Abstract:
A elongated plunger assembly for pressurized, conduit-enclosed travel utilized in recovery of hydrocarbon deposits in a ground penetrating oil or gas well. The plunger comprises an elongated mandrel, a plurality of radially movable curvilinear wear pads circumferentially disposed adjacent each end of the elongated mandrel, a pad-edge retaining housing extending on at least one end of the elongated mandrel to enclosably retain the longitudinally distal end of a circumferential array of wear pads onto the mandrel, and a centrally disposed wear pad securement ring arrangement to permit release of a worn wear pad, replacement of the worn wear pad at an inner longitudinal edge thereof, thus to permit simple field-accessable removal and replacement of any particular “conduit-worn” “wear” pad from the mandrel of the plunger.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This present invention relates to plunger lift systems for oil and gas wells, and more particularly to a gas lift plunger with an improved assembly arrangement, and is re-filing of Ser. No. 12/313,279, and is a continuation-in-part application of Ser. No. 11/715,216 filed on Mar. 7, 2007 now U.S. Pat. No. 7,748,448 and also of Ser. No. 12/217,756 filed on Jul. 8, 2008 now U.S. Pat. No. 7,793,728, which is a continuation of Ser. No. 11/350,367 filed on Feb. 8, 2006, now U.S. Pat. No. 7,395,865 which was based upon Provisional Patent Application 60/593,914, filed 24 Feb. 2005, each of which is incorporated herein by reference in its entirety. 
    
    
     2. Background Art 
     Plunger lift systems are artificial lift systems for use in oil and gas wells. U.S. Pat. No. 6,200,103 to Bender, incorporated herein by reference, discloses a gas lift plunger having a cylindrically elongated plunger body, in which the plunger is utilized to promote efficiency in producing oil and gas wells. However, this type of plunger is a solid body type of plunger which is subject to wear as the plunger moves up and down inside the conduits of the lift systems of the oil and gas wells. 
     The peripheral surface of these plungers provide a pressurized gas seal effect between the travelling plunger and the well&#39;s pipe or tubing in which the plunger travels. Re-building or re-conditioning typical worn prior art plungers is a time consuming process, and is often necessarily done in properly equipped repair shops, often far away from where the oil and gas wells are located, where tools, parts and good manufacturing processes are necessary for proper re-building of those worn plungers. Often, these worn plungers, which are expensive pieces of equipment, are typically just thrown away, wasting material and wasting natural resources. 
     It is an object of the present invention to overcome the disadvantages of the prior art. 
     It is a further object of the present invention, to provide a plunger assembly which may be repaired easily in the field, with minimal tools and equipment, and without wasting time or device components. 
     It is a further object of the present invention to permit the simple repair and/or replacement of one or more of “wear pads” on a “tubing-worn” plunger in the field, as one or more replacement pads may be needed, without having to dis-assemble and re-assemble the entire plunger to do the job. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention comprises a split-pad plunger for use in wells, particularly those wells producing natural gas as the primary hydrocarbon. The split-pad plunger of the present invention is utilized to cyclically travel between the top of the well to the bottom of the well and back, to drive the bulk of the liquid present in its travel conduit, to the surface. The plunger is comprised of an elongated central core or mandrel. The elongated core or mandrel consists of an elongated first half and an elongated second half. Each half is the duplicate of the other half. 
     The elongated mandrel has a central spine with an annular circumferential ring disposed centrally therearound. Each half of the spine or mandrel has two sets of longitudinally spaced-apart radial arrays of standoffs. A cylindrically shaped “retrieval-neck” is arranged longitudinally outwardly of each distalmost annular array of standoffs. Each retrieval neck has a bore extending therein which receives the distal end of the respective central spine or mandrel. A further embodiment contemplates the retrieval neck and the central spine or mandrel manufactured unitarily from for example, a solid casting. 
     An arrangement of curved sealing-surface pads are arranged to be supported on the radially outer end of the radially directed standoffs. The curved sealing-surface pads each have a cutout arranged on its longitudinally directed edges. Each cutout slidingly mates with the radially directed standoffs. A radial bias spring is arranged between the central spine or mandrel adjacent each radially directed standoff. The radial bias springs act to radially outwardly bias the curved sealing surface pads against the inner side of the conduit in which the split-pad plunger travels. The outward radial bias of the sealing-surface pads acts to minimize loss of pressure from the lower side of that conduit during its movement therein. The half retrieval-neck has an annular ring on its inner open end, which ring engages a lip on the distal side of the curved sealing-surface pads, and keeps them secured to the central spine or mandrel at each (outer or respective distal) end of that split-pad plunger arrangement. 
     An arcuately segmented split retainer ring, preferably of semi-circumferential shape, is disposed about the midpoint of the central spine or mandrel, and secures the other or “proximal” longitudinal edge of each curved sealing-surface pad in proper location about the central spine or mandrel. Each split retainer ring itself is held in place around its respective longitudinal mid-portion of the central spine or mandrel by a bolt and elongated manipulable lock washer. 
     That arcuately segmented split retainer ring thus permits easy assembly and disassembly of the respective curved sealing-surface pads from their respective half portions of the central spine or mandrel, as those curved sealing-surface pads have been worn down by frictional engagement with the inside wall of the tubing or conduit in which the plunger travels. Removal of the bolt and lock washer from the arcuately segmented split retainer ring facilitates the simple removal of the retrieval neck from the distal end of each respective curved surface pad. This thus permits the curved surface pads to be removed from their engagement with the radial bias springs, and replaced by new pads right at the “field” site. 
     The invention thus comprises a elongated plunger assembly for pressurized, conduit-enclosed travel utilized in recovery of hydrocarbon deposits in a ground penetrating oil or gas well, comprising: an elongated mandrel, a plurality of radially movable curvilinear pads circumferentially disposed adjacent each end of the elongated mandrel, a pad-edge retaining housing extending on each end of the elongated mandrel to enclosably retain the longitudinally distal end of the pads onto the mandrel, and a centrally disposed pad securement ring arrangement to permit release, and permit re-securement of an axially-inner longitudinal edge of one or more wear pads, thus to permit simple removal and replacement of at least one conduit-worn “wear” pad and/or “tired” bias springs from the mandrel. The curvilinear wear pads are preferably biased radially outwardly by a plurality of the bias spring members extending radially outwardly from the body of the elongated mandrel. The centrally disposed pad securement ring arrangement may be secured to a central ring-ridge by, for example, a releasably controlled bolt member therethrough. A single bolt member preferably secures a semi-circular securement ring to the central ring-ridge. The semi-circular securement ring preferably has an elongated slot for receipt of an elongated lock washer member. The elongated lock washer has, for example, one or more bendable tabs thereon to releasably secure the bolt thereby. 
     The invention also comprises method of replacing worn arcuate outer pads from a plunger assembly used in an oil or gas recovery well operation, comprising one or more of the following steps including: arranging a set of biased outwardly, elongated arcuate pads on an elongated oil/gas well plunger mandrel; securing the respective longitudinally ends of one annular set of the outer elongated arcuate pads to the mandrel by a retrieval neck member screwed onto an end of the mandrel; securing the inwardly directed ends of the one annular set of the outer elongated arcuate pads to the mandrel by a split ring releasably bolted to the mandrel. 
     The split ring preferably comprises a pair of semi-circumferential bands releasably attachable to the mandrel each by a bendable, field accessable lock washer. 
     The elongated plunger assembly may have a releasable lock washer as a visable “spring-capacity” indicator notch thereon to indicator to field repair personnel what capacity springs are being utilized to bias each wear pad outwardly. The wear pad in one preferred embodiment, may have a spiral array of grooves thereon to indicate levels of wear thereon, acting as a “wear indicator” on the pad. Signal generated sensors, such as “circuit-completion” contacts or rf signal generators through a proper buried circuit, or conspicuous visual indicators may also be embedded within the pads or grooves to indicate pad wear. The grooves in the pads also cause the plunger to rotate about its longitudinal axis, to promote “even” wear on those wear pads, (especially in wells with inclined tubing), and also to generate turbulence during the plunger&#39;s travels within the well&#39;s tubing. 
     The invention also may comprise a wear pad retaining housing which comprises a cylindrically shaped shoe on a lower end of the mandrel. The shoe on the lower end of the mandrel may has an array of spiraled flutes thereon to effect rotation of the plunger during its travels in a well. The wear pad retaining housing on the lower end of the mandrel may have an electronic sensor enclosure therein to protect and replaceably enclose a electronic sensor monitoring and control mechanism therein. The releasable lock washer preferably has at least one bendable tab thereon, to releasably secure the bolt thereby. The releasable lock washer preferably has a visable “spring-capacity” indicator thereon to indicate to field repair personnel the “stiffness-capacity” of the springs being utilized to bias each wear pad outwardly. At least one of the wear pads may have a spiral array of grooves thereon to indicate levels of wear thereon, to rotate the plunger and/or and to generate turbulence during the plunger&#39;s travels within the well&#39;s tubing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects and advantages of the present invention will become more apparent, when viewed in conjunction with the following drawings in which; 
         FIG. 1  is an “exploded” perspective view of the split pad-plunger assembly showing details of the construction according to the principles of the present invention; 
         FIG. 2  is a perspective view of the assembly shown at  FIG. 1  in its finished and assembled form; 
         FIG. 3  is a sectional view taken longitudinally along the plunger&#39;s longitudinal axis; 
         FIG. 4  is a side elevational view of the plunger shown in  FIG. 2 ; 
         FIG. 4A  is a side elevational view of the plunger in an alternative embodiment, with a fluted shoe on its lower end; 
         FIG. 5  is a perspective view of the split ring arrangement utilized to support the outer wear pads; 
         FIG. 6  is a cross-sectional view of the split rings taken along the lines  6 - 6  in  FIG. 5 ; and 
         FIG. 7  is a perspective view of the lock washer utilized to lock the securement bolt in place in one of the split rings. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in detail, and particularly to  FIG. 1 , there is shown in an “exploded” view, the present invention which comprises a split-pad plunger assembly  10  for use in wells, particularly those wells producing natural gas as the primary hydrocarbon. The split-pad plunger assembly  10  of the present invention, shown in an assembled embodiment in  FIG. 2 , is utilized to cyclically travel between the top of the well to the bottom of the well and back, to drive the bulk of the liquid present in its travel conduit, to the surface. The plunger assembly  10  is comprised of an elongated central core or mandrel  12 , shown in  FIGS. 1 and 3 . The elongated core or mandrel  12  consists of an elongated first half  14  and an elongated second half  16 . Each half  14  and  16  at least in this preferred embodiment, is preferably the duplicate of the other half  16  and  14 . 
     The elongated mandrel  12  has a mid-portion  18  with an annular circumferential securement ring ridge  20  disposed centrally therearound. Each half  14  and  16  of the spine or mandrel  12  has two sets of longitudinally spaced-apart radial arrays of supports  22 . A cylindrically shaped “retrieval-neck”  24  is arranged longitudinally outwardly of each distalmost annular array of supports  22 . Each retrieval neck  24  may have a bore  26  extending therein which threadedly receives the screw threaded distal end  28  of the respective central spine or mandrel  12 , as is seen in  FIG. 3 , and is represented in  FIG. 1 . In a further embodiment, not shown for ease of viewing, one or both of the retrieval necks  24  are part of a solid casting with the mandrel  18 , and are irremovable therefrom. In yet a further embodiment of the plunger assembly  10 , one of the retrieval necks  24 , herein designated as the “lower” end, for example purposes only, has a protective sensor enclosure  25 , shown in  FIG. 2 , for safely and replaceably enclosing proper wireless communicative electronic sensors and alarms  23 , for sensing well casing pressure, time, distance, fluid composition, viscosity, chemical makeup and the like, and also maintaining report/control functions and/or an antennae for the plunger assembly  10 . Such sensors  23  may be in proper communication with embedded sensors  27  embedded within an array of wear pads  30 , as represented in  FIG. 4A . A further embodiment of the lower retainer ring  24  is represented in  FIG. 4A , wherein a cylindrically shaped “shoe”  41  is utilized to secure the longitudinally outer end of one set of wear pads  30 , the shoe  41  having a plurality of spiraled flutes  43  therein to further effect rotation of the plunger  10  in its vertical/inclined travels within a well. 
     Relative to the “wear functions” of the plunger assembly  10 , an arrangement of for example, four curved sealing-surface pads  30  are circumferentially arranged about each mandrel half  14  and  16 , as represented in  FIGS. 2 and 3 , so as to be radiatively slidingly supported adjacent the radially outer end of each radially directed support  22 . The curved sealing-surface pads  30  each have a cutout  32  arranged on its longitudinally directed edges  34 . Each cutout  32  slidingly mates with the radially directed support  22 . A radial bias spring  36  is arranged between the central spine or mandrel  12  adjacent each radially directed support  22 . The radial bias springs  36  act to radially outwardly bias the curved sealing surface pads  30  against the inner side of the conduit “C” in which the split-pad plunger  10  travels. The outward radial bias of the sealing-surface pads  30  acts to minimize loss of pressure from the lower side of that conduit “C” during movement of the plunger  10  therein. One or more wear pad  30  may have a plurality of spiral grooves  70  thereon as shown in  FIG. 4 , to indicate wear patterns on the pads  30 , to generate rotation of the plunger  10  about its longitudinal axis (for even wear on the pads  30 ), and/or to stimulate turbulence within the well&#39;s tubing “C” during the plunger&#39;s travels therein. Each set of circumferentially adjacent pads  30  on each respective end  14  and  16  of the mandrel  12  have gaps  31  between one another, as may be seen in  FIGS. 1 ,  4  and  4 A. The gaps  31  are not in axial alignment with one another between the pads  30  on each end of the mandrel  12 , as also may be seen in  FIGS. 1 ,  4  and  4 A. Those pads  30 , may in a further embodiment, be of a “spiral” configuration  37  (e.g. curvilinear parallelogram), as represented o  FIG. 4A , to facilitate better wear patterns and rotational motion to the plunger assembly  10 . 
     Each half retrieval-neck  24  has an annular ring  38  on its inner open end, as represented in  FIG. 3 . This ring  38  engages a lip  40  on the distal side of the curved sealing-surface pads  30 , and keeps them secured to the central spine or mandrel  12  at each (outer or respective distal) end of that split-pad plunger  10 , as is represented in  FIG. 3 . 
     An arcuately segmented split retainer ring  50 , preferably of semi-circumferential shape, as represented in  FIGS. 1-6 , is disposed about the mid-point of the central spine or mandrel  12 , and has an annular lip  52  which secures the other or “proximal” longitudinal edge  54  of each curved sealing-surface pad  30  in proper location about the central spine or mandrel  12 . Each set of split retainer rings  50  is held in place around its respective longitudinal mid-portion of the central spine or mandrel  12  by a bolt  56  extending therethrough, with an elongated, adjustable lock washer  58 , as represented in an “exploded” configuration in  FIG. 1 . Each set of split rings  50  has an elongated slot  51  in each ring  50 ′, as represented in  FIG. 6 . 
     The adjustable lock washer  58 , shown best in  FIG. 7 , receives the bolt  56 , as is represented in  FIG. 1  and as is represented in phantom in  FIG. 6 . The washer  58  has at least one movable lock tab  60  thereon, as represented in  FIG. 7 , for easy manipulation at a “field” repair site. The washer  58  may also have spring-strength indicia thereon, as for example, a field personnel-visable indicator notch  61  on its periphery, as shown in  FIG. 7 , to indicate for example, what capacity (weak or standard) inner spring  36  is being utilized beneath each wear pad  30 . If there is no notch  61 , the spring  36  is for example, a “standard” strength spring  36 ; and for example, if there is a notch  61 , then a “weak” spring  61  for example, is visually indicated. The bolt  56  is screwed into the longitudinal load bearing central ring  20  on the central portion of the mandrel  12  through the hole in the elongated lock washer  58 . The tab(s)  60  on the washer  58  is/are bendable outwardly to lock against flats on the head of the bolt  56  in place until it is necessary to remove the conduit-worn wear pads  30  and replace them with fresh (full dimensioned, conduit pressure ensuring) wear pads  30 . Thus, simple “in-the-field” unbending of the tab(s)  60  from its/their retention position against the hex head of the bolt  56  in the respective split rings  50 , permits that bolt  56  to be easily backed-out of its/their threaded hole/s in the mandrel  12  into which it/they was/were screwed, and thus permitting the simple “field” removal of each ring  50 ′ of the set of spilt rings  50  without unnecessary, complicated tools or equipment otherwise necessary by the prior art plungers for their repair. 
     That arcuately segmented split retainer ring  50  thus permits easy assembly and disassembly of the respective curved sealing-surface wear pads  30  from their respective half portions of the central spine or mandrel  12 , as those curved sealing-surface pads  30  have been worn down by frictional engagement with the inside wall of the tubing or conduit “C” in which the plunger  10  travels. Removal of the bolt  56  and lock washer  58  from each arcuately segmented split retainer ring  50 ′ will permit the removal of its retrieval neck  24  from the other longitudinal side of each respective curved surface pad  30 , and then permits those curved surface pads  30  to be lifted from their engagement with the radial bias springs  36 , and replaced at the “field” site.