Abstract:
A borehole plug or packer for treating is designed to be flowed back to a surface location after use. When the treatment is concluded pressure from above is relieved or lowered, and well fluid is flowed back, so that the plug or plugs disengages at slips designed to resist differential pressure from above. The application of differential pressure from below causes the lower slips to release one or more of such plugs in the hole into specialized sub surface or surface capture equipment so that well pressure is relieved before removal of the plugs from specialized subsurface or surface capture equipment. At least one apparatus is used to bridge transitions in wellbore dimension on the way to the surface and close the gaps to allow produced formation fluid to continue taking a packer or plug past the well diameter transition.

Description:
PRIORITY INFORMATION 
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 15/605,716 filed on May 25, 2017, and a continuation-in-part of U.S. patent application Ser. No. 15/168,658 filed on May 31, 2016 
     
    
     FIELD OF THE INVENTION 
       [0002]    The field of the invention is borehole barriers and more particularly designs that see pressure from above and are retrieved to a surface or subsurface location by lowering pressure from above and flowing uphole through or below the plug above an established flow rate with the aid of an apparatus that bridges a gap to the surrounding tubular wall as the tubular increases in dimension toward a surface location. 
       BACKGROUND OF THE INVENTION 
       [0003]    Borehole plugs are used in a variety of applications for zone isolation. In some applications the differential pressure experienced in the set position can come from opposed directions. These plug typically have a sealing element with mirror image slips above and below the sealing element. The plug is set with a setting tool that creates relative movement between a setting sleeve that is outside the mandrel and the plug mandrel. The slips have wickers oriented in opposed directions and ride out on cones to the surrounding tubular. The sealing element is axially compressed after the first set of slips bite followed by setting of the other set of slips on the opposite side of the sealing element from the first slip set to set. The set position of these elements is maintained by a body lock ring assembly. Body lock ring assemblies are in essence a ratchet device that allows relative movement in one direction and prevents relative movement in the opposite direction. The relative movement that compresses the sealing element and drives the opposed slips out on respective cones is locked by a body lock ring. Body lock rings are threaded inside and out and sit between two relatively movable components. The thread forms are such that ratcheting in one direction only is enabled. A good view of such a design is shown in FIG. 13 of U.S. Pat. No. 7,080,693. The trouble with such a design in applications where the plug needs to be quickly milled out after use such as in treating or fracturing is that the shear loading on the ratcheting patterns is so high that the ratchet teeth break at loads that are well within the needed operating pressure range for the plug. With fracturing pressures going up and the use of readily milled components such as composites a new approach to locking was needed. The goal during treating is to hold the differential pressure from above while keeping the design simple so as not to prolong the milling time for ultimate removal. A typical zone treatment can involve multiple plugs that need to be removed. Elimination of upper slips when using the lock ring of the present invention also shortens milling time. Better yet, milling of the plugs can be avoided by lowering pressure from above to induce flow back from the stage below the targeted plug, until the slips of the plug or series of plugs to disengage and come up to a surface location such as into specialized surface or subsurface equipment where the pressure can be relieved and the plug or plugs safely removed. In some situations the casing or tubular string gets larger as it gets closer to the surface and if the plug or plugs are being flowed to the surface they can slow down or fail to finish the travel to be captured either below or above the wellhead due to a loss of contact with the borehole walls resulting in loss of upward force. In those situations at least one apparatus is used to facilitate not only pumping the plug into position but to also aid the movement of the plug back uphole in wells where the string size increases on the way toward the surface. 
         [0004]    The lock ring is preferably split to ease its movement when axial opposed forces are applied to set the plug. The ring is tapered in cross section to allow it to act as a wedge against reaction force tending to relax the components from the set position. The side of the ring facing the mandrel has a surface treatment that provides minimal resistance in the setting direction and digs into the mandrel to resist reaction forces from the compressed sealing element in the set position. Preferably the surface treatment is a series of extending members oriented downhole with sharp ends that can dig into the mandrel for a firm grip. These and other aspects of the present invention can be better understood by 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. 
         [0005]    Multicomponent body lock rings have been made of easily milled materials such as composites as illustrated in US 2014/0190685; U.S. Pat. No. 8,191,633; U.S. Pat. No. 6,167,963; U.S. Pat. No. 7,036,602; U.S. Pat. No. 8,002,030 and U.S. Pat. No. 7,389,823. The present invention presents a way to avoid milling altogether so that the use of composites that aid milling become an optional feature. This can reduce the cost of each plug in treatments that frequently involve multiple plugs. U.S. Pat. No. 8,240,390 is relevant to packer releasing methods. Wiper plugs typically used in cementing operations are well known and described in the following references: U.S. Pat. Nos. 9,080,422; 7,861,781 and 8,127,846. These plugs typically stay downhole and none are used to aid in plug recovery to the surface using formation pressure. 
       SUMMARY OF THE INVENTION 
       [0006]    A borehole plug or packer for treating is designed to be flowed back to a subsurface or surface location after use. The plug handles differential pressure from above using a lower slip assembly under a sealing element. A setting tool creates relative axial movement of a setting sleeve and a plug mandrel to compress the seal against the surrounding tubular and set the slips moving up a cone against the surrounding tubular to define the set position for the plug. The set position is held by a split lock ring having a wedge or triangular sectional shape and a surface treatment facing the mandrel that slides along the mandrel during setting movement but resists opposed reaction force from the compressed sealing element. The surface treatment can be a series of downhole oriented ridges such as a buttress thread that preferably penetrate the mandrel when holding the set position. When the treatment is concluded pressure from above is relieved or lowered so that the plug or plugs disengage at slips designed to resist differential pressure from above. The application of flow from below causes the slips to release one or more of such plugs in the hole in order to flow uphole into specialized surface or subsurface equipment so that well pressure is relieved before removal of the plugs from the well. To aid the plugs on the way up the borehole in situations where the tubular size increases on the way out of the borehole an apparatus is employed that can enlarge to bridge a growing gap on the way out of the borehole so that the plug velocity with formation pressure can continue to move the flowed plug back to capture equipment above or below the wellhead. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a section view of the plug in the run in position; 
           [0008]      FIG. 2  is a close up view of the lock ring shown in  FIG. 1  and 
           [0009]      FIG. 3  is an exterior view of the plug; 
           [0010]      FIG. 4  is a schematic view of recovery of packers or plugs with net differential pressure; 
           [0011]      FIG. 5  illustrates the use of wipers to bring up plugs where the tubular size increases up the hole; 
           [0012]      FIG. 6  illustrates the use of a single wiper to move multiple plugs up the hole; 
           [0013]      FIG. 7  illustrates using a dedicated wiper for each plug to bring the plugs up the hole; 
           [0014]      FIG. 8  shows a wiper fin design with fins oriented in opposed directions; 
           [0015]      FIG. 9  is the view of  FIG. 8  with the fins in a parallel orientation; 
           [0016]      FIG. 10  is a section view of a wiper peripheral member with a quadrilateral section shape; 
           [0017]      FIG. 11  is a section view of a wiper peripheral member with a circular section shape. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    Referring to  FIG. 1  the plug or packer  10  has a mandrel  12  preferably made of a readily milled material such as a composite. Mandrel  12  can optionally have a passage  13  that can be optionally closed with a ball landed on a seat or with a valve (not shown). Shoulder  14  supports sealing element  16 . A cone  18  has individualized tapered surfaces  20  on which a slip, drag block or other retainer collectively referred to as slip  22  is guided between opposed surfaces  24  and  26 . The slips  22  are each connected to a slip ring  28  that has a triangular undercut  30  when viewed in section in  FIG. 1  that extends for 360 degrees, preferably. The undercut is defined by surfaces  32  and  34  as better seen in  FIG. 2 . The undercut  30  and lock ring  36  may be inverted from the  FIG. 2  position in which case the ribs  56  will be oriented uphole to resist differential pressure in an uphole direction. Lock ring  36  has an outer surface  38  that is preferably parallel to surface  32  of undercut  30 . Bottom surface  40  of ring  36  is contacted by surface  34  of undercut  30  during the setting process. A shear pin or some other breakable member  42  allows the sealing element  16  to be compressed against a surrounding tubular that is not shown before the slips  22  are released to move up ramp surfaces  20  by the breaking of the shear pin  42 . Movement of ring  28  relative to mandrel  12  brings together surfaces  34  and  40  to push the lock ring  36  in tandem with ring  28  during setting with a setting tool that is well known and is not shown and which serves as the force to brace the mandrel  12  while applying compressive force to the sealing element  16  and then extending the slips  22  against the surrounding tubular. The slips  22  have a surface treatment such as wickers  44  that resist reaction force from the compressed sealing element  16  as well as applied pressure loads from uphole applied in the direction of arrow  46 . Because the wickers  44  are designed to hold pressure differential from above they are oriented downhole so that when the flow back rate is significantly increased the wickers  44  will disengage from the surrounding borehole wall, usually a tubular and the plug  10  will come loose. If there is a ball landed on a seat in the plug it may lift off and come uphole or lift and come uphole to seat on the next borehole plug. The flow through the plug will be sufficient to propel that plug into the plug above it, if any, and then further up the hole into specialized surface or subsurface equipment for isolation and depressurization so that the plug or plugs can be removed. 
