Abstract:
A plunger for well casings and other tubulars comprising: An elongate body having a flow passage with a lower inlet port and an upper outlet port; an internal valve positioned between the ports; at least one first flexible sealing member positioned around the body below the outlet port; an actuator which urges the first sealing member against the interior wall of the casing when the valve is closed; at least one second flexible sealing member positioned around the body and providing an outwardly expandable sealing chamber; and at least one flow port positioned below the valve and providing fluid communication between the flow passage and the sealed chamber. The second flexible sealing member(s) being outwardly expandable by increasing pressure in the sealed chamber.

Description:
FIELD OF THE INVENTION 
     The present invention relates to plungers operable for lifting fluids in well casings or other tubulars from subterranean formations. 
     BACKGROUND OF THE INVENTION 
     Various types of casing plungers have been used heretofore for lifting and recovering or removing oil, water, or other fluids from well casings. In some wells, due to relatively low formation pressures and/or other formation conditions, liquids tend to accumulate at some level in the well casing rather than flowing naturally out of the well. Casing plungers offer potential benefits over conventional pumps, submersible pumps, and other power operated devices for recovering or removing such fluids. 
     One type of casing plunger currently available comprises: an elongate housing assembly; one or more external sealing devices which project from the housing and sealingly contact the well casing as the plunger travels up and down in the well; a flow passage extending through the assembly and having openings below and above the external seal(s); and a valve assembly for opening and closing the flow passage. 
     In a typical production cycle wherein a casing plunger is used to recover or remove accumulated liquids from a well casing, the plunger is dropped from the upper end of the well casing with the plunger valve in open position. The fluid accumulated in the casing will thus flow internally through the housing flow passage so that the plunger will fall to a desired downhole position. The desired downhole position can be set, for example, by placing a stop structure in the well casing. 
     Upon reaching the desired downhole position, the plunger valve typically will close so that the plunger will effectively seal the casing. As formation gas builds beneath the sealed plunger, the pressure beneath the plunger increases. Eventually, the pressure beneath the plunger will increase to the point that the plunger will begin to rise in the casing, thus lifting the column of fluid on top of the plunger toward the surface and into an overhead product line. Upon reaching the top of the well, the plunger valve opens so that the pressure beneath the plunger is released and the plunger is ready for another production cycle. 
     Unfortunately, the casing plunger devices heretofore known in the art have had significant shortcomings. As indicated, for example, in U.S. Pat. No. 4,923,372, external elastomeric-type sealing elements are particularly desirable for sealing the gap between the plunger housing and the interior wall of the well casing. However, the continuous contact of the elastomeric seal with the casing wall as the plunger travels up and down in the well casing can cause the elastomeric seals to wear very rapidly, thus requiring frequent repair and replacement and sometimes resulting in valve failure. Alternatively, other prior art devices employ sealing elements which are mechanically engaged with the well casing as the plunger moves upward within the well but are supposed to be mechanically disengaged from the casing wall as the plunger falls downward. In practice, however, these devices typically bounce against the interior wall of the casing as they fall through the well, thus causing significant wear and damage to the exterior components of the plunger. 
     SUMMARY OF THE INVENTION 
     The present invention provides a plunger for well casings and other tubulars which satisfies the needs and alleviates the problems discussed above. In one aspect, the inventive plunger comprises: a body having a flow passage, the flow passage having at least one inlet port and at least one outlet port positioned above the inlet port; a valve positioned in the flow passage (preferably in the upper portion of the tool) between the outlet port and the inlet port; a flexible sealing member retained around the body; and an actuator engaging the flexible sealing member such that, when the valve is closed, the actuator will urge the flexible sealing against the interior wall of the well casing. 
     In another aspect, the inventive plunger comprises: an elongate body having a flow passage, the flow passage having at least one inlet port and at least one outlet port positioned above the inlet port; a valve positioned in the flow passage between the outlet port and the inlet port; a first flexible sealing member positioned around the body below the outlet port; an actuator operably linked to the flexible sealing member such that, when the valve is closed, the actuator will cause the flexible sealing member to contact and seal against the well casing; a second flexible sealing member positioned around the body and providing an outwardly expandable sealed chamber around the body; and at least one flow port, positioned below the valve, providing fluid communication between the flow passage and the sealed chamber. The second flexible sealing member is outwardly expandable by increasing pressure in the sealed chamber such that the second flexible member will contact and seal against the well casing. 
     Further objects, features, and advantages of the present invention will be apparent to those skilled in the art upon examining the accompanying drawings and upon reading the following description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cutaway elevational side view of one embodiment of the inventive casing plunger. 
     FIG. 2 is an exploded, cutaway elevational side view of the inventive plunger. 
     FIG. 3 is a plan view of a shift spider element  23  employed in the inventive plunger. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the inventive casing plunger is depicted in FIGS. 1-3. The inventive plunger comprises: an elongate body assembly  50 ; an elongate valve rod  1  slidably extending through body assembly  50 ; a flow channel  52  extending through the interior of body assembly  50 ; a valve element  5  (e.g., a spherical valve element, a conical element, a combination spherical and conical element, or other type of valve element) secured to valve rod  1  and positioned within flow channel  52 ; a valve seat ring  6  retained within flow channel  52  and sized and shaped for receiving valve element  5  to thereby close flow channel  52 ; one or more inlet flow ports  26  extending from the lower end of flow channel  52  through the lower end portion of body assembly  50 ; one or more outlet flow ports  4  positioned above valve seat  6  and extending from the upper end of flow channel  52  through the upper portion of body assembly  50 ; an upper elastomeric sealing cup assembly  54  secured on the exterior of body assembly  50  at a position spaced below outlet flow ports  4  and valve seat  6 ; a lower elastomeric sealing cup assembly  56  secured on the exterior of body assembly  50  below upper sealing cup assembly  54 ; a plurality of optional bow-type centralizer drag springs  11  projecting from body assembly  50  above upper sealing cup assembly  54 ; a plurality of optional bow-type centralizer drag springs  36  projecting from body assembly  50  beneath lower sealing cup assembly  56 ; and an actuating mechanism  74  for actuating lower sealing cup assembly  56  as valve rod  1  moves valve  5  to its closed position. 
     Elongate body assembly  50  comprises: an upper cap  2  having outlet flow port(s)  4  formed therethrough and an upper fishing neck  42 ; a body adaptor  9  threadedly connected to the lower end portion of upper cap  2 ; a set screw  7  for locking the threaded connection between body adaptor  9  and upper cap  2 ; a body tube  12  threadedly secured to the lower end portion of body adaptor  9 ; a set screw  93  locking the threaded connection between body tube  12  and body adaptor  9 ; a lower shoe  27  threadedly attached to the lower end portion of body tube  12  and having lower flow port(s)  26  formed therethrough; and a set screw  94  for locking the threaded connection between lower shoe  27  and body tube  12 . 
     The fishing neck  42  of upper cap  2  has a central bore  58  formed therethrough for guiding the sliding movement of valve rod  1 . A central hole  68  is also provided through the bottom of lower shoe  27  for guiding the sliding movement of valve rod  1 . Internal valve seat  6  is clamped between the upper end of body adaptor  9  and an interior radial shoulder  60  formed in upper cap  2 . The lower end of upper cap  2  is positioned adjacent to an exterior radial shoulder formed on body adaptor  9  to thereby provide an external slot  8  extending around the inventive plunger. As discussed hereinbelow, slot  8  is a catcher slot used for holding and launching the inventive device. 
     Longitudinal recess grooves  64  are formed in the exterior of body adaptor  9  for receiving upper bow springs  11 . Bow springs  11  are retained in recess grooves  64  by machine screws  10 . In the same manner, lower bow springs  36  are retained by machine screws  37  in longitudinal recess grooves  66  formed in lower shoe  27 . 
     The upper sealing cup assembly  54  preferably comprises: at least one elastomeric sealing cup  13  having an upper collar  70  which is positioned around body tube  12 ; an upper cup thimble  89  positioned around body tube  12  for receiving the collar  70  of sealing cup  13  and which abuts the lower end of body adaptor  9 ; a seal-retaining ring  16 , positioned around an upper spacer sleeve  17  provided over body tube  12 , for retaining the lower circular end of sealing cup  13 ; a clamp ring  14  which sealingly secures the lower end of cup  13  to retaining ring  16 ; and an O-ring or other sealing member  28  for sealing retaining ring  16  around upper spacer sleeve  17 . The sealing of the lower circular end of sealing cup  13  by retaining ring  16 , clamp ring  14 , and O-ring  28  results in the formation of a sealed pressure chamber  29  within sealing cup  13 . 
     In a manner similar to upper sealing cup assembly  54 , the lower sealing cup assembly  56  preferably comprises: at least one elastomeric sealing cup  30  having an upper collar  72 ; a lower cup thimble  91  which receives the collar  72  of sealing cup  30  and abuts against the lower end of upper spacer sleeve  17 ; a retaining ring  32  for retaining the lower circular end of cup  30  around body tube  12 ; and a clamp ring  43  for securing the lower end of sealing cup  30  to retaining ring  32 . 
     In addition to upper spacer sleeve  17 , the inventive plunger preferably includes a lower spacer sleeve  24 . Upper spacer sleeve  17  is positioned around body tube  12  within upper cup retaining ring  16  and extends from the upper end of lower cup collar  72  to the lower end of upper cup collar  70 . Lower spacer sleeve  24  is positioned around body tube  12  within lower cup retaining ring  32  and extends from the upper end of lower shoe  27  to the lower end of the collar  72  of lower sealing cup  30 . Thus, when lower shoe  27  is securely attached to body tube  12 , upper sleeve  17  and lower sleeve  24  act to clamp the collars  70  and  72  of elastomeric cups  13  and  30 . The compression of the elastomeric cups by spacer sleeves  17  and  24  is effective to seal the upper ends of cups  13  and  30  around body tube  12  and to seal the ends of spacer sleeves  17  and  24 . The inventive plunger preferably further comprises an upper retaining ring stop sleeve  90  positioned between upper cup retaining ring  16  and lower thimble  91  and a lower stop sleeve  92  positioned between retaining ring  32  and lower shoe  27 . 
     One or more apertures  65  provided in upper spacer sleeve  17  are sized and positioned to align with corresponding ports  15  formed through body tube  12  to thereby provide lateral fluid passages from interior flow channel  52  to the pressure chamber  29  provided beneath upper elastomeric cup  13 . 
     The actuating mechanism  74  for automatically engaging and releasing lower sealing cup  30  preferably comprises: a shift spider  23  positioned in flow channel  52  and retained on valve rod  1  between an upper valve opening spring  19  and a lower actuating spring  25 ; a spring collar  18  and a snap ring or other locking device  34  which retain the upper end of opening spring  19  on valve rod  1 ; a spring collar  33  and snap ring  35  which retain the lower end of actuating spring on valve rod  1 ; a spiral wound retaining ring  20  positioned within an interior groove formed in lower cup retaining ring  32 ; and a plurality of screws  21  extending through a bushing  22  from the internal shift spider  23  to exterior retaining ring  32  via a corresponding number of longitudinal slots  31  formed through body tube  12  and through lower spacer sleeve  24 . 
     As will be understood by those skilled in the art, the inventive plunger can be retained at the top end of the well casing by a lubricator assembly (not shown) or other structure having a catch mechanism receivable in the external catcher slot  8  of the inventive device. When the inventive plunger is positioned at the top of the well at the beginning of the production cycle, the valve element  5  of the inventive device is retained in the open position depicted in FIG. 1 by detent screws  3  extending radially into the neck  42  of upper cap  2 . Detent screws  3  are releasably received in a groove  78  formed in the upper end portion of valve rod  1 . When valve  5  and valve rod  1  are secured in the open position depicted in FIG. 1, the lower end  80  of valve rod  1  projects from the bottom opening  68  of lower shoe  27 . 
     When released by the catch mechanism, the inventive plunger will fall downwardly through the well casing. Drag springs  11  and  36  slide against the interior wall of the casing, slow the descent of the plunger, and guide and center the inventive plunger as it falls such that the plunger does not bounce against the interior wall of the casing. Although not essential, the outside diameters of sealing cups  13  and  30  are preferably not greater than, and are more preferably less than, the inside diameter of the well casing such that no significant wear of the sealing cups will occur as the inventive plunger falls through the casing. When the plunger reaches the column of liquid which has accumulated within the casing, the liquid flows through the internal flow channel  52  and through valve seat  6  of the plunger so that the plunger will continue to fall through the casing. 
     The downward travel of the inventive plunger continues until the plunger reaches a downhole stop structure (not shown) secured at a desired downhole position within the casing. As the inventive plunger travels downwardly, the protruding lower end  80  of valve rod  1  will eventually strike the downhole stop structure. At the same time, the weight and downward momentum of the plunger body assembly  50  will force valve rod  1  to slide upwardly within the body assembly, thus disengaging the detent screws  3  from detent groove  88  and causing valve element  5  to seal against valve seat  6 . Valve rod  1  also carries shift spider  23 , actuation screws  21 , and the clamp ring  43  of lower sealing cup assembly  56  upward such that lower elastomeric cup  30  deflects outwardly and seals against the interior wall of the casing. To assist in holding valve element  5  in engagement with valve seat  6  until sufficient pressure builds beneath the plunger to keep the valve closed, additional detent screws  85  are provided in the neck  42  of upper cap  2  for releasable engagement with a second groove  87  formed around valve rod  1 . 
     When the valve element  5  is closed and the lower sealing cup  30  is flexed outwardly in sealing position, the inventive plunger effectively seals the casing and blocks all upward flow. Consequently, formation gas pressure within the sealed interior of the plunger and in pressure chamber  29  will increase such that upper elastomeric sealing cup  13  is also eventually caused to expand outwardly and seal against the interior wall of the casing. Internal pressure also assists in holding and sealing lower cup  30  against the casing wall. 
     As the gas pressure beneath the inventive plunger continues to increase, the plunger is eventually forced to rise within the casing, thus lifting the column of fluid above the plunger and forcing it toward the surface and into an overhead product line (not shown). When traveling upwardly through the well casing with valve element  5  and valve rod  1  in their closed positions, the upper end of valve rod  1  projects from the top opening of upper cap  2 . When the plunger eventually reaches the lubricator assembly at the top of the well, the protruding upper end of valve rod  1  strikes the lubricator such that valve rod  1  and spherical valve element  5  are returned to the open positions depicted in FIG.  1 . As the valve opens, the gas accumulated beneath the plunger is allowed to flow through the plunger flow channel  52  and into the overhead product line. At the same time, actuating mechanism  74  releases the lower elastomeric sealing cup  30  and the sealing pressure within upper sealing cup  13  is released. Thus, the plunger is returned to its original open position and is ready for another cycle through the well casing. 
     Thus, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those skilled in the art. Such changes and modifications are encompassed within the spirit of this invention as defined by the appended claims.