Patent Publication Number: US-9885229-B2

Title: Disappearing expandable cladding

Description:
FIELD OF THE INVENTION 
     The field of the invention is subterranean completions and more particularly where existing wellbore penetrations are covered to facilitate a procedure and the clad used for such covering later disintegrates to allow recapture the previous inside diameter for subsequent operations. 
     BACKGROUND OF THE INVENTION 
     In some wells the existing perforations start trailing off on production and the need arises to enhance production from the well with additional perforations into the producing formation at different locations from the original perforations that can then be fractured. 
     The task of sealing off the old perforations has been undertaken in a variety of ways. They can be straddled with swelling packers as in US 20150053397. Another way is to pump material into the existing perforations such as a controlled electrolytic material also known as CEM into the existing perforations while making new perforations followed by delivering material to the borehole that removes the CEM from the existing perforations. This is illustrated in U.S. Pat. No. 8,857,513. An older technique involved pumping a solidifying material into the existing perforations to seal them and then making new perforations for the continuation of production. This method is illustrated in U.S. Pat. No. 5,273,115. 
     There are uncertainties in the technique that seeks to plug the existing perforations with a material in that the completeness of the delivery into the perforations cannot easily be determined. Additionally the pressure needed to deliver such materials into the perforations deep enough to get a seat, even if that seal is temporary, can adversely affect subsequent production. Then there are some doubts that all the plugging material has been effectively disintegrated from inside the perforations, which can also impede subsequent production. 
     The present invention seeks to overcome such uncertainties of prior methods by providing an expandable tubular that can span the perforations in the borehole to facilitate making new perforations and fracturing the new perforations or otherwise performing a treatment operation through the new perforations. The expandable tubular will degrade or disintegrate with time to allow the original well drift diameter to be resumed as well as the original perforations to reopen when production or injection resumes. These and other aspects of the present invention be more readily apparent to those skilled in the art from a review of the detailed description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention can be determined from the appended claims. 
     Also relevant in general to the subject of barriers that disappear or degrade are U.S. Pat. Nos. 8,794,335; 8,668,019; 8,297,364; 7,661,481; 7,461,699; 7,451,815; 5,103,911; 3,216,497; 2,261,292; 2,214,226 and 2014/0027127. 
     SUMMARY OF THE INVENTION 
     Perforations in an existing borehole are covered with an expandable clad or elongated tubular that is expanded on location with the expansion equipment then removed. The clad is made of a disintegrating material such as a controlled electrolytic material known as CEM and is expanded into position to cover the existing perforations. One or more plugs are run in with perforating guns and the plugs set with the guns moved away from the set plug and fired to make new perforation. After each new perforation is made a ball is delivered to the plug to isolate a portion of the well and the new perforations are treated such as in a fracturing or another operation. Over time or with exposure to well fluids or temperatures the clad disintegrates and the original well drift diameter is regained so that subsequent production or injection is not impeded. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of the clad delivered into an existing well over existing perforations with the expansion equipment; 
         FIG. 2  is the view of  FIG. 1  after expansion and removal of the expansion equipment and with the bottom hole assembly in position after the plug has been set and the perforating gun repositioned and fired and an object released to allow the plug to hold pressure for treatment of a new perforation; 
         FIG. 3  is the view of  FIG. 2  after completion of all the treatment of the new perforations; and 
         FIG. 4  is the view after the clad has disintegrated. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1  borehole  10  has existing perforations  12  and  14 . A clad or long tubular  16  is run in with a swage  18  at a lower end and an anchor/stroker  20  of a type known in the art on the upper end with the assembly supported from the surface by a string or wireline or equivalent for proper positioning to straddle the existing perforations  12  and  14 . While two existing perforations are shown any number of perforations can be spanned by the clad  16 . The borehole  10  can be cased with perforations such as  12  having an adjacent sliding sleeve  24 . The clad  16  can be expanded over the opening  26  or/and the sliding sleeve  24  that is generally positioned in a recess in the tubular that defines the borehole  10 . Alternatively, the borehole  10  can be in open hole. 
       FIG. 2  shows the clad  16  expanded after the swage  18  is forced through it and the expansion tools shown in  FIG. 1  replaced with a bottom hole assembly  28  that is delivered into the clad  16 . However, before the bottom hole assembly  28  is run in, additional equipment could be run prior to re-perforating to ensure the pressure integrity of the clad  16  is sufficient to withstand upcoming hydraulic fracturing operations. Item  30  schematically represents a setting tool for the plug  32  and a perforating gun. The plug  32  is set and the gun is released from it and repositioned and fired to create a new perforation  34  after which the remaining BHA is retrieved. The new perforations such as  34  or  38  can be made through the clad  16  or in other parts of the wellbore spaced from the clad, as needed. From surface the ball  36  is dropped into a seat around a passage in the plug so that the plug  32  fully acts as an isolator. As an alternative the clad  16  can be expanded with a variable swage (not shown) to create a seat in the clad  16  which can accept an object from the surface for isolation purposes and to enable a treatment procedure. As another alternative the clad  16  may be formed with a profile that later accepts a plug to create a barrier that facilitates the subsequent treatment with fluid pressure. Pressure is then introduced to fracture the perforation  34  or to otherwise treat the new perforation. Preferably the new perforations are made right through the clad  16  in a bottom up order to ensure each sequential plug isolates the previously treated perforations. Thus for example, perforation  38  is made before perforation  34 . The assembly  30  can be rapidly deployed on wireline  40  and pumped to the location taking advantage of exterior cup seals in a manner known in the art. The assembly  30  is of a type known in the art and can be pulled out each time the gun is fired. The plugs such as  32  and the balls  36  can also be made of disintegrating materials to aid in ultimate removal in a manner that is also known in the art. 
     After all the additional perforations such as  38  and  34  are created and the bottom hole assembly  30  pulled out of the hole for the last time, the clad  16  remains for a time as shown in  FIG. 3 . The plugs such as  32  have been either milled out or allowed to disintegrate and over time or with exposure to well fluids, heat or through added fluids in the borehole the clad  16  which is preferably made of a controlled electrolytic material or CEM disintegrates and the view of  FIG. 4  illustrates that the original bore drift dimension  42  is regained as the clad is no longer present. Controlled electrolytic materials have been described in US Publication 2011/0136707 and related applications filed the same day. Other materials that degrade or disintegrate are also contemplated to save an intervention into the borehole. As shown in  FIG. 4  both the original perforations  12  and  14  and the new perforations  34  and  38  are open for production with the clad  16  having disintegrated or otherwise been removed. The use of the clad  16  takes away the uncertainties of past methods when trying to close off the existing perforations. The complete removal of the clad  16  after new perforations  34  and  38  are created and then treated allows production or injection into all the perforations with the original drift dimension of the well regained. Treatment methods encompass but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc. Although a single clad  16  can cover all or less than all of the existing perforations or access locations to a formation, a clad for each perforation access location to a formation is also envisioned. 
     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: