Abstract:
The present invention provides wellbore cleaning tool and method featuring a wiper assembly which allows fluid to bypass the tool in one direction while diverting the well fluid through a filter screen in another direction. This may be achieved by either circulation of the fluid in the wellbore or by moving the tool relative to the fluid in the wellbore. The wiper assembly includes multiple groups or series of wiper elements wherein one petal shaped element aligns with a slot to form a seal when the tool body is retrieved from the well.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. Provisional Patent Application Ser. No. 62/175,618, filed Jun. 15, 2015, which is incorporated herein by reference and to which priority is hereby claimed. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable 
       REFERENCE TO A “MICROFICHE APPENDIX” 
       [0003]    Not applicable 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present invention relates to the removal of debris from oil and gas wells. More particularly, the present invention relates to an improved method and apparatus for removing debris from an oil and gas well tubular or tube shaped member or pipe (e.g., casing) wherein the apparatus employs specially configured petals and slots that enable flow outside the tool body in both up and down directions. 
         [0006]    2. General Background of the Invention 
         [0007]    In general, the removal of debris from oil and gas wells is well documented. There are many examples of prior art which include scrapers and brushes to mechanically clean the interior surface of casing of the well. Likewise, there are examples of tools designed to remove the debris from the wellbore after it has been scraped and/or brushed. This is an important function of a wellbore cleanup operation as the removal of junk and debris help mitigate against failure of downhole equipment, particularly when circulation of wellbore fluid alone is insufficient to ensure hole cleaning. Magnets are often used for this purpose, however not all wellbore debris is ferrous. Therefore, some debris must be removed by a mechanical means. 
         [0008]    Some prior art devices (e.g., see U.S. Pat. No. 6,250,387) use a wiper cup made of a flexible but high strength rubber, typically supported by metal wires which are moulded into the rubber. The rubber and wire work together to provide sealing and wiping capability as well as resistance to tearing. One problem with this type of device is that the wiper cup is adapted from use as a one directional seal whereby fluid pressure on the inside of the cup bellows the cup outwards to create a seal. 
         [0009]    Fluid pressure on the outside of the cup causes it to partially collapse, allowing pressure to bypass the cup. The wiper cup can hold pressure in only one direction. It cannot allow significant volumes of fluid or debris laden fluid to flow past it in the opposite direction, particularly the volumes required to perform an effective wellbore cleanup. This is due to the shape of the cup which form a continuous seal on the inside of the wellbore, as well as the materials used which while being rubberized are still relatively stiff and resilient in order to be robust enough to work in a downhole environment. 
         [0010]    In order to allow the high volume of debris laden fluid to pass the tool, the device of U.S. Pat. No. 6,250,387 discloses a series of check valves. This allows fluid to pass through the tool in one direction bypassing the filter, and works in conjunction with the wiper cup to divert fluid through the screen in another direction. The check valves which act as a diversion means for the filtered fluid often become blocked by larger debris and junk resulting in the wellbore fluid partially or completely bypassing the filter and therefore rendering the tool useless. The wire wrapped screen used on this device is prone to damage whereby junk becomes trapped in the annular volume between the screen and the casing. Due to rotation of the tool, the wire screen can become damaged and fail catastrophically. 
         [0011]    The largest external components are used for stand-off and are attached such that they rotate with the tool. It is commonly accepted that wellbore cleanup tools which feature non-rotating centralizers (centralizers which can remain stationary while the tool rotates) prevent casing and tool wear. The ‘burst disks’ used on the U.S. Pat. No. 6,250,387 as an emergency bypass are prone to opening accidentally which allows partial or complete bypass of the filter, which occurs most often when the drilling rig ‘pumps a slug’ (a method of lowering the fluid level in the wellbore by placing an artificially high density pill into the work-string which over-pressures the burst disk). 
       SUMMARY 
       [0012]    In one embodiment, the present invention provides an improved wellbore (e.g., tubular casing) cleaning and filtration tool. The present invention addresses the issues of wiping the casing and filtering the wellbore fluid of debris while being removed from the well. 
         [0013]    The apparatus of the present invention is structurally comprised of a top “sub” (i.e., short length of pipe or tubular) and a mandrel which are mated together via an internal connection (e.g., threaded) to form a tool body. The tool body provides an open ended axial bore running throughout its length. An upper connection is provided on the top “sub” and a lower connection on the bottom of the mandrel. The upper and lower connections are employed to connect the tool body to a conventional drill string. A wiper assembly on the tool body separates an upper annulus from a lower annulus. The tool body includes a debris chamber as defined by a perforated filter screen and filter shroud located on the mandrel. The tool body also features a centralizer ring to prevent damage to the apparatus while downhole. This ring can be the largest non-flexible outer diameter (O.D.) surface of the tool body. 
         [0014]    During use, the apparatus is connected to the drill string and lowered into the wellbore. The wiper assembly is slightly larger than the internal diameter of the wellbore (i.e., casing) so as to cause an interference between to wipe the internal wall of the wellbore while the tool body is lowered into the well. 
         [0015]    The wiper assembly consists of a series of overlapping wiper elements. Each wiper component can be a petal or petal shaped member. The wiper elements include a non-flexible backing ring made of steel or other metal to which is bonded a flexible wiper petal ring made of a flexible wiper compounds (e.g., rubber, polymer) such that the two pieces form a composite part. The external surfaces of the ring and wiper petal ring can be tapered so as to bias the wiper petal ring to deform in one direction while preventing it from deforming in another direction. 
         [0016]    There are a series of circumferentially spaced apart slots which extend longitudinally through the backing ring and wiper petal ring. The petals and slots are so positioned that when the wiper elements are stacked together all the petals of a lower wiper element can deform and form a reasonably tight fit with the slot of the wiper element immediately above it. The petals are circumferentially spaced apart. As an example, there can be ten (10) petals spaced thirty-six degrees apart for a first wiper ring or group. The next, adjacent wiper ring or group could also have ten (10) petals spaced thirty six (36) degrees apart. However, the petals of the first group are spaced circumferentially eighteen degrees from the petals of the second group. In this fashion, gaps between petals of the first group align with petals of the second group. A third group of petals aligns with the gaps of the second group. 
         [0017]    Each wiper element can be stacked on and bonded to a wiper inner sleeve and arranged so that each group or series of petals and slots form an interlocking pattern whereby when fluid passes in one direction the petals can retract fully inside the slots of the wiper element immediately above it, and also that when fluid flows in an opposite direction that the interlocking petals form a rudimentary seal which largely prevent fluid from passing in the opposite direction. While this invention discloses a composite part consisting of multiple stacked elements, it is also possible to manufacture the wiper assembly by using a single moulding. 
         [0018]    Whilst tool is lowered into the wellbore, debris laden fluid passes from the lower annulus to the upper annulus and outside the perforated filter screen and past the outside of the wiper assembly which deforms to a collapsed position in the manner described. An axial bore allows for pumping of chemicals and fluids to assist in cleaning the well. 
         [0019]    When the tool body is removed from the wellbore, the wiper assembly wipes the internal wall of the wellbore. The petals prevent debris from passing around the wiper assembly and diverts debris laiden fluid from the upper annulus through fluid entry ports/courses and into the debris chamber. A perforated filter screen traps the debris in the debris chamber while at the same time allowing filtered/clean fluid to pass through the perforated filter screen and the filter shroud to the outside of the tool body and exit into the lower annulus. 
         [0020]    In the event that the debris chamber fills completely, a pressure differential is created between the debris chamber and the lower annulus which causes the bypass valve to open enabling fluid to drain from the upper annulus to the lower annulus, bypassing the perforated filter screen. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0021]    For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein: 
           [0022]      FIG. 1  is a longitudinal, sectional view of a preferred embodiment of the present invention. 
           [0023]      FIG. 2  is longitudinal, sectional view of the embodiment shown in  FIG. 1  being lowered, and showing the wiper assembly in a retracted condition. 
           [0024]      FIG. 3  is an enlarged sectional view of  FIG. 2  schematically illustrating flow around the embodiment of  FIG. 1  during lowering, and showing the wiper assembly in a retracted condition. 
           [0025]      FIG. 4  is longitudinal, sectional view of the embodiment shown in  FIG. 1  being raised, and showing the wiper assembly in an extended condition. 
           [0026]      FIG. 5  is an enlarged sectional view of  FIG. 4  schematically illustrating flow through the filtering system of the embodiment of  FIG. 1  during raising, and showing the wiper assembly in an extended condition. 
           [0027]      FIG. 6  is a sectional view taking through lines  6 - 6  of  FIG. 3 . 
           [0028]      FIG. 7  is a sectional view taking through lines  7 - 7  of  FIG. 6 . 
           [0029]      FIG. 8  is an enlarged perspective view of the embodiment of  FIG. 2  schematically illustrating flow around the embodiment of  FIG. 1  during lowering, and showing the wiper assembly in a retracted condition. 
           [0030]      FIG. 9  is an exploded perspective view of the embodiment of  FIG. 2  schematically illustrating the condition for flow during lowering, and showing the wiper assembly in a retracted condition, and showing the plurality of wiper rings and wiper elements making up the wiper assembly. 
           [0031]      FIG. 10  is a sectional view taking through lines  10 - 10  of  FIG. 5 . 
           [0032]      FIG. 11  is a sectional view taking through lines  11 - 11  of  FIG. 10 . 
           [0033]      FIG. 12  is an enlarged perspective view of the embodiment of  FIG. 4  schematically illustrating flow through the filtering system during raising, and showing the wiper assembly in an extended position. 
           [0034]      FIG. 13  is an exploded perspective view of the embodiment of  FIG. 4  schematically illustrating flow through the filtering system during raising, and showing the wiper assembly in an extended condition, and showing the plurality of wiper rings and wiper elements making up the wiper assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    The apparatus of the present invention is designated generally by the numeral  5 . Apparatus  5  provides an elongated tool comprised of a top sub  11  and of a mandrel  12  which are mated together via an internal connection  31 . Top “sub”  11  is simply a short length of pipe or tubular materials. Such “subs” are known and commercially available. The tool body  6  features an open ended axial bore  32  running through out its length. Tool body  6  has an upper connection  30  on the top sub  11  and a lower connection  37  on the mandrel  12 . 
         [0036]    The upper and lower connections  30  and  37  are employed to connect the tool body  6  to a conventional drill string. Wiper assembly  26  separates upper annulus  33  from the lower annulus  36 . The tool body  6  includes a debris chamber  35  having perforated filter screen  19  and filter shroud  20  located over the mandrel  12 . The tool body  6  also features non-rotating, contact, centralizer ring  15  to prevent damage to the tool while downhole. This is the largest non-flexible OD (outer diameter) surface of the tool body  6 . In order to clean bore  10 , the tool body  6  is connected to a drill string and lowered into the wellbore  10 . 
         [0037]    An o-ring  13  can be placed at the connection  31 . Centralizer bearing ring  15  is mounted to the outside of tool body  6  in between wiper assembly  26  and debris chamber  35 . Bearing ring  14  is mounted to tool body  6  in between debris chamber  35  and lower connection  37 . Tool body  6  includes split ring  16 , conical spring  17  and back out bolt  18 . 
         [0038]    In one embodiment apparatus  5  can include wiper assembly  26 . The identifiers ′, ″, ′″, and ″″ are used to indicate items of substantially the same construction, but of a different piece. 
         [0039]    In one embodiment, the wiper assembly  26  consists of a series or groups of wiper groups  28 ,  28 ′,  28 ″,  28 ′″, and  28 ″″. In one embodiment each wiper group  28  can include a flexible wiper petal ring  39  and a relatively non-flexible backup ring  38 . In one embodiment flexible petal ring  39  can have a plurality of circumferentially spaced apart wiper elements. 
         [0040]    The flexible petal rings  39 ,  39 ′,  39 ″,  39 ′″, and  39 ″″ can be mounted next to relatively non-flexible backing rings  38 ,  38 ′,  38 ″,  38 ′″, and  38 ″″ which can be made of steel or other metal. The flexible petal rings  39 ,  39 ′,  39 ″,  39 ′″ can be made of rubber or other flexible compounds. The non-flexible backing rings  38 ,  38 ′,  38 ″,  38 ′″, and  38 ″″ can be respectively bonded to the flexible petal rings  39 ,  39 ′,  39 ″,  39 ′″, and  39 ″″ such that each of the respective set of two pieces form a composite part. 
         [0041]    The external surfaces of the backing rings  38  and wiper petal rings  39  can be tapered so as to bias each wiper petal ring  39  to deform in one direction while preventing it from deforming in another direction. 
         [0042]    Each petal ring  39  can have a plurality of circumferentially spaced apart wiper elements (e.g., petal rings  39 ,  39 ′,  39 ″,  39 ′″, and  39 ″″ respectively each having plurality of wiper elements  45 ,  46 ,  47 ,  48 ) which wiper elements can be in the shape of a petal  44 . There can be spaces or slots  43  between each pair of wiper elements (see  FIGS. 8-9 and 12-13 ). 
         [0043]    There can be a series of slots  43  which extend longitudinally through the plurality of backing rings  38 ,  38 ′,  38 ″,  38 ′″, and  38 ″″ and wiper petal rings  39 ,  39 ′,  39 ″,  39 ′″, and  39 ″″ which are patterned circumferentially. Each petal ring  39  thus includes alternating petals  44  and slots  43 . The width of the slots  43  are only slightly larger than the width of the petal  44  such that when the wiper elements  45 ,  46 ,  47 , and  48  are stacked together all the petals  44  of a lower wiper ring can deform and form a reasonably tight fit with the slot  43  of the wiper ring immediately above it. 
         [0044]    Each wiper element (e.g., sets of wiper elements  45 ,  46 ,  47 ,  48 ) can be stacked on and bonded to a wiper inner sleeve  40  and arranged so that each group or series of petals  44  and slots  43  form an interlocking pattern whereby when fluid passes in one direction the wiper elements  45 ,  46 ,  47 , and  48  can retract fully inside the slots  43  of the wiper element immediately above it (respectively wiper elements  45  into  46 ,  46  into  47 , and  47  into  48 —see  FIGS. 7-9 ). When fluid flows in an opposite direction (e.g., schematically shown be arrows  21 ) the interlocking petals  44  form a rudimentary seal which largely prevents fluid from passing in the opposite direction (see  FIGS. 4,5, and 11-13 ). 
         [0045]    Each backup ring  38  can have a plurality of circumferentially spaced apart backup prongs  60  which can be located immediately below one of the respective wiper elements to provide backup up support to the respective wiper element when the apparatus  5  is being pulled up (schematically indicated by arrow  110 ). Additionally the spaced apart backup prongs  60  can be spaced such that wiper elements of a lower backup ring can fit between the gaps in the backup prongs  60  of the next located upper backup ring (see  FIG. 8 ). 
         [0046]    While the present invention discloses a composite part consisting of multiple stacked wiper groups  28 ,  28 ′,  28 ″,  28 ′″,  28 ″″, it is also possible to manufacture the wiper assembly  26  by using a single moulding. 
         [0047]    As schematically shown in  FIGS. 2 and 3 , while tool body  6  is lowered into the wellbore  10  (schematically indicated by arrow  100 ), debris laden fluid passes from lower annulus  36  to upper annulus  33  outside the perforated filter screen  19  and past the outside of wiper assembly  26  (see arrows  13 ,  FIGS. 3,7, and 8 ) which deforms in the manner described to a collapsed position. Arrows  102  in  FIG. 7  schematically indicate that, as apparatus  5  is lowered in the direction of arrow  100 , the wiper elements of wiper assembly  26  are placed in a retracted state by fluid flow relative to wiper assembly in direction of arrow  13 . 
         [0048]    In one embodiment, the wiper assembly  26  can be slightly larger than the internal wall of the wellbore  10  so as to cause an interference between the two, and wipe the internal wall  9  of the wellbore  10  while the apparatus  5  is lowered into the wellbore  10 . 
         [0049]    As schematically shown in  FIGS. 4 and 5 , when the tool body  6  is removed from the wellbore  10  (schematically indicated by arrow  110 ), the wiper assembly  26  wipes the internal surface or internal wall  9  of the wellbore  10 . The wiper elements  45 ,  46 ,  47 , and  48  prevent debris from passing around the wiper assembly  26  and diverts debris laiden fluid from the upper annulus  33  through the fluid entry ports/courses  34  (see arrows  21 ,  FIG. 5 ) and into the debris chamber  35  (see arrows  21 ,  FIG. 5 ) which collects the filtered out debris  50 . Arrows  112  in  FIG. 11  schematically indicate that, as apparatus  5  is raised in the direction of arrow  110 , the wiper elements of wiper assembly  26  are placed in an extended state by fluid flow relative to wiper assembly in direction of arrow  21 . 
         [0050]    The perforated filter screen  19  traps the debris  50  in chamber  35  while at the same time allowing filtered/clean fluid to pass through the perforated filter screen  19  and the filter shroud  10  and exit into the lower annulus  36 . 
         [0051]    In one embodiment, axial through bore  32  allows for pumping of chemicals and fluids to assist in cleaning the well during the process of lowering (arrow  100 ) and/or raising (arrow  110 ) apparatus  5 . 
         [0052]    In one embodiment can be included a bypass valve  13  for the debris chamber  35 . In the event that the debris chamber  35  fills completely, the a pressure differential is created between the debris chamber  35  and the lower annulus  26  which causes the bypass valve  13  to open and the fluid to drain from the upper annulus  33  to the lower annulus  26 , bypassing the perforated filter screen  19 . 
         [0053]    The following is a list of parts and materials suitable for use in the present invention: 
       PARTS LIST 
       [0054]      
         [0000]                                          PART            NUMBER   DESCRIPTION                                5   apparatus       6   tool body       8   casing       9   inside surface/internal wall       10   wellbore       11   top sub       12   mandrel       13   arrow       14   arrow       15   centralizer ring       19   perforated filter screen       20   filter shroud       21   arrows       23   bypass valve       26   wiper assembly       28   wiper group       30   upper connection       31   internal connection       32   axial bore       33   upper annulus       34   fluid entry ports       35   debris chamber       36   lower annulus       37   lower connection       38   wiper backing ring       39   wiper petal ring       40   wiper inner sleeve       41   petal bonding location       42   fluid path       43   slots       44   petal       45   wiper element       46   wiper element       47   locking pin       50   collected debris       100   arrow       102   arrow       110   arrow       112   arrow                    
All measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise. All materials used or intended to be used in a human being are biocompatible, unless indicated otherwise.
 
The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.