Patent Publication Number: US-11021922-B2

Title: Locking collar stop

Description:
FIELD OF THE INVENTION 
     The present application generally relates to a plunger lift systems used to produce hydrocarbon wells. More specifically, a locking collar stop is provided that may define a bottom of a plunger well where a seating nipple is not utilized. 
     BACKGROUND 
     Well bores of oil and gas wells extend from the surface to permeable subterranean formations (‘reservoirs’) containing hydrocarbons. These well bores are drilled in the ground to a desired depth and may include horizontal sections as well as vertical sections. In any arrangement, piping (e.g., steel), known as casing, is inserted into the well bore. The casing may have differing diameters at different intervals within the well bore and these various intervals of casing may be cemented in-place. Other portions (e.g., within producing formations) may not be cemented in place and/or include perforations to allow hydrocarbons to enter into the casing. Alternatively, the casing may not extend into the production formation (e.g., open-hole completion). 
     Disposed within a well casing is a string of production piping/tubing, which has a diameter that is less than the diameter of the well casing. The production tubing may be secured within the well casing via one or more packers, which may provide a seal between the outside of the production piping and the inside of the well casing. The production tubing provides a continuous bore from the production zone to the wellhead through which oil and gas can be produced. 
     The flow of fluids, from the reservoir(s) to the surface, may be facilitated by the accumulated energy within the reservoir itself, that is, without reliance on an external energy source. In such an arrangement, the well is said to be flowing naturally. When an external source of energy is required to flow fluids to the surface the well is said to produce by a means of artificial lifting. One means of artificial lift is plunger lift. A plunger lift system utilizes gas present within the well as a system driver. A plunger lift system works by cycling a plunger into and out of the production tubing of the well. During a cycle, a plunger typically descends through the tubing to the bottom of a well passing through fluids within the well. Once the liquids are above the plunger, these liquids may be picked up or lifted by the plunger and brought to the surface, thus removing most or all liquids in the production tubing. The gas below the plunger will push both the plunger and the liquid on top of the plunger to the surface completing the plunger cycle. In some instances, plunger lift may be combined with gas lift where air/gas is injected into the production tubing to reduce the hydrostatic pressure within the tubing. 
     SUMMARY 
     Disclosed herein is a collar stop configured for insertion into well production tubing where the collar stop provides an interference fit with a collar recess disposed between two adjacent sections of production tubing. The collar stop may be utilized to provide a bottom hole assembly at a desired location in a well bore. The collar stop device is configured to lock once positioned. Such locking prevents accidental removal during high fluid flows. 
     In an arrangement, the collar stop is a generally cylindrical device configured for disposition within production tubing. The collar stop includes a mandrel body and a casing engagement body. The casing engagement body forms a lower portion of the device and incudes an upper end having a central aperture. As used herein, upper and lower define portions of the device as located in a vertical section of production tubing. In an embodiment, the upper end is an annular ring having an internal opening (e.g., central aperture) extending therethrough. At least first and second legs or arms extend (e.g., cantilever) downwardly from generally opposing edges of the upper end (e.g., annular ring). Outside surface of each arm include a casing engagement tab configured for receipt in a collar recess between adjacent section of production tubing. Such engagement tabs are typically located proximate to a free end of each arm. 
     A mandrel body slidably engages the casing engagement body. In an arrangement, the mandrel body includes upper and lower mandrels connected by an axial rod, which passes through the central aperture in the upper end of the casing engagement body. The lower mandrel is disposed between the arms of the casing engagement body while the upper mandrel is disposed above the upper end of the casing engagement body. The mandrel body is configured to move relative to the casing engagement body between a lower surface of the upper mandrel and an upper surface of the lower mandrel. 
     A mechanical connector is configured to lock the mandrel body in a lowered or closed position where the upper mandrel is disposed proximate to the upper end of the casing engagement body. In an arrangement, the mechanical connector is a two-piece connector having a first piece (e.g., first connector) attached to an upper portion of the mandrel body and a second piece (e.g., second connector) attached to the upper end of the casing engagement body. When the upper mandrel is disposed (e.g., compressed) towards the upper end of the casing engagement body, the first and second connectors mechanically engage locking the mandrel body in the lowered position. Any mechanical connector may be utilized. 
     In one aspect, a first connector is attached to the axial rod proximate to a connection point between the upper mandrel and the axial rod. In an arrangement, the first connector is a split ring connector that fits over the axial rod. In such an arrangement, split ring connector has a generally cylindrical body with a hollow interior and a split/slit extending along the entire length of its sidewall. An outside surface of the split ring connector may include a plurality of serrations (e.g., annular ridges and valleys). Such serrations may be configured to engage a plurality of mating grooves (e.g., annular ridges and valleys) formed in the central aperture of the upper end of the casing engagement body. An inside diameter of the split ring connector may have a diameter that is greater than an outside diameter of the axial rod. This increased diameter permits the split ring connector to compress when the serrations engage the grooves in the upper end (e.g., about the periphery of the central aperture) of the casing engagement body. This allows the serrations to pass over at least a portion of the grooves locking the mandrel body to the casing engagement body. The serrations and grooves may be configured to permit unidirectional movement. In a further arrangement, the first connector includes a plurality of serrations integrally formed on an outside surface of the axial rod. In this arrangement, the serrations of the axial rod engage a plurality of grooves formed in the central aperture of the upper end of the casing engagement body. In such an arrangement, a split ring connector may be disposed within the central aperture. Alternatively, the central aperture may include an axial slot to permit the central aperture to flex when engaged by the serrations of the axial rod. 
     In an arrangement, the split ring connector is attached to the axial rod via a shear pin. Such a shear pin permits separating the axial rod form the split ring connector when an axial force is applied to the upper mandrel (e.g., by a wireline device). This allows removing the collar stop from the production tubing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a production tubing is disposed within a casing of an oil and gas well. 
         FIG. 2A  is a perspective view of a prior art collar stop. 
         FIGS. 2B-2D  illustrate the operation and installation of the collar stop of  FIG. 2A . 
         FIG. 3A  is a perspective view of a locking collar stop in accordance with the present disclosure. 
         FIG. 3B  is an exploded view of the collar stop of  FIG. 3A . 
         FIGS. 4A and 4B  show side and side cross-sectional views, respectively, of a collar stop in an open position. 
         FIG. 4C  shows a side cross-sectional view of a collar stop in a closed and locked position. 
         FIG. 5  shows a perspective view of a two-piece connector for locking the collar stop in a closed position. 
         FIG. 6  shows a close up view of the two-piece connector locking the collar stop in the closed position. 
         FIG. 7  illustrates an alternate embodiment of a locking collar stop in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the accompanying drawings, which at least assist in illustrating the various pertinent features of the presented inventions. The following description is presented for purposes of illustration and description and is not intended to limit the inventions to the forms disclosed herein. Consequently, variations and modifications commensurate with the following teachings, and skill and knowledge of the relevant art, are within the scope of the presented inventions. The embodiments described herein are further intended to explain the best modes known of practicing the inventions and to enable others skilled in the art to utilize the inventions in such, or other embodiments and with various modifications required by the particular application(s) or use(s) of the presented inventions. 
     A typical installation plunger lift system  50  can be seen in  FIG. 1 . The system includes what is termed a lubricator assembly  10  disposed on the surface above a well bore including casing  8  and production tubing  9 . The lubricator assembly  10  is operative to receive a plunger  100  from the production tubing  9  and release the plunger  100  into the production tubing  9  to remove fluids (e.g., liquids) from the well. Fluid accumulating above of the plunger  100  at the bottom of the well may be carried to the top of the well by the plunger  100 . Specifically, after passing through the liquids at the bottom of the well, gasses accumulate under the plunger lifting the plunger and any fluid above the plunger to the surface. The lubricator assembly  10  controls the cycling of the plunger into and out of the well. The exemplary lubricator assembly  10  includes a cap  1 , top bumper spring  2 , striking pad  3 , and a receiving tube  4 , which is aligned with the production tubing. When utilized with a bypass plunger, the lubricator may further include a rod  17  that may extend through a plunger received by the lubricator to open a bypass valve or valve element of the plunger. 
     Surface control equipment usually consists of motor valve(s)  14 , sensors  6 , pressure recorders  16 , etc., and an electronic controller  15  which opens and closes the well at the surface. Well flow ‘F’ proceeds downstream when surface controller  15  opens well head flow valves. Controllers operate based on time, or pressure, to open or close the surface valves based on operator-determined requirements for production. Alternatively, controllers may fully automate the production process. 
     In some embodiments, the lubricator assembly  10  contains a plunger auto catching device  5  and/or a plunger sensing device  6 . The sensing device  6  sends a signal to surface controller  15  upon plunger  100  arrival at the top of the well and/or dispatch of the plunger  100  into the well. A master valve  7  allows for opening and closing the well. Typically, the master valve  7  has a full bore opening equal to the production tubing  9  size to allow passage of the plunger  100  there through. The bottom of the well is typically equipped with a seating nipple/tubing stop  12 . A spring standing valve/bottom hole bumper assembly  11  may also be located near the tubing bottom. The bumper assembly or bumper spring is located above the standing valve and can be manufactured as an integral part of the standing valve or as a separate component. 
       FIG. 1  illustrates a plunger lift system  50  as installed in a vertical well where a seating nipple is installed at the bottom of the well. In such an arrangement, the plunger cycles between the bottom hole assembly (e.g., seating nipple and spring) and the lubricator assembly. However, in a number of situations, a seating nipple is not installed or is installed at a location that will not work for plunger lift. For instance, lateral wells have a vertical section that extends from the surface and transitions to a horizontal section. Typically, plungers can only fall to about 40-60 degrees from vertical. Nonetheless, such lateral wells can benefit from plunger lift. To permit use of plunger lift in lateral wells or in wells lacking a seating nipple, a temporary/removable bottom assembly or ‘collar stop’ may be inserted at a desired location within the well (e.g., in a vertical or mostly vertical section of a lateral well). This collar stop may form a bottom hole assembly at a desired location within the well. 
       FIGS. 2A-2D  illustrates one embodiment of a prior art collar stop  110 . The collar stop  110  is configured for insertion into well production tubing where it provides an interference fit with a collar recess disposed between two adjacent sections of production tubing. As shown in  FIG. 2A , the collar stop  110  is a generally cylindrical device having a mandrel body  112  and a casing engagement body  120 . The mandrel body includes upper and lower mandrels  114 ,  116 , respectively, connected by an axial rod  118 , which is disposed through the casing engagement body  120 . The casing engagement body  120  is configured to engage a casing recess to lock the collar stop in production tubing at a desired location, as further described herein. 
     As shown, the upper mandrel  114  and lower mandrel  116  each have a diameter that is larger than a diameter of the axial rod  118 , which passes through (e.g., is slidably received within) an aperture formed in of a top end of the casing engagement body  120 . In the illustrated embodiment, the top end of the casing engagement body  120  is a generally annular element having a central aperture, which extends there through, and is referred to herein as an ‘annular ring’  122 . However, it will be appreciated that the annular ring  122  need not be strictly annular in shape. What is important is that the annular ring  122  forms an upper or top end of the casing engagement body and includes an aperture (e.g., central aperture) for slidably receiving the axial rod  118  of the mandrel body  112 . Diameters of the upper mandrel  114  and lower mandrel  116  are larger than the diameter of the central aperture extending through the annular ring  122 . Accordingly, once the axial rod  118  is disposed through the central aperture of the annular ring  120 , the mandrel body  112  may slide through the annular ring  120  between a bottom end  115  of the upper mandrel  114  and an upper end  117  of the lower mandrel  116 . That is, the mandrel body  112  moves relative to the casing engagement body  120 . 
     The casing engagement body  120  further includes first and second legs or arms  124   a ,  124   b  (hereafter  124  unless specifically referenced) that extend from a lower end of the annular ring  122 . That is, the arms  124  cantilever from the lower end of the annular ring  122 . The lower mandrel  116  is disposed between the inside surfaces of the arms  124 . Disposed proximate to the free end of each of the arms  124  on their outside surfaces are casing engagement tabs  126   a ,  126   b  (hereafter  126  unless specifically referenced). Also attached to lower end of each arm  124  are tripwires  128   a ,  128   b  (hereafter  128  unless specifically referenced). The tripwires  128  are configured to hold the arms  124  toward one another when the arms are deflected to permit inserting the collar stop  110  into production tubing. More specifically, the tripwires are pivotally attached near the free ends of the arms  124  and configured to hold the free ends of the arms  124  toward one another (See  FIGS. 2A and 2B ), in a first position, and release the free ends of the arms  124  (See.  FIG. 2C ), in a second position. 
     When the tripwires  128  hold the free ends of the arms  124  together, an outward diameter measured between opposing outside surfaces of the casing engagement tabs  126  is reduced to a dimension that is less than an inside diameter of production tubing in which the collar stop  110  is inserted. This allows lowering the collar stop  110  downward through production tubing. Along these lines, the upper mandrel  114  may include a fishing neck  108 , which may comprise a standard American Petroleum Institute (API) fishing neck. The fishing neck  108  may be engaged by a wireline device (not shown), as known by those skilled in the art. The wireline lowers the collar stop through the production tubing to a desired location while the tripwires  128  hold the free ends of the arms  124  toward one another/together. Once lowered to a desired depth, the wireline raises the collar stop  110  until free ends  129  of the tripwires  128  engage a collar recess between adjacent joints of production tubing. That is, when pulled upward, the tripwires snag on a collar recess  140  formed by a collar  144  connecting adjacent sections of production tubing  146 . See, e.g.,  FIG. 2D . This releases the tripwires freeing the arms  124 , which expand outward. The collar stop  110  may then be raised or lowered until the casing engagement tabs  126  encounter the collar recess  140 . See  FIG. 2D . The cantilevered arms  124  press the engagement tabs  126  into the recess  140 . 
     Once the engagement tabs  126  are engaged with the collar recess  140 , the mandrel body  112  is pushed downward until the lower mandrel  116  is positioned between lower portions of the arms  124 , which prevents the arms from flexing inward. See  FIG. 2D . This locks the casing engagement tabs  126  in the collar recess  140 . To maintain the mandrel body  112  in the lowered position (See  FIG. 2D ), the lower mandrel  116  is pushed downward until its upper end  117  is disposed below locking tabs  130   a ,  130   b  formed in the inside surfaces of the arms  124 . This engagement helps maintain the mandrel body  112  in the lowered position and maintains the collar stop  110  in place. Once secured in position, the upper end of the collar stop  110 , may then support other components (e.g., bumper springs etc.). Such components may engage the fishing neck to secure them to the collar stop  110 . Of further note, the mandrel body  112  includes an axial passageway  106  that permits well fluids to pass through the collar stop  110 , when secured within the production tubing. 
     The collar stop  110  may be removed by engaging the fishing neck  108  and lifting the mandrel body  112 . This removes the lower mandrel  116  from behind the arms  124  permitting the arms  124  to flex such that the engagement tabs  126  may move inward and out of the collar recess  140  disengaging the collar stop  110  from the collar recess. The collar stop may then be lifted to the surface. 
     Aspects of the present disclosure are based on the realization that in certain wells with high flow rates, the flow of fluids through the axial passageway  106  of the mandrel body  112  tends to dislodge or lift the mandrel body  112  from the lowered position. That is, such high fluid flows move the mandrel body  112  upward releasing the engagement tabs  126  of the casing engagement body  120 . In such situations, high fluid flows lift the collar stop  110  to the surface. To counteract such high flow conditions, the presented collar stop utilizes a locking connector which locks the axial rod  118  of the mandrel body  112  to the annular ring  122  of the casing engagement body  120  when the mandrel body is in the lowered position. 
       FIGS. 3A and 3B  illustrate one embodiment of a locking collar stop  210  in accordance with the present disclosure. As illustrated, the locking collar stop  210  shares numerous component as the prior art collar stop described in relation to  FIGS. 2A-2D  and common reference numbers are utilized to refer to common components. The locking collar stop  210  incudes a mandrel body  112  that moves relative to a casing engagement body  120 . More specifically the mandrel body  112  includes upper and lower mandrels  114 ,  116  connected by an axial rod  118  while the casing engagement body  120  incudes an annular ring  122  having first and second arms  124   a ,  124   b  (hereafter  124  unless specifically referenced) that cantilever from a lower end of the annular ring  122 . The axial rod  118  passes through the annular ring permitting the mandrel body  112  to move relative to the casing engagement body  120 . Likewise, the arms  124  each include casing engagement tabs  126   a ,  126   b  (hereafter  126  unless specifically referenced) on their outside surfaces disposed near their free ends. Tripwires  128   a ,  128   b  (hereafter  128 , specifically referenced) are also attached near the free ends of the arms for use in deflecting and holding the arms  124  toward one another as illustrated in  FIG. 3A . The arms also include locking tabs  130   a ,  130   b  formed their inside surfaces for engaging the upper end of the lower mandrel  116  when the mandrel body  112  is in the lowered position. The locking collar stop  210  is inserted into production tubing in a manner that is substantially similar to the process described in relation to  FIGS. 2B-2D . 
     As best shown in  FIGS. 3A-4B , the locking collar stop  210  further incorporates a locking connector which mechanically engages (e.g., locks) the axial rod  118  of the mandrel body  112  to the annular ring  122  of the casing engagement body  120 , when the mandrel body  112  is in the closed position. In the illustrated embodiment, the locking connector is a two-piece connector having a first connector attached to the mandrel body  112  and a second connector (e.g., mating connector) attached to the casing engagement body  120 . In the illustrated embodiment, the first connector is split ring connector  150  that is disposed about the axial rod  118  proximate to the point of connection between the axial rod  118  and the upper mandrel  114 . As illustrated, the split ring connector  150  is attached to the axial rod  118  via a shear pin  152  that passes through an aperture  154  in a sidewall of the split ring connector  150  and extends into a mating aperture  155  in the axial rod  118 . See  FIG. 3B . In the illustrated embodiment, the second connector is formed within the central aperture of the annular ring  122 , as more fully discussed herein. 
       FIG. 5  shows a close up view of the split ring connector  150  and the mating connector  160  formed within the central aperture  124  of the annular ring. As shown, the split ring connector  150  is a generally cylindrical and hollow element having a sidewall sized to fit over/around an outside surface of the axial rod. The outside surface of the sidewall of the connector  150  has a series of serrations (e.g., annular grooves)  156 . This serrated outside surface (e.g., sawtooth surface) of the split ring connector  150  is configured for receipt within mating serrations  160  (e.g., second connector) formed in the interior surface of the annular ring  122 . That is, the inside peripheral surface of the central aperture  123  includes serrations/grooves  160  that are configured to mate with the serrations  156  on the outside surface of the split ring connector  150 . Of note, the inside diameter ‘ID’ of the connector  150  is slightly larger than the outside diameter ‘OD’ of the axial rod such that the split ring connector  150  may compress slightly. See, e.g.,  FIG. 6 . That is, a split  158  extending along the entire length of a sidewall of the connector  150  allows for slightly compressing the connector  150  around the axial rod. Accordingly, when the connector  150  is forced into the central aperture  123  of the annular ring  122 , the split ring connector  150  may compress such that the serrations  156  on its outside surface may pass over the serrations  160  formed on the inside surface of the annular ring  122 . 
       FIGS. 4A-4C  illustrate the locking collar stop  210  in open and locked configurations. More specifically,  FIGS. 4A and 4B  illustrates a side view and a cross-sectional side view, respectively, of the collar stop  210  in an open configuration while  FIG. 4C  illustrates a cross-sectional side view of the collar stop in a closed and locked configuration. As illustrated, when the mandrel body  112  moves from the open configuration (e.g.,  FIG. 4B ) to the closed configuration (e.g.,  FIG. 4C ) the split ring connector  150  is forced into the central aperture of the annular ring  120  such that the serrations  156  of the connector  150  mate with the serrations  160  of the annular ring  122 . This is best illustrated in  FIG. 6 , which shows a close up of the engagement of the split ring connector  150  and the annular ring  122 . As shown in  FIG. 6 , the serrations  156  and  160  may be shaped to permit unidirectional movement of the split ring connector  150  into the annular ring  122 . Once the serrated surfaces are engaged, the mandrel body  112  is locked in the lowered/closed position. 
     In application, the locking collar stop  210  is positioned in production tubing such that the collar engagement tabs are disposed within a collar recess (See, e.g.,  FIG. 2D ). Once the engagement tabs are engaged with the collar recess, the mandrel body  112  is pushed downward until the lower mandrel  116  is positioned between a lower portion of the arms  124 , which prevents the arms from flexing inward. The force(s) applied to the mandrel body  112  also forces the split ring connector  150  into the aperture of the annular ring  122  locking the collar stop  210  in place. Once locked, the collar stop is able to withstand high fluid flow passing through its axial passageway  106  that tend to dislodge the prior art collar stops. 
     Once the locking collar stop is locked with the split connector engaged with the annular ring, the locking collar stop  210  is highly resistant to removal. However, most collar stops are designed for periodic removal from production tubing. To allow removal of the locking collar stop  210 , the split ring connector is attached to the axial rod via the shear pin  152  (e.g., set screw) that passes through an aperture in a sidewall of the split ring connector  150  and extends into a mating aperture  156  in the axial rod  118 . See.  FIG. 6 . The shear pin  152  is typically formed of a material having a hardness and shear strength that is significantly less that the hardness and shear strength of the axial rod  118  and split ring connector  150 . In a non-limiting embodiment, the shear pin may be formed from brass while the axial rod and split ring connector are formed of steel (e.g., stainless steel). Other materials are possible. To remove the locking collar stop  210 , a wireline attaches to the fishing neck and applies an upward force to the mandrel body. This upward force shears the shear pin freeing the axial rod  118  from the split ring connector  150 . The mandrel body  112  may then be moved upward removing the lower mandrel  116  from behind the arms  124  permitting the arms  124  to flex such that the engagement tabs  126  may move inward out of the collar recess  140  and thereby allowing the locking collar stop  210  to be lifted to the surface. 
       FIG. 7  illustrate another embodiment of a locking collar stop  310  in accordance with the present disclosure. As illustrated, the locking collar stop  310  shares numerous component as the prior art collar stop described in relation to  FIGS. 3A-6  and common reference numbers are utilized to refer to common components. The locking collar stop  310  incudes a mandrel body  112  that moves relative to a casing engagement body  120 . More specifically the mandrel body  112  includes upper and lower mandrels  114 ,  116  connected by an axial rod  118  while the casing engagement body  120  includes an annular ring  122  having first and second arms  124   a ,  124   b  (hereafter  124  unless specifically referenced) that cantilever from a lower end of the annular ring  122 . The axial rod  118  passes through the annular ring permitting the mandrel body  112  to move relative to the casing engagement body  120 . Likewise, the arms  124  each include casing engagement tabs  126   a ,  126   b  (hereafter  126  unless specifically referenced) on their outside surfaces disposed near their free ends. The locking collar stop  310  is inserted into and removed from production tubing as described above. 
     As illustrated, in the embodiment of  FIG. 7 , the upper mandrel  114  further includes a bumper spring  180 . That is, as opposed to the upper mandrel  114  terminating in a fishing neck  108 , the upper mandrel may further include one or more components, such as the bumper spring  180 . In such an embodiment, rather than placing the locking collar stop within production tubing and then utilizing the fishing neck of the locking collar stop to attach one or more components to the locking collar stop, such components may be placed within the production tubing with the collar stop. These components may be integrally formed or otherwise connected to the collar stop. Further, it will be appreciated that various different components may be attached to the upper mandrel. 
     The foregoing description has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the inventions and/or aspects of the inventions to the forms disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and skill and knowledge of the relevant art, are within the scope of the presented inventions. The embodiments described hereinabove are further intended to explain best modes known of practicing the inventions and to enable others skilled in the art to utilize the inventions in such, or other embodiments and with various modifications required by the particular application(s) or use(s) of the presented inventions. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.