Patent Publication Number: US-8528912-B2

Title: Method and apparatus for injecting packing into stuffing boxes for reciprocating rods

Description:
This application is a divisional of U.S. application Ser. No. 11/137,285, filed May 25, 2005, which was a continuation of U.S. application Ser. No. 10/403,323, filed Mar. 31, 2003, which application was a continuation-in-part of U.S. application Ser. No. 60/369,499, filed Apr. 2, 2002, and a continuation-in-part of U.S. application Ser. No. 60/403,148, filed Aug. 13, 2002. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to stuffing boxes that are used to provide a seal around a reciprocating rod or shaft, such as might be found on a rod pumped oil or gas well. 
     BACKGROUND OF THE INVENTION 
     Downhole, or subsurface, pumps are commonly used to lift fluids, such as crude oil, to the surface. The pump is located in the well below the level of the oil. A string of sucker rods extends from the pump up to the surface, to a pump jack device, or beam pump unit. The pump jack is connected to the sucker rod string by way of a polished rod that reciprocates in a stuffing box. The stuffing box provides a seal around the polished rod, allowing the flow of downhole fluids to be directed to an outlet line. 
     Stuffing boxes for wellhead polished rods typically use friction type seals constructed from a rubber-based material. Common friction type seals used in wellhead stuffing boxes are conical seals, such as shown in U.S. Pat. Nos. 3,084,946 and 4,560,176 and pressure seals. The seals, which are pressurized either by a gland or by well bore pressure, wear and must be periodically replaced. 
     Replacing conventional seals is fraught with problems; well operators do not like to do so because of the time involved and other reasons. For example, the well must be shut down to stop the movement of the polished rod. Furthermore, before the seals are removed, they must be isolated from the pressure inside of the well. This is accomplished by closing a packer or a blowout preventer located below the stuffing box. Occasionally, the ability of the packer to maintain a seal is compromised by factors such as age or even wear, as the operator may have relied on the packer to compensate for leaking stuffing box seals. If this happens, the packer seal could fail when the operator is removing the stuffing box seals, resulting in a dangerous pressure release of hydrocarbons or gas. 
     Furthermore, the seals are out of sight in the stuffing box. The operator has no adequate way to determine if the seals are in satisfactory condition, other than to stop the pump jack and open the stuffing box to visually inspect the seals, or to wait for crude oil to leak from the stuffing box. As U.S. Pat. Nos. 5,209,495 and 6,302,401 teach, the leakage of crude oil from the stuffing box is environmentally unsound. 
     Stuffing boxes can be provided with an injectable packing, such as is taught by Cox, U.S. Pat. No. 4,162,078. Such injectable packing is useful for many pumps, such as the multiplex-type pump, where the reciprocating rod or piston moved along a fixed axis. In a well bore pump however, the axis of movement of the polished rod is itself subject to movement. Any such movement of the polished rod axis causes gaps and shifts in the packing material, resulting in lost seal integrity. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method and apparatus for providing a wellhead stuffing box with a seal that can be replaced without stopping the pump. 
     It is another object of the present invention to provide a method and apparatus that automatically provides replacement packing material to a stuffing box. 
     It is another object of the present invention to provide a method and apparatus that provides a visual indication of the status or quantity of packing material. 
     It is another object of the present invention to provide a method and apparatus that negates exposing an operator to a potentially dangerous pressure release when resupplying seal material to a stuffing box. 
     The present invention provides an apparatus for use on wellhead equipment having a reciprocating polished rod. The apparatus comprises a stuffing box having a wall defining a stuffing chamber with two ends. The ends have openings for receiving the polished rod and the polished rod reciprocates relative to the stuffing box wall. At least one opening through the wall communicates with the stuffing chamber. A reservoir is structured and arranged to contain injectable packing material. The reservoir communicates with the opening to the stuffing chamber. A pressure source applies pressure to the packing material in the reservoir so as to inject the packing material from the reservoir into the stuffing chamber. 
     With the present invention, the sealing material is automatically replenished during the operation of the reciprocating polished rod. Therefore, the polished rod need not be stopped for maintenance of the stuffing box. Furthermore, as the stuffing box provides a seal around the polished rod, pressures on the wellhead side of the polished rod need not be vented or sealed off in order to replenish the sealing or packing material. This is an important safety advantage to protect the operators. 
     In accordance with another aspect of the present invention, the at least one opening through the wall communicating with the stuffing chamber further comprises a plurality of openings circumferentially spaced about the stuffing box chamber. A collar is coupled to the stuffing box wall, with the collar having a circumferential passage therein. The circumferential passage communicates with the openings through the stuffing box wall. The reservoir communicates with the collar passage. 
     In accordance with another aspect of the present invention, the reservoir is mounted to the collar. 
     In accordance with still another aspect of the present invention, the collar rotates about the circumference of the stuffing box. Thus, the reservoir can be pivoted or rotated about the stuffing box in order to avoid any obstacles. 
     In accordance with still another aspect of the present invention, the reservoir communicates with the stuffing box chamber opening by a passage, which passage has a check valve therein to prevent packing from flowing from the stuffing box chamber to the reservoir. 
     In accordance with another aspect of the present invention, a piston is located inside of the reservoir. The pressure source acts on the piston. 
     In accordance with another aspect of the present invention, the pressure source comprises fluid acting on the piston. In the alternative, the pressure source comprises a spring acting on the piston. 
     In accordance with still another aspect of the present invention, a shaft is coupled to the piston, which shaft extends out of the reservoir and provides a visual indication of the amount of packing in the reservoir. 
     In accordance with still another aspect of the present invention, the shaft has a fill passage therethrough that communicates with the reservoir. 
     In accordance with still another aspect of the present invention, the apparatus further comprises an indicator of the amount of packing material contained in the reservoir. 
     In accordance with still another aspect of the present invention, the stuffing box is mounted to the wellhead by bearings, wherein the stuffing box maintains alignment with an axis of reciprocation of the polished rod. Thus, the present invention allows the stuffing box to align itself with the reciprocation axis of the polished rod. This reduces or minimizes wear on stuffing box components that contain the packing within the stuffing box, thereby ensuring that the packing will not extrude or leak out of the stuffing box due to misalignment problems. 
     The present invention also provides a method of sealing a stuffing box on wellhead equipment having a reciprocating polished rod. A supply of packing is provided. A connection is provided between the supply of packing to the stuffing box. The supply of packing is pressurized and injected into the stuffing box. 
     In accordance with one aspect of the present invention, the step of injecting the packing into the stuffing box occurs while the polished rod reciprocates. 
     In accordance with another aspect of the present invention, the polished rod is reciprocated in and out of wellhead fluids. 
     In accordance with another aspect of the present invention, the step of injecting the packing into the stuffing box further comprises injecting the packing into circumferentially spaced locations about the polished rod. 
     In accordance with still another aspect of the present invention, an indication of the supply of packing in the stuffing box is provided. 
     In accordance with still another aspect of the present invention, the stuffing box is allowed to move so that the stuffing box maintains alignment with an axis of reciprocation of the polished rod. 
     The present invention provides a stuffing box for use with a downhole pump, a reciprocating polished rod and sucker rods connecting the polished rod to the pump. The stuffing box comprises a housing that forms a closed chamber therein. The chamber has first and second ends, with each of the first and second ends having an opening for receiving the polished rod. One of the first or second ends is structured and arranged to couple to wellhead equipment. A valved port in the housing allows selective communication between the exterior of the housing and the chamber. Injectable packing is located in the chamber. 
     In accordance with one aspect of the present invention, the stuffing box further comprises a pressure application member in contact with a portion of the injectable packing and applying pressure to the packing in the chamber. 
     In accordance with another aspect of the present invention, the pressure application member is located inside of the housing. 
     In accordance with still another aspect of the present invention, the pressure application member forms a bushing in the chamber. 
     In accordance with still another aspect of the present invention, the pressure application member is structured and arranged to contact the fluid pumped uphole by the downhole pump. 
     In accordance with another aspect of the present invention, the pressure application member is exposed to a pressure source. 
     In accordance with still another aspect of the present invention, the pressure application member is located exteriorly of the housing. 
     In accordance with still another aspect of the present invention, the stuffing box further comprises an indicator of the amount of packing located in the chamber. 
     The present invention also provides a stuffing box for use with a polished rod of a downhole pump that comprises a housing having a chamber therein. The chamber is structured and arranged for receiving the polished rod and allows the polished rod to reciprocate therein. The chamber has two ends. A first bushing is located at one end of the chamber and a second bushing is located at the other end of the chamber. The second bushing is movable with respect to the first bushing. A valved port is in the housing and allows selective communication between an exterior of the housing and the chamber. Malleable packing is located in the chamber between the first and second bushings. 
     In accordance with one aspect of the present invention, the second bushing has first and second ends with the first end located in contact with the packing and the second end located out of contact with the packing. The second bushing first end has a first surface area and the second bushing second end has a second surface area. The first surface area is different than the second surface area. 
     In accordance with another aspect of the present invention, the first surface area is smaller than the second surface area. 
     In accordance with still another aspect of the present invention, the second end is structured and arranged to be in contact with the fluid produced by the pump. 
     In accordance with still another aspect of the present invention, an indicator is coupled to the second bushing, with at least a portion of the indicator located exteriorly of the housing in selected positions of the second bushing in the chamber. 
     The present invention also provides a method of providing a seal around a polished rod for a downhole pump. A closed chamber is provided having first and second openings therethrough for receiving the polished rod. Packing is injected into the chamber. 
     In accordance with one aspect of the present invention, the step of injecting packing into the chamber occurs while the polished rod is reciprocating. 
     The present invention also provides a method of providing a seal around a polished rod for a downhole pump wherein a closed chamber is provided. The chamber has first and second openings therethrough for receiving the polished rod. The chamber is filled with a malleable packing, and the packing is compressed. 
     In accordance with one aspect of the present invention, the packing is compressed by diminishing a volume of the chamber. 
     In accordance with another aspect of the present invention, the volume of the chamber is diminished by pressurizing the chamber with fluid produced by the pump. 
     The present invention also provides a method of providing a seal around a polished rod for a downhole pump. A closed chamber is provided having first and second openings therethrough for receiving the polished rod. Packing is inserted into the chamber. The amount of packing is indicated during the reciprocation of the polished rod. 
     The present invention also provides a stuffing box for use with a downhole pump, a reciprocating polished rod and sucker rods connecting the polished rod to the pump. The stuffing box comprises a chamber that is structured and arranged to receive the reciprocating polished rod. The chamber comprises an annulus around the polished rod when the polished rod is received in the chamber. Malleable packing is located in the annulus. The annulus comprises a first member that exerts pressure on the malleable packing, the annulus changes volume according to the quantity of packing located therein. An indicator of the quantity of packing located in the annulus is provided, with the indicator being visible from an exterior of the stuffing box. 
     In accordance with one aspect of the present invention, the indicator comprises a second member coupled to the first member. 
     In accordance with another aspect of the present invention, the annulus is sealed and the second member is coupled to the first member outside of the sealed annulus. 
     The present invention also provides an apparatus for use in a well having a downhole pump, a reciprocating polished rod and sucker rods connecting the polished rod to the pump. The apparatus comprises a stuffing box, which in turn comprises a housing having a chamber therein. The chamber is structured and arranged to receive the reciprocating polished rod and has an annulus around the polished rod when the polished rod is received within the chamber. A piston is located at one end of the chamber, with the piston being annular so as to receive the polished rod. One end of the piston is located within the chamber annulus, with another end of the piston being structured and arranged to be exposed to well fluids. Malleable packing is located in the chamber annulus and in contact with the piston, the packing being pressurized by the piston. 
     In accordance with one aspect of the present invention, the housing further comprises an inlet port that communicates with the chamber so that the packing can be added to the chamber. 
     In accordance with still another aspect of the present invention, there is an indicator member coupled to the piston and visible from an exterior of the housing. 
     In accordance with another aspect of the present invention, the other end of the piston that is exposed to well fluids is sized according to the pressure of the well fluids. 
     In accordance with another aspect of the present invention, the apparatus further comprises upper and lower sacrificial bushings for receiving the polished rod and a bearing arrangement to maintain the alignment of the polished rod with the stuffing box. The bearing arrangement is coupled to the stuffing box. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a well, shown with pumping equipment. 
         FIG. 2  is a cross-sectional view of the stuffing box of the present invention, in accordance with a preferred embodiment. 
         FIG. 3  is a bottom plan view of the collar reservoir member base, taken along lines III-III of  FIG. 2 . 
         FIG. 4  is a longitudinal cross-sectional view of the stuffing box of the present invention, in accordance with another embodiment. 
         FIG. 4A  is an exterior view of the stuffing box of  FIG. 4 . 
         FIG. 4B  is a cross-sectional view of the lower end of the stuffing box of  FIG. 4 , shown in accordance with another embodiment 
         FIG. 5  is a longitudinal cross-sectional detail view of an indicator, in accordance with another embodiment. 
         FIG. 6  is a longitudinal cross-sectional view of the stuffing box of the present invention, in accordance with still another embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIG. 1 , there is shown a schematic diagram of a producing oil well  11 . The well has a borehole that extends from the surface  13  into the earth, through an oil-bearing formation  15 . The borehole has been completed and therefore has casing  17  which is perforated at the formation  15 . A packer or other device (not shown) optionally isolates the formation  15  from the rest of the borehole. Tubing  19  extends inside of the casing from the formation  15  to the surface  13 . 
     A subsurface pump  21  is located in the tubing  19  at or near the formation  15 . A string of sucker rods  23  extends from the pump  21  up inside of the tubing  19  to a polished rod  31 . The polished rod  31  is connected, by way of a cable, to a pump jack unit  24 . The pump jack unit  24  reciprocates up and down due to a prime mover  26 , such as an electric motor, a gasoline or diesel engine, or a gas engine. 
     The polished rod  31  reciprocates up and down inside of a stuffing box  33 , which stuffing box maintains a seal around the polished rod. 
     The present invention continually applies sealing or packing material to the stuffing box  33  during the operation of the pump. A reservoir  34  provides a reserve quantity of packing material. The reservoir  34  can be located exteriorly of the stuffing box housing, as shown, or interiorly. The supply of packing material can be replenished while the pump is in operation, and without the necessity of stopping the pump. 
     The pump jack unit  24  may become misaligned with the well  11 . Such misalignment may be caused, for example, by shifting or movement of the earth surface  13 . The pump jack unit  24  is not directly coupled to the well head  139 . Consequently, the polished rod  31 , which has one end coupled to the pump jack unit  24 , and descends through the stuffing box into the well, can become misaligned within the well. In such an event, the polished rod is not parallel to the longitudinal axis of the well casing. 
     In the description that follows, “upper” and “lower” will be used to describe various components; these terms are used with reference to the orientation shown in  FIG. 2 . 
       FIG. 2  shows a cross-sectional view of the apparatus of the present invention. The stuffing box  33  has a cylindrical wall  35  forming a cylindrical chamber  37 . The chamber  37  is open at one end  39  and has an inwardly extending shoulder  41  at the opposite end. The shoulder surrounds an opening  43 . 
     The polished rod  31  extends through the chamber  37  and the opening  43 . The polished rod reciprocates relative to the chamber  37 . 
     An injectable packing  45  is located in the annular region in the chamber  37  around the polished rod  31 . The packing  45  is contained inside of the chamber by upper and lower anti-extrusion rings  47 ,  49 . The lower anti-extrusion ring  49  bears on the shoulder  41 , while the upper anti-extrusion ring  47  bears on the packing  45  in the chamber  37 . The anti-extrusion rings  47 ,  49  effectively close off the upper and lower ends of the annular space around the polished rod to the packing. Upper and lower bronze bushings  48 ,  50  are provided to contain the anti-extrusion rings  47 ,  49 . 
     The upper end  39  of the chamber is closed by a cap  53  that threads onto the wall  35 . The cap  53  has an opening  55  therethrough for the polished rod  31 . The cap  53  prevents upward movement of the upper bushing  48 . 
     The injectable packing  45  is believed to be a mixture of plastic pieces, or synthetic fibers, and lubricants, such as is described in Cox, U.S. Pat. No. 4,162,078, the disclosure of which is incorporated herein by reference. The packing is malleable and in general lacks resiliency. The packing can be injected through hoses, lines, etc. The packing  45  is packable within the chamber  57 . In the preferred embodiment, the specific injectable packing used is a commercially available product from Teadit, sold under the name JamPak or, alternatively, a commercially available product from Utex Industries, sold under the name U-Pak. 
     The wall  35  surrounding the chamber  37  has one or more openings  57  therethrough. The openings  57  are located between the upper and lower rings  47 ,  49 . In the preferred embodiment, there are three openings  57 , spaced 120 degrees apart around the circumference of the chamber  37 . Of course, there could be fewer or more openings; there could be only a single opening  57 . 
     A collar  59  is located around the wall. The collar  59  has a circumferential chamber  61  that communicates with the openings  57 . A passage  63  extends from the chamber  61  radially outward to a counterbore  65 , which counterbore receives a ball  67 . The ball  67  is part of a check, or one-way, valve. The collar  59  is mounted to the stuffing box wall  35  so as to rotate freely. This allows the collar  59  and the reservoir  34  to be positioned favorably about the stuffing box. The collar  59  bears on a stop shoulder (not shown) of the stuffing box  33 . The shoulder stops downward movement of the collar  59 . A locking ring  73  prevents upward movement of the collar  59 . The clearances between the collar  59  and the stuffing box wall  35  are small so that packing does not extrude therefrom. 
     The reservoir  34  includes a reservoir member  69 . The reservoir member  69  has a reservoir chamber  75  formed by a wall  77 . In the preferred embodiment, the wall  77  is cylindrical. At the lower end of the wall  77  is a base  79 . The reservoir chamber  75  is open at the upper end  81 ; a cap  83  is threaded onto the upper end of the wall  77 . The cap  83  has an o-ring seal  85  therein between the cap and the wall. The upper end of the cap  83  has a threaded opening  87  therethrough for receiving a fitting  89 . 
     The lower end of the reservoir chamber  75  has a stop shoulder  91  extending radially inward. Below the stop shoulder  91  is an ante chamber  93  of reduced inside diameter relative to the reservoir chamber  75 . Below the ante chamber  93  is an opening  95  through the bottom wall of the chamber. The ante chamber  93  has a passage  97  that extends to the outside of the base  79 . The outermost portion of the passage  97  is formed into a valve seat  99 . 
     The reservoir member base  79  is designed to couple to the collar  59 . Both the base  79  and the collar  59  have flat surfaces  101  that face each other (see  FIG. 3 ). Bolts  103  secure the base  79  to the collar  59  wherein the base passage  97  is aligned with and communicates with the collar passage  63  ( FIG. 2 ). The ball  67  is located in the counterbore  65  of the stuffing box passage and is designed to seat against the base valve seat  99  to form a one-way, or check, valve. 
     The reservoir chamber  75  has a piston  105  therein that moves freely up and down inside of the chamber. The piston  105  is fitted to a shaft  107  that extends through the opening  95 . The shaft  107  has a passage  109  from its free end to near the piston, where a transverse bore  111  extends through the shaft, intersecting the passage  109 . The shaft has a fitting  113  at its free end to couple to a supply of packing material. The passage  109  has a one-way valve  115  therein. The valve  115  fits against a seat  116 . 
     The operation of the stuffing box will now be described. When the stuffing box is installed, packing material  45  is put in the stuffing box chamber  37  around the polished rod  31 . Although the packing can be put in through the open end of the chamber  37  (for example, using a putty knife to pack the chamber), it is preferred that the chamber  37  be filled with packing from the openings  57  to purge air from the passages. Packing is injected into the reservoir chamber  75  by an injection gun (not shown), a conventional and commercially available device. The injection gun is coupled to the shaft fitting  113 . Once coupled, the gun is operated to inject packing  45  into the shaft passage  109  and into the chambers  75 ,  93 . As packing  45  continues to be injected, the piston  105  will rise in the reservoir chamber  75 . The piston  105  will stop against the cap  83 , wherein the reservoir chamber is full of packing. Any additional packing will be injected into the passage  97 , through the one-way valve  67 ,  99 , into the outer passage  63 , the chamber  61  and the openings  57 . When all of the chambers and passages are full, the ring  47 , bushing  48  and cap  53  are installed. The injection gun is removed from the fitting  113 . The one-way  115  valve prevents packing from exiting the reservoir chamber through the fitting  113 . In  FIG. 2 , packing is not shown in passages, channels and openings  57 ,  61 ,  63 ,  65 ,  97 ,  109  and  111  for clarity. 
     The reservoir chamber  75  is coupled to a pressure source to force the piston down and expel the packing material. The collar  59  allows the reservoir  34  to pivot about the stuffing box to avoid obstacles. In the preferred embodiment, the pressure source can be any pressure source located at the wellhead. For example, a line  117  can be extended from the fitting  89  in the cap  83  to a pressurized location on the wellhead, such as a tap off of a pressure gauge, flow line  119 , etc. Thus, fluid pressure (whether from liquid or gas) from the well can be applied to the piston. A diaphragm can be used to isolate well fluids from the reservoir. Other sources of pressure can be used, such as an air pump, chemical pump, gravity fed weights, etc. Alternatively, a spring  121  (shown in dashed lines in  FIG. 2 ) can be located inside of the reservoir chamber  75  between the cap  83  and the piston  105  to force the piston in a direction that will expel the packing material. A spring-energized device can be located exteriorly of the reservoir to apply pressure to the piston  105 . 
     During operation, the polished rod  31  reciprocates up and down through the stuffing box. Well fluids  151  (hydrocarbons such as crude oil and gas) are located in the well just below the stuffing box  33 , and contact the lower anti-extrusion ring  49  and the lower bushing  50 . Eventually, the quantity of the packing  45  in the chamber  37  will diminish due to the operation of the polished rod. However, with the present invention, the supply of packing material in the stuffing box is maintained by the reservoir. The piston  105  injects the packing  45  into the collar  59  and into the stuffing box  33 . The check valve  67 ,  99  prevents packing from reentering the reservoir chamber  75 . Thus, the stuffing box is always provided with a proper seal around the polished rod  31 , so long as the reservoir is maintained with packing material. 
     The piston shaft  107  provides a visual indication of the amount of packing inside of the reservoir chamber  75 . If the reservoir is full, the shaft  107  will be mostly inside of the reservoir. If the reservoir is empty or nearly so, the piston will be extended below the reservoir. An operator can thus visually determine if more packing should be added to the reservoir. The shaft and piston can be configured to operate in an opposite manner, that is, when the shaft is extended, the reservoir is full of packing. Alternatively, the wall  77  can be transparent to allow an operator to see the position of the piston  105 . 
     The operator can add packing to the reservoir while the polished rod  31  continues to reciprocate. In other words, the well pump need not be shut down to maintain the integrity of the stuffing box seal. The operator need not directly access the stuffing box and break the seal. The check valve isolates the pressures developed in the stuffing box from the reservoir. 
     Note that while the present invention has been described as mounting the reservoir to the stuffing box, this need not be the case. The reservoir can be mounted to equipment other than the stuffing box; it can be mounted to the ground. Furthermore, the use of a collar around a stuffing box is not mandated. The collar provides a convenient arrangement for delivering the packing to different locations of the stuffing box. However, one or more lines or hoses can be coupled to one or more of the openings  57  in the stuffing box. 
     Furthermore, the reservoir containing the supply of injectable packing material need not be configured as shown. Other arrangements besides a piston and cylinder can be used to force the packing material into the stuffing box. 
     Polished rods and pump jack units may move side-to-side due to changes in alignment. The polished rod reciprocates along an axis, which axis  123  is typically vertical, or nearly so. The axis may shift or translate laterally, or it may rotate somewhat or move at a combination of translation and rotation. 
     Such movement by the axis of reciprocation of the polished rod tends to move the polished rod within the stuffing box. With conventional stuffing boxes, this movement can create gaps in the anti-extrusion rings  47 ,  49  and/or bushings  48 ,  50 . The packing, being somewhat putty-like in consistency, and under pressure, may extrude from the stuffing box through the gap. 
     The present invention accommodates such axial movement in several ways. First, the packing is injected into the chamber at positions around the circumference. Thus, for the example described above, packing is injected through openings  57 , wherein the gap is filled. 
     In addition, the present invention allows the stuffing box to move laterally and rotationally. The base of the stuffing box has a radially extending flange element  131 . The flange element  131  has upper and lower surfaces that bear on upper and lower bearings  133 ,  135 . The stuffing box  33  can thus move in translation as the flange element  131  moves in a generally horizontal manner between the bearings  133 ,  135 . In addition, the stuffing box  33  can pivot about the base  137  which is fixed to the wellhead  139 . The base  137  has spherical surfaces  141 ,  143  that allows the bearing  135  and a cap  145  to pivot about the base  137 . This in turn allows the stuffing box  33  to pivot. The self-aligning arrangement is described in PCT/AU00/00176, the disclosure of which is incorporated herein. In addition, other self-aligning supports are discussed in U.S. Pat. Nos. 5,112,140 and 5,590,966, the disclosures of which are incorporated herein by reference. The stuffing box  33  and reservoir  34  move in unison relative to the base  137 . 
