Patent Publication Number: US-2018045017-A1

Title: Slip Assembly for Anchoring Downhole Plugs and Retainers

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     THIS APPLICATION CLAIMS PRIORITY OF UNITED STATES PROVISIONAL PATENT APPLICATION SERIAL NO. 62/373,419, FILED AUG. 11, 2016, INCORPORATED HEREIN BY REFERENCE. 
    
    
     STATEMENTS AS TO THE RIGHTS TO THE INVENTION MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT: 
     NONE 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention pertains to a downhole assembly including, without limitation, a drillable plug assembly that can be installed at a desired location within a subterranean wellbore. More particularly, the present invention pertains to a plug assembly that is capable of providing a fluid pressure seal within a wellbore, while being capable of being drilled, milled or mechanically broken up more efficiently than conventional wellbore plugs. More particularly, the present invention pertains to a plug that can permit selective fluid pumping through said plug (including, without limitation, as a cement retainer). 
     2. Brief Description of the Prior Art 
     Bridge plugs, retainers or other anchoring and/or sealing devices are frequently installed within subterranean wellbores such as oil and gas wells. Such assemblies can be installed to isolate one portion of a wellbore from another, to prevent fluid flow between segments of a wellbore, and/or to provide a fluid pressure sealing barrier within said wellbore. In most instances, said plugs are set inside the internal through bore of pipe that is installed within a wellbore (typically a casing or tubing string). 
     Conventional bridge plugs used to isolate one portion of a wellbore from another typically comprise at least one anchoring system that grips the inner surface of said surrounding wellbore and locks said plug in place against axial movement. Such plugs typically also include at least one expandable sealing/packing element that provides a fluid pressure seal against said internal wellbore surface (that is, between the outer surface of the plug and the inner surface of the surrounding wellbore). Cement retainers are similar to such bridge plugs, but also permit the selective pumping of cement slurry or other fluid through said devices; as used herein, the terms “plugs” or “bridge plugs” shall also include cement retainers. 
     Although many bridge plugs are designed to be permanently installed, certain other bridge plugs are designed to be removed by being drilled with a bit, mill or other device when isolation of a portion of a wellbore is no longer desired. Such conventional “drillable” bridge plugs are typically constructed of drillable cast iron, aluminum, non-metallic materials or some combination thereof; such drillable plugs can generally be drilled or milled faster and more efficiently than plugs that are constructed from metallic components. 
     Such conventional drillable bridge plugs are frequently difficult and time consuming to drill out, mill up or otherwise mechanically break apart. In certain applications, multiple drillable plugs are installed within a single wellbore. In such cases, the time (and associated cost) of drilling, milling or otherwise removing said multiple plugs is compounded. 
     Thus there is a need for a drillable plug that securely anchors in place within a wellbore and provides a reliable fluid pressure seal against the inner surface of said wellbore. When desired, said plug assembly should be capable of being drilled, milled or otherwise mechanically broken apart more easily and efficiently than conventional bridge plugs (including, without limitation, drillable bridge plugs). 
     SUMMARY OF THE INVENTION 
     In a preferred embodiment, the present invention comprises a slip assembly for use with downhole wellbore plugs and/retainers such as, for example, in oil or gas wells penetrating subterranean formations. In a preferred embodiment, certain components of the slip assembly of the present invention can be beneficially constructed, at least in part, from material(s) that can be relatively easily milled or drilled, such as, for example, non-metallic composite material (including, without limitation, glass filed epoxy resin) or other material exhibiting similar qualities and characteristics. 
     Said slip assembly of the present invention can be utilized with a fully sealing plug assembly. In operation, the slip assembly of the present invention can be attached to a conventional setting tool and conveyed into a well to a desired depth via continuous wire (such as, for example, electric line or slick one), coiled tubing or jointed pipe. Once said plug assembly has been placed at a desired location within said wellbore, said setting tool can be actuated to extend said at least one slip assembly outward to grip the surrounding wellbore. At least one sealing member (such as, for example, an elastomeric ring) can also extend outward to engage against and form a fluid pressure seal against the inner surface of the surrounding wellbore. 
     The assembly of the present invention allows for elimination of composite bands or other conventional retention devices typically used to hold slip members in place prior to setting/engagement of said slip members. Said bands or conventional retention devices can sometimes obstruct slips from properly anchoring to a casing wall. Further, such bands or other conventional retention devices can often become damaged/broken, allowing slip members to become detached and fall within a wellbore, thereby resulting in costly fishing operations and/or additional inherent risk of loss or damage. By eliminating said bands or conventional retention devices, the present invention eliminates such risk. 
     When desired, a plug assembly equipped with the slip assembly of the present invention can be drilled, milled or otherwise mechanically broken apart more easily and efficiently than conventional bridge plugs including, without limitation, drillable bridge plugs. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS/FIGURES 
       The foregoing summary, as well as any detailed description of the preferred embodiments, is better understood when read in conjunction with the drawings and figures contained herein. For the purpose of illustrating the invention, the drawings and figures show certain preferred embodiments. It is understood, however, that the invention is not limited to the specific methods and devices disclosed in such drawings or figures. 
         FIG. 1  depicts a side perspective view of a slip assembly of the present invention in a non-engaged or “running-in” configuration. 
         FIG. 2  depicts a side perspective view of a slip assembly of the present invention in an engaged or “set” configuration within a partially cut-away section of casing. 
         FIG. 3  depicts a side sectional view of a portion of the slip assembly of the present invention operationally attached to a conventional setting tool while being run in a wellbore. 
         FIG. 4  depicts a side sectional view of a portion of the slip assembly of the present invention operationally attached to a conventional selling tool within a wellbore during an intermediate engagement step. 
         FIG. 5  depicts a side sectional view of a portion of the slip assembly of the present invention operationally attached to a conventional setting tool within a wellbore while being set. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
       FIG. 1  depicts a side perspective view of a slip assembly  100  of the present invention in a non-engaged or “running-in” configuration, such as when said slip assembly  100  comprises part of a downhole plug assembly and is being conveyed in a wellbore on wireline, continuous tubing or jointed pipe string. It is to be observed that slip assembly  100  can be installed in connection with a downhole plug assembly well known to those having skill in the art; such plug assembly can comprise multiple slip assemblies  100 , as well as at least one elastomeric sealing member that can be selectively engaged to form a fluid pressure seal against the inner surface of a surrounding wellbore. 
     As depicted in  FIG. 1 , slip assembly  100  of the present invention comprises a plurality of wedge shaped slip members  10  operationally attached to push ring  20 . Said wedge shaped slip members  10  are moveably disposed on inclined ramp surfaces  31  of cone member  30 , although said slip members  10  can be selectively locked against movement as described herein. Slip members  10  have leading edge or end  11  and trailing end  12 . Leading end  11  generally forms a tapered edge, while trailing end  12  has lateral dovetail extensions or projection members  13  that extend laterally outward from slip members  10 . Wedge shaped slip members  10 , push ring  20  and cone member  30  are disposed on a central mandrel, discussed in more detail below; in the embodiment depicted in  FIG. 1 , the upper portion of said central mandrel forms extension or collar  22 . 
     Said dovetail projection members  13  are slidably received within matching mortise-like dovetail recesses  21  formed in push ring  20 . Each of said dovetail projection members  13  can travel within recesses in a direction that is substantially normal to push ring  20  and the longitudinal axis of central mandrel  40 . Wedge-shaped slip members  10  also have angled lateral ledge extensions  14  that are slidably received within tracks or grooves  32  of cone member  30 ; said tracks or grooves  32  are positioned adjacent, and oriented generally parallel, to inclined ramp surfaces  31  and run along the length of said ramp surfaces  31  on the sides of said ramp surfaces. 
     Dovetail projection members  13  on each slip member  10  keep said slip members operationally linked to push ring  20 , and prevent said slip members  10  from moving in an axial direction apart from said push ring  20 . Further, angled lateral ledge extensions  14  on the sides of slip members  10  keep said slip members  10  from extending radially outward while said slip assembly  100  is being conveyed in a well. 
     Slip assembly  100  of the present invention can include, but does not require composite bands or other conventional retention devices to hold slip members  10  in place prior to setting/engagement of said slip members (such as when said slip assembly  100  is being run into a well on wireline or pipe). As previously noted, said bands or conventional retention devices can sometimes obstruct slips from properly anchoring to a casing wall. Further, such bands or other conventional retention devices can often become damaged/broken, allowing slip members to become detached and fall within a wellbore, thereby resulting in costly fishing operations and/or additional inherent risk of loss or damage. By eliminating said bands or conventional retention devices, slip assembly  100  of present invention eliminates such risk. 
       FIG. 2  depicts a side perspective view of a slip assembly  100  of the present invention in an engaged or “set” configuration within a partially cut-away section of casing  200  having inner surface  201 . As depicted in  FIG. 2 , during the setting process push ring  20  applies axial force on wedge-shaped slip members  10 , causing said slip members  10  to ride along inclined ramp surfaces  31  (obscured from view in  FIG. 2 ) of cone member  30  and, in turn, forcing outer surfaces  15  of said slip members  10  in a radially outward direction toward inner surface  201  of casing  200 . In the configuration depicted in  FIG. 2 , upper cylindrical extension  22  faces generally up hole within casing  200 . 
     Still referring to  FIG. 2 , as said slip members  10  extend radially outward, dovetail extensions or projection members  13  of said slip members  10  can radially protrude from dovetail recesses  21 ; however, said slip members  10  remain operationally linked to push ring  20  to prevent independent axial movement of said slip members  10  and push ring  20  relative to each other. Wickers or buttons  16  made of powdered metal and composite matrix material are molded in slip members  10  allowing said slip members  10  to grip or bite into said inner surface  201  of said casing  200  (including, without limitation, hardened pipe such as Q-125 casing). 
       FIGS. 3 through 5  depict a series of side sectional schematic views of a portion of the slip assembly  100  of the present invention during a running in, and engagement/setting sequence. Referring to  FIG. 3 , slip assembly  100  is attached to conventional setting tool  300  having outer setting sleeve  301 ; conventional setting tool  300  is well known to those having skill in the art Tapered or wedge-shaped slip member  10  is operationally attached to push ring  20 , which is slidably disposed along the outer surface of central mandrel  40 . Wedge shaped slip member  10  has outer surface  15  having powdered metal wickers or buttons  16  disposed thereon. As depicted in  FIGS. 3 through 5 , said buttons  16  are received within holes or apertures formed in spaced relationship along said outer surface  15  and at least partially extend beyond said outer surface  15 . Inclined inner surface  17  of slip member  10  is disposed on inclined ramp surface  31  of cone member  30 . In the configuration depicted in  FIG. 3 , push ring  20  is prevented from axial downward movement (during such running in operations) by at least one shear pin  23  constructed of material having a known or predetermined shear strength. 
     Referring to  FIG. 4 , after said slip assembly  100  has been conveyed to a desired location within a wellbore, conventional setting tool  300  is actuated causing opposing axial forces to act on push ring  20  and central mandrel  40 . Prior to such actuation, shear phi  23  locks slip assembly  100  in the running position until said setting tool  300  is actuated; thereafter, setting sleeve  301  applies axial force to push ring  20 , while central mandrel  40  is forced in the opposite axial direction or secured against said axial movement, thereby forcing shear pin  23  to shear or separate, effectively unlocking push ring  20  and permitting axial movement of said push ring  20 . Once “unlocked”, push ring  20  can be axially moved toward cone member  30 . 
     Referring to  FIG. 5 , setting sleeve  301  applies axial force to push ring  20  which, in turn applies axial force to wedge-shaped slip members  10 . Such axial force causes said slip members  10  to interact with inclined ramp surfaces  31  of cone member  30 , thereby driving outer surface  15  (and wickers or buttons  16  disposed thereon) of said slip member  10  in a radially outward direction. As said slip member  10  extends radially outward, said slip member  10  remains operationally linked to push ring  20  to prevent independent axial movement of said slip member  10  and push ring  20  relative to each other. Referring back to  FIG. 2 , when said slip members  10  are extended radially outward, buttons  16  disposed on the outer surfaces  15  of said slip members  10  can contact in gripping relationship with inner surface  201  of wellbore casing  200 , thereby anchoring slip assembly  100  against axial movement within said wellbore. 
     During the setting process, leading ends  11  of slip members  10  ride along inclined ramp surfaces  31  of cone member  30 , travelling in a direction that is substantially parallel to the longitudinal axis of central mandrel  40 . As said slip members  10  travel along inclined ramp surfaces  31  said slip members  10  cooperate with said inclined ramp surfaces  31  and expand radially outward toward the inner surface of a surrounding tubular or wellbore. Angled lateral ledge extensions  14  of slip members  10  travel in grooves  32  that are oriented substantially parallel to inclined surface  31 ; said lateral ledge extensions  14  cooperate with said grooves  32  to ensure that slip members  10  remain engaged against ramp surfaces  31  of cone member  30 . Trailing ends  12  of slip members  10  have dovetail projection members  13  that extend laterally outward from said slip members  10 . Said dovetail projection members  13  are slidably received within mating dovetail recesses  21  in push ring  20 . 
     A common problem with existing conventional cement retainer designs is that they typically utilize frangible bands or a full circular ring of steel slips that frequently break prior to the plug reaching a desired setting depth in a well. Such premature breakage causes the tool to inadvertently “pre-set”, which can require significant time and expense to remedy. By contrast, with the present invention, angled lateral ledge extensions  14  of slip members  10  travel in grooves  32 , while dovetail projection members  13  at trailing ends  12  of slip members  10  are engaged into the mating dovetail recesses  21  of push ring  20 . As a result, slip members  10  remain locked radially inward as push ring  20  is spread apart from cone member  30 . This ensures that said slip members  10  are drawn tight inwardly against mandrel  40 , and that said slip members  10  are held securely in place, during the running process and prior to desired setting of slip assembly  100  and engagement of said slip members  10  against a surrounding tubular or wellbore surface. Shear pin  23  acts to keep slip members  10  (such as the upper slip members of a plug assembly) from prematurely setting until setting tool  300  is activated. Said push ring  20  is typically one of the first components to move during the setting process. 
     The cooperating dovetail design of slip member  10  and push ring  20  also serves as an anti-rotational feature during the drilling process (such as when slip assembly  100  is being drilled or milled) and eliminates the need for conventional slip retaining rings. Additionally, upon drilling or milling of said slip assembly  100 , drilled up components of said slip assembly  100  can be easily and conveniently circulated out of a wellbore using well fluids. 
     Notwithstanding anything to the contrary contained herein, all dimensions, specifications and material selections are illustrative only and are not intended to be, and should not be construed as, limiting in any way. Moreover, except for said powdered metal wickers and shear pins, ail other components of the slip assembly of the present invention can be constructed of composite or non-metallic material. 
     The above-described invention has a number of particular features that should preferably be employed in combination, although each is useful separately without departure from the scope of the invention. While the preferred embodiment of the present invention is shown and described herein, it will be understood that the invention may be embodied otherwise than herein specifically illustrated or described, and that certain changes in form and arrangement of parts and the specific manner of practicing the invention may be made within the underlying idea or principles of the invention.