Patent Publication Number: US-10767424-B2

Title: Device arranged for attaching a pipe stem on a tubular body

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 14/412,953, filed Jan. 5, 2015, which application published as US 2018/0181892 on Jul. 9, 2015 and granted to U.S. Pat. No. 9,982,494 on May 29, 2018, which application is the U.S. national stage application of International Application PCT/NO2013/000031, filed Jul. 10, 2013, which international application was published on Jan. 16, 2014, as International Publication WO2014/011056 in the English language. The international application is incorporated herein by reference, in entirety. The international application claims priority to Norwegian Patent Application No. 20120803, filed Jul. 12, 2012, Norwegian Patent Application No. 20121235, filed Oct. 22, 2012 and Norwegian Patent Application No. 20130208, filed Feb. 7, 2013, which applications are incorporated herein by reference, in entirety. 
    
    
     FIELD 
     The present invention relates to an attachment device for an element made to be arranged on a downhole tubular body. 
     BACKGROUND 
     In the oil and gas industry, elements that are attached to a downhole tubular body, for example to a production tubing, are used for a number of purposes. An example of such elements is so-called stabilizers or centralizers placed externally on the tubular body. The purpose of a stabilizer may be to ensure that a downhole unit is stabilized centrally in a surrounding tubular body. On casing, for example, stabilizers are used as spacers ensuring sufficient radial spacing between two casings, so that the introduction of cement is done in a satisfactory way. For other downhole units, stabilizers may be used to reduce the radial movement, especially for long, slim units like bottom-hole assemblies (BHA), for example. In one embodiment, the stabilizers are fixedly arranged on the jacket surface of a relatively short mandrel which, when necessary, is slipped over the tubular body, which is to be equipped with stabilizers, and attached there. The stabilizers may exhibit a wide variety of shapes; both straight and helical stabilizer elements are well known in the trade. Stabilizer assemblies of this kind, termed stabilizer pipes in the further description, may be floatingly arranged on the downhole body, that is to say they are fixed only axially on the downhole unit so that the stabilizer pipe may rotate on the downhole unit and thereby be stationary when the downhole unit rotates, the axial fixing being provided by means of stop sleeves that are attached to the downhole unit by shrinking, pressing, screws and so on. In other applications, the stabilizer pipe is fixed in a rotationally rigid manner to the downhole unit in order to follow as the downhole unit rotates. The attachment is carried out in the same manner as that mentioned for the stop sleeves. An attachment of this kind may require large and expensive tools, and some of the attachment methods, for example pressing, often cause lasting deformation of the contact surfaces of the relevant downhole unit. 
     Stabilizers and centralizers are also found as pipe sections which are mounted in the pipe string in need of stabilization (stabilizer sub) by the pipe section being provided, at its ends, with threaded portions corresponding to the threaded portions of the adjacent pipes. This invention does not relate to this form of stabilizers and centralizers. 
     Other examples of elements that require attachment to a downhole tubular body are sand filters in a production tubing and conduits arranged externally on the production tubing for conveying control signals, hydraulic fluid and so on. 
     SUMMARY 
     The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art. 
     The object is achieved through features which are specified in the description below and in the claims that follow. 
     On an end portion of a sleeve, an attachment portion is arranged. The attachment portion includes a clamping portion extending from the end of the sleeve and is provided with one or more clamping elements arranged to be moved in a radial direction towards an encircled tubular body. The clamping element may be a lip projecting in the axial direction of the sleeve, the clamping portion being lobed. The slits are preferably parallel, typically running in the axial direction. Alternatively, the clamping element may be formed as a loose clamping piece which is arranged in a recess in the clamping portion. The inward displacement of the clamping piece in the recess is preferably restricted, typically by means of projecting portions that may rest against corresponding ledges on the side edges of the recess. Adjacent to the clamping portion and on the jacket surface of the sleeve, an external locking portion is arranged, which is arranged to be surrounded by an adapter sleeve. 
     In one embodiment, the locking portion is composed of an externally threaded portion arranged to receive the adapter sleeve formed as a nut. The nut is provided with an engagement portion in the form of an internally threaded portion extending substantially from an end of the nut. 
     In another embodiment, the adapter sleeve engages the attachment portion by means of a catch system, for example by the locking portion being provided with one or more external catches, each extending in the circumferential direction across an area of the attachment portion which is slit by slits penetrating parts of the attachment portion, for example the slits of the lobed clamping portion mentioned above. Internally to the locking portion, the attachment portion exhibits a recess which, with its diameter larger than that of the adjacent portions of the centre bore of the mandrel, extends beyond the axial extent of the locking portion. The slitting of the attachment portion together with the corresponding internal recess allows the locking portion to be pressed inwards when the adapter sleeve, which, in this embodiment, is provided with one or more engagement elements projecting inwards, is moved in over the locking portion. The catch(es) is/are typically provided with a first conical side face facing the end of the clamping portion, for example with a pitch in the range of 20-35°. The opposite second side face forms an abutment surface, for example as a shoulder standing perpendicularly to the centre axis of the clamping portion. Correspondingly, the engagement element/elements on the adapter sleeve may have a cross section complementary to the cross section of the catch, so that an engagement element will slide with its conical inward side face on the conical outward side face of the catch as the locking portion is compressed in the radial direction until the engagement element engages behind said catch by its axially supporting abutment against the abutment surface of the catch. In this embodiment, the engagement elements are typically similarly shaped and regularly spaced axially. The locking portion may typically be provided with several catches spaced apart axially, the axial spacing pitch corresponding to the distance between the engagement elements of the adapter sleeve. Alternatively, the engagement elements may be made up of one or more pawls. 
     Adjacent to the internal threads, or the area provided with engagement elements, of the adapter sleeve a conical abutment portion is arranged, exhibiting a decreasing diameter in the direction away from the threaded portion. 
     By moving the adapter sleeve in over the sleeve, the conical abutment portion of the adapter sleeve successively forces the clamping element(s) of the clamping portion inwards in a radial direction into abutment against the tubular body on which the sleeve is placed. The adapter sleeve is brought to be axially fixed on the sleeve through engagement between the threads by rotation of the adapter sleeve, or between the catch(es) and the engagement element/elements by axial displacement of the adapter sleeve. Provided that the jacket surface of the tubular body has a circular cross section, the clamping elements will, when several clamping elements are distributed over the entire circumference of the sleeve, rest evenly against the tubular body. The sleeve which is formed in accordance with the invention could be clamped to any portion of the jacket surface of the tubular body without deforming the jacket surface. 
     The lip-shaped clamping element preferably has a decreasing thickness in the direction away from the externally threaded portion, that is to say towards its free end, as an inward contact surface is gently conical in order to form, in an active position, a best possible abutment against the tubular body. Correspondingly, the separate clamping piece is provided with conical abutment surfaces corresponding to the conical abutment portion of the adapter sleeve. 
     To prevent the adapter sleeve in the form of a nut from unscrewing during the rotation of the tubular body, it is an advantage for the thread direction to be the opposite of the normal rotational direction of the tubular body. 
     To further secure the adapter sleeve in the form of a nut, the nut may include a securing system, the nut being provided with a locking portion which includes one or more elevations projecting inwards, which are arranged to engage a latch groove arranged within the externally threaded portion of the sleeve. It is an advantage if the sleeve is provided with several latch grooves arranged in parallel in the axial direction of the sleeve. The nut may thereby lockingly engage the sleeve in several axial positions. The locking portion of the adapter sleeve may be continuous or interrupted, that is to say sectioned. 
     The securing system may alternatively have a design corresponding to that of the catch system described above. 
     The sleeve may form a mandrel, on a jacket surface of which, one or more function elements are fixed, for example stabilizing or centralizing elements, typically in the form of ribs projecting from and evenly distributed on the circumference of the mandrel. A sleeve in the form of an elongated mandrel may be provided with an attachment portion integrated in both end portions of the mandrel. The sleeve can also be used separately from a mandrel of this kind, but is used as an end abutment limiting the axial movement of the mandrel and allowing the mandrel to rotate freely on the tubular body which is to be provided with said function elements. 
     The invention does not exclude the use of the same technical solution for positioning other elements which are to be placed temporarily or permanently in such a way that they project from the circumference of a downhole tubular body. The sleeve may be provided with attachment elements for function elements extending along a tubular body, for example conduits for carrying electric signals or fluid, typically a hydraulic conduit. In its simplest form, the attachment element may be a projecting pin or a recess in the sleeve. 
