Abstract:
A pump for efficiently producing gas in wells having some liquids. The pump may be driven by a walking beam or horsehead pump. The pump of the invention produces gases and liquids separately. Gases may be produced up the annulus between the casing and hollow sucker rods. A plunger seals the opening in the cage during downstroke. Gases and liquids are trapped in the cage above an inner barrel. Liquids are forced up the hollow sucker rod where they are retained by a one-way valve. On the upstroke, the one-way valve seats and gases are forced out of the cage and up the annulus. Gases are, therefore, produced up the annulus and liquids are produced up the drill string. In another embodiment, liquids are retained in a trap and are produced up hollow sucker rods, while gases are produced up the annulus between the hollow sucker rods and the casing.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application No. 60/781,857, filed Mar. 13, 2006, entitled “Reciprocal Pump for Gas and Liquids,” which application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     A pump that efficiently produces gas in wells having some liquids. More particularly, the pump of the invention is a reciprocating pump that produces gases and liquids separately.  
       BACKGROUND OF THE INVENTION  
       [0003]     As energy needs become more pressing and the price of natural gas rises, it will become economically feasible and desirable to conserve and utilize natural gas from oil wells, including substantially depleted oil wells. One problem with wells that produce gas and some liquids is that when liquids accumulate in pumps designed to produce gas, the liquids put a heavy load on the pumps.  
       SUMMARY  
       [0004]     Therefore, it is desirable to provide a pump that is designed to efficiently produce gas in wells having some liquids. Preferably, the pump will be driven by common existing equipment, such as an existing walking beam or horsehead pump. The described pump produces gases and liquids separately.  
         [0005]     In one embodiment, gases are produced up the annulus between the casing and the hollow sucker rods. A plunger seals the opening in the cage during downstroke. Gases and liquids are trapped in the cage above an inner barrel. Liquids are forced up the hollow sucker rod where they are retained by a one-way valve. On the upstroke, the one-way valve seats and gases are forced out of the cage and up the annulus. In this way, gases are produced up the annulus and liquids are produced up the drill string.  
         [0006]     In another embodiment, liquids are retained in a trap and are similarly produced up the hollow sucker rods, while gases are produced up the annulus between the hollow sucker rods and the casing.  
         [0007]     A well that utilizes the first above described embodiment utilizes a reciprocating pump for efficiently pumping both gas and liquids. An outer barrel is secured to an inside of the casing. The outer barrel defines a central orifice/gas port on an upper end. Hollow sucker rods, e.g., a tubing string, extends into the casing and pass through the central orifice/gas port on the upper end of the outer barrel. A sliding seal is affixed to an exterior of the hollow sucker rods for selective engagement with the central orifice/gas port on the outer barrel. A one way liquid valve is provided in the hollow sucker rods. An inner barrel is received within the outer barrel. The inner barrel has a shoulder seal section affixed to a lower end of the hollow sucker rods. The inner barrel further defines a chamber having an upper surface and a lower surface. The upper surface of the chamber defines an output gas port. The lower surface of the chamber defines an intake port selectively closed by a one way valve, e.g., by a ball and seat valve or other suitable valve, wherein the intake port one way valve opens during downstroke and closes during upstroke;  
         [0008]     When the hollow sucker rods are stroked in a downward direction, the inner barrel is moved downwardly with respect to the outer barrel, and the intake one way valve opens to allow liquid and gas to enter the chamber through the intake port. Liquid and gas pass through the output gas port on the upper surface of the chamber. The sliding seal sealingly engages an upper end of the outer barrel for sealing the central orifice/gas port defined by the outer barrel. The liquid in the chamber is forced into the hollow sucker rods and through the one way valve on the hollow sucker rods.  
         [0009]     When the hollow sucker rod is stroked in an upward direction, the inner barrel is moved upwardly with respect to the outer barrel. The intake one way valve closes to prevent gas and liquid from escaping through the intake port. The sliding seal then disengages from the central orifice/gas port on an upper end of the outer barrel to allow gas to escape into the casing annulus. The shoulder seal engages the central orifice/gas port to prevent further liquids and gases from escaping through the central orifice/gas port.  
         [0010]     A well utilizing the second above described embodiment utilizes a reciprocating pump for efficiently pumping both gas and liquids. The well includes an outer barrel secured to an inside of the casing. The outer barrel defines a central orifice/gas port on an upper end.  
         [0011]     An inner barrel is received within the outer barrel. The inner barrel defines a central orifice on an upper end and further defines a chamber having an upper surface and a lower surface.  
         [0012]     A liquid trap collects fluid draining from within the chamber. The upper surface of the chamber defines an output port. The lower surface of the chamber defines an intake port selectively closed by a one way valve, such as a ball and seat valve.  
         [0013]     Hollow sucker rods extend into the casing and pass through the central orifice/gas port on the outer barrel. A one way liquid valve is located in the hollow sucker rods. A plunger is provided on a lower end of the hollow sucker rods for sealingly engaging an inner surface of the liquid trap. A sliding seal is affixed to an exterior of the hollow sucker rods for engaging the central orifice/gas port on the outer barrel during a lower portion of a stroke of the hollow sucker rods.  
         [0014]     When the hollow sucker rods are stroked in a downward direction, the inner barrel is moved downwardly with respect to the outer barrel. The intake port one way valve opens to allow liquid and gas to enter the chamber through the intake port, and allows the liquid and gas to pass through the output port on the upper surface of the chamber. The sliding seal sealingly engages an upper end of the outer barrel for sealing the central orifice/gas port defined by the outer barrel. The liquid in the liquid trap is forced into the hollow sucker rods and through the one way liquid valve on the hollow sucker rods.  
         [0015]     When the hollow sucker rods are stroked in an upward direction, the inner barrel is moved upwardly with respect to the outer barrel. The intake port one way valve closes to prevent gas and liquid from escaping through the intake port. The plunger disengages from the liquid trap to allow liquid in the chamber to drain into the liquid trap. And the sliding seal disengages from the orifice/gas port on an upper end of the outer barrel to allow gas to escape into the casing annulus. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1   a  is a cross-sectional view of a well having a first embodiment of a reciprocal pump for producing gas and liquids, showing the pump at mid-stroke on the downstroke.  
         [0017]      FIG. 1   b  is a cross-sectional view of a well showing the pump of  FIG. 1   a  during upstroke as the pump approaches an uppermost position.  
         [0018]      FIG. 1   c  is a cross-sectional view of a well showing the pump of  FIG. 1   a  during downstroke as the pump approaches a lowermost position.  
         [0019]      FIG. 2   a  is a cross-sectional view of a well having a second embodiment of a reciprocal pump for producing gas and liquids, showing the pump during upstroke as the pump approaches an uppermost position.  
         [0020]      FIG. 2   b  is a cross-sectional view of a well showing the pump of  FIG. 2   a  during downstroke as the pump approaches a lowermost position.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     Before explaining the present invention in detail, it is important to understand that the invention is not limited in its application to the details of the embodiments and steps described herein. The invention is capable of other embodiments and of being practiced or carried out in a variety of ways. It is to be understood that the phraseology and terminology employed herein is for the purpose of description and not of limitation.  
         [0022]     Referring now to  FIGS. 1   a - c , well  10  is shown utilizing a first embodiment  12  of a reciprocating pump for efficiently pumping both gas and liquids. Well  10  includes well casing  14 . Outer barrel  16  is secured to an inside surface of casing  14 . Although this description utilizes the term “well case” or “casing” throughout, it should be understood that casing refers not only to well casing as the term is typically understood in the art, but also to any large tubing within which the pump of the invention may be deployed. Outer barrel  16  has an upper end  20  that defines a central orifice/gas port  18 . Hollow sucker rods  22 , e.g., a tubing string or a coiled tubing string acting as sucker rods and flow path extends into casing  14  and passes through central orifice/gas port  18  on upper end  20  of outer barrel  16 . A sliding seal  24  is affixed to an exterior of said hollow sucker rods  22  for selective engagement with central orifice/gas port  18  on outer barrel  16 . One-way liquid valve  26  is provided in said hollow sucker rods  22 .  
         [0023]     Inner barrel  28  is received within outer barrel  16 . Inner barrel  28  has a shoulder seal section  30  that is affixed to a lower end of hollow sucker rods  22 . Inner barrel  28  further defines a chamber  32  having an upper surface  34  and a lower surface  36 . Upper surface  34  of chamber  32  defines an output gas port  38 . Lower surface  36  of chamber  32  defines an intake port  40  selectively closed by one-way valve  42 , e.g. check valve or ball and seat. Intake port one-way valve  42  opens during downstroke and closes during upstroke.  
         [0024]     Referring now to  FIGS. 2   a - b , shown is a well  100  for utilizing a second embodiment  112  of a reciprocating pump for efficiently pumping both gas and liquids. Well  100  utilizes well casing  114 . Outer barrel  116  is secured to an inside surface of casing  114 . Outer barrel  116  has upper end  120  that defines a central orifice/gas port  118 .  
         [0025]     An inner barrel  122  is received within outer barrel  116 . Inner barrel  122  has an upper end  120  that defines a central orifice  124 . Inner barrel  122  further defines a chamber  128  having an upper surface  130  and a lower surface  132 . Liquid trap  134  is provided for collecting fluid from within said chamber  129 . Upper surface  130  of chamber  128  defines an output port  136 . Lower surface  132  of chamber  128  defines an intake port  138  selectively closed by a one-way valve  140 , such as a ball and seat valve.  
         [0026]     Hollow sucker rods  142  extends into casing  114  and passes through central orifice/gas port  118  on outer barrel  116 . One-way liquid valve  144 , e.g., a check valve or a ball and seat valve, is provided in hollow sucker rods  142 . Plunger  146  is located on a lower end of hollow sucker rods  142  for sealingly engaging an inner surface of liquid trap  134 . Sliding seal  148  is affixed to an exterior of said hollow sucker rods  142  for engaging central orifice/gas port  118  on outer barrel  116  during a lower portion of a stroke of said hollow sucker rods  142 .  
         [0027]     In use, embodiment  12 , shown in  FIGS. 1   a - c , operates as follows. Referring first to  FIG. 1   c , shown is a first embodiment  10  of the reciprocal pump of the invention during downstroke as pump  10  approaches a lowermost position. As hollow sucker rods  22  is stroked in a downward direction, inner barrel  28  is moved downwardly with respect to said outer barrel  16 . Intake one-way valve  42  lifts off of intake port  40  to allow liquid and gas to enter chamber  32 . The liquid and gas fill chamber  32  and pass through output gas port  38  on upper surface  36  of chamber  32  into a space defined by hollow sucker rods  22 , outer barrel  16  and upper end  20 . During mid-stroke ( FIG. 1   a ) gas is free to escape through orifice/gas port  18  into the casing annulus. As hollow sucker rods  22  and attached inner barrel  28  move downwardly, sliding seal  24  sealingly engages upper end  20  of said outer barrel  16  for sealing said central orifice/gas port  18 .  
         [0028]     Referring now primarily to  FIG. 1   b , first embodiment  10  of the reciprocal pump of the invention is shown during upstroke as pump  10  approaches an uppermost position. As hollow sucker rods  22  is stroked in an upward direction, inner barrel  28  is moved upwardly with respect to outer barrel  16 . Intake one-way valve  42  seats on intake port  40  to prevent liquid from escaping from chamber  32  through intake port  40 . As hollow sucker rods  22  and inner barrel  28  move upwards, sliding seal  24  lifts off of orifice/gas port  18 . As hollow sucker rods  22  and inner barrel  28  continue to move upwards the area defined by hollow sucker rods  22 , outer barrel  16  and upper end  20  is reduced in size, which forces gas through orifice/gas port  18 , as upper surface  34  of chamber  32  approaches upper end  20  of outer barrel  16 . As pump  10  approaches an uppermost position, shoulder seal section  30  on hollow sucker rods  22  forms a seal with orifice/gas port  18 . As hollow sucker rods  22  and attached inner barrel  28  travel though the last portion of the upstroke, liquid is forced back through output gas ports  38  on upper surface  34  of chamber  32  and upwards into the interior of hollow sucker rods  22 . As liquid passes upwardly through hollow sucker rods  22 , the liquid passes through one-way liquid valve  26 , such as a ball and seat valve. A preferred condition for operation of the pump of the invention is operation in a well having mostly gas with some associated liquids.  