     By allowing the stuffing box  33  to align with the polished rod axis  123 , the formation of gaps in the anti-extrusion rings  47 ,  49  and the bushings  48 ,  50  will be minimized and the packing  45  will be contained within the chamber  37 . If the reservoir  34  is properly supplied with packing material  45 , then shutting down the pump  21  need only occur for reasons other than the stuffing box  33 . 
     In  FIGS. 4 and 4A , there is shown the stuffing box  151 , in accordance with another embodiment. Instead of utilizing an exterior reservoir for the packing, the stuffing box  151  is self-contained. The packing  45  inside of the stuffing box is maintained in a compacted condition. In  FIG. 4 , the packing  45  is only partially shown. Furthermore, in  FIGS. 4 and 4A , a few exemplary bolts are shown, which bolts are used to couple the various components together. 
     The stuffing box  151  has a housing  153 , which housing has an upper wall  155  that forms a chamber  157  around the polished rod  31 . When the polished rod  31  is installed in the chamber  157 , an annular region or space is formed around the polished rod. This annular region is filled with the injectable packing  45 . The chamber  157  has upper and lower ends, which are closed respectively by the anti-extrusion rings  47 ,  49  and by upper and lower bushings  159 ,  161  (preferably of bronze or brass). Both the upper and lower bushings  159 ,  161  have central openings  163  therethrough for receiving the polished rod  31 . In the preferred embodiment, there is provided a pair of upper anti-extrusion rings  47 , and a pair of lower anti-extrusion rings  49 . A spacer  162  is located between the lower anti-extrusion rings  49  and the lower bushing. The upper bushing  159  and the spacer  162  have ribs that contact the anti-extrusion rings. 
     The upper bushing  159  extends into the chamber  157  and has a lip  165  for bearing on the upper end  167  of the housing wall  155 . A cap  53  threads onto the upper end of the housing wall and clamps the upper bushing  159  in place. The upper bushing  159  is thus fixed in the chamber  157 . The cap  53  has a central opening for receiving the polished rod  31 . The portion of the upper bushing  159  that extends into the chamber  157  has a circumferential groove that receives an o-ring  168 . 
     The lower bushing  161  is located partially within the chamber  157  so as to telescope within the chamber. In the preferred embodiment shown in  FIG. 4 , the lower bushing  161  is constructed to obtain a mechanical advantage. The upper end  171  of the lower bushing  161  has a smaller surface area than does the lower end  173 . While the inside diameter of the lower bushing  161  is constant along its length, the outside diameter of the upper end  171  is smaller than the outside diameter of the lower end  173 . The lower end of the lower bushing forms a flange  173 . The lower end  175  of the housing  153  is enlarged to accommodate the flange  173 ; thus the housing has a lower chamber  176  that has a larger inside diameter than does the chamber  157  with the packing  45 . The lower bushing  161  has a circumferential groove at its upper end and another groove at its lower end; the grooves receive respective o-rings  177 . 
     The upper wall  155  of the housing has two fittings  181  (see  FIG. 4A ) diametrically opposed from one another. Each fitting  181  communicates with openings  179  into the chamber. The fittings  181  each have a one-way, or check, valve. The packing is injected into the chamber through the fittings and openings  179 . The number and location of the fittings  181  and openings  179  can vary. The openings  179  are located at the upper end of the chamber  157 . Thus, even when the chamber is at its smallest volume, the openings  179  are able to inject packing therein. 
     The lower end  175  of the housing has a mounting flange  183 . The mounting flange  183  allows the housing to be mounted to the wellhead  139  or to other wellhead equipment. For example, the stuffing box housing can be mounted to a self-aligning apparatus  131 ,  133 ,  135 ,  137  and  145  as shown in  FIG. 2 . The mounting flange  183  would be coupled to an adapter which in turn would be coupled to the flange element  131 . The housing need not be mounted to a self-aligning apparatus. Well fluid  189 , such as oil and water, can pass through member  185  to contact the flange  173  of the lower bushing  161 . All of the embodiments of the stuffing box of the present invention can be used in conjunction with a self-aligning apparatus as well as other apparatuses. 
     If used with a self-aligning apparatus or other apparatus, the lower bushing  161  need not serve as a bushing. Instead, the other apparatus can provide the bushing. The lower bushing  181  would remain, to compress the packing, as described in more detail below. To prepare the stuffing box for operation, packing  45  is placed in the chamber  157  around the polished rod  31 . The packing can be packed inside by removing the cap  53 , the upper bushing  159  and the rings  47  and then inserting the packing through the open upper end, as described above. Once the chamber  157  is filled with packing, the ring  47 , the upper bushing  159  and the cap  53  are replaced to close the chamber. Alternatively, packing can be injected into the chamber through one or both fittings  181 . The injection gun discussed above is coupled to the fitting  181 . The packing is forced under pressure into the chamber  157 . The lower bushing  161  is pushed down as the chamber  157  fills with packing. The mounting flange  183  serves as a stop to prevent the lower bushing  161  from exiting the chamber  157 . Likewise, the lower flange  173  stops the upward movement of the lower bushing all the way into the chamber, due to a stop surface  187  on the housing. 
     Once the stuffing box  157  has a sufficient charge of packing, the prime mover is started to reciprocate the polished rod  31  and operate the pump down in the well. The well fluid  189 , which can be liquid or gas, exerts an upward force on the lower bushing  161 , which acts like a piston. The well fluid  189  is pressurized by the downhole pump, or by residual pressure within the well. The piston  161  compacts and pressurizes the packing  45  in the chamber  157 , thereby minimizing any voids or spaces in the packing and avoiding any possible leakage paths. By maintaining pressure on the packing  45 , the packing is kept packed and in a sealing condition. The amount of force that is applied to the packing  45  is determined by the ratio of the areas of the upper and lower ends  171 ,  173  of the lower bushing  161 . Thus, this force cannot be tampered with by an operator, ensuring adequacy of the seal around the polished rod. 
     Continued reciprocation of the polished rod will diminish the quantity of packing  45  inside the chamber  157 . The stuffing box  151  automatically compensates and adjusts for a reduction in the amount of the packing  45 . The lower bushing  161  is pushed up into the chamber  157  by the well fluid pressure, maintaining the packing in a packed and compressed condition. 
     Referring back to  FIG. 4 , the lower flange  173  of the lower bushing  161  is equipped with one or more pins  191  that extend upwardly. Each pin  191  is radially offset from the center of the stuffing box so as to extend through an opening in a wall  193  between the upper and lower housing portions, to the exterior of the housing. A groove, or hole,  196  is formed in the outside wall of the housing; the pin  191  moves in the groove. The groove  196  provides protection for the pin. The pin  191  provides a visual indication of the quantity of the packing inside of the chamber. As the lower bushing  161  moves up in the chamber  157 , the pin  191  rises on the outside. The operator can thus visually gauge the amount of packing in the stuffing box by looking at how far the pin has moved toward the upper end of the groove  196  or extruded through the hole. The pin can also be colored so that as the pin appears to grow longer, different colors show at its base (for example, green shows first, followed by yellow, and then red). Also, the outside of the housing can be marked or scribed with lines and indications so that the height of the pin can be correlated to the amount of the packing inside the chamber. 
     Packing  45  is added to the chamber through the fitting  181 , as discussed above. The stuffing box  151  need not be opened to add the packing. Thus, the well operator need not be exposed to any potential pressure releases from the well. Furtherstill, the packing can be added while the pump is in operation, while the polished rod  31  reciprocates in the stuffing box  151 . The packing  45  can be added through one or both fittings. Packing can be added alternatively or simultaneously to the fittings. As the packing  45  is injected into the chamber, the lower bushing  161  descends, as does the indicator pin  191 . The operator fills the chamber  157  with packing, wherein the lower bushing  161  contacts the mounting flange  183 . The chamber  157  can be filled with packing when the polished rod is reciprocating, or is not reciprocating. 
     Utilizing a cylindrical sleeve as a lower bushing, such as shown as  50  in  FIG. 2 , produces a one-to-one ratio. That is, for every one pound per square inch (psi) of pressure exerted on the lower end by the well fluid, the packing is subjected to one psi on the upper end. With the lower bushing  161  configured as shown in  FIG. 4 , and described, the lower end  173  has a larger area than does the upper end  171 . This is done to achieve an amplification, or hydraulic advantage, and force the lower bushing into the packed chamber  157 . The relative sizes of the upper and lower end surfaces can vary in accordance with the size of the polished rod, the pressures developed by the well fluid, and so on. In  FIG. 4 , the lower bushing shown has a fairly high amplification. That is, a relatively small well fluid pressure will satisfactorily compact the packing  45  without causing binding in the movement of the polished rod. The amplification can be reduced by making the lower end  173  surface smaller. It is believed that amplification ratios ranging from 1:1 to 3.5:1 will operate in a satisfactory manner. 
       FIG. 4B  shows an embodiment of the stuffing box similar to that of  FIG. 4 , but modified for a high pressure well. The length of the lower chamber has been increased to accommodate a reducer  192 , which is coupled to the bottom of the lower bushing  161 . The reducer  192  has a smaller outside diameter than does the lower flange  173  of the lower bushing  161 . The housing has a third chamber  194 , or throat, that receives the reducer  192 . The well fluid contacts the reducer. The reducer is sized so that the higher pressure well fluid forces the lower bushing into the chamber  157  with the desired amount of force. By changing the diameter of the reducer  192  and the third chamber  194 , a variety of well pressures can be accommodated. In  FIG. 4B , the lowermost o-ring can be placed on the reducer  194 . 
     If the flange  173  of the lower bushing is sufficiently decreased in outside diameter, the indicator pins  191  may no longer be radially offset enough to extend exteriorly of the housing.  FIG. 5  shows an alternate embodiment of an indicator pin  191 . The pin is perpendicular to the polished rod longitudinal axis and is coupled to the lower bushing  161 . It extends through a slot  195  in the housing. The pin  191  traverses the slot  195  as the lower bushing  161  moves up and down in the housing. O-rings  177  isolate the slot  195  from well fluids and from the packing. The location of the pin  191  in the slot  195  indicates how much packing is in the chamber. The slot can be slightly longer than the distance of travel of the lower bushing, to avoid having a pin serve as a stop. 
     As an alternative to the embodiment of  FIG. 4B , which requires the piston assembly  161 ,  192  to be sized in diameter according to the well pressure, the piston  161  of  FIG. 4  could be used in conjunction with a counteracting hydrostatic pressure. The portion of the lower chamber  176  (see  FIG. 4 ) that is above the flange  173  of the lower bushing, or piston,  161  can contain oil (such as hydraulic fluid). The fluid above the flange  173  thus counteracts the well pressure exerted below the flange. The fluid above the flange can exit the lower chamber via the groove, or hole,  196  and be routed to an accumulator. 
     In operation, when the stuffing box has sufficient packing, the well pressure pushes the piston  161  into the packing. If the pressure is too high, resulting in too much pressure on the packing, the lower chamber  176  can be filled with fluid. This will lessen the pressure on the packing. As the piston moves up due to the packing volume diminishing from normal use, the fluid exits the lower chamber and flows into the accumulator. When new packing is injected into the stuffing box, the piston is pushed back down and the fluid returns to the lower chamber from the accumulator. 
     The use of fluid above the piston reduces the number of part sizes, as only one size piston need be made and inventoried for a particular sized polished rod. If the well is subject to variations in well pressure, the use of the fluid damps out these variations. It is possible to regulate the amount of pressure applied to the packing by regulating the hydrostatic pressure or by regulating a gas head exit. 
       FIG. 6  shows a stuffing box  201  in accordance with still another embodiment. The stuffing box  201  is similar to the stuffing box  151  of  FIG. 4  in that it is a self-contained stuffing box. However, the source of pressure on the packing is different. Instead of using well fluid pressure acting on the bottom of the packing, the stuffing box uses a force on the upper bushing  203 . Thus, the upper bushing  203  is movable within the chamber  157  while the lower bushing  50  is fixed. The upper bushing  203  is a ring; the lower bushing  50  is also a ring or a cylinder but is fixed from moving downward by a lip  204 . The upper and lower bushings  203 ,  50  can be provided with o-ring seals. 
     The upper bushing  203  is forced down into the chamber  157  by a pressure source. Once such pressure source is a spring  205 , located between the upper bushing  203  and the cap  53 . Another pressure source is weights. 
     One or more indicator pins  207  are coupled to the upper bushing  203  and extend up out of the cap  53 . As the upper bushing  203  moves down within the chamber, the pin  207  becomes less and less visible. 
     The chamber  157  is recharged with packing  45  through the fitting  181  as described above, causing the upper bushing  203  and its anti-extrusion ring  47  to rise within the chamber. 
     As an alternative to the embodiment of  FIG. 6 , springs can be used on both the upper and lower ends of the packing  45 . The upper end remains the same, while the lower bushing  50  would have the same diameter as the upper bushing  203 . Springs would push against the housing so as to force the lower bushing into the packing. Alternatively, the lower bushing could be forced into the packing by well fluid, as discussed with respect to  FIGS. 4A and 4B . 
     The stuffing box of the present invention reduces inventory because the same type of packing is used no matter what the type or size of stuffing boxes. In the prior art, packing glands of various sizes (inside diameter and outside diameter) must be stocked in order to accommodate different sizes of polished rods and stuffing boxes. This is not so with the present invention. (Size sensitive anti-extrusion rings will still need to be maintained in inventory.) 
     The proper amount of force can be predetermined and applied to the stuffing, resulting in a lower coefficient of friction between the seal and the polished rod. In the prior art, some seal ring type stuffing boxes have used a high clamping force on the seal rings. The invention produces consistently lower power requirements. 
     By continually pressurizing the packing, even when some of the packing has worn away, leakage is eliminated. This means that the well operator need not spend much time monitoring the stuffing box and cleaning up leaks. In addition, once a stuffing box has been on a well for some period of time, its maintenance can be predicted so as to be scheduled to produce operator efficiency. 
     The stuffing box of the present invention utilizes an injectable packing to provide a seal around the reciprocating polished rod. With prior art stuffing boxes, misalignment of the longitudinal axis of the polished rod may lead to leaks in the stuffing box. But, with the present invention, the packing is conformable to any shift of the polished rod in the chamber. The application of pressure to the packing serves to close any voids in the chamber, thereby minimizing leaks. 
     The bronze or brass bushings of the stuffing box are sacrificial. Thus, if the polished rod reciprocates off of the center line of the stuffing box, the bushings will wear. Wear on the polished rod will be minimal. The use of sacrificial bushings could lead to misalignment of the polished rod. The self-aligning apparatus of  FIG. 2  reorients the stuffing box so as to be aligned with the polished rod, thus reducing the wear on the bushings. 
     The stuffing box of the present invention can be used without the self-aligning apparatus. However, it is suggested that the stuffing box be equipped with non-sacrificial bushings, such as carbide bushings. The bushings will not wear as much and the packing will continue to be contained within the stuffing box. 
     The packing can be pressurized, compacted or squeezed by varying the volume of the packed chamber or by injecting additional packing in a fixed volume chamber. 
     Other visual indicators besides pins  191  could be used. For example, the housing  155  could be transparent, such as plastic. A plastic housing would be suitable for low pressure applications, and possibly even high pressure applications. 
     The foregoing disclosure and showings made in the drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense.