Abstract:
Non-rotating tubular wellbore cleaning devices are described which include a central tool mandrel with radially surrounding stabilizers and a cleaning member subassembly. A rotational bearing is provided that is partially radially recessed, thereby improving the overall strength of the cleaning device.

Description:
[0001]    This application claims priority to U.S. Provisional Patent Application Ser. No. 61/106,674 filed Oct. 20, 2008 and U.S. Provisional Patent Application Ser. No. 61/149,632 filed Feb. 3, 2009. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates generally to systems and methods for cleaning the interior of tubular members. In particular aspects, the invention relates to methods and devices for scraping wellbore casing. 
         [0004]    2. Description of the Related Art 
         [0005]    Wellbore cleaning devices include casing scrapers and brushing devices. These mechanisms are used to remove mud, cement sheath, perforation burrs, rust, scale, paraffin, and other debris from the internal surface of wellbore casing. The casing scraper or brush is typically attached to a drill string for operation. The drill string and cleaning device are then disposed within the casing members to be scraped, and rotated. 
         [0006]    Typical casing scrapers include a central scraping body and one or more scraping blades that extend radially outwardly therefrom. Conventional casing scrapers generally fall into one of two categories: rotating and non-rotating. With a rotating scraper, the scraping body and the scraping blades are securely affixed to each other so that both rotate with the drill string. In applications where the drill string is rotated for long periods of time, rotating scrapers can cause serious wear and damage to the interior surface of casing. With a non-rotating scraper, only the scraping body rotates with the drill string. The scraper blades are not affixed to the central scraping body, but are urged radially outwardly from it by compression springs in order to provide a force for removal of debris. An example of this type of arrangement is found in U.S. Pat. No. 7,311,141 issued to Tulloch et al. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention provides methods and devices for cleaning the interior of tubular members, such as casing members. Exemplary non-rotating tubular cleaning devices are described which include a central tool mandrel with radially surrounding stabilizers and a cleaning member subassembly. The cleaning member subassembly includes one or more scraper blades that are secured around the tool mandrel. In one embodiment, a scraper device is described wherein each scraper blade of a scraper blade subassembly includes a blade housing having blade windows. Scraper blades are retained within the blade housing so that the scraper blades are biased radially outwardly through the windows. In another embodiment, a brush-type wellbore cleaning device is described wherein the cleaning member subassembly includes a brush attachment having a central collar with cleaning bristles. 
         [0008]    A rotation interface is disposed between the cleaning member subassembly and stabilizers and ensures that the stabilizers and cleaning members can rotate with respect to the mandrel. In preferred embodiments, the interface includes sets of rotational bearings or bushings, and preferably roller bearings that enable the cleaning member subassembly to easily rotate with respect to the tool mandrel. Exemplary rotation interfaces feature annular indentations and split ring and split sleeve components that fit into the indentations to allow portions of the rotation interface to be recessed radially inwardly. 
         [0009]    The construction of the cleaning devices permit these tools to have improved strength and resistance to axial and torsional forces within the work string within which the cleaning device is used. The threaded connection of the tool mandrel largely governs the strength of the tool overall. The use of annular indentations and inner bearing race and rotational sleeve components permits the diameter of the threaded portion of the tool mandrel to be radially enlarged relative to the indentations. As a result, the cleaning tools are stronger and more resistant to axial and torsional stresses and forces. 
         [0010]    In other aspects, the invention relates to improved tools for cleaning the interior of a surrounding tubular and wherein the rotation interface permits the central mandrel to rotate within the cleaning members. In various embodiments, the cleaning members may be scraper blades or brushes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The advantages and further aspects of the invention will be readily appreciated by those of ordinary skill in the art as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawing and wherein: 
           [0012]      FIGS. 1A-1C  are a side, cross-sectional view of an exemplary scraper device constructed in accordance with the present invention. 
           [0013]      FIG. 2  is a side, external view of the scraper device shown in  FIGS. 1A-1C . 
           [0014]      FIG. 3  is a side, cross-sectional view of an exemplary split sleeve used in the scraper device of  FIGS. 1A-1C  and  2 , shown apart from the other components. 
           [0015]      FIG. 4  is an axial cross-section taken along the lines  4 - 4  in  FIG. 3 . 
           [0016]      FIG. 5  is a side, cross-sectional view of an exemplary spacer used in the scraper device of  FIGS. 1A-1C  and  2 , shown apart from the other components. 
           [0017]      FIG. 6  is an axial cross-section taken along the lines  6 - 6  in  FIG. 5 . 
           [0018]      FIG. 7  is a side, cross-sectional view of an exemplary scraper blade sleeve used in the scraper device of  FIGS. 1A-1C  and  2 , shown apart from the other components. 
           [0019]      FIG. 8  is an axial cross-section taken along lines  8 - 8  in  FIG. 7 . 
           [0020]      FIG. 9  is a further enlarged view of lower portions of the scraper device shown in  FIGS. 1A-1C  and  2 . 
           [0021]      FIG. 10  is an isometric view of an exemplary scraper blade used with the scraper device of  FIGS. 1A-1C  and  2 , shown apart from other components of the scraper device. 
           [0022]      FIG. 11  is an end view of the scraper blade shown in  FIG. 10 . 
           [0023]      FIG. 12  is a cross-sectional view taken along the lines  12 - 12  in  FIG. 11 . 
           [0024]      FIG. 13  is an isometric detail view of an exemplary inner bearing race used with the scraper device shown in  FIGS. 1A-1C  and  2 . 
           [0025]      FIG. 14  is an isometric view of an exemplary bearing used with the scraper device shown in  FIGS. 1A-1C  and  2 . 
           [0026]      FIGS. 15A-15C  present a side, cross-sectional view of an exemplary cleaning device in accordance with the present invention and incorporating a brush-type cleaning assembly. 
           [0027]      FIG. 16  is an axial cross-section taken along lines  16 - 16  in  FIG. 15A . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]      FIGS. 1A-1C  and  2  illustrate a first exemplary wellbore cleaning device constructed in accordance with the present invention. The first cleaning device is in the form of an exemplary tubular scraper device or tool  10  that is useful for incorporation into a wellbore work string and disposed within a wellbore. The scraper device  10  includes a generally cylindrical tool mandrel, generally indicated at  12 . The tool mandrel  12  defines a central flowbore  14  along its length. The upper end of the tool mandrel  12  preferably includes a box-type threaded connection  16  so that the scraper device  10  may be secured to other portions of a wellbore work string (not shown). As shown in  FIG. 1C , the lower to end of the tool mandrel  12  is secured by a threaded connection  18  to a bottom sub  20 . 
         [0029]    The tool mandrel  12  presents an outer radial surface having a number of different diameter portions. There is an upper, enlarged-diameter portion  22  and a reduced diameter lower shaft, generally shown at  24 . The lower shaft  24  includes a plurality of annular indentations  26 ,  28 ,  30 ,  32 ,  34 ,  36 ,  38  which are preferably spaced apart from one another along the length of the lower shaft  24 . The indentations  26 ,  28 ,  30 ,  32 ,  34 ,  36 ,  38  have a diameter that is less than the diameter of the lower shaft  24 . 
         [0030]    An upper wear ring  40  surrounds the lower shaft  24  immediately below the upper enlarged diameter portion  22 . An upper stabilizer  42  surrounds the lower shaft  24  below the wear ring  40 . A cleaning member subassembly or scraper blade subassembly, generally indicated at  44 , is located below the upper stabilizer  42  on the lower shaft  24 . Lower stabilizer  46  surrounds the lower shaft  24  below the scraper blade subassembly  44 . The upper and lower stabilizers  42 ,  46  are of a type known in the art and function to centralize the scraper blade subassembly  44  within a surrounding casing member. Lower wear ring  48  is disposed below the lower stabilizer  46  and on the bottom sub  20 . 
         [0031]    The scraper blade subassembly  44  includes an outer tubular cleaning member housing, or blade housing  50  which radially surrounds the lower shaft  24  of the tool mandrel  12 . The blade housing  50  defines a plurality of cleaning member windows, or blade windows  52 . The construction of the blade housing  50  may be better understood by further reference to  FIGS. 7 and 8 , which show the blade housing  50  apart from the other components of the scraper device  10 . As shown there, the blade housing  50  includes a central axial bore  54  along its longitudinal length. The bore  54  includes an upper, enlarged diameter bearing chamber  56  and a reduced diameter engagement section  58 . The bearing chamber  56  has a smooth, cylindrical shape. However, the engagement section  58  preferably includes a plurality of radially inwardly directed engagement flats  60 .  FIG. 8  shows the engagement section  58  having a hexagonal shape which provides six flats  60 . However, other suitable cross-sectional shapes may also be used (i.e., pentagon, square), and there may be more or fewer than six engagement flats  60 . In the exemplary embodiment shown in  FIGS. 1A-1C  and  7 , the bore  54  of the blade housing  50  also includes two radially-enlarged blade chambers  62  and  64  which are separated by a radially inwardly-projecting annular flange  66 . The blade chambers  62 ,  64  contain the blade windows  52 . In addition, the bore  54  of the blade housing  50  contains a lower, enlarged diameter bearing chamber  68 . 
         [0032]    Cleaning members in the form of scraper blades  70  are disposed radially within the blade housing  50 .  FIGS. 10 ,  11  and  12  depict an exemplary scraper blade  70 . Each scraper blade  70  includes a blade body  72  which presents radially outward-facing scraping surfaces  74 . The radially interior face  76  of the scraper body  72  is radially curved to generally match the curvature of the tool mandrel  12 . A spring-retaining recess  78  is formed within the interior face  76  (see  FIG. 12 ). Retaining flanges  80  extend laterally outwardly from the blade body  72 . When a blade  70  is disposed within a window  52  of the blade housing  50 , the retaining flanges  80  prevent the blade  70  from falling radially outside of the window (see  FIGS. 1A and 1B ). Compression springs  82  reside within the spring-retaining recess  78  of each blade  70  and bias the scraper blade  70  radially outwardly from the tool mandrel  12 . The configuration of the compression springs  82  are adapted to allow for the exertion of a symmetrical force between the scraper blade  70  and rotation sleeve  104 . 
         [0033]    A rotation interface, generally indicated at  84  in  FIGS. 1A-1C , is disposed radially between the lower shaft  24  and the surrounding stabilizers  42 ,  46  and scraper blade subassembly  44 . The rotation interface  84  allows the stabilizers  42 ,  46  and the scraper blade subassembly  44  to rotate freely around the lower shaft  24 . In one embodiment, the rotation interface  84  includes a plurality of rotational bearings that are in the form of roller bearing sets  86 . In the exemplary embodiment depicted in  FIGS. 1A-1C , there are six roller bearing sets  86 . However, there may be more or fewer than six sets. Each of the roller bearing sets  86  is made up of an inner bearing race  88 , an outer bearing race  90 , and a plurality of rollers  92  that are disposed in between the inner and outer bearing races  88 ,  90 . Alternatively, a bushing may be used in place of outer bearing race  90 , rollers  92  and spacer  116 . The rollers  92  are preferably cylindrically shaped members, as illustrated in  FIG. 14 . However, spherical roller bearings might also be used. The inner bearing race  88  of each roller bearing set  86  is preferably made up of two halves  94 ,  96 , as illustrated in  FIG. 13 . Alternatively, if desired, an inner bearing race  88  could also be made up of three or more separate race portions which could be assembled within an indentation  26 ,  28 ,  30 ,  34 ,  36 , or  38  to make up a complete annular bearing race. When the roller bearing set  86  is assembled, the rollers  92  will rotate upon the outer radial surface  98  of the inner bearing race  88  and, due to rolling contact of the rollers  92  with both the inner and outer bearing races  88 ,  90 , the bearing races  88 ,  90  will easily rotate with respect to one another. The outer bearing races  90  of the roller bearing sets  86  are in contact with, and preferably secured to portions of either the scraper blade subassembly  44  or the stabilizers  42 ,  46 .  FIG. 9  shows, for example, that the outer bearing race  90  of the roller bearing set  86  that is mounted within indentation  34  is in contact with the surrounding scraper blade housing  50  and is secured in place against the scraper blade housing  50  by spacers  116  on each axial side. As a result, the scraper blade housing  50  will rotate about the tool mandrel  12  with the outer bearing race  90 . Similarly, the outer bearing races  90  of the roller bearing sets  86  that are located in indentations  36  and  38  are in contact with the lower stabilizer  46  so that the lower stabilizer  46  will rotate about the tool mandrel  12  with those outer bearing races  90 . Alternative cleaning elements may be used in place of scraper blades  70 , such as magnets or brushes. This may be achieved by removing outer bearing races  90 , rotation sleeve  104  and scraper blade subassembly  44 , and engaging the alternative cleaning element to the inner bearing race  88 . 
         [0034]      FIGS. 15A-15C  and  16  depict an alternative exemplary cleaning tool  10 ′ configured with an alternative cleaning member. The cleaning member of the cleaning tool  10 ′ is in the form of a brush  101  wherein cleaning brush bristles extend radially outwardly from a central collar. In this instance, the rotation interface includes bearing races  88 , which are disposed between the mandrel  12  and the brush  101 . 
         [0035]    Referring once again to the scraper-type cleaning tool  10  shown in  FIGS. 1A-1C  and  2 - 14 , the rotation interface  84  also includes a split rotation sleeve  104  which underlies scraper blades  70  of the scraper device  10 . An exemplary rotation sleeve  104  is depicted in detail in  FIGS. 3 and 4  wherein it can be seen that the sleeve  104  is preferably made up of two sleeve halves  106 ,  108 . If desired, there may be more than two sleeve halves  106 ,  108  which can be assembled about the lower shaft  24  to form a complete or substantially complete annular sleeve  104 . The rotation sleeve  104  preferably presents a smooth cylindrical outer radial surface  110  along most of its length. One axial end of the rotation sleeve  104  includes an outer interengagement surface  112  that presents engagement flats  114 . In the exemplary embodiment shown in  FIG. 4 , there are six engagement flats  114 . However, there may be more or fewer than six, if desired. Alternatively, the interengagement surfaces  112 ,  58  may comprise teeth as opposed to engagement flats, so long as both surfaces are complimentary to one another. The engagement flats  114  of the split sleeve  104  are shaped and sized to abut the engagement flats  60  of the blade housing  50 . This complimentary engagement permits the rotation sleeve and the blade housing  50  to rotate together without the need to affix them to one another with a fastener or otherwise. The rotation sleeve  104  halves  106 ,  108  are placed radially around the shaft portion  24  of the tool mandrel  12 , and will readily rotate about the mandrel  12 . 
         [0036]    In preferred embodiments, spacer rings  116  are located between roller bearing sets  86  under the stabilizers  42 ,  46 . The spacer rings  116  serve to retain the roller bearing sets  86  in axial spaced relation to one another.  FIGS. 5 and 6  illustrate an exemplary spacer ring  116  apart from the other components of the scraper device  10 . 
         [0037]    As best seen in the enlarged view provided by  FIG. 9 , roller bearing sets  86  are preferably abutted by elastomeric lip seals  122  of a type known in the art for creating a fluid seal against the bearing set  86 . In addition, the lip seals  122  will drag on the shaft portion  24  of the tool mandrel  12  to prevent the scraper blade subassembly  44  and stabilizers  42 ,  46  from floating freely with respect to the tool mandrel  12 . The retaining ring  124  and spacer  116  mechanically secure the roller bearing set  86  in place axially. The fluid seal  122  prevents or limits the escape of lubricant from the bearing set  86 . In an alternative embodiment, the roller bearing sets  86  may be replaced by an annular bushing. 
         [0038]    Removable pipe plugs  130  are preferably provided in each of the stabilizers  42 ,  46  and the blade housing  50 . The pipe plugs  130  are preferably removably secured by threading and may be removed to allow lubricant to be supplied to the roller bearing sets  86 . 
         [0039]    To assemble the scraper device  10 , the inner bearing races  88  for each of the roller bearing sets  86  are placed into the indentations  26 ,  28 ,  30 ,  34 ,  36 ,  38 . This is possible because the inner bearing races  88  are each formed of multiple components (i.e. halves  94 ,  96 ) which can be assembled within the indentations to form a complete annular bearing race  88 . Stabilizers are preassembled with lip seals  122 , outer bearing races  90  with rollers  92 , spacer ring  116  and retaining ring  124 . The upper stabilizer  42  is slid onto the shaft  24  to a position wherein it abuts the upper wear ring  40 . Springs  82  are installed in spring retaining recesses  78 . Spacer  116 , lip seals  122  and outer bearing race  90  with rollers or annular bushing  92  for blade housing  50  are slid onto shaft  24 . The rotation sleeve  104  is assembled around the shaft  24  in indentation  32 . The scraper blades  70  are disposed into the windows  52  of the blade housing  50 . Thereafter, the blades  70 , springs  82 , and blade housing  50  are slid onto the shaft  24 . The engagement section  58  of the blade housing  50  is positioned onto the outer surface  112  of the rotation sleeve  104  so that the engagement flats  114  of the split sleeve  104  are interengaged with the engagement flats  60  of the blade housing  50 . As a result of this interengagement, the blade housing  50  and split sleeve  104  will rotate as one about the shaft  24  of the tool mandrel  12 . Spacer  116 , lip seals  122 , and outer bearing race  90  with roller  92  are slid onto shaft  24 , and pushed inside of blade housing  50 . The lower stabilizer assembly  46  is then slid onto the shaft  24 . Thereafter, the wear ring  48  and bottom sub  20  are secured to the shaft  24 . It will be appreciated that the rotation interface  84  permits the stabilizers  42 ,  46  and the scraper blade subassembly  44  to rotate freely about the tool mandrel  12 . 
         [0040]    The internal diameters of the stabilizers  42 ,  46  and the blade housing  50  are slightly larger than the external diameter of the threaded portion  18  of the tool mandrel shaft  24 . The internal diameters of the split bearing races  88  are smaller than the diameter of the threaded portion  18 . The use of split bearing races  88  reduces the amount of wear and frictional heat sustained on the surface of the mandrel  12 , when compared to the amount of wear and frictional heat a person of ordinary skill in the art would expect to occur if the stabilizers  42 ,  46  and blade housing  50  were allowed to rotate on the surface of the mandrel  12 , by allowing for rotation about the split bearing races  88 . As  FIG. 9  depicts, the outer diameter D 1  of each of the indentations (as illustrated at indentation  38 ) is less than the outer diameter D 2  of the shaft  24  at the point where the threaded connection  18  begins. Diameter D 2  is essentially the diameter of the shaft portion  24  where there are no indentations  26 ,  28 ,  30 ,  32 ,  34 ,  36  and  38 . The inventors have determined that the strength of a scraper device within a work string and its resistance to damage from axial and torsional stresses is largely a function of the strength of the threaded connection  18 . The provision of split inner bearing races  88  and rotation sleeve  104 , which reside in a radially recessed manner within the indentations  26 ,  28 ,  30 ,  32 ,  34 ,  36  and  38 , allows the threaded connection portion  18  of the shaft portion  24  to be provided with a larger diameter, thereby increasing the strength of the connection to bottom sub  20 , the overall strength of the tool  10  and the resistance to damage from applied forces within a wellbore. As a result, the threaded connection  18  substantially approximates full gauge (D 2 ) while at least a portion of the rotational interface is disposed upon the shaft portion  24  radially within the full gauge diameter D 2  by being recessed at less than full gauge (to the depth D 1  of the indentations  26 ,  28 ,  30 ,  32 ,  34 ,  36  and  38 ). 
         [0041]    The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope and the spirit of the invention.