Abstract:
A tapered mandrel is advanced into a spirally cut sleeve having a corresponding taper to the mandrel. The outer surface of the sleeve conforms to the surrounding borehole and features an exterior recess in which a sealing element is mounted. The sleeve diameter expands as the tapered mandrel is axially advanced. Axial cuts in the spiral sleeve further reduce the force needed for setting. A leading nose is provided for the uphole end of the sealing element to allow high treatment flow rate while the sealing element is protected from the erosive effects of high velocities.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation in part of U.S. application Ser. No. 14/694,399 filed Apr. 23 2015. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The field of the invention is borehole plugs and more particularly those having a body passage selectively closed by an object landing on a seat surrounding the passage and integrating functions of anchoring, sealing and prevention of sealing element extrusion 
       BACKGROUND OF THE INVENTION 
       [0003]    In downhole industries including hydrocarbon exploration and recovery and carbon dioxide sequestration, it is often necessary or desirable to provide for seals and anchors within a tubular body. There have been many different types of configurations to effect such seals and or anchors, each having its advantages and drawbacks. Since the industries noted above experience nearly infinite particular situations, each of which might be better solved by one technology or another, there is a continuing need for alternate configurations to support the vast need and to provide enhancements in various instances. 
         [0004]    Further, the art is always receptive to configurations that can reduce required axial length and reduce cost of production. Prior designs have combined a setting tool that creates relative axial movement between a tapered body advanced relatively to a sleeve that has an external gripping surface and an adjacent sealing element. Slots have been provided in an axial direction to reduce the expansion force needed for contact with the surrounding tubular. In some embodiments the slots actually break causing the sleeve to turn into adjacent segments pressed against a surrounding tubular by the tapered mandrel. There are two issues with this design, first when pumping the plug assembly (guns, adapter kit, setting tool &amp; plug) in the horizontal the seal has low resistance to swab off and swabs off at low flowrates (typically 5 bpm) and second the backup ring does not have zero extrusion gap leading to packing element extrusion under HPHT conditions (15,000 psi &amp; 350° F.). This design, in several variations, is shown in US 2013/0186616. 
         [0005]    The present invention addresses the shortcomings of the design discussed above with a combination of features such as a spiral cut slip segment that spreads radially with minimal force but provides a barrier circumferentially with no gaps to retain the sealing element in position. The sealing element is secured to the slip segment short of the uphole end of the slip segment so that flow from an uphole location around the plug initially engages a tapered uphole end of the slip segment to deflect the fluid and protect the sealing element from swab effects of fluid velocity. These and other aspects of the present invention will be more readily apparent from a review of the detailed description of the preferred embodiment and the associated drawings while understanding that the full scope of the invention is to be determined from the literal and equivalent scope of the appended claims. 
       SUMMARY OF THE INVENTION 
       [0006]    A tool including a cone having a single ramp surface; a backup disposed on the ramp surface; a pusher having one or more slips, the pusher in contact with the backup and configured to force the backup along the ramp surface during use of the tool. 
         [0007]    A backup including a tubular body; a helical cut line through the body that terminates prior to reaching an end face of the body. 
         [0008]    A method for fracturing a formation through which a borehole passes including applying an occluding member to a tool as claimed in claim  1 , the tool having been installed in a borehole; pressuring up on the borehole against the occluding member and tool; and fracturing the formation. 
         [0009]    In an embodiment, a tapered mandrel is advanced into a spirally cut sleeve having a corresponding taper to the mandrel. The outer surface of the sleeve conforms to the surrounding borehole and features an exterior recess in which a sealing element is mounted. The sleeve diameter expands as the tapered mandrel is axially advanced. Axial cuts in the spiral sleeve further reduce the force needed for setting. A leading nose is provided for the uphole end of the sealing element to allow high flow rate while the sealing element is protected from the swab effects of high velocities. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0011]      FIG. 1  is a cross sectional illustration of a seal and anchor tool; 
           [0012]      FIG. 2  is a perspective illustration of the backup illustrated in  FIG. 1 ; 
           [0013]      FIG. 3  is a perspective illustration of an alternate backup ring for the configuration of  FIG. 1 ; and 
           [0014]      FIG. 4  is a cross sectional illustration of an alternate seal and anchor tool; 
           [0015]      FIG. 5  is a section view in the run in position of the plug with the spiral cut slip; 
           [0016]      FIG. 6  is a perspective view of the spiral cut slip; 
           [0017]      FIG. 7  is a section view of the spiral cut slip; 
           [0018]      FIG. 8  is the view of  FIG. 6  with axial scores to reduce expansion force; 
           [0019]      FIG. 9  is the view of  FIG. 7  with the axial cut scores. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
         [0021]    Referring to  FIG. 1 , a seal and anchor tool  10  is illustrated in cross section that is actuated by axial compression force. A cone  12  appears at an uphole end of the figure and provides a single ramp surface  14  (i.e. eliminating an opposing ramp surface at an opposite axial end of a cone structure like that of the prior art) and in some embodiments an occluding member seat  16 . The surface exhibits an angle ranging from about 2 degrees to about 20 degrees from a longitudinal axis of the cone in some embodiments. A seal  18  is disposed about the surface  14  and exhibits a matching angle surface  20  at an inside thereof to the angle of surface  14 . The seal  18  provides an outside diameter surface  22  that is cylindrical in order to reasonably closely match an inside diameter surface  24  of a tubular in which the seal and anchor tool  10  are to be set. Adjacent the seal  18  is a backup  26  whose purpose is to prevent or substantially reduce extrusion of the seal  18  when the seal and anchor tool  10  experiences a pressure differential across the seal  18 . It is to be appreciated from  FIG. 1  that the diameter of the seal  18  appears greater than the diameter of the backup  26 . This is intended since the seal diameter is, in one embodiment, configured with a diameter from about 0.005 to about 0.500 inch greater than that of the backup  26  in order to assure that the seal is fully seated and compressed to the surface  24  prior to the backup making contact with the surface  24 . This configuration ensures that sufficient compressive load on the seal  18  will be imparted before the load axially applied to the tool  10  begins to be taken up by the backup  26  and the anchor (described below). 
         [0022]    The anchor or slip ring pusher  28  is a full ring type that is designed to break apart into a number of slips  30  upon axial compression forcing the pusher  28  up the ramp surface  14 . The slips  30  engage the surface  24  as will be understood by one of ordinary skill in the art. Due to the breakage of the pusher  28 , there are potentially, circumferential gaps that could allow the seal  18  to extrude under a sufficient pressure differential. The backup  26 , because it bridges across such gaps, operates to prevent or reduce extrusion of the seal  18 . The backup will also prevent or reduce extrusion of the seal annularly adjacent surface  24 . 
         [0023]    Based upon  FIG. 1 , an artisan skilled in the art will recognize that the convention two sided cone member is eliminated in the configuration of the disclosed tool. Rather only one cone is provided. This is contrary to conventional teaching and results in a reduced axial length of the tool as well as a reduced cost of manufacture thereof while still retaining the ability to support a fracturing operation. Both of these features will be well received by the art. 
         [0024]    One embodiment of the backup  26  features a body  38  comprising single piece of material  40  composed at least in part of polymeric materials including but not limited to, Polytetrafluoroethylene (PTFE), Polyetheretherketone (PEEK), etc. and metal materials including but not limited to brass, aluminum, magnesium etc. The backup  26  is helically cut through a portion of the material but not all of the material. Reference is made to  FIG. 2  wherein the material  40  is shown with a cut line  42  that terminates prior to reaching an end face  46  of the backup  26 . It will be appreciated in the drawing that the cut line  42  does reach the opposite end face  48  of the backup  26  at  50  but it is to be understood that the cut line  42  could also terminate short of end face  48 , if desired. In an embodiment, a range of uncut portion  44  over which the cut line  42  does not extend is from about 0.005″ to about 1.00″. The uncut portion  44  functions, in this embodiment, to provide for an initiation pressure before the backup will start to move up the ramp  14 . This will help avoid premature actuation and give more positive feedback during intended deployment. As the backup  26  moves up the ramp, once the uncut portion(s)  44  tear, the diameter increases by the material  40  sliding over itself along the cut line  42 . Since the material stays circumferentially complete, any axial openings along the slips  30  will be bridged by the backup  26 . The result is zero extrusion gap and minimal actuation force required. 
         [0025]    Referring to  FIG. 3 , the backup  26  is similar but not identical to that of  FIG. 2 . Rather, in  FIG. 3 , there are two cut lines  52  and  54  through material  40 . Each cut line  52  and  54  are helically arranged making two helical parts  56  and  58  that are nested with each other. At least one, and as shown both of the cut lines  52  and  54  terminate prior to reaching an end face  60  leaving uncut portion  62  and  64 . A range of uncut portion  62  and  64  over which the cut lines  52  and  54  do not extend is from about 0.005″ to about 1.00″. It is to be understood that more cut lines may be added to produce more helical parts if desired. In the case of embodiments such as  FIG. 3 , the uncut portions serve not only to provide for initiation pressure before deployment as in  FIG. 2  but also to hold the helical parts together prior to deployment. In this embodiment of backup  26  as in the previous embodiment, both annular and axial extrusion gaps are minimized or eliminated. 
         [0026]    It is to be appreciated that in the case of  FIGS. 2 and 3 , the backup is not limited to employment in the tool described herein (and as noted the tool does not necessarily require the particular backup) although they do work well together. The backup as described may be employed with any other tool requiring a backup and the tool described herein may use other backups that provide sufficient resistance to seal extrusion. 
         [0027]    In another embodiment, referring to  FIG. 4 , a tool  70  is illustrated that eliminates the seal  18  as described above but maintains other components of the tool  10  of  FIG. 1 . It has been determined that the backup  26  can be used alone to provide sufficient differential pressure holding capability to support a fracking operation without a seal  18 . Therefore, for certain operations that are cost sensitive, it may be beneficial to employ the tool illustrated in  FIG. 4 . 
         [0028]    Referring to  FIG. 5 , a bottom sub  70  has thread  72  for attaching part of a setting tool that is not shown but can be an E-4 tool sold by Baker Hughes, a GE company that is well known in the art. Another part of the tool pushes down on mandrel  74  and that force is schematically represented by arrow  76 . A setting rod that is not shown passes through passage  78  to releasably connect to threads  72  when the sealing element  80  and wickers  82  of slip sleeve assembly  84  contact the surrounding tubular or the borehole wall that is not shown. Slip sleeve assembly  84  can be one piece comprising portions  110 ,  118  and  82  or it can be multiple connected pieces with  110  being an end regardless of there being one or more pieces. During the setting, radial surface  86  is advanced toward mandrel  74  until sufficient tension in the rod that is connected to thread  72  is reached at which time the rod that is not shown shears and the bottom sub falls in the borehole. Eventually the bottom sub  70  breaks up or disintegrates as it responds to well fluids or other well conditions. Bottom sub  70  can be made of a controlled electrolytic material that is known and also offered by Baker Hughes, a GE company of Houston, Tex. USA. Other materials that degrade or disintegrate or otherwise go away are also contemplated. The setting rod component above the shear break during setting comes out with the known setting tool as is well known in the art. 
         [0029]    The slip sleeve assembly  84  has an internal taper  88  that conforms to the tapered outer surface  90  of frustoconically shaped mandrel  74 . Seat  92  surrounds passage  78  at top end  94  of mandrel  74 . An object that is preferably a ball  96  can be pumped or otherwise delivered to seat  92  after the setting tool that is not shown is removed. Although shown in a single location those skilled in the art will appreciate that a plurality of the illustrated assemblies can be used at axially spaced locations in a borehole to treat more than one portion of a producing interval. The plug P can be delivered with a perforating gun and a ball dropped that are not shown so that after the plug P is set and the perforating gun is fired successfully a ball  96  is released to seat  92  and a treatment into the formation against plug P can begin. It should be noted that the wickers  82  in the run in position have a cylindrical shape while the internal wall  88  is a taper that is preferably the same angle as taper  90  but some angular offset is envisioned. 
         [0030]    Referring to  FIGS. 5-7  a spiral cut  98  extends preferably from downhole end  100  to uphole end  102  but ending the cut short of either end is also contemplated. 
         [0031]    “Spiral cut” is a generic term meant to include complete through the wall cuts or scores starting from the inside wall or the outside wall or a spiral form with gaps such as a coiled spring or no gaps, with the spiral being continuous or segmented or having one or more than one pattern nested patterns. In general, the term applies to a circular treatment for a generally cylindrically shaped object that is put there to reduce force when increasing its outer dimension when engaging a surrounding borehole surface for support therefrom. 
         [0032]    As mandrel  74  is axially advanced toward downhole end  100  that rests on surface  86  of bottom sub  70  the wickers  82  move radially. Preferably adjacent coils such as  104  and  106  remain abutting after the set position is achieved but the amount of radial extension of each can vary somewhat to conform to irregularities of the surrounding borehole wall or the surrounding tubular. An external groove  108  is presented below end  102  leaving a leading tapered segment  110  of the slip sleeve assembly  84  uphole of the sealing element  80  shown in the groove  108  in  FIG. 5 . Preferably, the sealing element  80  has a leading taper  112  that preferably is a continuation of the taper on the segment  110  although it is envisioned that taper  112  can extend radially either more or less than the taper of segment  110 . Sealing element  80  has a preferably cylindrical segment  114  downhole from taper  114  that preferably extends radially beyond wickers  82  so that by the time the wickers  82  engage the borehole wall or the surrounding tubular, the sealing element  80  is radially compressed against the surrounding borehole wall or tubular for a seal. The outer dimension of the slip sleeve assembly  84  grows radially as the mandrel  74  is axially advanced during the setting. The spiral cut allows this radial growth to occur while keeping abutting coils such as  104  and  106  in an abutting relationship to close of an extrusion path in a downhole direction responsive to treatment pressure applied from a surface location against sealing element  80 . While sealing element  80  is generically represented as a single component it can be a multi-component assembly. In the set position the radial extension of the sealing element  80  and the wickers  82  is approximately the same particularly if the set is against a surrounding tubular so that the slip sleeve assembly  84  functions to anchor and to operate as an extrusion barrier at the same time. The slip sleeve assembly  84  using recess  108  holds the sealing element  80  in position. The leading taper  110  of the slip sleeve  84  helps to deflect fluid flowing around the seal. Thus reducing the pressure differential around the sealing element  80 . As used herein, “taper” is used generically to refer to different shapes that function to reduce swabbing as the plug is delivered to a predetermined location. Thus taper encompasses a transitional surface bigger in diameter at the seal end and smaller in diameter at end  102 . In between it can be a wavy surface or an arcuate surface; it can be smooth or rough with surface irregularities such as peaks or valleys or grooves, for example. Should any flow get past the sealing element  80  it will be stopped or at least slowed by the wickers  82  engaging the surrounding tubular or the borehole wall. By placing the sealing element  80  in groove  108  the prospect of fluid bypass under the sealing element  80  through the groove  108  is also minimized. Inside there is an internal groove  109  with seal  111  to engage mandrel  74  to close off an internal leak path. Thin walled section  118  is more flexible than adjacent portions of the slip sleeve assembly  84  and gets reaction force radially from the set sealing element  80  to close off a leak path between the mandrel  74  and the slip sleeve assembly  84 . Seal  80  can be bonded, molded or 3-D printed into groove  118 . Various components of the plug P can be made of disintegrating materials to avoid a need for milling out after the treatment is over. The mandrel  74  with ball  96  can be made of disintegrating materials. In some cases the slip sleeve assembly or parts thereof can be made of a disintegrating material or material that otherwise goes away without well intervention of tools. In some instances at least a part of the sealing element  80  can also disintegrate or otherwise disappear.  FIGS. 8 and 9  show axial scores  120  that can extend to downhole end  100  to make radial expansion of the slip sleeve assembly  84  easier to accomplish with a reduced force. One or more such scores can be used or other weakening devices to reduce expansion force needed can be used. Preferably such scores or undercuts do not extend to an exterior surface where the wickers  82  are located. Scores  120  also come up short of the groove  108  as shown in  FIG. 9 , Scores  120  could optionally be on the outside as an alternative or as an addition to those shown on the inside. It should be noted that the increase in radial dimension of the slip sleeve assembly  84  comes with a decrease of its axial length that also has the effect of adding an axial compression force to the sealing element  80  although the applied axial forces from the setting tool establish a wedging action due to relative axial movement of the slip sleeve assembly  84  with sealing element  80  relative to mandrel  74 . 
         [0033]    The teachings of the present disclosure may be used in a variety of well operations. These operations may involve using one or more treatment agents to treat a formation, the fluids resident in a formation, a wellbore, and/or equipment in the wellbore, such as production tubing. The treatment agents may be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Illustrative treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, anti-corrosion agents, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers etc. Illustrative well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc. 
         [0034]    It is also contemplated for any or all of the components/tools described above that materials such as a controlled electrolytic metallic material (Intallic® commercially available from Baker Hughes, Houston Tex.) or other dissolvable or disintegrable material be employed so that the entirety or some portion of the entirety of the tools may be removed through dissolution via natural borehole fluids or applied fluids at an appropriate time. 
         [0035]    The tool embodiments disclosed herein are particularly suited to fracturing a formation through which a borehole passes while reducing expense in production of the tool, reducing longitudinal axial length of the installed to and optionally reducing costs for removal of the tool. The fracturing operation comprises: installing one of the embodiments set forth above in a borehole; applying an occluding member on the tool; pressuring up on the borehole against the occluding member and tool; fracturing a formation adjacent the borehole and removing the tool from the borehole. 
         [0036]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should further be noted that the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). 
         [0037]    While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited.