Abstract:
A plunger mechanism has an internal shock absorber apparatus that operates to absorb shock during plunger fall and rise, thereby promoting a more reliable plunger lift system. The present apparatus can be used in well applications with or without a bumper spring. With the added reliability of the present system, well applications could be implemented such that fewer restrictions are encountered by a plunger at the well bottom. In addition, added reliability can help reduce plunger damage, whereby plunger life can be extended. Similarly, the present apparatus can minimize damage and extend the life of well components.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a plunger lift apparatus for the lifting of formation liquids in a hydrocarbon well. More specifically the plunger consists of an internal shock absorber apparatus that operates to absorb shock during plunger fall and high velocity plunger rise. 
   BACKGROUND OF THE INVENTION 
   A plunger lift is an apparatus that is used to increase the productivity of oil and gas wells. Nearly all wells produce liquids. In the early stages of a well&#39;s life, liquid loading is usually not a problem. When rates are high, the well liquids are carried out of the well tubing by the high velocity gas. As a well declines, a critical velocity is reached below which the heavier liquids do not make it to the surface and start to fall back to the bottom exerting back pressure on the formation, thus loading up the well. A plunger system is a method of unloading gas in high ratio oil wells without interrupting production. In operation, the plunger travels to the bottom of the well where the loading fluid is picked up by the plunger and is brought to the surface removing all liquids in the tubing. The plunger also keeps the tubing free of paraffin, salt or scale build-up. A plunger lift system works by cycling a well open and closed. During the open time a plunger interfaces between a liquid slug and gas. The gas below the plunger will push the plunger and liquid to the surface. This removal of the liquid from the tubing bore allows an additional volume of gas to flow from a producing well. A plunger lift requires sufficient gas presence within the well to be functional in driving the system. Oil wells making no gas are thus not plunger lift candidates. 
   A typical installation plunger lift system  100  can be seen in  FIG. 1 . Lubricator assembly  10  is one of the most important components of plunger system  100 . Lubricator assembly  10  includes cap  1 , integral top bumper spring  2 , striking pad  3 , and extracting rod  4 . Extracting rod  4  may or may not be employed depending on the plunger type. Contained within lubricator assembly  10  is plunger auto catching device  5  and plunger sensing device  6 . Sensing device  6  sends a signal to surface controller  15  upon plunger  200  arrival at the well top. Plunger  200  can represent the plunger of the present invention or other prior art plungers. Sensing the plunger is used as a programming input to achieve the desired well production, flow times and wellhead operating pressures. Master valve  7  should be sized correctly for the tubing  9  and plunger  200 . An incorrectly sized master valve  7  will not allow plunger  200  to pass through. Master valve  7  should incorporate a full bore opening equal to the tubing  9  size. An oversized valve will allow gas to bypass the plunger causing it to stall in the valve. If the plunger is to be used in a well with relatively high formation pressures, care must be taken to balance tubing  9  size with the casing  8  size. The bottom of a well is typically equipped with a seating nipple/tubing stop  12 . Spring standing valve/bottom hole bumper assembly  11  is located near the tubing bottom. The 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 of the plunger system. The bumper spring typically protects the tubing from plunger impact in the absence of fluid. Fluid accumulating on top of plunger  200  may be carried to the well top by plunger  200 . 
   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 on time, or pressure, to open or close the surface valves based on operator-determined requirements for production. Modern electronic controllers incorporate features that are user friendly, easy to program, addressing the shortcomings of mechanical controllers and early electronic controllers. Additional features include: battery life extension through solar panel recharging, computer memory program retention in the event of battery failure and built-in lightning protection. For complex operating conditions, controllers can be purchased that have multiple valve capability to fully automate the production process. 
     FIGS. 2 ,  2 A,  2 B,  2 C are side views of the upper sections of various plunger embodiments. Various existing sidewall geometries can be used in conjunction with the present apparatus.
         A. Plunger mandrel  20  is shown with solid ring  22  sidewall geometry. Solid sidewall rings  22  can be made of various materials such as steel, poly materials, Teflon®, stainless steel, etc. Inner cut grooves  30  allow sidewall debris to accumulate when a plunger is rising or falling.   B. Plunger mandrel  80  is shown with shifting ring  81  sidewall geometry. Shifting rings  81  allow for continuous contact against the tubing to produce an effective seal with wiping action to ensure that all scale, salt or paraffin is removed from the tubing wall. Shifting rings  81  are individually separated at each upper surface and lower surface by air gap  82 .   C. Plunger mandrel  60  has spring-loaded interlocking pads  61  in one or more sections. Interlocking pads  61  expand and contract to compensate for any irregularities in the tubing, thus creating a tight friction seal.   D. Plunger mandrel  70  incorporates a spiral-wound, flexible nylon brush  71  surface to create a seal and allow the plunger to travel despite the presence of sand, coal fines, tubing irregularities, etc.   E. Flexible plungers (not shown) are flexible for coiled tubing and directional holes, and can be used as well in straight standard tubing.       
   In each of  FIGS. 2 ,  2 A,  2 B,  2 C, an upper section of the plunger embodiment comprises a top collar shown with a standard American Petroleum Institute (API) internal fishing neck A. If retrieval is required, a spring loaded ball within a retriever and protruding outside its surface would thus fall within the API internal fishing neck at the top of the plunger, wherein the inside diameter of the orifice would increase to allow the ball to spring outward. This condition would allow retrieving of the plunger if, and when, necessary. As shown, each upper section comprises an upper end sleeve  41  and an upper threaded male section  42  used to attach various bottom ends, which will be described below. 
   Recent practices toward slim-hole wells that utilize coiled tubing also lend themselves to plunger systems. Because of the small tubing diameters, a relatively small amount of liquid may cause a well to load-up, or a relatively small amount of paraffin may plug the tubing. 
   Plungers use the volume of gas stored in the casing and the formation during the shut-in time to push the liquid load and plunger to the surface when the motor valve opens the well to the sales line or to the atmosphere. To operate a plunger installation, only the pressure and gas volume in the tubing/casing annulus is usually considered as the source of energy for bringing the liquid load and plunger to the surface. 
   The major forces acting on the cross-sectional area of the bottom of the plunger are:
         The pressure of the gas in the casing pushes up on the liquid load and the plunger.   The sales line operating pressure and atmospheric pressure push down on the plunger.   The weight of the liquid and the plunger weight push down on the plunger.   Once the plunger begins moving to the surface, friction between the tubing and the liquid load acts to oppose the plunger.   In addition, friction between the gas and tubing acts to slow the expansion of the gas.       

   In certain wells, a plunger will fall towards the well bottom at a relatively high velocity. As the plunger collides with the well bottom, the spring standing valve/bottom hole bumper assembly  11 , and/or the seating nipple/tubing stop  12 , the impact is absorbed in part by the plunger, the spring standing valve/bottom hole bumper assembly  11 , the seating nipple/tubing stop  12  and the well bottom ( FIG. 1 ). A higher velocity could lead to greater impact force and can result in damage to the plunger, and/or the spring standing valve/bottom hole bumper assembly. Bumper springs could collapse over time due to repeated stress caused by impact force. Also, plunger damage can occur resulting in more frequent plunger replacement. Because some wells do not have a bumper spring at the bottom, more of the impact could be absorbed by the plunger itself. A plunger could also rise at a high velocity from the well bottom to the well top. This can occur when liquid levels are low or when an operator allows the plunger to lift prior to proper liquid loading. A high velocity rise could cause damage to the well top apparatus and to the plunger itself. Damage to well apparatus and plunger lift equipment typically increases well maintenance costs. 
   Prior art designs have utilized plungers with externally located springs to help absorb the energy generated by the plunger force hitting the well bottom. A prior solution is shown in  FIG. 3 , which shows prior art pad plunger mandrel  60  geometry (see  FIG. 2 ) with a fishing neck top section A, and the addition of an external bottom spring  32  attached via weld  31 . The prior art solution with such an external spring, acting as a shock absorber, tends to add reliability problems to both the plunger and well bottom assembly. Failures of the weld and/or spring can occur. In addition, a failed plunger can place more wear and tear on the well bottom seating nipple/tubing stop and spring standing valve/bottom hole bumper assembly. 
   SUMMARY OF THE INVENTION 
   The present apparatus provides a plunger lift system with a more reliable shock absorber. With more reliability, wells could be constructed with or without bumper spring assemblies, which typically operate to slow a plunger&#39;s travel. In well applications which do not utilize bumper spring assemblies, fewer obstructions or restrictions are encountered by a plunger at the well bottom. In these cases, plunger travel can be more optimal and plunger damage can be reduced or minimized. 
   By utilizing an internal placement of the shock absorbing components, plunger structure has less effect on the physical restrictions of a well bottom and any equipment housed therein. The present apparatus can be used if a reduction of well top damage (as in the case of high velocity plunger rise) and a reduction of well bottom damage (as in the case of high velocity plunger fall), is desired. In addition, the components of the present apparatus are easy to manufacture and easy to assemble. 
   The main aspect of the present invention is to provide an internal shock absorber plunger apparatus in a high liquid well when plunger falling velocity produces a large impact force at the well bottom. 
   Another aspect of the present invention is to provide an internal shock absorber plunger apparatus that will protect the well top apparatus and the plunger when a high velocity plunger rise occurs. 
   Another aspect of the present invention is to provide a spring within the plunger to function as the shock absorbing body. 
   Another aspect of the present invention is to allow for fewer restrictions on a well bottom. 
   Another aspect of the present invention is to provide a shock absorber plunger that will increase reliability levels. 
   Another aspect of the present invention is to provide a shock absorber plunger that will efficiently force fall inside the tubing to the well-hole bottom with increased speed without impeding plunger or well bottom damage. 
   Another aspect of the present invention is to provide a shock absorber plunger that can be used with any existing plunger sidewall geometry. 
   Another aspect of the present invention is to allow for a shock absorber plunger that can be easily manufactured. 
   Other aspects of this invention will appear from the following description and appended claims, reference being made to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views. 
   The present invention comprises a plunger apparatus having an internal shock absorber to increase plunger life as well as to increase life of components found at a well bottom and a well top. Although the internal shock absorber can comprise an elastomer spring, die coil spring or wave spring, other shock absorbing mechanisms can be used. An actuator rod within the plunger hits the bottom of the well and compresses the internal spring, which absorbs all or part of the impact shock. 
   The present invention comprises a plunger lift apparatus consisting of a top section, which is typically a standard American Petroleum Institute (API) fishing neck, or other designs; a solid core mid section allowing for various aforementioned sidewall geometries; and a lower internal shock absorber section. The lower internal shock absorber section can be designed in various ways but will basically consist of an actuator rod, a captive actuator and an internal spring. The internal spring can be a wave spring, a die coil spring, or an elastomer-type spring (i.e. Viton®, etc.), which offers excellent resistance to aggressive fuels and chemicals. One of the additional embodiments of the present invention will incorporate dual shock absorber sections, that is, a shock absorbing element at each end section, one at the top and one at the bottom of the plunger. Yet another additional embodiment will incorporate a mid-section shock absorber element. 
   The internal shock absorber plunger of the present invention allows for improved reliability in wells that have high fluid velocities with respect to falling plungers. It allows for fewer restrictions at the well bottom, high reliability, ease of manufacture, and incorporation of the design into existing plunger geometries. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  (prior art) is an overview depiction of a typical plunger lift system installation 
       FIGS. 2 ,  2 A,  2 B,  2 C (prior art) are side view depictions of the upper section of a well plunger, each having a different sidewall geometry. 
       FIG. 3  (prior art) is a side view of pad plunger with an externally attached spring. 
       FIG. 4  is a side cross-sectional view of a lower section of an internal shock absorber embodiment using a standard die coil spring. 
       FIG. 5  is an isometric exploded view of the lower section of the internal shock absorber plunger embodiment shown in  FIG. 4 . 
       FIG. 6  is a side cross-sectional view of a lower section of the internal shock absorber plunger of an alternate embodiment using a standard die coil spring. 
       FIG. 7  is an isometric exploded view of the lower section of the internal shock absorber plunger embodiment shown in  FIG. 6 . 
       FIGS. 8 ,  8 A,  8 B,  8 C are side view depictions of the internal shock absorber plunger utilizing various sidewall geometries. 
       FIGS. 9 ,  9 A,  9 B,  9 C are side view depictions of the central section of a dual internal shock absorber plunger embodiment shown in conjunction with existing prior art sidewall geometries. 
       FIG. 10  is a side cross-sectional view of an upper assembly for an embodiment comprising a dual internal shock absorber. 
       FIG. 11  is an isometric exploded view of the upper shock absorbing assembly of  FIG. 10  for the dual internal shock absorber. 
       FIG. 12  is a side cross-sectional view of an alternate embodiment of an upper shock absorbing assembly for a dual internal shock absorber plunger. 
       FIG. 13  is an isometric exploded view of the upper shock absorbing assembly of  FIG. 12  for the dual internal shock absorber plunger. 
       FIG. 14  is side view, including a mid-section cross-sectional view, of an internal shock absorber plunger embodiment having a shock absorbing mid-section. 
       FIG. 15  is an isometric exploded view of the casing assembly of a mid-section internal shock absorber plunger. 
   

   Before explaining the disclosed embodiment of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the particular arrangement shown, since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation. 
   DETAILED DESCRIPTION OF THE INVENTION 
   The drawings depict an internal shock absorber plunger apparatus that can improve productivity levels in high liquid wells when plunger falling velocity produces a large impact force at the well bottom. The present apparatus can be used in well applications with or without a bumper spring. In certain wells, the rising velocity can be several times faster than a falling velocity due to well pressure conditions. As stated above, high velocity lift can occur in low liquid wells, as well as in instances when an operator will cycle the plunger prior to liquid loading. The present invention can also protect the plunger and the apparatus at the well top in the case of a high velocity lift. 
     FIG. 4  shows lower removable assembly  300  of the internal shock absorber plunger housing an internal shock absorber. Lower removable assembly  300  can be added to any aforementioned geometric upper section. In this embodiment, lower removable assembly  300  comprises actuator rod (piston)  36  having external thread interface  52 A, captive nut (cap)  35  having external thread interface  54 A, shock absorbing elastomer spring  49 , seal nut  34  having internal thread interface  52 B, and case housing (cylinder wall)  33  having internal thread interface  54 B at its lower end, also having an inner lower ledge to contain the upper end of shock absorbing elastomer spring  49 . To mate with the upper sections shown in  FIGS. 2 ,  2 A,  2 B,  2 C, case housing  33  has internal cavity  57  for accepting an upper end sleeve  41 . Upper threaded male section  42  (see  FIGS. 2 ,  2 A,  2 B,  2 C) is received by threaded female section  56 . It should also be noted that shock absorbing elastomer spring  49  could be replaced with any suitable shock absorbing mechanism. For example, a shock absorbing die coil spring  48  or a shock absorbing wave type spring  47  as shown in  FIG. 7 ) can be used. Shock absorbing elastomer spring  49  can be Viton® or any other type elastomer. Material selections can be tuned to well conditions such as temperature, falling/rising distance, resistance to fuels or chemicals present in the fluid, etc. The present invention is not limited by the type of or by the design of the internal spring. 
   Spanner holes (not shown) could be easily added to parts such as seal nut  34 , captive nut  35 , and other parts as required, to aid in fastening. 
   The following steps are used to describe a construction of a basic sub-assembly of lower removable assembly  300 :
         a) Place shock absorbing elastomer spring  49  into case housing  33 ;   b) Slip captive nut (cap)  35  over actuator rod  36 ;   c) Screw seal nut  34  onto actuator rod  36  via thread interface  52 ;   d) Slide actuator rod  36  with attached seal nut  34  and with captive nut  35  into case housing  33 ;   e) Screw captive nut  35  into case housing at thread interface  54  to complete removable assembly  300 .   f) Screw lower removable assembly  300  into an upper section (see  FIGS. 2 ,  2 A,  2 B,  2 C) via placing internal cavity  57  onto upper end sleeve  41  and screwing threaded female section  56  to upper threaded male section  42 .       

   When the plunger falls to the well bottom, actuator rod  36  will hit the seating bumper spring assembly that is located near the tubing bottom. In well applications having no bumper spring, the plunger will hit a hard stop at the well bottom. Both the bumper spring assembly and the internal shock absorber plunger of the present invention will absorb a portion of the force generated by the impact. If a bumper spring does not exist, impact force will be absorbed by the internal shock absorber. Upon impact, actuator rod  36  will move in direction ‘R’ and into shock absorbing elastomer spring  49  which will absorb a portion (or all) of the impact force. The ability of the plunger to self-absorb shock at the well bottom will thus increase reliability levels. It will reduce the probability of bumper spring collapses, reduce damage to the plunger itself, and reduce damage to the well bottom itself. It also provides the ability to have less restriction at the well bottom, that is, elimination of the need for bumper spring assemblies at the well bottom. Thus the internal shock absorber plunger will efficiently force fall inside the tubing to the well-hole bottom without impeding plunger or well bottom damage. If the plunger rises with a high velocity, the present invention provides an internal plunger shock absorption as the plunger top hits a top striking pad or other well top apparatus. 
     FIG. 5  is an isometric exploded view of lower removable assembly  300  of  FIG. 4 . It shows the basic five parts of lower removable assembly  300 ; actuator rod  36  has anvil B design with anvil groove  64  at one end has external thread interface  52 A at its other end, captive nut  35  with external thread interface  54 A, seal nut  34  with inner thread interface  52 B, shock absorbing elastomer spring  49 , and case housing  33 . Access external hole  62 A is for tightening lower removable assembly  300  to the upper section onto upper threaded male section  42 . It should be noted that anvil B design could easily be replaced with other end type designs. Assembly to upper sections is completed via threaded female section  56 . 
     FIG. 6  is an alternate embodiment of the present invention showing alternate lower removable assembly  400  of the internal shock absorber plunger containing the internal shock absorber. Here, the internal shock absorber comprises a shock absorbing die coil spring  48 . Lower removable assembly  400  is an alternate design to lower removable assembly  300  shown in  FIGS. 4 ,  5 . Alternate lower removable assembly  400  can be added to any aforementioned geometric top section in the same manner as previously described herein. Alternate lower removable assembly  400  comprises actuator rod (piston)  44 , shock absorbing die coil spring  48 , case housing (cylinder wall)  46  with internal female housing threaded area  51 B, and lock nut  45  which has internal female threaded area  53  for accepting an upper threaded male section  42 , and external male threaded section  51 A for mating with housing  46  via internal female housing threaded area  51 B. Grip holes  39  in lock nut  45  are used to grasp and mechanically tighten lock nut  45 . Actuator rod  44  has an outer flange at its upper surface to hold it within case housing  46 , which has an inner flange surface on its bottom side to hold actuator rod  44  within. Shock absorbing die coil spring  48  can be replaced with a more suitable shock absorbing element. As shown in dotted line format, shock absorbing wave spring  47  or with shock absorbing elastomer-type spring  49  could be used. The present invention is not limited by the spring type or by the spring design. 
   When the plunger falls to the well bottom, actuator rod  44  will hit the seating bumper spring assembly or hit a hard stop at the well bottom. Upon impact, actuator rod  44  will move in direction ‘R’ and into shock absorbing coil spring  48  which will absorb a portion (or all) of the impact force. Likewise, when a plunger rises to the well top with a high velocity, damage is avoided as the top of the plunger hits well top apparatus and the internal shock absorbing coil spring  48  will absorb a portion (or all) of the impact force. 
     FIG. 7  is an isometric blow-up view of lower removable assembly  400  of  FIG. 6 . Lower removable assembly  400  consists of actuator rod (piston)  44 , die coil spring  48 , case housing  46 , and lock nut (threaded cap)  45  with internal female threaded area  53  for accepting upper threaded male section  42  (see  FIGS. 2 ,  2 A,  2 B,  2 C), and outside male threaded area  51 A for mating with housing  46  which has internal female housing threaded area  51 B. Grip holes  39  are used to grasp and mechanically tighten lock nut  45 . As previously discussed, shock absorbing die coil type spring  48  can also be replaced with shock absorbing wave spring  47  or with an elastomer-type spring  49 . Access external hole  62 B is for tightening lower removable assembly  400  to the upper section onto upper threaded male section  42 . 
   Viewing  FIG. 7  it can be seen that this embodiment basically consists of four parts in lower removable assembly  400 ; actuator rod  44 , shock absorbing die coil spring  48 , case housing  46  with internal female housing threaded area  51 B, and lock nut  45  with inside female threaded area  53  for accepting upper threaded male section  42  (see  FIGS. 2 ,  2 A,  2 B,  2 C), and outside male threaded area  51 A for mating with inner female threaded area  51 B on case housing  46 . As previously discussed, shock absorbing die coil type spring  48  can also be replaced with any suitable shock absorbing element such as a shock absorbing wave spring  47  or a shock absorbing elastomer-type spring  49 . Assembly to upper sections is also via a simple thread at threaded interfaces  51 ,  53 . 
   It should be noted that although both removable assemblies have been shown with upper female type receptacles and upper plunger sections have been shown with lower male type sections for joining each other, other designs could easily be employed to have removable assemblies with male upper sections and female upper plunger sections with female lower sections for mating. 
     FIGS. 8 ,  8 A,  8 B,  8 C are side views of the internal shock absorber plunger utilizing various sidewall geometries (including but not limited to mandrel geometries  22 ,  61 ,  71 ,  81 ). For illustrative purposes, lower removable assembly  300  is shown in conjunction with plunger mandrel  20  having solid ring  22  geometry (see  FIG. 8B ) and plunger mandrel  80  having shifting ring  81  geometry (see  FIG. 8C ). Lower removable assembly  400  is shown in conjunction with plunger mandrel  60  (see  FIG. 8 ) and plunger mandrel  70  (see  FIG. 8A ). It should be noted that the present invention is not limited to any specific sidewall geometry and that any sidewall geometry can be used. 
   Although any top geometry can readily be used with the present invention, a standard American Petroleum Institute (API) internal fishing neck top A is shown in  FIGS. 8 ,  8 A,  8 B,  8 C. 
   A dual internal shock absorber embodiment is shown in  FIGS. 9 ,  9 A,  9 B,  9 C,  10 ,  11 ,  12 ,  13 . ‘Dual shock absorbing sections can provide for additional shock absorption. This embodiment can be constructed by adding a second shock absorbing upper assembly to a first shock absorbing assembly. The additional shock absorbing assembly can allow for improved internal shock absorption as needed based on well conditions. 
     FIGS. 9 ,  9 A,  9 B,  9 C are side view depictions of the section between sleeves  41 A,  41 B of a dual internal shock absorber plunger embodiment shown in conjunction with existing prior art sidewall geometries. As compared to  FIGS. 2 ,  2 A,  2 B,  2 C, this embodiment comprises end sleeves  41 A,  41 B and threaded male sections  42 A,  42 B for accepting more than one shock absorber assembly. All geometries depicted can be found in present industrial offerings. Similar geometries also exist and will have internal orifices.  FIGS. 10 ,  11  as described below, depict a shock absorbing section embodiment that can be added to sleeve end  41 B via screwing onto upper threaded male section  42 B. Each mandrel central section  600 ,  700 ,  200 ,  800  is symmetrically designed to hold both an upper shock absorbing assembly  300 A or  400 A ( FIGS. 10 ,  11 ,  12 ,  13 ) and a lower shock absorbing assembly  300  or  400  ( FIGS. 4 ,  5 ,  6 ,  7 ). 
     FIG. 10  shows upper shock absorbing assembly  300 A for the dual internal shock absorber housing an elastomeric spring  49 . Elastomeric spring  49  can be replaced with other type springs such as a wave spring or a die coil spring. All elements of  FIG. 10  are as described in  FIG. 4  with the exception that actuator rod  36 A comprises a fishing neck A design. Upper shock absorbing assembly  300 A mates with central section  600 ,  700 ,  200 ,  800  (see  FIGS. 9 ,  9 A,  9 B,  9 C) via internal cavity  57  for accepting end sleeve  41 B and threaded male section  42 B is received by threaded female section  56 . Threaded female section  56  of a lower shock absorbing assembly  300  or  400  can receive threaded male section  42 A. Internal cavity  57  may accept end sleeve  41 A. Thus, upper assembly  300 A provides for a second shock absorbing assembly forming a dual internal shock absorbing plunger embodiment. 
     FIG. 11  is an isometric exploded view of the upper shock absorbing assembly  300 A of  FIG. 10 . All parts of removable assembly  300 A are as previously described in  FIG. 5  above with the exception that actuator rod  36 A has fishing neck A design for retrieval purposes. 
     FIG. 12  is a side cross-sectional view of an alternate embodiment  400 A of an upper assembly for a dual internal shock absorber plunger. Upper assembly  400 A is an alternate design to upper assembly  300 A shown in  FIG. 10 . All elements of  FIG. 12  are as described in  FIG. 6  with the exception that actuator rod  44 A has fishing neck A design. In addition, the present embodiment houses a shock absorber element comprising a die coil spring  48 . As stated above, any suitable shock absorbing element could be used. Upper shock absorbing assembly  400 A mates with central section  600 ,  700 ,  200 ,  800  via internal threads  53  for accepting threaded male section  42 B (see  FIGS. 9 ,  9 A,  9 B,  9 C). Upper assembly  400 A provides for a second shock absorbing assembly forming a dual internal shock absorbing plunger. 
     FIG. 13  is an isometric exploded view of upper shock absorber assembly  400 A shown in  FIG. 12 . All parts of removable assembly  400 A are as previously described in  FIG. 7  above with the exception that actuator rod  44 A has fishing neck A design for retrieval purposes. 
     FIG. 14  is a side view, including a mid-section cross-sectional view, for a mid-section internal shock absorber plunger  500  embodiment. For a rising plunger condition, upper mandrel section  502  will hit the well top and for a falling plunger condition, lower mandrel section  504  will hit the well bottom. In either case a shock absorber such as elastomer spring  49  will absorb some or all of the impact energy. In this embodiment, casing assembly  506  houses mid-section casing  66  having threaded interfaces at either ends, one internal elastomer spring  49 , two captive nuts  34  for attaching upper mandrel  502  and lower mandrel  504 , and two captive nuts  35  for containing both mandrel sections. Shock absorbing elastomer spring  49  could be replaced with any suitable shock absorbing mechanism. For example, a shock absorbing die coil spring  48  or a shock absorbing wave type spring  47  (as shown in  FIG. 7 ) can be used. 
   At an upper end, upper mandrel section  502  comprises a fishing neck A design, while lower mandrel section  504  comprises an anvil B end design as previously shown in  FIGS. 4 ,  5 ,  8 ,  8 A,  8 B,  8 C. In this example, mandrel sections  502 ,  504  are shown with shifting ring geometry. Shifting rings  81 , are individually separated by air gaps  82 . It should be noted that although a shifting ring geometry is shown, other previously described sidewall geometries could also be used. 
     FIG. 15  is an isometric exploded view of casing assembly  506 . Assembly of this plunger embodiment can be described as follows:
         a) Slide upper mandrel  502  thru upper captive nut  35  and thread upper seal nut  34  onto it via seal nut threads  52 B mating to upper mandrel threads  52 C.   b) Slide lower mandrel  504  thru lower captive nut  35  and thread lower seal nut  34  onto it via seal nut threads  52 B mating to lower mandrel threads  52 D.   c) Place elastomer spring  49  into casing  66 .   d) Thread upper captive nut  35  via threads  54 A onto casing  66  via upper casing threads  54 C, thereby securing upper mandrel  502  to casing  66 .   e) Thread lower captive nut  35  via threads  54 A onto casing  66  via lower casing threads  54 C (not shown), thereby securing lower mandrel  504  to casing  66 , thus completing assembly of the mid-section internal shock absorber plunger third embodiment of the present invention.       
   The present invention can optimize well efficiency and plunger reliability. An internal shock absorber allows the present apparatus to quickly travel to the well bottom, or to quickly travel to the well top, while reducing damage caused by a forcible impact of the plunger against various well components. Thus, the internal shock absorber plunger can increase plunger life (by reducing plunger damage) as well as the life of components found at a well top and well bottom. The internalized design can also result in a well application with fewer restrictions at the well bottom. With the present apparatus, wells could be operated without equipment such as a bumper spring assembly, if desired. The internal shock absorber can utilize any suitable shock absorbing element to absorb all or part of the impact shock. Examples of such could include elastomer springs, die coil springs, wave springs, etc. 
   It should be noted that although the hardware aspects of the of the present invention have been described with reference to the exemplary embodiment above, other alternate embodiments of the present invention could be easily employed by one skilled in the art to accomplish the internal shock absorber aspect of the present invention. For example, it will be understood that additions, deletions, and changes may be made to the internal shock absorber plunger with respect to design, shock absorber mechanisms (such as spring types etc.), plungers with bypass functions, geometric designs other than those described above (snake plungers etc.), and various internal part designs contained therein. 
   Although the present invention has been described with reference to preferred embodiments, numerous modifications and variations can be made and still the result will come within the scope of the invention. No limitation with respect to the specific embodiments disclosed herein is intended or should be inferred.