Abstract:
A backflush valve may open a traveling valve and a standing valve both at the same time so production tubing and a rod pump can be backflushed. The backflush valve may be adapted to connect to a pump barrel between the traveling valve and the standing valve and may be actuated by collapsing the pump.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a backflush valve for a reciprocating rod pump assembly and a method of backflushing a pump assembly. 
       BACKGROUND OF THE INVENTION 
       [0002]    Reciprocating downhole pump systems are used to elevate production fluids from an oil and gas well to the surface, A typical pump system includes a pump jack or other device at the ground surface that reciprocates an attached sucker rod alternately in upstrokes and downstrokes. The sucker rod is attached at its bottom end to a plunger that reciprocates within a hollow pump barrel of a downhole pump assembly. The plunger includes a travelling valve assembly, for example a ball and seat valve or a flapper valve, to regulate the flow of a production fluid from below to above the plunger, while the pump barrel includes a standing valve assembly to regulate the flow of the production fluid into the barrel from the producing perforations of a well, A retaining device such as a pump seating nipple is needed to hold the barrel of the downhole pump assembly in a fixed position within the production tubing string as the travelling plunger moves up and down. 
         [0003]    On the upstroke of the plunger, the travelling valve closes, so that the plunger lifts a column of production fluid in the pump barrel, upwards in the production string, towards the ground surface. Simultaneously, the standing valve is opened so that the plunger draws additional production fluid from the producing perforations of the well into the pump barrel below the plunger. On the downstroke of the plunger, the standing valve closes to prevent the production fluid below the plunger from flowing back into the production tubing or well reservoir. Simultaneously, the pressure exerted by the production fluid in the pump barrel below the travelling valve forces the traveling valve to open. This allows the production fluid to flow into the pump barrel above the plunger and charges the pump barrel with a new column of production fluid to be lifted on a subsequent upstroke. 
         [0004]    On occasion, wax build up or a blockage due to solids build up impairs pump operation. In these cases, it is desirable to backflush the downhole pump assembly through the production tubing. However, this conventionally requires unseating the pump from the pump seating nipple because the standing valve prevents reverse flow of fluid out of the pump barrel into the surrounding formation. 
         [0005]    There is a need in the art for a device which would allow selective opening of the travelling and standing valves for a backflush operation. 
       SUMMARY OF THE INVENTION 
       [0006]    In one aspect, the present invention provides a backflush valve to open the traveling valve and the standing valve both at the same time so the production tubing and rod pump can be backflushed. In one embodiment, the backflush valve is adapted to connect to a pump barrel between a traveling valve and a standing valve, and comprises:
       a. a hollow cylindrical housing having an upper end adapted to connect to a pump barrel and a lower end adapted to connect to a standing valve assembly comprising a standing valve ball and valve seat;   b. a push rod disposed and centralized within the housing, the push rod having an upper end and a lower end, wherein the lower end comprises a ball wedge;   c. wherein the push rod may reciprocate within the housing from a relaxed position where the ball wedge is positioned away from the standing ball valve to a deployed position where the ball wedge displaces the standing ball valve off the standing valve seat;   d. a spring contained within the housing and acting on the push rod to bias into its relaxed position.       
 
         [0011]    In one embodiment, the push rod is centralized by at least one centralizing insert defining at least one flow passage. 
         [0012]    In another aspect, the invention may comprise a method of backflushing a reciprocating pump assembly having a backflush valve adapted to connect to a pump barrel between a traveling valve and a standing valve, the backflush valve comprising a centralized pushrod having an upper end and a lower end comprising a ball wedge, comprising the steps of
       a. collapsing the pump such that the traveling valve falls and contacts the push rod, thereby opening the traveling valve; and   b. urging the push rod downwards such that the ball wedge contacts the standing valve ball, displacing it off the standing valve ball seat.       
 
         [0015]    In one embodiment, the traveling valve comprises a traveling valve ball which contacts the push rod to push it downwards. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The invention will now be described by way of an exemplary embodiment with reference to the accompanying simplified, diagrammatic, not-to-scale drawings. Any dimensions provided in the drawings are provided only for illustrative purposes, and do not limit the invention as defined by the claims. In the drawings: 
           [0017]      FIG. 1  is a sectional view of a reciprocating downhole pump system incorporating one embodiment of the backflush valve of the present invention; 
           [0018]      FIG. 2  is a cut-away sectional view of a one embodiment of the backflush valve of  FIG. 1 ; 
           [0019]      FIG. 3  is a partial cut-away view of one embodiment of the push rod and centralizing inserts of one embodiment of the present invention; and 
           [0020]      FIG. 4  is a view of the embodiment of  FIG. 3 , in a disassembled state. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    The present invention provides a backflush valve for facilitating a backflush process of a downhole pump assembly in a production tubing string. When describing the present invention, all terms not defined herein have their common art-recognized meanings. To the extent that the following description is of a specific embodiment or a particular use of the invention, it is intended to be illustrative only, and not limiting of the claimed invention. The following description is intended to cover all alternatives, modifications and equivalents that are included in the spirit and scope of the invention, as defined in the appended claims. 
         [0022]    As used herein, the term “up” or “upwards” refers to the direction of the surface end of the well, while “down” or “downwards” refers to the direction towards the bottom or toe end of the well. These references are intended to describe the relative orientation or direction of movement of components, and not to describe the actual orientation of the components at any time. As one skilled in the art will understand, the downhole pump assembly may be installed in any position between a vertical or a horizontal orientation. 
         [0023]    In one aspect, the present invention provides a backflush valve ( 10 ) adapted to connect to a pump barrel (B) between a traveling valve (T) and a standing valve (S), the backflush valve comprising:
       a. a hollow cylindrical housing ( 12 ) having an upper end adapted to connect to the pump barrel and a lower end adapted to connect to the standing valve assembly (S) comprising a standing valve ball (B) and valve seat (SVS);   b. a push rod ( 14 ) disposed and centralized within the housing, the push rod having an upper end ( 16 ) and a lower end ( 18 ), wherein the lower end comprises a ball wedge ( 20 );   c. wherein the push rod ( 14 ) may reciprocate within the housing ( 12 ) from a relaxed position where the ball wedge ( 20 ) is positioned away from the standing ball valve to a deployed position where the ball wedge ( 20 ) displaces the standing ball valve off the standing valve seat;   d. a spring ( 22 ) contained within the housing and acting on the push rod to bias it into its relaxed position.       
 
         [0028]    In one embodiment, the push rod is centralized by at least one centralizing insert ( 24 ) defining at least one flow passage. As shown in the Figures, in a preferred embodiment, two centralizing inserts ( 24 ) fit onto the push rod, and have an outside diameter closely matching the inside diameter of the housing ( 12 ). Each insert ( 24 ) defines peripheral flow passages and each insert defines a spring cavity ( 26 ). An alignment pin ( 28 ) which inserts into the centralizing inserts ensures the peripheral flow passages are aligned when the device ( 10 ) is assembled. The inserts ( 24 ) are retained in place between opposing seats ( 30 ,  32 ) defined by the inside of the housing. For ease of assembly, the housing may comprise two halves which attach together, for example, by a threaded connection. 
         [0029]    The spring ( 22 ) acts between the lower portion of the lower insert ( 24 ) and a pin ( 34 ) affixed to the push rod ( 14 ). 
         [0030]    In normal pump operation, the push rod ( 14 ) is in its relaxed position, and production fluid flows through the backflush valve without undue restriction. The upper end ( 16 ) of the push rod may be used in combination with a gas locking relief device (not shown) such as that described in co-owned U.S. application Ser. No. 13/583,667 entitled Downhole Gas Release Apparatus, the entire contents of which is incorporated herein by reference, where permitted. In this case, an adapter ( 40 ) may be fitted to the upper end of the push rod, to facilitate its interaction with a gas locking relief device. 
         [0031]    A nut (not shown) or stop formed on the pushrod may be used to limit travel of the pushrod by bearing on the top of an insert ( 24 ). Too much force on the pushrod may bend the rod, or damage the standing valve. 
         [0032]    When installed in a downhole pump assembly and during production, the backflush valve ( 10 ) does not influence either the traveling valve or the standing valve. Production fluid bypasses the valve ( 10 ) through the flow passages. In a backflush operation, the pump is collapsed by letting the sucker rods fall to the bottom. As a result, the traveling valve falls toward its lowest point, and the traveling valve ball contacts the top of the push rod ( 14 ), either directly or indirectly, and is thus unseated. The traveling valve then urges the push rod ( 14 ) downwards, compressing the spring ( 22 ) as shown in  FIG. 3 , and moving the ball wedge ( 20 ) into contact with the standing valve ball, displacing it off the standing valve ball seat. 
         [0033]    As a result, the production tubing and pump assembly is now entirely open to the formation, and a fluid may be backflushed through the production tubing and the rod pump, without unseating the pump barrel. 
         [0034]    As will be apparent to those skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the scope of the invention claimed herein.