Abstract:
A magnetic wellbore cleaning tool having a plurality of magnetic ridges spaced longitudinally between top and bottom centralizers. In operation, the magnetic ridges modify the velocity of passing fluid circulating in the wellbore such that the fluid remains in close proximity to the tool&#39;s magnetic field thereby allowing for collection of ferromagnetic debris suspended in cleaning fluid circulating in a wellbore.

Description:
BACKGROUND OF THE INVENTION 
     I. Field 
     The present invention relates to wells for producing gas and oil and, more particularly, to wellbore cleaning tools, and more particularly, to magnetic wellbore cleaning tools which collect ferromagnetic materials suspended in wellbore fluid. 
     II. Background 
     Various drilling and cleaning operations in the oil and gas industry create debris that becomes trapped in a wellbore, including ferromagnetic debris. Generally, fluids are circulated in such a wellbore to washout debris before completion of the well. Several tools have been developed for the removal of ferromagnetic debris from a wellbore. There is a continuing need for a more effective magnetic wellbore cleaning tool. 
     BRIEF SUMMARY OF THE INVENTION 
     Other types of magnetic cleaning tools have a limited amount of collection space. Still others utilize only one pole of the magnets included in the tool, thereby potentially wasting a portion of the magnets&#39; attractive force. Yet others involve slots or recesses in the tool body itself, thereby, I speculate, exposing the tool to stress points that can shorten the life of the tool and potentially lead to a break occurring during cleaning operations. 
     Thus, it is an object of the present invention to create a simple, strong magnetic cleaning tool with maximized collection area. It is a further object of the present invention to create a more effective ferromagnetic debris collection tool by repeatedly changing the velocity of passing circulating fluid so that the ferromagnetic particles suspended in said fluid are, I speculate, caught in turbulent eddies which I further speculate keep said particles within the tool&#39;s magnetic field for a longer period of time and consequently, I further speculate, facilitating more effective collection by the present invention via magnetic attractive force. 
     In a preferred embodiment, the magnetic wellbore cleaning tool designed to remove ferromagnetic debris from a wellbore includes a tool body adapted to be attached to a work string and lowered into a wellbore case; an upper and a lower centralizer adapted to maintain a set distance between the tool body and the wellbore casing; a plurality of magnetic ridges further including one or more magnets arranged circumferentially around the tool body; and a plurality of circumferential collection areas located between adjacent magnetic ridges wherein the diameter of the tool body is smaller in the recessed collection areas than the diameter of the tool body at the magnetic ridges. 
     The magnetic ridges are evenly spaced along the central portion of the tool body between the top and bottom centralizers. The magnetic ridges may be formed directly from the tool body, or they may be formed by adjacent flanged ends of sleeves secured around the circumference of the central tool body. 
     Where the magnetic ridges are formed from the tool body itself, the magnetic ridges include two sides that are generally inclined with respect to the longitudinal access of the tool body as well as an apex that is generally parallel to the longitudinal axis of the tool body. One or more recesses are formed in each generally inclined side such that each generally inclined side holds one or more magnets which may include magnets in a stacked configuration. These magnets are held in place against the tool body by a removable retaining ring that is itself held in place by two bolts. In one embodiment the retaining ring also forms the apex of the magnetic ridge. A flexible seal, such as an o-ring, may also be included between the retaining ring and the magnets held thereby. 
     Where the magnetic ridges are formed from the flanged ends of adjacent sleeves, the respective flanged ends are aligned such that one or more recesses formed on the outer surface of each flanged end form one or more cavities between the secured flanged ends wherein each cavity holds at least one magnet. 
     In either disclosed embodiment of the present invention, adjacent magnetic ridges are separated by a circumferential secondary collection area wherein I speculate that ferromagnetic debris is collected due to the magnetic force created by the magnets held in the magnetic ridges. The tool diameter is smaller in the secondary collection areas than it is at the magnetic ridges; therefore, the annulus between the tool body and the wellbore casing is correspondingly larger. I speculate that this change in the size of the annulus will reduce the velocity of passing fluid, thereby creating eddy currents that will keep ferromagnetic debris that is suspended in the fluid within range of the magnetic attractive force of the present invention. I further speculate that this increased exposure to the magnetic attractive force of the present invention will enable the present invention to more effectively collect ferromagnetic debris suspended in passing circulating fluids. 
     In either disclosed embodiment, the magnets included in each magnetic ridge may or may not be covered or otherwise isolated from the harsh or caustic environment of the wellbore. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a further understanding of the nature and objects of the present invention, reference should be had to the following description taken in conjunction with the accompanying drawings in which like parts are given like reference numerals. 
         FIG. 1  illustrates a view of a first embodiment of the present invention installed in a wellbore. 
         FIG. 2   a  illustrates a second view of a first embodiment of the present invention outside of a wellbore. 
         FIG. 2   b  illustrates a cross sectional view along plane A-A of the tool of  FIG. 2   b.    
         FIG. 3   a  illustrates a cross-sectional view of two magnetic ridges of a first embodiment of the present invention. 
         FIG. 3   b  illustrates a cross sectional view along plane B-B of the tool of  FIG. 2   b.    
         FIG. 3   c  illustrates a side view of a retaining ring. 
         FIG. 4   a  illustrates a cross-sectional view of a signal magnetic ridge of a first embodiment of the present invention. 
         FIG. 4   b  illustrates a cross sectional view along plane C-C of the tool of a magnet and a magnet cover as shown in  FIG. 4   a.    
         FIG. 5   a  illustrates a view of a second embodiment of the present invention installed in a wellbore. 
         FIG. 5   b  illustrates a cross sectional view along plane Z-Z of the tool of  FIG. 5   a.    
         FIG. 6  illustrates a perspective view of several sleeves of a second embodiment of the present invention coupled together. 
         FIG. 7  illustrates a second perspective view of several sleeves of a second embodiment of the present invention coupled together. 
         FIG. 8  illustrates a three-dimensional rendering of several sleeves of a second embodiment of the present invention coupled together. 
         FIG. 9  illustrates a tool body of a second embodiment of the present invention without any sleeves attached thereto. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and particularly to  FIGS. 1 and 2   a , a first exemplary embodiment of the magnetic wellbore cleaning tool contemplated by the present invention is generally referenced as numeral  10 . The magnetic wellbore cleaning tool  10  comprises, in general, a tool body  11  including top tool joints  2   a  for connection with an upper tubing string X 1  and bottom tool joint  2   b  for connection with lower tubing string X 2 , top and bottom slotted centralizers  12   a  and  12   b  secured around the circumference of said tool joints  2   a  and  2   b  and configured to centralize the tool body  11  in the wellbore casing  5 , a central tool body  13  with a plurality of circumferential magnetic ridges  20  distributed longitudinally (that is, axially) along the length thereof, and a plurality of recessed secondary collection areas  25  located between adjacent magnetic ridges  20 . 
     The tool body  11  (including the plurality of magnetic ridges  20  and secondary collection areas  25 ) is a single-piece, unitary machined structure. As noted above, the tool body  11  has a top tool joint  2   a  and a bottom tool joint  2   b  for coupling the tool  10  to upper and lower tubing strings X 1  and X 2 . The top and bottom tool joints  2   a  and  2   b  are shown as threaded. Thus, tool  10  may be directly connected to upper and lower tubing strings X 1  and X 2  which may include, in addition to other tubing, various devices such as junk collecting baskets, circulating tools, scrapers, brushes or other downhole tools. The tool body  11  is generally cylindrically shaped and includes an inlet port Y 1  for receiving fluid from the upper tubing string X 1 , a hollow cylindrical center C for communicating fluid therethrough, and a exit port Y 2  for passing fluid to the lower tubing string X 2 . 
     The tool body  11  is configured to receive the top and bottom centralizers  12   a  and  12   b  on the innermost portions  3   a  and  3   b  of tool joints  2   a  and  2   b , respectively. As shown in  FIGS. 1 and 2   a , the centralizers  12   a  and  12   b  have an effective diameter greater than any other portion of the tool body  11  such that during cleaning operations in wellbore casing  5  the magnetic ridges  20  do not engage the wellbore sidewall  6 . Centralizers  12   a  and  12   b  have a plurality of slots  14  which allow fluid to flow in the annulus  201  between the tool joints  2   a  and  2   b  and the wellbore sidewall  6 . Bolts, rivets, or other conventional fasteners  12   c  secure the separate portions of the centralizers  12   a  and  12   b  around the tool body  11 , thus allowing easy removal and replacement as the centralizers  12   a  and  12   b  wear with age and use or to place a different size centralizer  12   a  or  12   b  more appropriate for a given size wellbore casing  5 . 
     The central tool body  13  is comprised of the portion of the tool body  11  between upper tool joint  2   a  and lower tool joint  2   b  and includes an alternating series of circumferential magnetic ridges  20  and secondary circumferential collection areas  25 . As best shown in  FIGS. 3   a  and  4   a , each magnetic ridge  20  has inclining, sloping, curved or slanted circumferential surfaces  21   a  and  21   b  from the adjacent circumferential secondary collection area  25  to the circumferential apex  40  of said magnetic ridge  20 . In a preferred embodiment, as best shown in  FIGS. 3   a  and  4   a , each magnetic ridge  20  has a trapezoidal longitudinal cross-section including: (1) two circumferential surfaces  21   a  and  21   b , each of which is generally flat and inclined with respect to the longitudinal axis  55  of the tool body  11  so that the planes in which said surfaces reside intersect at a point external to the tool body  11 ; and (2), one flat surface  22  that is generally parallel to the longitudinal axis  55  of the primary tool body  11  and forming the apex  40 . 
     At the top and bottom edge of the central tool body  13 , where it meets tool joints  2   a  and  2   b , half magnetic ridges  19   a  and  19   b  are formed that are comprised of only a single surface  21   a  and  21   b , respectively and a flat surface  22 . 
     More specifically, the magnetic ridges  20  are formed from the tool body  11  as a result of the plurality of secondary collection areas  25  being milled out of tool body  11  via machining. The depth to which the secondary collection areas  25  are machined is generally dictated by the tubing size of the tubing string X 1  and X 2 . For example, a 3.5 inch tool would result in a tool  10  wherein the outer diameter  75  of the secondary collection areas  25  would be no less than 3.5 inches, and, in a preferred embodiment, would be 3.5 inches. By contrast, the outer diameter of the magnetic ridges  20  (measured from center of surface  22  and denoted as  85 ) is generally equivalent to the outer diameter of the tool joints  2   a  and  2   b . (See  FIGS. 1 and 2   a ). It is noted, however, that the removable retaining ring  23  and the magnets  26 , described in more detail below, are not part of the tool body  11 , but rather are added to the tool body  11  for operation thereof. 
     The magnetic ridges  20  are longitudinally (to wit, axially) spaced along the central tool body  13  between the centralizers  12   a  and  12   b . The magnetic ridges  20  are generally spaced between 4.5 inches and 5 inches (center to center) apart, where larger spacing is typically used for larger diameter tools (for example, 5.5 inch tool might employ 4.5 inch spacing, while a 7 inch tool or 9.625 inch tool would employ a 5 inch spacing). 
     Each surface  21   a  and  21   b  includes a series of cavities or recesses  24  drilled or otherwise machined in said surfaces  21   a  and  21   b  at regular intervals around the circumference of the tool body  11 , each recess  24  intended to house a single or stacked set of disk-shaped magnet(s)  26 . The center portion  65  of each magnetic ridge  20  is comprised of a circumferential groove  27  machined into the tool body  11  between the surfaces  21   a  and  21   b  of each magnetic ridge  20  and a removable retainer ring  23  which fits into said groove  27  wherein said retainer ring  23 , when tightened via fasteners  23   a , secures the magnets  26  placed into the recesses  24 . Some compressible material, such as an “O-ring” or other flexible seal  28 , may be placed between the retainer ring  23  and the tool body  11  for securing the magnets  26  thereto. 
     The outer surface  23   b  of the retainer ring  23  comprises the surface  22  of the magnetic ridge  20 . Note that while the surface  22  is shown as being generally parallel to the longitudinal axis  55  of the tool body  11  in the first exemplary embodiment, it need not be, but may be configured in other shapes or orientations. For example, surface  22  could be curved or it could be slanted relative to the longitudinal axis  55  of the tool body  11 . 
     Each magnet  26  may also be covered by a magnet cover  26   a  designed to snugly fit around a magnet  26  and to protect said magnet  26  from the often harsh and corrosive exterior environment of the wellbore  5 . In lieu of a magnet cover  26   a , some other covering or coating may be applied to protect the magnets  26  from the hard environment of the wellbore and consequently inhibiting or preventing corrosion of the magnets  26 . For example, grease or epoxy may be applied to the magnets  26 . 
     In the first exemplary embodiment, a single disk-shaped Neodymium magnet  26  resides in each recess  24  and thus is secured within the magnetic ridge  20  by the retainer ring  23 . Each magnet  26  generally has an axial height less than, or equal to, its diameter, but the size of the magnets  26  are not limited to these dimensions. Similarly, a stack of disk magnets can be used to form a single magnet  26 . The plurality of magnet recesses  24  are arranged circumferentially around the tool body  11  in each magnetic ridge as shown in  FIGS. 1 ,  2   a ,  2   b  and  3   b . As such, the magnets  26  create a 360 degree magnetic field. 
     In the first exemplary embodiment, the magnets  26  are oriented such that any two opposing surfaces  21   a  and  21   b  (to with, a surface  21   a  and a surface  21   b  which are separated by a secondary collection area  25 ; or, in other words, a surface  21   a  on a first magnetic ridge  20  and a surface  21   b  on a second magnetic ridge  20  between which said first and second magnetic ridges  20  lies a secondary collection area  25 ) each show the opposite polarity to the exterior of the tool body  11 . For example, if the magnets  26  along a surface  21   a  are oriented such that the positive magnetic pole faces somewhat outward from the surface of tool body  11  (due to the inclined surface  21   a ) and over a secondary collection area  25 , then the magnets  26  along the opposing surface  21   b  are oriented such that the negative magnetic pole faces somewhat outward (due to the inclined surface  21   b ) from the surface of tool body  11  yet over the same secondary collection area  25 . 
     Further, all of the magnets  26  located on a given surface  21   a  (or similarly located on a given surface  21   b ) of a magnetic ridge  20  are oriented such that the same magnetic polarity faces somewhat outward from tool body  11 , and over a secondary collection area  25 , for each magnet  26 . ( FIG. 4   a ). However, other arrangements and configurations of the magnetic polarity of the respective magnets  26  may be employed. For example, the magnets  26  in a given surface  21   a  or  21   b  can be oriented such that the magnets  26  have alternating (in a circumferential direction) polarities facing somewhat outward from the surface of tool body  11 . Further still, the polarities of opposing surfaces  21   a  and  21   b  may be the same (i.e., perhaps more of a “bucking” arrangement”), as opposed to the configurations described above. 
     In addition to the primary collection area  29  formed by the surface of the magnetic ridges (in other words, the combination of surfaces  21   a ,  21   b  and  22 ), the area of the tool body  11  between each ridge  20  serves as a secondary collection area  25  for collecting iron debris or other magnetically attracted metals. It is speculated that a secondary magnetic force is projected into the secondary collection areas  25  such that a significant amount of material is collected not only on the primary collection area  29  but also in the secondary collection area  25 . 
     A second exemplary embodiment of the present invention is shown in  FIGS. 5   a - 9 . This second embodiment is generally referred to as numeral  100 . The magnetic wellbore cleaning tool  100  generally comprises a tool body  111  including top tool joint  102   a  for connection with an upper tubing string X 10  and bottom tool joint  102   b  for connection with lower tubing string X 20 , top and bottom slotted centralizers  112   a  and  112   b  secured around the circumference of said tool joints  102   a  and  102   b  and configured to centralize the tool body  111  in the wellbore casing  105 , and a central tool body portion  130  found between the top and bottom tool joints  102   a  and  102   b.    
     The tool body  111  is a single-piece, unitary machined structure. The tool body  111  has a top tool joint  102   a  and a bottom tool joint  102   b  for coupling the tool  100  to upper and lower tubing strings X 10  and X 20 , respectively. The top and bottom tool joints  102   a  and  102   b  are shown as threaded. Thus, tool  100  may be directly connected to upper and lower tubing strings X 10  and X 20  which may include, among other things, various devices such as junk collecting baskets, circulating tools, scrapers, brushes or other downhole tools. The tool body  111  is generally cylindrically shaped and includes an inlet port Y 10  for receiving fluid from the upper tubing string X 10 , a hollow cylindrical center C 1  for communicating fluid therethrough, and an exit port Y 20  for passing fluid to the lower tubing string X 20 . 
     The tool body  111  is configured to receive the top and bottom centralizers  112   a  and  112   b  on the innermost portions  103   a  and  103   b  of tool joints  102   a  and  102   b , respectively. As shown in  FIG. 5   a , the centralizers  112   a  and  112   b  have an effective diameter greater than any other portion of the tool body  111  such that during cleaning operations in wellbore casing  105  the magnetic ridges  120  do not engage the wellbore sidewall  1066 . Centralizers  112   a  and  112   b  have a plurality of slots  114  which allow fluid to flow in the annulus  201  between the tool joints  102   a  and  102   b  and the wellbore sidewall  106 . Bolts, rivets, or other conventional fasteners  112   c  secure the separate portions of the centralizers  112   a  and  112   b  around the tool body  111 , thus allowing easy removal and replacement as the centralizers  112   a  and  112   b  wear with age and use or to place a different size centralizer  112   a  or  112   b  more appropriate for a given size wellbore casing  105 . 
     Central tool body portion  130  is machined with an outer diameter  175  ( FIG. 9 ) along the entire length of central body portion  130 . Tool  100  includes removable semi-circular flanged sleeves  115  that, when bolted or otherwise fastened together end-to-end as shown in  FIGS. 5   a  and  6 - 8 , completely encircle and cover the central tool body portion  130  ( FIG. 5   a ). Each sleeve  115  has a flange  125   a  on one end and  125   b  on the other end. Each flange  125   a  and  125   b  has formed on an outboard side  127  a plurality of recesses  135  which, when the flanges  125   a  and  125   b  of two adjacent sleeves  115  are brought together as shown in  FIGS. 6-8 , form cavities  124  in which magnets  126  are intended to be housed, thereby creating magnetic ridges  120  at the intersection of adjacent sleeves  115 . The sleeves  115  may be made of stainless steel, plastic, or some other non-magnetic material. The sleeves  115  may rotate independently of the tool body  111  or may be fixedly coupled thereto. 
     A plurality of sleeves  115  are arranged longitudinally along the axial length  155  of the central tool body portion  130  as shown in  FIG. 5   a . The magnetic ridges  120  may completely enclose the magnets  126 , protecting them from the exterior environment of the wellbore  105 , or they may have openings  145  formed on the inboard side  128  of each flange (see, e.g.,  FIGS. 6-8 ) allowing the surface of the magnets  126  to act as collection areas for ferromagnetic debris. The magnets  26  used in tool  100  are small, disk-shaped Neodymium magnets, sized to fit, either singly or in a stack, within the cavities  124  formed between the flanges  125   a  and  125   b.    
     At the top and bottom edge of the central tool body  130 , where it meets tool joints  102   a  and  102   b , half magnetic ridges  119   a  and  119   b  are formed that are comprised of only a single flange  125   a  and  125   b , respectively. The tool body  11  in the form of the tool joints  102   a  and  102   b  serve to hold the magnets  126  in the recesses  135  in each respective half magnetic ridge  119   a  and  119   b.    
     Turning to back  FIG. 1 , circulating fluid is generally pumped down into the wellbore through the center of the tool body  11  (see Arrow A showing cleaning fluid being pumped down through central opening C). This fluid is eventually circulated back up the wellbore  5  in the annulus  200  between the tubing string X 2  and the wellbore sidewall  6  as shown by Arrow B. The upward-moving circulating fluid passes through the slots  14  in the bottom centralizer  12   b  and enters the annuls  204  adjacent to the bottom-most section of central tool body  13  as shown by Arrow D. Due to the reduced outer diameter of the tool body  11  at the first secondary collection area  25  (found between the centralizer  12   b  and the magnetic ridge  20  closest to said centralizer  12   b ), as compared to the outer diameter of the tool body  11  at the tool joint  2   b , the annulus  204  between the tool body  11  and the wellbore sidewall  6  is greater than the annulus  201  between the tool joint  2   b  and the wellbore sidewall  6 , thereby, I speculate, reducing the velocity of the circulating fluid. I speculate that this change in velocity will create an eddy effect as shown by Arrow D. I further speculate that said eddy effect which will cause ferromagnetic debris suspended in the circulating fluid to remain in the vicinity of the magnetic attractive force of the magnetic ridges  20 , and thereby make said debris more susceptible to collection via said magnetic force. 
     As the circulating fluid continues to move upward along the wellbore  5 , as shown by Arrow E, it will necessarily pass over the primary collection area  29  and encounter each successive magnetic ridge  20  thereby providing additional opportunities to collect passing ferromagnetic debris as I speculate that a higher volume of passing fluid will be forced into contact with the magnetic field of the various magnetic ridges  20 . As the fluid approaches and eventually reaches the apex  40  of each magnetic ridge  20 , the annulus  202  between said magnetic ridge  20  and the wellbore sidewall  6  will be reduced due to the increasing diameter of the tool body  11  between the edge of the secondary collection area  25  and the apex  40  of said magnetic ridge  20 . It is expected that this reduced annulus  202  will increase the velocity at which the circulating fluid moves past the tool  10 , only to have said velocity reduced again as the outer diameter of the tool body  11  is again reduced creating annulus  203 , thereby, I speculate, creating another eddy current and another opportunity for ferromagnetic debris to become entrapped in the magnetic field of the magnetic wellbore cleaning tool  10 . This process is repeated until the circulating fluid reaches the top centralizer  12   b  and passes further up the wellbore as shown by Arrow F. It is speculated that this repeated change in the velocity of the passing circulating fluid will create turbulence such that suspended ferromagnetic particles will remain within the magnetic field of tool  10  for a longer period of time, thereby creating a more effective magnetic cleaning tool. 
     It is observed that the above described process applies equally to either embodiment disclosed herein. 
     The foregoing description of the embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. 
     PARTS LIST 
     
         
           2   a  Top Tool Joint 
           2   b  Bottom Tool Joint 
           3   a  Innermost Portion of Top Tool Joint  2   a    
           3   b  Innermost Portion of Bottom Tool Joint  2   b    
           5  Wellbore Casing 
           6  Sidewall of Wellbore Casing 
           10  First Embodiment of Magnetic Wellbore Cleaning Tool 
           11  Primary Tool Body 
           12   a  Top Slotted Centralizer 
           12   b  Bottom Slotted Centralizer 
           12   c  Fasteners 
           13  Central Tool Body Portion of First Embodiment 
           14  Slots in Centralizers 
           15   a  Top End of Tool Body 
           15   b  Bottom End of Tool Body 
           19   a  Half Magnetic Ridge 
           19   b  Half Magnetic Ridge 
           20  Circumferential Magnetic Ridges 
           21   a  Surface of Magnetic Ridge  20   
           21   b  Surface of Magnetic Ridge  20   
           22  Surface of Magnetic Ridge  20   
           23  Removable Retaining Ring 
           23  a Fasteners 
           23   b  Outer Surface of Retaining Ring  23   
           24  Recess 
           25  Circumferential Secondary Collection Areas 
           26  Magnet 
           26   a  Magnet Cover 
           27  Circumferential Groove in Magnetic Ridge  20   
           28  Flexible Seal 
           29  Primary Collection Area 
           40  Circumferential Apex 
           55  Longitudinal Axis of Tool Body 
           65  Center Portion of Magnetic Ridge 
           75  Outer Diameter of Secondary Collection Area 
           85  Outer Diameter of Magnetic Ridge 
           100  Second Embodiment of Magnetic Wellbore Cleaning Tool 
           102   a  Top Tool Joint 
           102   b  Bottom Tool Joint 
           103   a  Innermost Portion of Top Tool Joint 
           103   b  Innermost Portion of Bottom Tool Joint 
           105  Wellbore Casing 
           106  Sidewall of Wellbore Casing 
           111  Primary Tool Body 
           112   a  Top Centralizer 
           112   b  Bottom Centralizer 
           112   c  Fastener 
           114  Slot 
           115  Semi-Circular Flanged Sleeve 
           119   a  Half Magnetic Ridge 
           119   b  Half Magnetic Ridge 
           120  Magnetic Ridge 
           124  Cavity Formed Between Flanges by Adjacent Recesses  135   
           125   a  Flange 
           125   b  Flange 
           126  Magnet 
           127  Outboard Side of Flange 
           128  Inboard Side of Flange 
           130  Central Tool Body Portion of Second Embodiment 
           135  Recess in Flange 
           145  Opening 
           150   a  Top End of Tool body 
           150   b  Bottom End of Tool Body 
           200  Annulus Between Tubing String and Wellbore Sidewall 
           201  Annulus Between Tool Joint and Wellbore Sidewall 
           202  Annulus Between Secondary Collection Area and Wellbore Sidewall 
           203  Annulus Between Magnetic Ridge and Wellbore Sidewall 
           204  Annulus Between Secondary Collection Area and Wellbore Sidewall 
         C Central Opening 
         C 1  Central Opening 
         A Fluid Being Pumped Down Through Work String 
         B Fluid Flowing Up Wellbore 
         D Eddy Current 
         E Fluid Flowing Past Magnetic Ridge 
         F Fluid Passing Up Wellbore Beyond Magnetic Wellbore Cleaning Tool 
         X 1  Upper Tubing String 
         X 2  Lower Tubing String 
         Y 1  Upper Inlet Port 
         Y 2  Lower Exit Port 
         X 10  Upper Tubing String 
         X 20  Lower Tubing String 
         Y 10  Upper Inlet Port 
         Y 20  Lower Exit Port