Abstract:
A method of circulating through a reciprocating downhole tubing pump and a reciprocating downhole tubing pump. The reciprocating downhole tubing pump has a standing valve assembly and a travelling valve. The method involves displacing and disabling, without removing, the standing ball valve assembly and the travelling valve. This can be done with pins which knock the balls out of position or by enclosing the balls in cages which can be mechanically moved out of position with linkages. With the standing ball valve assembly and the travelling valve disabled, circulation can occur through the reciprocating downhole tubing pump. This has a number of advantages, such as removal of blockages due to sand accumulation.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a method of circulating through a reciprocating downhole tubing pump and a reciprocating downhole tubing pump which has been modified in accordance with the teachings of the method.  
       BACKGROUND OF THE INVENTION  
       [0002]     A reciprocating downhole tubing pump has a standing ball valve and a travelling ball valve positioned downhole. Blockages periodically occur in the tubing string. The blockages are usually the result of an accumulation of sand below the standing ball valve of such downhole tubing pumps, although the blockages can occur above or in the downhole tubing pump. When this occurs, the entire tubing string and downhole tubing pump are pulled from the well using a service rig. The blockage is then removed from the tubing at surface. Before the production string is run back in, it is necessary to bail or circulate to remove sand accumulations down hole in order to reposition the down hole tubing pump at the desired depth.  
       SUMMARY OF THE INVENTION  
       [0003]     What is required is a method of circulating through the standing ball valve assembly and travelling valve of a downhole tubing pump, without having to pull the tubing string and the downhole tubing pump from the well.  
         [0004]     According to one aspect of the present invention there is provided a method of circulating through a reciprocating downhole tubing pump which has a standing ball valve and a travelling ball valve positioned downhole. A first step involves providing first means for mechanically displacing and disabling, without removing, a ball from a ball seat on the travelling ball valve. A second step involve providing second means for mechanically displacing and disabling, without removing, a ball from a ball seat on the standing valve assembly. A third step involves activating the first means to prevent the ball from engaging the ball seat on the travelling ball valve and the second means to prevent the ball from engaging the ball seat on the standing ball valve assembly and circulating fluids through both the travelling ball valve and the standing ball valve assembly.  
         [0005]     According to another aspect of the present invention there is provided a reciprocating downhole tubing pump which includes a barrel and a piston axially movable along the barrel. A travelling ball valve is carried by the piston. The travelling valve has a ball seat which receives a ball. First means are provided for mechanically displacing and disabling, without removing, the ball from the ball seat on the travelling ball valve. A standing ball valve assembly is positioned within the barrel. The standing ball valve assembly includes a ball seat which receives a ball. Second means are provided for mechanically displacing and disabling, without removing, the ball from the ball seat on the standing valve assembly. Means are provided for activating the first means to prevent the ball from engaging the ball seat on the travelling ball valve and the second means to prevent the ball from engaging the ball seat on the standing ball valve assembly, such that a circulation of fluids can occur through both the travelling ball valve and the standing ball valve assembly.  
         [0006]     The above described method sets forth the broad aspects of the present invention. Once the inventive concept is understood, there may be different ways of putting it into effect. As will be hereinafter described, in a preferred embodiment an upstanding first pin is secured on top of the standing ball valve assembly. This first pin is in axial alignment with a ball seat, which receives a ball on the travelling ball valve. A rigid pivot linkage is provided having a first end and a second end. The first end is secured to the ball cage with a fulcrum positioned between the first end and the second end, such that when a downward force is exerted on the second end of the pivot linkage, the pivot linkage pivots about the fulcrum lifting a ball cage from an operative position to a circulating position in which the raised ball cage lifts the ball on the standing ball valve assembly from the ball seat. An upstanding second pin is secured to the second end of the pivot linkage extending above the standing ball valve assembly adjacent to the first pin. When the travelling ball valve is lower onto the standing ball valve assembly, the first pin extends through the valve seat to prevent the ball from engaging the ball seat on the travelling ball valve and the second pin acts upon the pivot linkage to pivot the ball cage to the circulating position to prevent the ball from engaging the ball seat on the standing ball valve assembly. This permits an unfettered circulation of fluids through both the travelling ball valve and the standing ball valve assembly.  
         [0007]     In another preferred embodiment, the standing ball valve is axially movable along the barrel with axial travel being limited by an underlying axial stop. An upstanding first pin is secured on top of the standing ball valve assembly. The first pin is in axial alignment with the ball seat on the travelling ball valve assembly. An upstanding second pin is mounted below the standing ball valve assembly. The second pin protrudes above the axial stop in axial alignment with the ball seat on the standing ball valve assembly. A spring is positioned between the standing ball valve and the axial stop. The spring biases the standing ball valve assembly into an operative position spaced above the second pin. Upon the travelling ball valve engaging the standing ball valve assembly and a compressive force being exerted upon the spring, the standing ball valve assembly is moved to a circulating position with the first pin preventing the ball from engaging the ball seat on the travelling ball valve and the second pin preventing the ball from engaging the ball seat on the standing ball valve assembly. This permits a circulation of fluids through both the travelling ball valve and the standing ball valve assembly. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to in any way limit the scope of the invention to the particular embodiment or embodiments shown, wherein:  
         [0009]      FIG. 1  is a side elevation view, in section, of a reciprocating downhole tubing pump constructed in accordance with the teachings of the present method with the standing ball valve assembly and the travelling valve in an operative position.  
         [0010]      FIG. 2  is a side elevation view, in section, of the reciprocating downhole tubing pump illustrated in  FIG. 1 , with the standing ball valve assembly and the travelling valve in a circulating position.  
         [0011]      FIG. 3  is a detailed side elevation view, in section, of an offset transfer ball cage and pivot linkage constructed in accordance with the teachings of the present method.  
         [0012]      FIG. 4  is a side elevation view, in section, of a reciprocating downhole tubing pump constructed in accordance with the teachings of the present method with the standing ball valve assembly and the travelling valve in an operative position.  
         [0013]      FIG. 5  is a side elevation view, in section, of the reciprocating downhole tubing pump illustrated in  FIG. 4 , with the standing ball valve assembly and the travelling valve in a circulating position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]     The preferred embodiment, a reciprocating downhole tubing pump generally identified by reference numeral  10 , will now be described with reference to  FIGS. 1 through 5 .  
         [0015]     Structure and Relationship of Parts:  
         [0016]     Referring to  FIG. 1 , reciprocating downhole tubing pump  10  has a barrel  12 . A piston  13  transports a travelling ball valve  14  having a first ball seat  16  and a first ball  18  is axially movable along barrel  12 . A standing ball valve assembly  20  having a second ball seat  22  and a second ball  24  is positioned within barrel  12 . Second ball  24  is confined within a ball cage  26 . An upstanding first pin  28 , in axial alignment with first ball seat  16  and first ball  18  of travelling ball valve  14 , is secured on top of standing ball valve assembly  20 . Standing ball valve assembly  20  is further adapted with a rigid pivot linkage  30 , an offset transfer body  31  and a screen  32 . Referring to  FIG. 3 , rigid pivot linkage  30  has a first end  33  and a second end  34 . A fulcrum  36  is positioned between first end  33  and second end  34 . When a downward force  38  is exerted on second end  34 , linkage  30  pivots about fulcrum  36 , lifting ball cage  26  and second ball  24  from an operative position to a circulating position. An upstanding second pin  40  is secured to second end  34  of linkage  30  and extends above standing ball valve assembly  20  adjacent to first pin  28 . Referring to  FIG. 2 , when piston  13  transports travelling ball valve  14  onto standing ball valve assembly  20 , first pin  28  extends through first valve seat  16 , preventing first ball  18  from engaging first ball seat  16  in travelling ball valve  14 . Upon contact with travelling ball valve  14 , second pin  40  acts upon pivot linkage  30 , pivoting ball cage  26  to a circulating position by preventing second ball  24  from engaging second ball seat  22  of standing ball valve assembly  20 , allowing an unfettered circulation of fluids through both travelling ball valve  14  and standing ball valve assembly  20 .  
         [0017]     Referring now to  FIG. 4 , there is shown another embodiment of the reciprocating downhole tubing pump  10 . As in the embodiment shown in FIGS.  1  to  3 , reciprocating downhole tubing pump  10  has barrel  12 , travelling ball valve  14  having first ball seat  16  which receives first ball  18 , and standing ball valve assembly  20  having second ball seat  22  which receives second ball  24 . In this embodiment, axial travel of standing ball valve assembly  20  is limited by an underlying axial stop  42 . Upstanding first pin  28  is secured on top of standing ball valve assembly  20 . First pin  28  is in axial alignment with first ball seat  16  on travelling ball valve  14 . An upstanding second pin  44 , positioned below standing ball valve assembly  20 , protrudes above axial stop  42  and is in axial alignment with second ball seat  22  on standing ball valve assembly  20 . A spring  46  is positioned between standing ball valve assembly  20  and axial stop  42 . A spring sealer  48  seals spring  46  at axial stop  42 . Spring  46  biases standing ball valve assembly  20  in an operative position spaced above second pin  44 . Referring to  FIG. 2 , where travelling ball valve  14  contacts standing ball valve assembly  20  and a compressive force  50  is exerted upon spring  46 , standing ball valve assembly  20  is moved to a circulating position with first pin  28  preventing first ball  18  from engaging first ball seat  16  on travelling ball valve  14 . Further, second pin  44  prevents second ball  24  from engaging second ball seat  22  on standing ball valve assembly  20 , thereby permitting an unfettered circulation of fluids  52  through both travelling ball valve  14  and standing ball valve assembly  20 .  
         [0018]     Operation:  
         [0019]     The use and operation of the first embodiment of reciprocating downhole tubing pump  10  in accordance with the teachings of the preferred method, will now be described with reference to  FIGS. 1 through 3 . Referring to  FIG. 1 , where a blockage of sand or other impediment occurs below standing ball valve assembly  20 , piston  13  with travelling ball valve  14  is positioned within barrel  12  above standing ball valve assembly  20  as provided. Referring to  FIG. 3 , as piston  13  with travelling ball valve  14  is lowered and contact is made with standing ball valve assembly  20 , upstanding second pin  40  exerts downward force  38  onto second end  34  of rigid pivot linkage  30 , lifting ball cage  26  and unseating second ball  24  from second seat  22  and opening standing ball valve  20  for circulation. Referring to  FIG. 2 , similarly, upstanding first pin  28  unseats first ball  18 , opening travelling ball valve  14  for circulation. As both valves are in a circulating position, any blockages may then be cleared by the flow of fluid. The blockage is then removed from the tubing at surface. Very little extra preparation is required to get the well into production again. This concept saves the need of removing the reciprocating downhole tubing pump, circulating or running a sand bailer, and then reinstalling the reciprocating downhole tubing pump.  
         [0020]     The use and operation of the second embodiment will now be described with reference to  FIGS. 3 and 4 . Referring to  FIG. 3 , where a blockage of sand or other impediment occurs below standing ball valve assembly  20 , travelling ball valve  14  is lowered onto standing ball valve assembly  20  and a compressive force  50  is exerted upon spring  46  to move standing ball valve assembly  20  to the circulating position as shown in  FIG. 4 . Referring to  FIG. 4 , first pin  28  prevents first ball  18  from engaging first ball seat  16  on travelling ball valve  14 , and second pin  44  prevents second ball  24  from engaging second ball seat  22  on standing ball valve assembly  20 . It should be noted that compressive force  50  may be provided by the weight of a tubing string or by fluid under pressure.  
         [0021]     Variations:  
         [0022]     It should be noted that the dislodging and disabling of the ball on the travelling valve and the ball on the standing valve can be done in either order or simultaneously. In field trials the ball on the standing valve was dislodged and disabled first. The reason for this was that the ball on the standing valve is not subjected to the same fluid pressure, as the ball on the travelling valve is generally holding the fluid weight in the tubing.  
         [0023]     It is desirable to place a screen below the standing ball valve assembly. The screen serves two valuable functions. When fluid is flowing in an upward direction through the standing ball valve assembly, it prevents debris which cannot be pumped from entering and acts as a vortex to break up fluid composition prior to entering pump. When fluid is flowing in a downward direction, it acts as a spray nozzle.  
         [0000]     Advantages:  
         [0024]     There are a number of advantages obtainable through the use of the method and apparatus, as described above: 
    1. At the present time hours of rig time are spent during pump installation to circulate fluids to clean out sand fill or using bailers to bail sand accumulations to clean up the cellar. With the present invention, one can circulate the reciprocating downhole tubing pump into the desired landing depth. One way this may be done is by pinning the pump with shear screws. Once in position, an anchor can be set and a force can be exerted upon the pump to shear the shear screws to open up the pump stroke.     2. The ability to circulate enables you to pump fluid into the formation, to assist in opening up the perforations or the formation.     3. If the formation is tight, you could circulate the entire hole over by sending fluid down tubing and up and out the casing.     4. If a blockage should occur in the pump, above the pump or below the pump, the blockage can be addressed by direct circulation of fluids which flushes the tubing string of blockages. While blockages mainly occur below the pump, they sometimes occur elsewhere in the tubing string.     5. The described invention can be used in conjunction with other tools, such as a scraper, a casing swabbing device or drill out equipment to accomplished several tasks in one operation.    
 
         [0030]     In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.  
         [0031]     It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the claims.