Abstract:
A disintegrating plug uses a setting tool to push a swage into the plug body that has external ribs that contact the wall of the surrounding tubular. The ribs retain the body to the surrounding tubular wall with frictional contact. Some leakage may ensue but in fracturing some leakage does not matter if enough volume under the right pressure reaches the formation. The sheared member during the setting comes out with the mandrel that is part of the setting tool. In an alternative embodiment one or more o-rings are used to seal while anchoring is assisted by the hardened insert(s) that can be snap fitted in using rib flexing or that can be a c-ring that is expanded and snapped in. The o-ring(s) are axially spaced from the insert(s).

Description:
FIELD OF THE INVENTION  
       [0001]    The field of the invention is barrier plugs for use in subterranean locations for formation treatment and more particularly plugs that substantially disintegrate when the treatment has ended. 
       BACKGROUND OF THE INVENTION  
       [0002]    In certain types of treatments such as fracturing, a series of barriers with ball seats are used for the purpose of sequentially isolating intervals that have already been fractured so that the next interval uphole can be perforated and fractured. Typical of such plug devices is Us2013/0000914. Here sleeves are expanded that have an external seal and a lower end ball seat. At the end of the fracturing operation all the sleeves that were used have to be milled out. 
         [0003]    US 2014/0014339 shows the use of a plug with an external rubber seal that is expanded with a swage moved by a wireline setting tool where the swage has a ball seat and is made of a disintegrating material. The design uses a shear device to the setting tool mandrel that remains behind as well as a rubber sleeve. 
         [0004]    U.S. Pat. No. 7,784,797 shows the use of hardened insert segments with square bases that are dropped into an associated recess and then overlaid with rubber to retain the insert for running in. On setting, the hardened particles emerge through the rubber to aid in fixation of the expanded liner hanger. This being a liner hanger installation there is no need for any components to later disintegrate. 
         [0005]    Several features are included in the present invention such as the use of degradable ribs without any seals for a fracturing application. While the ribs alone may not create a perfect seal on expansion and may not penetrate the surrounding tubular, a fracturing application can tolerate some leakage as long as the required flow can be delivered at the needed pressure to the formation. Additionally hardened materials, while having a benefit to enhance wall penetration into the surrounding tubular for enhanced grip are still limited in their degree of expansion and are not materials that are degradable. This can then leave residue when degrading other parts of a fracturing plug. The design of the shear tab from the fracturing plug is such that it extends into a mandrel of the setting tool that is removed from the plug when using a wireline setting tool such as the E-4 setting tool offered by Baker Hughes Incorporated of Houston, Tex. 
         [0006]    An alternative design features the use of flexing ribs that do not necessarily penetrate the wall of the surrounding tubular but that can be made of a disintegrating material. These are combined with an o-ring seal to minimize the non-degrading parts when the plug is no longer needed and has to be removed to facilitate other completion steps or production. Hardened inserts are provided at a spaced location from the o-ring. The inserts can be in the shape of a c-ring and spread and snapped in or using flexing of an adjacent rib inserted as discrete units to be retained with a potential energy force from the adjacent flexed rib. The discrete units are multiple segments cut from a continuous ring. Cutting the ring into several segments reduces the space between hardened inserts after the sleeve is swaged over a cone. Reducing the distance that there is not external support for the cone will reduce the likelihood that the cone will fail when hydraulic pressure is applied to the plug. While the hardened inserts and the o-rings do not disintegrate the bulk of the plug will disintegrate facilitating subsequent operations. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims. 
       SUMMARY OF THE INVENTION  
       [0007]    A disintegrating plug uses a setting tool to push a swage into the plug body that has external ribs that contact the wall of the surrounding tubular. The ribs retain the body to the surrounding tubular wall with frictional contact. Some leakage may ensue but in fracturing some leakage does not matter if enough volume under the right pressure reaches the formation. The sheared member during the setting comes out with the mandrel that is part of the setting tool. In an alternative embodiment one or more o-rings are used to seal while anchoring is assisted by the hardened insert(s) that can be snap fitted in using rib flexing or that can be a c-ring that is expanded and snapped in. The o-ring(s) are axially spaced from the insert(s). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0008]      FIG. 1  is a half section view of an embodiment using disintegrating ribs that friction grip with no seal; 
           [0009]      FIG. 2  is an alternative embodiment with o-ring(s) seal and hardened inserts that snap in with a c-ring shape or are segmented ring pieces pressed in with an interference fit from rib flexing. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0010]      FIG. 1  shows a setting sleeve  20  and a mandrel  22  that are part of a wireline setting tool that is not shown. The mandrel  22  supports the plug  24  due to tab  26  being positioned on shoulder  28  and retained there by retaining nut  30  which is further retained by set screw  32 . During the setting the wireline setting tool such as an E-4 made by Baker Hughes Incorporated of Houston, Tex. pushes down on sleeve  20  while pulling up on mandrel  22  so that the cone  34  ramps out the top end  36  of the plug  24 . Near the top end  36  are a series of ribs  38  made preferably from a disintegrating material when exposed to certain well conditions or fluids. One such material is a controlled electrolytic material or CEM as described in US Publication 2011/0136707 and related applications filed the same day. The related applications are incorporated by reference herein as though fully set forth. As a result when the proper conditions are obtained the plug  24  will fully disintegrate as it constituent components such as the cone  34  and it body now missing tab  26  that was sheared off when the plug  24  was set and the mandrel  22  removed from the plug  24  are now all made from the disintegrating material. It should be noted that the lower end  40  of the cone  34  will come to a stop before or at travel stop  42 . The use of the disintegrating material for the creation of the ribs allows the points  44  of the ribs  38  to move out radially into contact with the surrounding tubular that is not shown. In applications such as fracturing an absolute seal is not required as long as enough volume under the needed pressure gets delivered to the formation. While the points  44  do not necessarily penetrate the surrounding tubular and when made of a disintegrating material will most likely provide a friction grip, the advantage of the use of the disintegrating material is that there is no well residue when the disintegration is initiated because the entirety of the plug is from a disintegrating material. Contrary to the prevalent though of those skilled in the art, hardened materials that penetrate the surrounding tubular are not required particularly if the treatment is fracturing because some leakage is tolerable while the fracturing gets done. The number of ribs  38  may be increased for additional grip. The use of the disintegrating material also makes the expansion easier and requires less force with a reduced chance for cracking due to overexpansion. Additionally, the configuration of the plug  24  is such that on setting the tab  26  is sheared off and removed with the mandrel  22  when the running tool that is not shown is actuated to set the plug  24  and removed from the borehole. As a result, the embodiment of the plug  24  that is made of a fully disintegrating material results in complete removal after the plug  24  has served its purpose as a barrier. Beyond that a piece of the body of the plug  24  in the form of tab  26  has already been sheared off. It should be noted that the top of the cone  34  has a formed seat for an object such as a ball for isolation. With the mandrel  22  removed during the expansion that sets the plug  24  the seat  44  is exposed to accept an object such as a ball that is not shown. The cone  34  defines a drift dimension through the plug in the set position. 
         [0011]      FIG. 2  shows an alternative embodiment that differs from  FIG. 1  in the sense that there is an o-ring  4  in an associated groove that is designed to engage the surrounding tubular that is not shown. Unlike the consensus in the past designs that provided a long rubber sleeve that was secured to the plug body, the present design dispenses with building up a wide rubber sleeve and putting ribs within the rubber or at opposed ends for an extrusion barrier. In the present design, it has been determined that one or more o-rings  4  in respective grooves on the plug body  8  will provide adequate sealing in applications such as fracturing where liquid tightness is not mandatory as long as there is enough pressure retention that allows the desired volume at the desired pressure to get into the formation to fracture the formation. While the o-ring(s)  4  do not disintegrate when the treatment with the plug body  8  is completed the other plug components can be made of a disintegrating material such as CEM so they can disintegrate when needed. In an option for the design with the o-ring  4  there can also be hardened inserts that can take the form of discrete segments or a split ring that can be snapped over the body  8 . The segments form of the inserts  6  can be forced in an interference fit using elastic flexing of a nearby rib  50 . On the other hand when using a c-ring shape for the insert  6  there is the availability of the potential energy in the snap ring that is initially flexed and then released into an associated groove. Such a groove can be formed with an adjacent rib such as  50  to get the combined effect of the potential energy in the ring and the interference fit from the flexing rib. While the hardened insert(s)  6  penetrate the surrounding tubular wall for enhanced grip they also do not disintegrate after use so that there is some residue from removal of the plug body  8  and the cone  2 . As with the  FIG. 1  embodiment, the setting process involves pushing with setting sleeve  12  and pulling the mandrel  10 . As before when that happens the tab  52  is sheared off and taken out with the mandrel  10 . While a single o-ring  4  and a single hardened insert  6  are shown multiple rows can also be used with the understanding that more material will not disintegrate at the end of the treatment procedure. The insert  6  can be induction hardened cast iron, carburized low alloy steel, carbide, or polycrystalline diamond and it is designed to penetrate the surrounding tubular that is not shown for a grip. The points  54  of the ribs  50  do not penetrate the surrounding tubular and in this embodiment it is not even necessary that they even engage the surrounding tubular. This is because the anchoring is accomplished substantially by the insert(s)  6 . As before the shoulder  56  can act as a travel stop but it is more likely that the cone  2  will stop well before reaching shoulder  56  as the inserts  6  penetrate the surrounding tubular. Tab  52  is retained by retaining nut  14  that is further held on with a set screw  16 . 
         [0012]    Those skilled in the art will appreciate that the illustrated plug designs can be used for treating operations at a subterranean location such as fracturing, injection, acidizing or conditioning the formation for production among other uses. In the  FIG. 1  embodiment the plug is fully disintegrating after use as it is made from disintegrating materials that respond to well conditions created after use so that no residue remains for the subsequent operations or to injure other equipment that is in the vicinity. The plug can permit some leakage and still be useful for operations like fracturing even with a plurality of ribs that friction grab the surrounding tubular rather than penetrating the surrounding tubular. Additional anchoring can be obtained with adding more ribs but it has been determined that hardened inserts are not mandatory for functionality in fracturing service. An elongated rubber seal is also not needed if some leakage flow is tolerated. The advantage is the full disintegrating capability of a plug made from such materials in its entirety. On the other hand,  FIG. 2  represents a design that leaves some but a minimal amount of residue while the balance of the plug disintegrates after use. It uses a spaced apart o-ring from a hardened insert. The use of one or more o-rings leaves less residue than larger rubber sleeves that had been used before to not only secure the inserts in position but to also give what was then thought to be the needed sealing area. As it turns out, one or more o-rings can give the needed or adequate sealing capability even if some leakage ensues from tubular out of roundness. The inserts are secured with an interference fit or a snap action independently of the o-rings. Rather than anchoring with a friction fit with rib tips as in the  FIG. 1  embodiment, the  FIG. 2  design uses the hardened inserts to penetrate the surrounding tubular so that the rib tips can either add the friction force for anchoring or simply not even contact the surrounding tubular. On the other hand when it comes time to disintegrate the plug there will be some residue to contend with since the carbide or diamond nature of the inserts will not disintegrate and neither will the rubber of the o-ring seals. However, at least 80% of the volume of the plug will disintegrate making the  FIG. 2  design a more practical compromise design for some applications where very high pressure differentials are expected or where some leakage is also not tolerated as well. In both cases the cone has a seat for an object that is exposed when the plug is set and the setting mandrel comes out bringing with it the sheared tab from the plug body. 
         [0013]    The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: