Patent Publication Number: US-2012043070-A1

Title: Magnetic Slip Retention for Downhole Tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional of U.S. application Ser. No. 12/409,661, filed 24 Mar. 2009, which is incorporated herein by reference and to which priority is claimed. 
    
    
     BACKGROUND 
     When a downhole tool, such as a packer or liner hanger, is run downhole, fluid and debris traveling past the tool can sometimes move the tool&#39;s slips outward, potentially damaging the slips, hindering the tool&#39;s deployment, or affecting the function of the slips once the tool is set at depth. 
     In  FIG. 1 , for example, a slip  20  is positioned on a tool housing or mandrel  10  between a movable wedge  12  and another (fixed or movable) wedge  14 . When the tool mandrel  10  is set at depth, activation of the tool moves the wedges  12  and  14  closer together to push the slip away from the mandrel  10  so it can engage the inside of a surrounding tubular. To retain the slip  20  during deployment, a plurality of rings  30  fit through the slip  20  and around the mandrel  10 . When the wedges  12 / 14  are separated as shown, the rings  30  hold the slip  20  next to the mandrel  10  so that the slip  20  does not extend beyond the tool&#39;s profile. When pushed out from the mandrel  10 , however, the slip  20  overcomes the hold of the rings  30 . 
     In addition to rings, other features such as springs, shear pins, and cages may be used to retain the slips in place until the tool is set at its desired depth. For example, a bow or leaf spring  32  can be positioned in  FIG. 1  between the cage  16  and the slip  20  to bias the slip  20  against the mandrel  10 . Although some of these features can retain the slip  20  while the tool is both run-in and pulled-out-of the hole, retaining the slips  20  with some of these features can be used only for running-in hole. For example, a shear pin may no longer be used to retain the slip once broken. Therefore, problems with debris and fluid passing around the unretained slip may occur as the tool is pulled out of the hole. 
     Although shown in a diagrammatic fashion in  FIG. 1 , use of the rings  30  (as well as other features such as springs, pins, and the like) to mechanically retain the slips  20  typical requires some mechanical complexity to achieve the desired retention on an actual tool. The mechanical complexity makes manufacture and assembly of a tool more involved and expensive, and can lead to a higher potential for mechanical failure in the tool. What is needed is a technique to retain slips on a downhole tool that requires less complexity and that can be effective as the tool is run-in and pulled-out-of a hole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a slip held to a mandrel using rings according to the prior art. 
         FIG. 2A  illustrates a slip held to a mandrel using magnets on the mandrel. 
         FIG. 2B  illustrates a slip held to a mandrel using magnets on the slip. 
         FIG. 2C  illustrates a slip held to a mandrel using attracting magnets on the mandrel and the slip. 
         FIG. 2D  illustrates a slip held to a mandrel using opposing magnets on the mandrel and the slip. 
         FIG. 3  illustrates portion of a packer having slips held to the valve&#39;s mandrel using magnets on the slip. 
         FIG. 4  illustrates portion of a compression-set retrievable service packer having slips held to the packer&#39;s mandrel using opposing magnets on the slip and mandrel. 
         FIG. 5  illustrates portion of a retrievable bridge plug having slips held to the packer&#39;s mandrel using attracting magnets on the slip and mandrel. 
         FIG. 6  illustrates portion of a retrievable casing packer having slips held to the packer&#39;s mandrel using separately located magnets on the slip and mandrel. 
         FIG. 7  illustrates a tubing stop having slips held to the packer&#39;s mandrel using magnets on the mandrel. 
         FIGS. 8 ,  9 , and  10  illustrate liner hangers having slips held using various arrangements of magnetic components. 
     
    
    
     DETAILED DESCRIPTION 
     Rather than relying solely on mechanically retaining slips on a tool by using rings, springs, shear pins, cages, or the like,  FIGS. 2A-2D  illustrate several ways to retain slips in place using magnetic components while a tool is run-in and pulled-out-of a hole. The tool can be any tool that has retractable slips or other gripping or cutting devices used to engage a surrounding tubular when set at depth in a hole. For example, the downhole tool can be a packer, a liner hanger, a plug, or a tubing stop. The magnetic components can replace or augment any springs or other features that mechanically retain the slips on such tools. 
     As the setting force is applied to the tool (e.g., packer, liner hanger, etc.), the force pulls the slip away from the magnetic component that retains the slip, allowing the slip to engage a surrounding tubular. The magnetic component can be inserted into the tool&#39;s mandrel, into the slip, or into both the mandrel and the slip. The magnetic component can also be affixed to the mandrel or to some other component that retains the slip. Using the magnetic component advantageously reduces the mechanical complexity required to retain the slip on a tool and eliminates the creation of debris. 
     In  FIG. 2A , a slip  20  is positioned adjacent a tool mandrel  10  between activation bodies (e.g., wedge members)  12  and  14 . A center strip  16  of a cage that may be part of the tool&#39;s mandrel  10  may ultimately prevent the slip  20  from becoming loose from the mandrel  10 . In addition to or in place of any rings or other mechanical features, one or more magnetic components  40  on the mandrel  10  retain the slip  20  adjacent the mandrel  10  as long as a setting force is not applied by the wedge members  12  and  14 . In this arrangement, the slip  20  can be composed of a ferromagnetic material, such as steel or the like, allowing it to be attracted to the magnetic components  40  on the mandrel  10 . For its part, the mandrel  10  can also be composed of a ferromagnetic material, but could be composed of something else, such as a composite or other non-ferromagnetic material. 
     Although two magnetic components  40  are shown in  FIG. 2A , only one or more than two magnetic components  40  can be used depending on the size of the slip  20  and depending on the power of the magnetic force required, along with other factors. For their part, these magnetic components  40  can be rare earth magnets or other types of permanent magnets. In addition, the magnetic components  40  can be affixed to the mandrel  10  using any common technique. For example, the magnetic components  40  can be positioned in milled slots in the mandrel&#39;s outside surface and either welded or screwed therein or retained by a bracket member, cover, or other holding feature (not shown). 
     In a reverse arrangement shown in  FIG. 2B , magnetic components  42  on the slip  20  itself retain the slip  20  against the mandrel  10 . Here, the mandrel  10  is made of a ferromagnetic material attractive to the magnetic components  42 , which can be composed of rare earth magnets or the like. The slip  20  can be composed of any desirable material. 
     In a complimentary arrangement shown in  FIG. 2C , magnetic components  40  and  42  on both the mandrel  10  and the slip  20  retain the slip  20  against the mandrel  10 . These facing magnetic components  40  and  42  attract one another in an attractive relation to hold the slip  20 . For example, the components  40  and  42  may both be permanent magnets with one (e.g.,  40 ) having a North orientation and the other (e.g.,  42 ) having a South orientation. Alternatively, one of the components  40 / 42  can be a permanent magnet, while the other can be a ferromagnetic element. 
     In a reverse arrangement shown in  FIG. 2D , magnetic components  44  and  46  both on the slip  20  and portion  16  of the mandrel  10  retain the slip  20  against the mandrel  10 . Here, the facing magnetic components  44  and  46  are permanent magnets that oppose one another in a repulsive relation (e.g., North-to-North or South-to-South polarity configuration). In this way, the magnetic repulsion forces the slip  20  against the mandrel  10  as long as the wedge members  12  and  14  remain separated. As shown, the magnetic component  46  on the mandrel  10  can be disposed on a cage portion  16  that limits the slip  20 &#39;s movement, but the component  46  could be positioned elsewhere on the mandrel  10 . 
     Use of such magnetic components (e.g.,  40 ,  42 ,  44 ,  46 ) to retain slips  20  on a tool can be applied to a number of different downhole tools and slip arrangements, some of which are shown in  FIGS. 3 through 7 . For example,  FIG. 3  shows a portion of a packer  50  for passing in tubing and isolating the annulus. The packer  50  has a mandrel  52 , a packing element  54 , and slip cage  56  with slots  58 . Slips  60  position in the cage&#39;s slots  58  and can be pushed outward from the mandrel  52  by wedge members  62  and  64 . One or more magnetic components  42  retain on the slip  60  against the mandrel  52  (composed of ferromagnetic material), while the packer  50  is run-in and pulled-out-of tubing so that the slips  60  do not extend beyond the slots  58  and the cage  56 &#39;s profile. 
       FIG. 4  shows a portion of a compression-set retrievable service packer  70  used to isolate a wellbore annulus from a production conduit. The packer  70  has a mandrel  72  with upper and lower mandrels  74  and  76 . Slips  80  position between the mandrels  72  and  74  and are held partially in slots in the lower mandrel  76 . Opposing permanent magnets  44  and  46  (one  44  on the slip  80  and another  46  on the lower mandrel  76 ) retain the slips  80  against the mandrel  72 . When the space decreases between the upper and lower mandrels  72  and  74  during activation, a wedge portion  82  pushes the slips  80  out from the mandrel  72  against the opposing force of the permanent magnets  44  and  46 . 
       FIG. 5  shows a portion of a retrievable bridge plug  90  used for plugging tubing downhole. The plug  90  has a mandrel  92  with upper and lower mandrels  94  and  96  positioned thereon. Slips  100  have one end fixed to pivot at the upper mandrel  94  and have another end to engage a surrounding tubular when jarring movements push the lower mandrel&#39;s wedge member  102  against the slips  100 . In addition or alternative to springs  104  that mechanically retain the slips  100 , attractive magnetic components  40  and  42  respectively on the mandrel  92  and slips  100  retain the slips  100  adjacent the mandrel  92  as long as the tool is not set. Both components  40  and  42  can be permanent magnets to attract one another. Alternatively, one can be a permanent magnet, while the other can be a ferromagnetic element. 
       FIG. 6  shows a retrievable casing packer  110  used to isolate a wellbore annulus from a production conduit for low-pressure production, water-injection, and pressure applications. The packer  110  has slips  120  held by wickers  126  to a retention ring  124  on the mandrel  112 . Separately located magnets  40  and  42  retain the slips  120  to the mandrel  112  when the packer  110  is not set. For example, first magnets  40  on the mandrel  112  (at an intermediate ring) magnetically attract the slip&#39;s wickers  126 , which can be made of a ferromagnetic material. In addition, second magnets  42  on the underside on the ends of the slips  120  magnetically attract to the packer&#39;s mandrel  112  also composed of ferromagnetic material. 
       FIG. 7  shows a portion of a tubing stop  130  for setting in tubing and holding force from above from a gas lift bumper spring or the like. The stop  130  has slips  140  pivotably anchored at one end  144  and engagable by a wedge portion  142  of the mandrel  132  to be pushed outward toward a surrounding tubular. One or more large magnetic elements  40  in form of a sleeve on the stop&#39;s mandrel  132  retain the slips  140  to the mandrel  132  while not engaged by the wedge portion  142 . In addition to a sleeve shape, the elements  40  can have other suitable shapes. 
       FIGS. 8 ,  9 , and  10  show liner hangers  140 ,  160 , and  180  having slips held using various arrangements of magnetic components. In  FIG. 8 , for example, the liner hanger  140  has a mandrel  142  and a wedge member  152 . Slips  150  have wickers  156  with ends  154  attached adjacent the mandrel  142 . The slip  150 s′ second ends are movable by the wedge member  152  to engage a surrounding tubular. First and second magnetic components  40  and  42  on the mandrel  142  and slips  150  retain the slips&#39; ends adjacent the mandrel  142  while the hanger  140  is run in and out of the hole. Once the wedge member  152  activates the slips  150 , the magnetic retention is broken so the slips  150  can engage the surrounding tubular. The magnetic components  40  on the mandrel  142  can include a plurality of discrete permanent magnets disposed on the mandrel. Alternatively as shown, the magnetic component  40  can actually be a ring of permanent magnet material disposed around the outside of the mandrel  142 . 
     In  FIG. 9 , the liner hanger  160  has a mandrel  162  and dual wedges  172 / 173  for activating slips  170 . As shown, one end  174  of the slip  170  is pivotably connected to a cage  164  on the mandrel  162 , and the slip  170  is held within slots in the cage  164 . As long as the wedges  172 / 173  remain in the position shown in  FIG. 9 , the slips  170  are held adjacent to the mandrel  162 . 
     Here, the wedges  172 / 173  are composed either entirely or partially of permanent magnetic material, and the slips  170  are either composed entirely or partially of ferromagnetic material, permanent magnetic material, or a combination thereof to be attracted to the wedges  172 / 173 . Alternatively, the reverse arrangement is possible where the slips  170  are composed either entirely or partially of a permanent magnetic material and the wedges  172 / 173  are either composed entirely or partially ferromagnetic material, permanent magnetic material, or a combination thereof to be attracted to the slips  170 . 
     In  FIG. 10 , the liner hanger  180  has a mandrel  182 , wedge member  192 , and slip ring  194 . The ring  194  has slip ends  190  that extend along slip springs  196  from the ring  194 . Magnetic components  40 / 42  on the slip ends  190  and the adjacent portion of the mandrel  182  retain the slip ends  190  in place until activated by the wedge member  192 . 
     In any of the arrangement disclosed above, one or more magnetic components can be used. The magnetic components can be a ferromagnetic element or a permanent magnet, such as a rare earth magnet. In addition, the slips, wedges, or mandrel (either entirely or a portion thereof) can be composed of a permanent magnetic material. It is possible that downhole debris may be attracted to any permanent magnets used on the downhole tool. The extent of this issue depends on the size and strength of any permanent magnets used for a given implementation. However, the magnets are preferably not outwardly exposed on the downhole tool to avoid or minimize the collection of debris. For example, permanent magnets used for the arrangement of magnetic components  40 / 42  in  FIG. 5  will not be outwardly exposed on the tool  90  when the slips  100  are retained as shown or even when extended outwardly because the wedge  102  will at least partially cover the elements  40 / 42  on the mandrel  92  and slip  100 . The other arrangements disclosed herein may also have similar benefits. 
     Although the magnetic components are shown in the drawings as being exposed on the surfaces of the slip, mandrel, wedges, etc., it may be preferred to embed the magnetic components inside these elements. This may be useful depending on the magnetic material used and its ability to withstand direct contact with the downhole environment. Embedding the magnetic component may also be useful when the exposed portion of the slip, mandrel, wedge, etc. encounters friction or the like. For example, the magnetic components  40 / 42  on the liner hanger of  FIG. 10  may be exposed to friction when the slips  190  ride on the wedge  192  to extend outward from the mandrel  182 . Depending on the material used, it may be preferred that the magnetic component  42  on the slip  190  not be outwardly exposed and caused to ride directly on the wedge  192 . 
     The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.