     In a first aspect, the invention relates more specifically to an attachment device for an element made to be arranged on a downhole tubular body, characterized by an end portion of a sleeve, which is arranged to surround a portion of the tubular body, being provided with an attachment portion which includes at least one clamping element which is arranged to be displaced axially by the abutment of an abutment surface against a conical abutment portion of a surrounding nut. 
     The clamping element may be formed as a lip projecting in the axial direction from an external locking portion of the end portion. 
     The lip may have a gradually decreasing thickness in the direction from the external locking portion, as an inward contact surface is conical. 
     The clamping element may alternatively be formed as a curved clamping piece arranged in a recess in the end portion. 
     One or more of the side edges of the recess may form a ledge arranged to receive a corresponding collar portion arranged on the clamping element. 
     The locking portion may be formed as a threaded portion arranged to engage an internally threaded portion of the adapter sleeve. 
     The locking portion may be formed as at least one catch extending in the circumferential direction of a jacket surface of the attachment portion and being arranged to engage a corresponding engagement element projecting inwards on the adapter sleeve, the circumferential extent of the catch being defined by slits penetrating the locking portion at least and extending substantially in the axial direction of the attachment portion. 
     The attachment portion may be provided with an internal recess which is encircled by the locking portion and has an axial extent larger than the axial extent of the locking portion. 
     A jacket surface adjacent to the externally threaded portion may be provided with at least one latch groove arranged to receive a complementary engagement portion arranged inwards-projectingly on the adapter sleeve with a distance to the abutment portion. The engagement portion may be continuous or discontinuous. 
     The pitch direction of the threaded portions may be the opposite of the normal rotational direction of the tubular body. 
     The tubular body may be a casing, a liner or a bottom-hole assembly. 
     The locking portion may be formed as a threaded portion arranged to engage an internally threaded portion of the adapter sleeve, and the locking portion may include at least one catch extending in the circumferential direction of a jacket surface of the attachment portion and being arranged to engage a corresponding engagement portion projecting inwards on the adapter sleeve, the circumferential extent of the catch being defined by slits penetrating at least parts of the locking portion and extending substantially in the axial direction of the attachment portion. 
     The sleeve may be provided with one or more function elements taken from a group consisting of stabilizing elements, centralizing elements, sand screens and cable clamps. 
     The sleeve may be provided with one or more anchoring points for a function element. 
     The sleeve may be formed as a mandrel provided with one or more function elements projecting axially. 
     In a second aspect, the invention relates more specifically to a pipe string including several tubular bodies, characterized by one or more tubular bodies being provided with at least one mandrel fixed to said tubular bodies by an attachment device as described above being releasably engaged in a portion of said tubular bodies. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In what follows, an example of a preferred embodiment is described, which is visualized in the accompanying drawings, in which: 
         FIG. 1  shows a mandrel axially fixed with two sleeves according to the invention, the sleeves having been pulled slightly away from the end faces of the mandrel for the sake of exposure, and the mandrel being provided with stabilizers attached to an external jacket surface; 
         FIG. 2  shows, in perspective, two sleeves according to the invention integrated in the mandrel; 
         FIG. 3  shows, on a larger scale, an axial section through an attachment portion with an adapter sleeve formed as a nut screwed partially onto the attachment portion; 
         FIG. 4 a    shows, on a larger scale, an axial section through an alternative embodiment of the attachment portion; 
         FIG. 4 b    shows a radial section IV-IV according to  FIG. 4   a;    
         FIG. 5  shows, on a larger scale, an axial section of a section of an alternative embodiment of the attachment portion and the nut, a locking portion in an end portion of the nut being engaged in a latch groove in the mandrel; 
         FIG. 6  shows an axial section through an attachment portion and an adapter sleeve provided with a catch system, in which engagement elements projecting inwards on the adapter sleeve are being moved into engagement with corresponding catches on the attachment portions; 
         FIG. 6 a    shows an enlarged section of the catch system; and 
         FIG. 7  shows a view corresponding to  FIG. 6 , but where the engagement elements are fully engaged in the catches. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     In the figures, the reference numeral  1  indicates a sleeve in the form of an elongated mandrel provided with several function elements  2 , shown in  FIGS. 1 and 2  as ribshaped stabilizing elements projecting from a jacket surface  12  of the mandrel  1 . The mandrel  1  is arranged to releasably surround a portion of a tubular body  3 , shown schematically in  FIGS. 1 and 2  as a casing. In  FIG. 1 , the mandrel  1  is fixed by means of two separate sleeves  1   a , for example when it is desirable that the mandrel  1  with the function elements  2  should be rotatable on the tubular body  3 , as an attachment sleeve  1   a  is positioned in an axially supporting manner against both end portions  11  of the mandrel  1 , which, in this embodiment, have straight end faces  111 . The sleeves  1   a  are attached in a rotationally rigid manner to the tubular body  3  so that the mandrel  1  may rotate freely. In  FIG. 2 , attachment devices for the sleeves  1   a  are integrated in both end portions  11  of the mandrel  1  so that the mandrel  1  is attached to the tubular body  3  in a rotationally rigid manner. 
     In the following description, the attachment device is described in relation to the sleeve  1   a , but is valid also when the sleeve  1   a  forms an elongated mandrel  1  provided with said attachment device(s). 
     An end portion  11  of the sleeve  1   a  is provided with an attachment portion  13  which, in a first embodiment (see  FIG. 3 ) includes a clamping portion  131  arranged to abut in a holding manner against the tubular body  3 . The clamping portion  131  is formed from several lip-shaped clamping elements  1312  projecting in the axial direction from the sleeve  1   a , the clamping elements  1312  being separated by slits  1311 . The slits  1311  are shown here as straight-lined and parallel and are arranged in the axial direction of the sleeve  1   a , but other designs are possible as well. The internal side faces of the to clamping elements  1312  form clamping faces  1313  arranged to rest, in an active position, against the tubular body  3 . The clamping faces  1313  are gently conical with an increasing diameter towards the free ends of the clamping elements  13 , typically with a pitch angle in the range of 2-5°. The pitch angle roughly corresponds to the pitch angle of the abutment surface  142  of an encircling adapter sleeve  14  (see below) to provide the desired contact between the clamping faces  1313  and the surrounded tubular body  3 . In one embodiment (see  FIGS. 6 and 7 ), a portion of the clamping faces  1313  constitutes a gripping face  1313 ′, shown as toothed here, but other friction-enhancing designs may be used, for example serration. 
     In a second embodiment (see  FIGS. 4 a  and 4 b   ), the attachment portion  13  is provided with several recesses  132 , each accommodating a clamping element  1312 ′ in the form of a curved clamping piece provided with a conical, outward, abutment surface  1315  and a cylindrical, inward, clamping face  1313 . The clamping face  1313  is preferably rough, for example serrated, to exhibit sufficiently large friction against a surface. The recess  132  is provided with ledges  1321  arranged to receive corresponding collar portions  1314  having the effect of preventing the clamping element  1312 ′ from falling out of the recess  132 . 
     In one embodiment, a locking portion  133  is arranged to engage in the adapter sleeve  14  in an axially fixing manner as the locking portion  133  is formed as an externally threaded portion extending along a portion of the jacket surface  12  from the bottom of the slits  1311 . 
     In this embodiment, the adapter sleeve  14  is formed as a nut provided with an internally threaded portion  141  complementary to the externally threaded portion  133  of the sleeve  1   a . In the further description, the term “nut” is partly used when the adapter sleeve  14  is provided with an internally threaded portion  141 . 
     In another embodiment, the axial fixing of the adapter sleeve  14  on the attachment portion  13  is provided by a catch system, the locking portion  133  including several external catches  134 , each extending in the circumferential direction of the jacket surface  12  across a region of the attachment portion  13  which is split by slits, shown in  FIGS. 6 and 7  as the slits  1311  defining the clamping elements  1312 . Internally to the locking portion  133 , the attachment portion  13  exhibits a recess  135  which, with its diameter larger than that of the adjacent portions of the centre bore of the sleeve  1   a , extends beyond the axial extent of the locking portion  133 . The slitting of the attachment portion  13  together with the corresponding internal recess  135  allows the locking portion  133  to be pressed inwards when the adapter sleeve  14  (see  FIG. 7 ), which, in this embodiment, is provided with engagement elements  141  projecting inwards, is moved in over the locking portion  133 . In the embodiment shown, the catches  134  are provided with a first, conical side face  134   a  facing the end of the clamping portion  131 , for example with a pitch in the range of 20-35°, about 30° shown here. An opposite, second side face  134   b  forms an abutment surface, shown here as a shoulder standing perpendicularly to the centre axis of the clamping portion  131 . Correspondingly, the engagement elements  141  of the adapter sleeve  14  have a cross section complementary to the cross section of the catches  134  so that an engagement element  141  will slide with a conical, inward side face  141   a  on the conical outward side face  134   a  of the catch  134  as the locking portion  133  is compressed in the radial direction until the engagement element  141  engages behind said catch  134  by its axially supporting abutment against the abutment surface  134   b  of the catch  134 . In this embodiment, the engagement elements  141  are typically similarly shaped and arranged with regular axial spacing. Here, the locking portion is shown with several catches  134  spaced apart axially, the axial spacing pitch corresponding to the spacing of the engagement elements  141  of the adapter sleeve  14 . 
     Reference is now made to  FIGS. 3 and 4   a  in particular. Between the engagement elements  141  and a first end  14   a  of the adapter sleeve  14 , a conical abutment portion  142  extends with a diameter decreasing in the direction away from the engagement elements  141 . The pitch angle of the conical abutment portion  142  is preferably equal to the pitch angle of the clamping faces  1313  of the clamping element  1312  or the abutment surface  1315  of the clamping elements  1312 ′, in order thereby to provide good contact between the clamping faces  1313  of the lips  1312  or clamping pieces  1312 ′ and the surrounded tubular body  3  when the clamping elements  1312 ,  1312 ′ are in their active positions. 
     In the embodiment as a nut, the adapter sleeve  14  is provided with several grip portions  144  (se  FIGS. 3 and 4   a ), shown here as cut-outs extending through the conical portion of wall of the adapter sleeve  14 . The grip portions  144  are arranged to be releasably engaged by a tool (not shown) for rotating the nut  14 . 
     Reference is now made to  FIG. 5 , in which an embodiment with several parallel latch grooves  134 ′ arranged adjacent to the externally threaded portion  133  is shown. A complementary engagement element  141 ′ projects inwards like a ridge from the internal wall surface of the nut  14 , with a distance to the internally threaded portion  141 . The engagement element  141 ′ is arranged to be yielding so that by the axial displacement of the nut  14  on the externally threaded portion  133 , it may climb on the side edges of the latch grooves  134 . The engagement portion  141 ′ may, for example, be formed as a yielding one by the use of a small material thickness in the adjacent portion of the wall of the nut  14 , possibly by the engagement portion  141 ′ and the adjacent portion of the wall of the nut  14  being split with slits arranged axially (not shown). 
     Alternatively, the nut  14  may be provided with a catch system, as described above and shown in the  FIGS. 6 and 7 , to prevent the nut  14  from unscrewing. 
     It is obvious to provide both end portions  11  of a sleeve  1   a  formed as a mandrel  1   a  with attachment portions  13  of the kind as described above. It is also obvious to choose a thread direction that will prevent the nut  14  from unscrewing as the tubular body  3  is rotated in its normal direction of rotation. 
     When a pipe string that is being constructed from said tubular bodies  3  is to be provided with function elements  2 , for example a new casing is to be centred in a previously installed casing in such a way that sufficient clearance is ensured between the casings for the satisfactory introduction of cement, a mandrel  1  with function elements  2  and adapter sleeve/sleeves  14  is slipped over the relevant tubular body  3  and fixed in the desired position by the adapter sleeve/sleeves  14  being clamped in such a way that the clamping faces  1313  and possible gripping faces  1313 ′ of the clamping elements  1312  are pressed against the jacket surface of the tubular body  3 . By the use of attachment sleeves  1   a  according to the invention, the mandrel  1 , attachment sleeve/sleeves  1   a  and adapter sleeve/sleeves  14  are slipped over the tubular body  3  in the desired order and orientation. The attachment sleeve/sleeves  1   a  is/are attached in a manner corresponding to that described above. Correspondingly, the sleeve  1   a  is used as an attachment for one or more function elements  2  by the function element  2  being attached to a suitable anchoring point  136  on the sleeve, shown in  FIG. 6  as a threaded recess, and shown in  FIG. 7  as a projecting threaded pin.