         [0019]    The lock ring  36  has a surface treatment  48  on bottom surface  50  that faces the mandrel  12 . During setting when the ring  28  takes lock ring  36  with it the surface treatment  48  rides along surface  54  of mandrel  12  without penetration of surface  54 . However, after the set and release from the plug by the setting tool the reaction force from the sealing element  16  causes the downhole oriented ribs  56  to penetrate the surface of the mandrel  12  to brace the lock ring  36  so that it can act as a wedge using surface  38  to prevent motion of ring  28  in the direction of arrow  46 . 
         [0020]    Lock ring  36  can run continuously for nearly 360 with a single split to facilitate assembly to the mandrel  12 . Alternatively, there can be discrete spaced segments for the majority of the 360 degree extent of the undercut  30 . Undercut  30  can be continuous or discontinuous for 360 degrees to retain lock ring  36  when lock ring  36  is formed of discrete segments. The wedging action between surfaces  32  and  38  reduces the stress in an axial direction parallel to surface  54  to discourage shear failure of the ribs  56  while the preferred composite construction of the mandrel  12  encourages penetration through surface  54 . The wedging action creates a radial and axial component forces to the ribs  56  to increase the penetration into the mandrel  12  and to decrease the axial shear force component acting on the ribs  56  at the outer surface of said mandrel  12 . The ribs  56  can be parallel or one or more spiral patterns or a thread form such as a buttress thread. The rib spacing can be equal or variable. The lock ring  36  can preferably be made of composite material or a soft metallic that can be easily drilled. Optionally, if lock ring  36  is a continuous split ring the faces  58  and  60  that define the split can be placed on opposed sides of a tab  62  on mandrel  12  to rotationally lock the two together to prevent lock ring relative rotation with respect to the mandrel  12  when milling out. When segments are used for the lock ring  36  each segment can be rotationally retained in a dedicated undercut  30  in ring  28  to rotationally secure the components when milling out. Alternatively, some or all of the above described plug  10  apart from sealing element  16  can be made of a disintegrating controlled electrolytic material to forgo the milling out altogether. 
         [0021]    Optionally the ribs  56  can be omitted so that bottom surface  50  can make frictional contact with surface  54  with no or minimal penetration so that the retaining force is principally or entirely a frictional contact. Surface  50  can have surface roughening or it can even be smooth. While the ability to hold reaction force may be somewhat decreased without the ribs  50  there is still enough resistance to reaction force to hold the set position for some applications. Wedging action creates the frictional retention force. 
         [0022]      FIG. 4  shows packers  10  still in position and others already displaced by a new uphole force shown schematically as arrow  70 . This condition is normally accomplished by reducing pressure above the set packers  10  from a surface location. When a net uphole force is developed against any of the packers  10  the wickers at some level of net uphole force will no longer be able to retain the grip to the surrounding tubular and the packer  10  will move uphole. It wall pass lower valve  74  of surface or subsurface capture equipment  72  and will be stopped by the upper valve  76 . Once one or more of the packers  10  are in the specialized surface or subsurface capture equipment  72 , the bottom valve  74  is closed and a vent valve  78  is opened and the packers are removed out the top of the specialized surface or subsurface capture equipment  72  through valve  76 . Milling is only needed if one of the packers  10  fails to come to the surface under a net uphole flow from the formation schematically represented by arrow  70 . The specialized surface or subsurface capture equipment  72  can also feature a counter to give a local signal of how many packers  10  have passed into the specialized surface or subsurface capture equipment  72 . As previously stated the orientation of wickers  44  in a downhole direction allows them to function to hold the set of each packer  10  with a net force applied from uphole in a downhole direction such as when performing a treatment. Care must be taken to keep a constant net force in a downhole direction to keep the packer or packers  10  in position. When the treatment ends for the zone the surface pressure is reduced and the grip of the wickers  44  is overcome. The wickers need no radial retraction, they simply give up their grip in the uphole direction as wickers  44  are not oriented to dig in in the uphole direction. This makes the design suitable for treatment where the net pressure is in a downhole direction and later retrieval where the net force on the packer is reversed in direction to bring the packer or packers to the surface. With that the sealing element  16  cannot hold the packer  10  in position and the motion starts uphole into the specialized surface or subsurface capture equipment  72 . The one way oriented wickers  44  allow fixation under a net downhole pressure and retrieval under a net uphole flow. If the packers  10  have a landed object on a seat that closes a passage through the mandrel of a packer  10  it is possible for the object to lift off the seat and then flow through the packer  10  passage as well as the net uphole flow on the mandrel will bring that packer uphole. Bringing up one or more packers can also wipe the borehole of proppant or other solids that may have accumulated in the borehole. Optionally if the borehole has sliding sleeves for zone access, the recovery of the packers  10  with flow from below can also act to close sliding sleeves on the way out of the borehole. One such sliding sleeve  80  is shown adjacent treated formation  82  although multiple such sliding sleeves can be used and operated to close or to open by the passing packers  10  depending on the application. 
         [0023]      FIG. 5  illustrates a horizontal borehole  100  that has a smaller dimension than an upper section  102  with a transition  104  in between. Section  100  can be a liner with a top at transition  104  and the upper section can be casing. Two plugs  106  and  108  are illustrated although more can be used. The plug  106  is backed by wiper  110  and the plug  108  is backed by wiper  112 . Arrow  114  represents a net uphole force on the plugs  106  and  108  sufficient to dislodge their grip to the horizontal borehole after a treatment such as fracturing for example. This condition is typically accomplished by lowering the pressure above the plugs  106  and  108  such as by lowering the pressure above them from the surface for one example. The wipers  110  and  112  move with their respected plugs  106  and  108  out of section  100  and past transition  104  into casing  102 . As that happens the fins  116  oriented uphole and the fins  118  oriented downhole flex to a relaxed position as shown for wiper  110  that has passed the transition  104 . The wipers  110  and  112  each have a mandrel  120  with an open passage  122 . The lowermost wiper is preferably positioned uphole from tow perforations  124 . The wipers  110  and  112  can be delivered with their associated plug so that for example wiper  112  is delivered with plug  108  on a variety of conveyances such as coiled tubing, wireline or slickline. As an alternative to the arrangement in  FIG. 6  a single wiper or multiple stacked wipers  126  can be delivered first ahead of plugs  128 ,  130  and  132  as shown in  FIG. 6  so that a net uphole force represented by arrow  134  can bring up the wiper or wipers  126  with all the plugs above such as  128 ,  130  and  132  although a greater or lesser number of plugs can be retrieved in this manner. The opposed orientation of fins  116  and  118  allows pumping the associated wiper into the hole as well as recovering the associated wiper with a net uphole force from the formation with there being at least some fins in either direction of movement that engage the surrounding borehole wall to aid in the movement of the wiper in question. Note that sealing against the borehole walls of various dimensions on the way up the hole is not critical as long as flow is deterred sufficiently to allow the wiper in question to take up the hole however many plugs are used and that need recovery without a need to drill them out. 
         [0024]    Accordingly, as in  FIG. 7  a wiper  136  can be associated with a plug  138 . A wiper  140  can be associated with plug  142  and a wiper  144  can be associated with plug  146 . Typically the plugs illustrated in  FIG. 7  are identical and can be of the type that receive same sized balls in an uphole direction to close off a passage through them or depending on the treatment they can be straight plugs with no passage through them. Either way whether one wiper per plug is used or one wiper for a plurality of plugs, the goal is to be bring the plugs with the wiper or wipers to a capturing device above or below the wellhead as previously described. 
         [0025]      FIGS. 8-11  illustrate some alternative wiper designs.  FIG. 8  has been previously described and  FIG. 9  varies in that the fins, typically made of a resilient material such as rubber are extending radially perpendicular to the mandrel of the illustrated wiper. The wiper design can simply be a ring around a mandrel that may have a passage through the mandrel. The ring can have a quadrilateral shape as shown in  FIG. 10  or a round shape as shown in  FIG. 11  or triangular to name a few options. The ring may be flexible foam or some other material that can compress without undue resistance when going into a smaller dimension in the borehole and have some shape memory to expand on the way up the hole as the size of the hole increases one or more times. The rings need not be continuous because, as stated before, enough resistance to flow around the wiper is needed to keep the plug or plugs moving uphole at a reasonable speed. 
         [0026]    Typically the well is allowed to come in by opening a valve or valves at the surface to release the plugs so that the plugs with the associated wiper or wipers can come up the hole. The plugs may engage each other on the way up the hole after they are broken loose and start the trip up the hole. As long as there is a perforation for formation access below the lowest wiper, all the plugs and wiper(s) should come up to the capture device as the path of least resistance is toward the surface. 
         [0027]    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. 
         [0028]    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: