Patent Publication Number: US-7210529-B2

Title: Casing brush tool

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a casing brush for use in oil and gas wells. 
   When the work is conducted on a well casing the tubular casing members are stacked end-to-end and lowered into the well bore. New casing segments often have imperfections on the interior surfaces of the tubulars; old casing segments often have accumulated debris that clings to the inner walls. When production devices are run through the casings they scrape the sides of the casing and cause the debris that is on the casing to pile up downhole, which can eventually jam up the lowermost casing segment. With older pipes, the problem is also of a significant buildup of ferrous debris, such as bits and pieces of metal generated during drilling of a well. While some of the metal debris can be retrieved with magnetic retrieval tools, other obstructing pieces may not be removed from the interior walls of the casing to allow smooth operation of the downhole tools. 
   Conventionally, the interior of the casing can be cleaned with a scraper, which literally scrapes the walls of the casing to dislodge residue adhering to the walls or with brushes, which have flexible bristles that contact the walls of the casing and brush off the undesirable debris. Some of the brushes have bristles secured on the outer faces of cylindrical bodies and arranged in parallel axial vertical or horizontal rows. Some of the known devices use outwardly biased bristle members mounted on a cylindrical mandrel, with internal springs forcing the bristles to come into contact with the interior wall of the casing. The brush tools are usually pushed inside the casing, applying vertical force to the debris without rotating the brush in the casing. 
   However, conventional brushes tend to leave some of the debris on the surface. Particularly troublesome is the area of attachment of two casing segments, which are usually secured by exterior collars. The line of connection between the two casing segments tends to accumulate bits of extraneous material in the crevices formed at the joint line. These areas are more difficult to dislodge without several trips downhole. 
   The present invention contemplates elimination of drawbacks associated with the prior art and provision of an improved casing brush tool, which can be incorporated into a drill string and run downhole for cleaning the interior of the casing and substantially reducing the time required for cleaning the well casings. 
   SUMMARY OF THE INVENTION 
   It is, therefore, an object of the present invention to provide a well casing brush for use in oil and gas well bores. 
   It is another object of the present invention to provide a casing brush tool, which is easy to operate and inexpensive to manufacture. 
   It is a further object of the present invention to provide a brush assembly, which rotates while being inserted into the casing to facilitate cleaning of the casing walls. 
   These and other objects of the present invention are achieved through a provision of a casing brush tool, which has a free rotating sleeve mounted on an elongated mandrel. The sleeve carries a plurality of non-axial rows of bristles that are adapted to contacting the walls of the casing and dislodging the debris from the walls. The non-axial rows wind up, in a spiral or helical path, about the sleeve, substantially from one end of the sleeve to the other end of the sleeve. To facilitate rotation of the sleeve about the mandrel, a pair of bearing devices is mounted between the mandrel and the sleeve, one bearing device at the upper end of the sleeve, and one bearing device—adjacent a lower end of the sleeve. 
   The casing brush assembly may contain on or more of the brush tolls. If two of the brush tools are incorporated into the assembly, they may be connected end-to-end. In such a case, it is preferred that the bristle rows extend in helical rows of opposite directions. When lowered into the casing, the bristles of the first brush tool will cause rotation of the sleeve in one direction, for instance clockwise direction, while the bristles of the second brush tool will cause rotation of the second sleeve in the opposite, counterclockwise direction. As a result, the casing walls are “swept” by rotating bristles that are pushed down hole or removed from the down hole, thereby providing both vertical and rotational force on the bristles and facilitating a cleaning action of the casing inner walls. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference will now be made to the drawings, wherein like parts are designated by like numerals and wherein 
       FIG. 1  is a perspective view of the brush assembly in accordance with the present invention, with two brush tools incorporated in the assembly. 
       FIG. 2  is a perspective view of a sleeve having bristles particularly adapted for left hand or counter-clockwise rotation. 
       FIG. 3  is a perspective view of a sleeve particularly adapted for right hand or clockwise rotation. 
       FIG. 4  is a perspective detail view of the brush tool mandrel. 
       FIG. 5  is a perspective detail view of the upper bearing used in the tool of the present invention. 
       FIG. 6  is a perspective view of the lower bearing of the brush tool in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Turning now to the drawings in more detail, numeral  10  designates a brush tool comprising a brush tool body  12  having an upper connector member  14  and a mandrel  16 . A tool joint sub  18  is detachably secured on the lower end of the mandrel  16  by threaded engagement of connector member  20  with inner threaded joint  22  of the sub  18 . When assembled, the lower end of the mandrel  16  with exterior threads  22 , extends into the opening of the sub tool joint  18  provided with interior threads  20 . The mandrel  16  has an upper portion, which forms a tool joint  54 , and a reduced diameter portion  17 . 
   Mounted in a free rotational and in a surrounding relationship about the reduced diameter portion  17  is a hollow cylindrical sleeve  30 . The hollow cylindrical sleeve  30  has an interior diameter, which is slightly greater than the diameter of the reduced diameter portion  17  of the mandrel  16 . The sleeve  30  carries a plurality of rows of bristles  32 . The bristles  32  are secured on the exterior surface of the sleeve  30  and are arranged in non-axial rows, in spiral or helical rows extending from about the top  34  of the sleeve  30  to about the bottom  36  thereof. 
   It is envisioned that in the preferred embodiment, the bristles are secured in a helical path of constant pitch and diameter from the top end  34  to the lower end  36  of the sleeve  30 . The bristles  32  of the tool  12  are arranged in a right hand spiral or helical path. When lowered into the wellbore, the lowermost edge  38  of the bristles  32  first contacts the inner wall of the casing, with the remainder of the bristles following after the leading edge  38 . The downward force exerted on the tool body  12  causes rotation of the sleeve  30 , thus causing the bristles  32  to scrape against the inner surface of the casing and dislodge the settled particles, thereby cleaning the casing. When the tool body  12  is withdrawn from the wellbore, a leading edge  40  of the upper spiral segment becomes the first leading edge, helping to remove the dislodged particles from the wellbore. 
   The spiral winding of the bristles  32  about the sleeve  30  forms a more durable brush as compared with conventional brushes wherein the bristles extend radially from the tool body. In the conventional design, the bristles are subject to more wear because they contact the walls of the casing transversely to the force exerted on the brush pushed into the casing. In the design of the present invention, where the bristles arranged in a winding, spiral fashion, the angle of force is changed, exerting less wear on the bristles  32 . 
   To facilitate rotation of the sleeve  30  about the reduced diameter portion  16 , a top bearing assembly  42  and a lower bearing assembly  44  are secured the upper end  34  and below the lower end  36  of the sleeve  30  between the sleeve  30  and the mandrel portion  17 . 
   The casing brush assembly may contain one or more of the brush tools. As shown in  FIG. 1 , two of such brush tools may be incorporated into one brush assembly. A left hand rotating brush tool  50  can be connected end-to-end to the first brush tool  10 . The second brush tool  50  is similar in many respects to the first casing brush tool  10 . The tool brush  50  has a brush body  52 , which is provided with an upper tool joint  54  adapted for engagement with string subs (not shown) when the tool is run into the wellbore. A reduced diameter mandrel portion  56  extends downwardly from the tool joint portion  54 . A free rotating sleeve  58  is mounted above the mandrel  56  and a top bearing  60  is positioned in the sleeve  58 , between the mandrel portion  56  and the sleeve  58 . A lower bearing  62  is positioned adjacent a lower edge  64  of the sleeve  58 , between the sleeve  58  and the mandrel portion  56 . 
   Similarly to the sleeve  30 , the sleeve  58  carries a plurality of bristles  66  positioned in a plurality of non-axial rows, extending in a spiral fashion and winding from the top of the sleeve  58  to the bottom  64  of the sleeve  58 . Similarly to the bristles  32 , the bristles  66  can be arranged along a helical path of constant pitch and diameter from one end of the sleeve to the other. The helical path formed by the bristles  66  in the tool  50  forms a left hand helical path allowing the sleeve  58  to rotate counter-clockwise when positioned in the casing. When the left hand tool  50  is run in conjunction with the right hand tool  10 , a counter rotating effect is achieved when drifting in and out of the hole. As a result, a self-rotating sweeping action is created that dislodges the debris in the inner casing crevices, including the crevice created between adjoining casing segments. 
   The bearing assemblies  42  and  44  are housed in both ends of the sleeves  30  and  58 . They also slide on the mandrels  16  and  56 . When putting the tool brush assembly together, the bearing assembly is inserted into the brush sleeves at both ends and the brush sleeve is then placed over the mandrel and coupled with the tool joint component  18 . Torque is then applied to the mandrel and to the connector sub  18  to complete the assembly. The bearing assemblies  42  and  44  allow the brush sleeves  30  and  58  to rotate with ease when tripping in and out of the well bore. 
   It is possible to incorporate the brush tools  10  and  50  in the same string with magnetic well cleaning tools. When such magnets are installed above and below the brush tools  10  and  50  or between them, loosened ferrous material can be recovered and disposed of at the surface. The circulation of fluids in the casing facilitates removal of the debris. As a result, a clean wellbore environment is created allowing for trouble free installation of any necessary production equipment. The sleeves  30  and  58  rotate when the tools  10  and  50  are lowered into the wellbore. The brush bristles  32  and  66  make contact with the internal wall of the casing. The downward force generated by the rotation of the sleeves  30  and  58  generates sufficient rotation to scrub the internal wall of the casing. When the sleeves  30  and  58  are run together, the counter-rotating effect is achieved when the tools  10  and  50  are lowered and retrieved from the well bore. While it is extremely difficult to impart rotation on a casing brush when using conventional tool, the tools  10  and  50  of the present invention provide the desired rotational movement due to the particular arrangement of the bristle rows and free rotation of the sleeves  30  and  58 . The result is a rotationally cleaned casing, cleared of the accumulated or existing debris that is run in and out of the casing without the need to apply the rotation force from the surface. 
   The casing brush tool of the present invention allows to significantly reduce the time of casing cleaning and facilitates circulation of fluid through the casing. With conventional brushes, it is a problem to pump about two barrels a minute to lift debris from the wellbore. The tool brush of the present invention allows pumping of up to 10 barrels a minute while removing the debris from the casing and allowing full production of the wellbore. 
   Many changes and modifications can be made into the design of the present invention without departing from the spirit thereof. I therefore pray that my rights to the present invention be limited only by the scope of the appended claims.