         [0029]     A subsequent downstroke of pump  10  results in closure of one-way liquid valve  26  so that any liquids previously forced through one-way liquid valve  26  remain above the valve for production.  
         [0030]     Therefore, it can be seen that pump  12  of the invention is uniquely suited to produce large volumes of gas while simultaneously producing some associated liquids.  
         [0031]     One advantage associated with first embodiment  10  is that weight or pressure from the liquid column does not act on lower surface  36  and the attached hollow sucker rods  22  until near the top of the stroke and not at all if there is no liquids to be produced on any individual stroke.  
         [0032]     Referring now to  FIGS. 2   a  and  b , second embodiment  112  of the reciprocal pump of the invention is shown.  FIG. 2   b  shows second embodiment  112  during downstroke as pump  112  approaches a lowermost position. As hollow sucker rods  142  are stroked in a downward direction, plunger  146  is moved downwardly with respect to inner barrel  122  into liquid trap  134 . As plunger  146  moves towards the bottom of liquid trap  134 , any liquid located within the liquid trap  134  is forced into hollow sucker rods  142  and through one-way liquid valve  144 , such as a ball and seat valve. As hollow sucker rods  142  continues to move downwardly, plunger  146  will engage a bottom of liquid trap  134  and force inner barrel  122  to move downwardly with respect to outer barrel  116 . As hollow sucker rods  142  and attached inner barrel  122  move downwardly, sliding seal  148  sealingly engages upper end  120  of said outer barrel  116  for sealing said central orifice/gas port  118  and intake one-way valves  140  lift off of intake ports  138  to allow liquid and gas to enter chamber  128 . Liquid and gas fill chamber  128 . The liquid and gas are free to pass through central orifice  124  on upper surface  130  of chamber  128  and into a space defined by hollow sucker rods  142 , outer barrel  116  and upper end  120 . A stop  121  is provided below outer barrel  116  to stop inner barrel  122  on bottom of downstroke. Stop  121  may be attached to outer barrel  116  ( FIGS. 2   a ,  2   b ) or fixed to casing  114 .  
         [0033]     Referring now to  FIG. 2   a , shown is second embodiment  112  of the reciprocal pump of the invention during upstroke as pump  12  approaches an uppermost position. As hollow sucker rods  142  are stroked in an upward direction, plunger  146  is moved upwardly with respect to inner barrel  122  and liquid trap  134 . As plunger  146  moves out of liquid trap  134  and towards the upper surface  132  of chamber  128 , any liquid located within chamber  128  is free to flow out of chamber  128  and into liquid trap  134 . As hollow sucker rods  142  continues to move upwardly, plunger  146  will engage upper surface  132  of chamber  128  and force attached inner barrel  122  to move upwardly with respect to outer barrel  116 . As hollow sucker rods  142  and attached inner barrel  122  move upwardly, sliding seal  148  lifts off of upper end  120  of said outer barrel  116  and unseals central orifice/gas port  118  to allow gas to pass through central orifice/gas port  118  into the casing annulus. Intake one-way valves  140  seat in intake ports  138  to prevent liquid and gas from exiting chamber  128  through intake port  138 . Instead, liquid trapped in chamber  128  collects in liquid trap  134 .  
         [0034]     On a subsequent downstroke, plunger  146  forces the liquid in liquid trap  134  into hollow sucker rods  142 . Therefore, it can be seen that valve  112  of the invention is uniquely suited to produce large volumes of gas while simultaneously producing liquids.  
         [0035]     One advantage associated with second embodiment  100  is that the weight and pressure from the liquid column acting on upper surface  130  and carried by a higher load on hollow sucker rods  142  as long as liquid does not exceed the trap volume  134  and as such the pump might be sized to the well as one technique to consider various gas/liquid ratios and liquid volumes.  
         [0036]     Thus, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned above as well as those inherent therein. While presently preferred embodiments have been described for purposes of this disclosure, numerous changes and modifications will be apparent to those skilled in the art. Such changes and modifications are encompassed within the spirit of this invention as defined by the appended claims.