Patent Publication Number: US-2019186223-A1

Title: Well plugs and associated systems and methods

Description:
BACKGROUND 
     This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an example described below, more particularly provides an economical well plug with consistent setting. 
     A well plug (such as, a “frac” plug, a bridge plug, etc.) can be used to isolate one section of a wellbore from another section of the wellbore. A well plug can be set in a tubular string, in which case the plug can isolate sections of the tubular string from each other. 
     It will, thus, be readily appreciated that improvements are continually needed in the arts of designing, constructing and utilizing well plugs. Such improvements could be incorporated into a variety of different types of well plugs, and could be used in a variety of different well operations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a representative partially cross-sectional view of an example of a well system and associated method which can embody principles of this disclosure. 
         FIGS. 2A-D  are representative cross-sectional views of steps in a method of setting an example of a well plug embodying the principles of this disclosure. 
         FIGS. 3A-D  are representative cross-sectional views of steps in a method of setting another example of the well plug. 
     
    
    
     DETAILED DESCRIPTION 
     Representatively illustrated in  FIG. 1  is a system  10  and associated method which can embody principles of this disclosure. However, it should be clearly understood that the system  10  and method are merely one example of an application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited at all to the details of the system  10  and method described herein and/or depicted in the drawings. 
     In the  FIG. 1  example, a wellbore  12  penetrates an earth formation  14 . The wellbore  12  is generally vertical and is lined with casing  16  and cement  18 . In other examples, the wellbore  12  could be horizontal or otherwise deviated relative to vertical, and the principles of this disclosure may be practiced in an uncased or open hole section of the wellbore. 
     In order to isolate upper and lower sections of the wellbore  12  from each other, a well plug  20  is conveyed into the wellbore with a setting tool  22 . The well plug  20  and setting tool  22  may be conveyed by wireline, coiled tubing, or another type of conveyance. 
     The setting tool  22  is operatively connected to the well plug  20  with a setting tool adapter  24 . In other examples, the setting tool adapter  24  may not be used (e.g., if the setting tool  22  and well plug  20  are configured for direct connection to each other). 
     As depicted in  FIG. 1 , the setting tool  22 , when actuated, produces opposing longitudinal setting forces SF. A tensile setting force SF is applied upwardly to a setting rod  26  extending through the well plug  20 . An oppositely directed compressive setting force SF is applied to an outer housing  28  of the well plug  20 . As a result, the setting force SF is applied as a longitudinally compressive force to the well plug  20 . 
     The setting force SF may be applied by the setting tool  22  in any of a variety of different ways, including ignition of a propellant, hydraulic, electrical or mechanical actuation, etc.). Thus, the scope of this disclosure is not limited to use of any particular type of setting tool to apply the setting force SF to the well plug  20 . 
     A seal element  30  is positioned on an inner generally tubular mandrel  32  of the well plug  20  in the  FIG. 1  example. Application of the setting force SF to the seal element  30  causes it to extend radially outward into sealing contact with the casing  16 . If the wellbore  12  is uncased, the seal element  30  could sealingly engage an inner wall of the formation  14 . 
     In some examples, the seal element  30  could comprise an annular elastomeric material that extends radially outward in response to longitudinal compression. In other examples, other materials (such as, non-elastomers, plastics, composites, ceramics, metals, etc.) may be used. 
     In further examples, the seal element  30  could extend into sealing engagement with a surrounding well surface in response to the setting force SF, without the seal element itself being longitudinally compressed (e.g., the seal element could be radially displaced without being longitudinally compressed). Thus, the scope of this disclosure is not limited to any particular type of seal element or setting mechanism used with the well plug  20 . 
     The  FIG. 1  well plug  20  includes an anchor  34  for securing the well plug  20  against longitudinal displacement relative to the wellbore  12 . In this example, the well plug  20  includes slips  36  that grip an interior surface of the wellbore  12  (in this case, an interior surface of the casing  16 ). 
     The slips  36  extend radially outward into gripping engagement with the casing  16  in response to application of the compressive setting force SF to the well plug  20 . In the  FIG. 1  example, the slips  36  include multiple individual slip members, but in other examples a single barrel slip, longitudinally spaced apart gripping members, or other types of gripping members could be used. Thus, the scope of this disclosure is not limited to any particular configuration or structure of the anchor  34  used with the well plug  20 . 
     In the  FIG. 1  example, the setting rod  26  is connected to the well plug  20  with a releasable attachment  38 . The releasable attachment  38  releases the setting rod  26  from the well plug  20 , so that the setting tool  22 , the setting rod  26  and optionally the setting adapter  24  can be retrieved from the wellbore  12  after the well tool  20  has been set. 
     The releasable attachment  38  initially secures the setting rod  26  to the well plug  20 , thereby enabling the force SF produced by the setting tool  22  to be transmitted as a compressive force to the well plug, in order to set the well plug. The force SF produced by the setting tool  22  eventually reaches a predetermined level at which the well plug  20  has been set, with the seal element  30  sealingly engaging the wellbore  12  and the anchor  34  grippingly engaging the wellbore. 
     When the predetermined level is reached, the releasable attachment  38  releases, and the setting tool  22 , the setting rod  26  and optionally the setting adapter  24  can be retrieved from the wellbore  12 . As described more fully below with regard to certain examples of the well plug  20 , the releasable attachment  38  is designed so that it will release at a consistent predetermined setting force SF level (thereby ensuring that the well plug  20  is fully set when the release occurs), no or minimal debris is left in the well due to the release (thereby minimizing the possibility of delaying or fouling subsequent operations and equipment in the wellbore  12 ), and the releasable attachment is compact and economical to incorporate into the well plug assembly. 
     Referring additionally now to  FIGS. 2A-D , more detailed cross-sectional views of an example of the well plug  20  in various stages of a setting operation are representatively illustrated. For convenience, the  FIGS. 2A-D  well plug  20  is described below as it may be used in the system  10  and method of  FIG. 1 , but it should be understood that the well plug may be used in other systems and methods, in keeping with the principles of this disclosure. 
     The setting tool  22  and setting tool adapter  24  are not shown in  FIGS. 2A-D  for clarity. The setting rod  26  shown in  FIGS. 2A-D  may, however, be a part of the setting tool  22 , the setting tool adapter  24 , or another tool used to apply the setting force SF to the well plug  20 . 
     Note that the anchor  34  in the  FIGS. 2A-D  example comprises two barrel slips  36  longitudinally spaced apart on the mandrel  32 , with corresponding conical wedges  40  for outwardly deflecting the slips. The wedges  40  are also positioned straddling the seal element  30 , so that the seal element will be longitudinally compressed between the wedges when the setting force SF is applied. 
     As depicted in  FIG. 2A , the well plug  20  is in a run-in configuration. In this configuration, the well plug  20  can be conveyed to a desired location for setting in the wellbore  12 . 
     The seal element  30  and the anchor  34  are radially inwardly retracted. The setting rod  26  is releasably secured to the well plug  20  with the releasable attachment  38 . 
     In this example, the releasable attachment  38  includes an annular-shaped shear ring  42  secured to an end of the setting rod  26  with a fastener  44  (in this case, a threaded bolt or screw). The shear ring  42  and the fastener  44 , thus, are constrained to displace with the setting rod  26 . 
     The shear ring  42  is “annular” in shape, in that it is generally ring-shaped. In some examples, the shear ring  42  may not extend completely circumferentially about the fastener  44  (e.g., the shear ring could extend less than a full 360 degrees about the fastener). In other examples, the shear ring  42  may not be strictly circular in shape (e.g., the shear ring could have a non-circular shape, such as, oval, oblong, etc.). 
     The shear ring  42  is positioned longitudinally between an annular shoulder  46  formed on the fastener  44  and an oppositely facing annular shoulder  48  formed on the setting rod  26 . When the setting force SF is applied to the setting rod  26 , it is transmitted in shear through the shear ring  42  to the mandrel  32 . 
     In  FIG. 2B , the well plug  20  is depicted in a configuration in which the setting operation has been initiated, with the setting force SF being applied via the setting rod  26  to the well plug. The seal element  30  is longitudinally compressed by the setting force SF, causing it to extend radially outward into sealing engagement with the wellbore  12 . 
     The slips  36  are displaced radially outward by the wedges  40  into gripping engagement with the wellbore  12 . The releasable attachment  38  still releasably secures the setting rod  26  to the well plug  20 , so the setting force SF continues to be applied to the well plug. The setting force SF is experienced as a shear force in the shear ring  42  between the annular shoulders  46 ,  48 . 
     In  FIG. 2C , the setting force SF has reached the predetermined level, thereby causing the shear ring  42  to shear into two sections  42   a,b.  In this manner, the setting rod  26  is released from the well plug  20  for retrieval from the wellbore  12 . 
     In this example, the shear ring  42  comprises a material that provides a consistent shearing at the predetermined level of the setting force SF. The material can include, but is not limited to, fiber reinforced composite, plastic, phenolic, ceramic (e.g., zirconia, silicon nitride, alumina, cermet, etc.), ductile iron, alloy steel, non-ferrous alloys (e.g., brass, aluminum alloys, copper alloys, etc.), or materials dissolvable in a well environment (such as, magnesium alloys, aluminum alloys, poly-glycolic acid (PGA), poly-lactic acid (PLA), fiber reinforced PGA or PLA, etc.). In one example, a National Electrical Manufacturers Association (NEMA) G-11 laminate material (comprising a woven glass fabric and high temperature rated epoxy resin composite) marketed by Norplex-Micarta of Postville, Iowa USA may be used for the shear ring  42 . 
     In  FIG. 2D , the setting rod  26  is retrieved from the well, while the well plug  20  remains set in the wellbore  12 . Note that one section of the shear ring  42   a  is retrieved from the well with the setting rod  26  (retained by the fastener  44 ), and the other section of the shear ring  42   b  remains with the well plug  20  (for example, the shear ring section  42   b  could be press-fit, bonded, fastened or otherwise attached to the mandrel  32 ). Thus, neither of the shear ring sections  42   a,b  becomes loose debris in the wellbore  12 . 
     A flow passage  50  may extend longitudinally through the well plug  20 , after the shear ring  42  has been sheared and the setting rod  26  has been withdrawn from the well plug. When it is desired to prevent flow through the flow passage  50 , a plug device (such as, a ball, dart or other device, not shown, capable of blocking the flow passage  50 ) may be installed in the wellbore  12  to sealingly engage a seal surface or seat  52  formed at an upper end of the mandrel  32 . For example, in a fracturing or other stimulation operation, the sealed off flow passage  50  may prevent fracturing fluid pumped to a formation zone above the well plug  20  from being communicated to a previously fractured zone below the well plug. 
     Eventually, the isolation between zones provided by the well plug  20  may no longer be desired. In that case, the well plug  20  can be milled or drilled through, and for this purpose can comprise relatively easily milled or drilled materials. For example, some or all structural components of the well plug  20  (such as, the mandrel  32 , wedges  40  and outer housing  28 ) could be made of a filament wound and two-part epoxy composite material, or an aluminum alloy. 
     In some examples, the well plug may degrade in the wellbore  12  (e.g., by dissolving, dispersing, corroding, hydrating, etc.). If the well plug  20  degrades in the wellbore  12 , it may do so autonomously (such as, in response to passage of a predetermined period of time), without human intervention (such as, in response to exposure to downhole temperature or environment), or in response to an applied stimulus (such as, in response to spotting an acid or other degrading substance in the wellbore at the well plug). 
     A magnesium alloy could be readily dissolved by spotting an acid at the well plug  20 . A PGA or PLA material can be dissolved by hydration. An aluminum alloy can disperse by galvanic reaction. The scope of this disclosure is not limited to use of any particular material or combination of materials in the well plug  20 . In addition, it is not necessary for the well plug  20  to be drilled, milled, dissolved, dispersed or otherwise removed from its sealing and gripping engagement with the wellbore  12  as depicted in  FIG. 2D . 
     Referring additionally now to  FIGS. 3A-D , cross-sectional views of another example of the well plug  20  in various stages of a setting operation are representatively illustrated. For convenience, the  FIGS. 3A-D  well plug  20  is described below as it may be used in the system  10  and method of  FIG. 1 , but it should be understood that the well plug may be used in other systems and methods, in keeping with the principles of this disclosure. 
     The  FIGS. 3A-D  well plug  20  example is similar in many respects to the  FIGS. 2A-D  example, but the releasable attachment  38  in the  FIGS. 3A-D  example does not include the shear ring  42  for releasably attaching the setting rod  26  to the mandrel  32 . Instead, the  FIGS. 3A-D  example includes a sleeve  54  that abuts the annular shoulder  48  in the mandrel  32  and is thereby capable of transmitting the setting force SF from the setting rod  26  to the mandrel. 
     The sleeve  54  may be made of a material that is relatively easily drillable or millable, or that is self-degradable or otherwise degradable in the well. Suitable materials for use in the sleeve  54  can include fiber reinforced composite, plastic, phenolic, ceramic (e.g., zirconia, silicon nitride, alumina, cermet), ductile iron, alloy steel, non-ferrous alloys (e.g., brass, aluminum alloys, copper alloys, etc.), and dissolvable materials (e.g., magnesium alloys, aluminum alloys, PGA, PLA, fiber reinforced PGA or PLA, etc.). 
     The sleeve  54  is initially releasably secured to the setting rod  26  with a bond  56  between the sleeve and a surface  58  on or connected to the setting rod, as depicted in the run-in configuration of  FIG. 3A . In this example, the surface  58  is cylindrical and is formed on the fastener  44 , but in other examples the surface could be formed on the setting rod  26  or other structure. 
     An adhesive, thermoplastic or other material may be used for forming the bond  56  between the sleeve and the surface  58 . Preferably, the bond  56  has a consistent shear strength, so that the setting rod  26  is reliably released from the well plug  20  after it is set in the wellbore  12 , as described more fully below. Suitable materials for forming the bond  56  can include one or two part epoxies and cyanoacrylate adhesives, although other materials may be used in keeping with the scope of this disclosure. 
     In  FIG. 3B , the setting force SF is applied from the setting tool  22  (see  FIG. 1 ) to the well plug  20  via the setting rod  26 . The bond  56  between the surface  58  and the sleeve  54  permits the setting force SF to be transmitted from the setting rod  26  to the mandrel  32 , so that the seal element  30  and slips  36  extend radially outward into sealing and gripping engagement with the wellbore  12 . The setting force SF is applied as a shear force in the bond  56 . 
     In  FIG. 3C , the bond  56  between the sleeve  54  and the surface  58  is sheared when the setting force SF reaches the predetermined level. At this point, the well plug  20  is set in the wellbore  12  and the setting rod  26  is released from the well plug for retrieval. The sleeve  54  may be press-fit bonded, fastened or otherwise attached to the mandrel  32 , so that it does not become loose debris in the wellbore  12  after the bond  56  is sheared. 
     In  FIG. 3D , the setting rod  26  is withdrawn from the well plug  20 . As described above for the  FIGS. 2A-D  example, a ball, dart or other plug device (not shown) may subsequently engage the seat  52  to seal off the flow passage  50 . The well plug  20  may eventually be drilled or milled through, dissolved, dispersed or degraded downhole, or otherwise removed from its sealing and gripping engagement in the wellbore  12 . 
     It may now be fully appreciated that the above disclosure provides significant advancement to the arts of designing, constructing and utilizing well plugs. In examples described above, the releasable attachment  38  allows the setting rod  26  to be conveniently and economically attached to the well plug  20 , while also providing for consistent release at a predetermined setting force SF level, and minimizing debris left behind in the wellbore  12 . 
     A well plug  20  for use in a subterranean well is provided to the art by the above disclosure. In one example, the well plug  20  can include a generally tubular mandrel  32 , a seal element  30  positioned on the mandrel  32 , and a setting rod  26  releasably secured relative to the mandrel  32  by an annular shaped shear ring  42 . The setting rod  26  is releasable for longitudinal displacement relative to the mandrel  32  in response to a predetermined shear force SF applied to the shear ring  42 . 
     The shear ring  42  may be positioned longitudinally between a first annular shoulder  46  that displaces with the setting rod  26 , and a second annular shoulder  48  that displaces with the mandrel  32 . The first annular shoulder  46  may be formed on a fastener  44  that secures the shear ring  42  to the setting rod  26 . The second annular shoulder  48  may be formed in the mandrel  32 . 
     The seal element  30  may be positioned between first and second structures (such as, the wedges  40 ), and the seal element  30  may be outwardly extendable in response to a decrease in a longitudinal distance between the first and second structures  40 . The first structure  40  may displace with the mandrel  32 . 
     The predetermined shear force SF may be transmitted from the setting rod  26  to the mandrel  32  via the shear ring  42 . 
     Another example of a well plug  20  is provided to the art by the above disclosure. In this example, the well tool  20  can include a generally tubular mandrel  32 , a seal element  30  positioned on the mandrel  32 , and a setting rod  26  releasably secured relative to the mandrel  32  by a sleeve  54  bonded to a surface  58 , the setting rod  26  being releasable for longitudinal displacement relative to the mandrel  32  in response to a predetermined shear force applied to the sleeve  54 . 
     The surface  58  may be formed on a structure (such as, the fastener  44 ) that displaces with the setting rod  26 . 
     The sleeve  58  may engage an annular shoulder  48  formed on the mandrel  32 . 
     The sleeve  58  may be bonded to the surface  58  by an adhesive. 
     The predetermined shear force SF may be transmitted from the setting rod  26  to the mandrel  32  via the sleeve  54 . 
     A method of setting a well plug  20  in a subterranean well is also provided to the art by the above specification. In one example, the method can comprise: displacing a generally tubular mandrel  32  with a setting rod  26  relative to an outer housing  28  of the well plug  20 ; outwardly extending a seal element  30  of the well plug  20  in response to the displacing; and shearing a releasable attachment  38  securing the setting rod  26  relative to the mandrel  32 , the releasable attachment  38  comprising one of the group consisting of: a) an annular shaped shear ring  42  and b) a bond  56  between a sleeve  54  and a surface  58 . 
     The shearing step may include shearing the shear ring  42  between annular shaped shoulders  46 ,  48 . The shearing step may further include releasing the setting rod  26  for displacement relative to the mandrel  32  in response to a predetermined shear force SF being applied to the shear ring  42 . One of the annular shoulders  46  may displace with the setting rod  26 , and another annular shoulder  48  may displace with the mandrel  32 . 
     The shearing step may include displacing the surface  58  with the setting rod  26  relative to the mandrel  32 . The sleeve  54  may abut an annular shoulder  48  formed in the mandrel  32 . 
     Although various examples have been described above, with each example having certain features, it should be understood that it is not necessary for a particular feature of one example to be used exclusively with that example. Instead, any of the features described above and/or depicted in the drawings can be combined with any of the examples, in addition to or in substitution for any of the other features of those examples. One example&#39;s features are not mutually exclusive to another example&#39;s features. Instead, the scope of this disclosure encompasses any combination of any of the features. 
     Although each example described above includes a certain combination of features, it should be understood that it is not necessary for all features of an example to be used. Instead, any of the features described above can be used, without any other particular feature or features also being used. 
     It should be understood that the various embodiments described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of this disclosure. The embodiments are described merely as examples of useful applications of the principles of the disclosure, which is not limited to any specific details of these embodiments. 
     In the above description of the representative examples, directional terms (such as “above,” “below,” “upper,” “lower,” “upward,” “downward,” etc.) are used for convenience in referring to the accompanying drawings. However, it should be clearly understood that the scope of this disclosure is not limited to any particular directions described herein. 
     The terms “including,” “includes,” “comprising,” “comprises,” and similar terms are used in a non-limiting sense in this specification. For example, if a system, method, apparatus, device, etc., is described as “including” a certain feature or element, the system, method, apparatus, device, etc., can include that feature or element, and can also include other features or elements. Similarly, the term “comprises” is considered to mean “comprises, but is not limited to.” 
     Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the disclosure, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to the specific embodiments, and such changes are contemplated by the principles of this disclosure. For example, structures disclosed as being separately formed can, in other examples, be integrally formed and vice versa. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the invention being limited solely by the appended claims and their equivalents.