path, and thus should improve the torque anchor function, reliability and wear. Also, since this anchoring is achieved by placing the tubing string in tension, there is an added benefit of ensuring that the tubing follows the rod string as closely as possible, which helps minimize rod wear. 
         [0042]    Some further benefits are set out below. 
         [0043]    The configuration of the torque anchor, including the arrangement of the set screws with a given shear resistance below that of the drive pins  88 , provides a relatively fast and easy secondary unsetting of the torque anchor in case of an emergency or should a problem be encountered with the primary means of setting and unsetting via the L-shaped groove  80 . 
         [0044]    Referring to  FIG. 6   b , the slips  62  are configured not only to centre the torque anchor within the well conduit  12 , but radially protrude sufficiently from the slip retainer  60  to provide large by-pass spaces  78  between the torque anchor and the conduit, creating high flow areas for fluids (eg. gas) and solids (eg. sand) to pass by the torque anchor, and allowing coil tubing to more easily extend past the torque anchor, than other torque anchors. In the  FIG. 6   b  version, for instance, by-pass spaces  78  with 1.0 inch (25.4 mm) radial clearance are created between the 4.5 inch (114.3 mm) OD of the slip retainer  60  and the 6.5 inch (165.1 mm) ID of the well conduit  12 . 
         [0045]    The configuration of the torque anchor  10  permits capillary cable to be carried downhole via the large by-pass spaces  78  created by this novel torque anchor design. In particular, the fact that the torque anchor  10  is set and unset by longitudinal motion and a limited, quarter turn, permits its use with the capillary cable since the anchor stays relatively straight during use, thus avoiding wrapping of the cable around the anchor. In contrast, prior art anchors that require multiple full (360 degree) rotations—between two to seven full rotations for setting and unsetting—cause an undesirable wrapping of the cable around the anchor, which damages the cable. Alternately, the cables must be pre-wrapped when inserted with these prior art anchors, so that they unwrap as the anchor is twisted during setting, which is tedious and undesirable. 
         [0046]    The drag blocks  42  have been hardened, over prior art drag blocks, for longer life. The slips  62  are made of solid high strength metal for superior durability and grip on the well conduit wall  13 , and Inconel™ type springs  76  are employed for improved resistance to H 2 S and CO 2 . Further, the surface of the mandrel  20  is optionally coated with Teflon® for improved resistance to H 2 S and CO 2 , and to help maintain mandrel strength. 
         [0047]    The above description is intended in an illustrative rather than a restrictive sense, and variations to the specific configurations described may be apparent to skilled persons in adapting the present invention to other specific applications. Such variations are intended to form part of the present invention insofar as they are within the spirit and scope of the claims below.