Reciprocating subsurface pump

Abstract

A reciprocating pump includes an open-bottomed barrel adapted for attaching to the lower end of a production tubing string; a seating assembly having a cylindrical bore and adapted for mounting to a seating nipple at the upper end of the barrel; and a plunger assembly adapted for attaching to the lower end of a sucker rod string. The plunger assembly includes concentric upper and lower plunger sections interconnected by a double-valve, ported valve cage. The plungers are sized for sealing reciprocating engagement within, respectively, the bore of the seating assembly and the bore of the pump barrel. The lower plunger and the ported valve cage define a production chamber within the pump barrel. The upper plunger has ports allowing fluid flow from the tubing into the production chamber. Optionally, the upper plunger and the barrel may be provided with flush ports facilitating flushing of the pump to eliminate vapor lock.

Claims

1. A pump assembly comprising: (a) a pump barrel having a cylindrical wall, an upper end adapted for mounting to a lower end of a tubing string, and an open lower end; (b) a pump-seating nipple adapted for mounting to the lower end of the tubing string; (c) a seating assembly having a cylindrical bore, said seating assembly being in seating engagement with the pump-seating nipple; (d) a plunger assembly comprising: d.1 an upper plunger having a cylindrical wall, an upper end, and a lower end, said upper plunger defining an upper plunger chamber and having a fluid port extending through the wall and located proximal to the upper end of the upper plunger and adapted for allowing fluid entry from the tubing string into the upper plunger chamber, and said upper plunger being reciprocatingly and sealingly movable within the bore of the seating assembly; d.2 a lower plunger having a cylindrical wall, an upper end, and a lower end, with the outer diameter of the cylindrical wall of the lower plunger being larger than the outer diameter of the cylindrical wall of the upper plunger, said lower plunger being reciprocatingly and sealingly movable within the pump barrel; and d.3 a transition section contiguously disposed between the lower end of the upper plunger and the upper end of the lower plunger, said transition section housing an upper valve proximal to the lower end of the upper plunger, and a lower valve proximal to the upper end of the lower plunger; said transition section having a wall having at least one fluid port therethrough, and defining a valve chamber bounded by the wall and the upper and lower valves; wherein: (e) the portion of the pump barrel below the lower valve defines a barrel chamber; (f) the lower valve regulates fluid flow from the barrel chamber into the valve chamber; and (g) the upper valve regulates fluid flow from the valve chamber into the upper plunger chamber.

2. The pump assembly as in claim 1, wherein: (a) an upper plunger flush port is provided through the wall of the upper plunger; (b) a barrel chamber flush port is provided through the wall of the pump barrel; and (c) the plunger assembly is selectively movable to a position lower than the bottom of its normal downstroke, such that fluid can flow from the upper plunger chamber through the upper plunger flush port into an annular space between the transition section and the wall of the pump barrel, and out of said annular space through the barrel chamber flush port.

3. The pump assembly as in claim 1 wherein the transition is of frustoconical configuration.

4. The pump assembly as in claim 1 wherein the upper and lower valves comprise ball-type valves.

5. The pump assembly as in claim 1, further comprising stop means for limiting the downstroke of the plunger assembly.

6. The pump assembly as in claim 1, further comprising an elastomeric packing element disposed within a seal-receiving groove formed in the bore of the seating assembly.

7. A plunger assembly comprising: (a) an upper plunger having a cylindrical wall, an upper end, and a lower end, said upper plunger defining an upper plunger chamber and having a fluid port extending through the wall and located proximal to the upper end of the upper plunger and adapted for allowing fluid entry from a tubing string into the upper plunger chamber, and said upper plunger being reciprocatingly and sealingly movable within a bore of a seating assembly; (b) a lower plunger having a cylindrical wall, an upper end, and a lower end, with the outer diameter of the cylindrical wall of the lower plunger being larger than the outer diameter of the cylindrical wall of the upper plunger, said lower plunger being reciprocatingly and sealingly movable within a pump barrel; and (c) a transition section contiguously disposed between the lower end of the upper plunger and the upper end of the lower plunger, said transition section housing an upper valve proximal to the lower end of the upper plunger, and a lower valve proximal to the upper end of the lower plunger; said transition section having a perimeter wall having at least one fluid port therethrough, and defining a valve chamber bounded by the wall and the upper and lower valves.

8. The plunger assembly as in claim 7, wherein an upper plunger flush port is provided through the wall of the upper plunger.

9. The plunger assembly as in claim 7 wherein the transition is of frustoconical configuration.

10. The plunger assembly as in claim 7 wherein the upper and lower valves comprise ball-type valves.

11. The plunger assembly as in claim 7, further comprising a seating assembly having a cylindrical bore, said seating assembly being adapted for seating engagement with a pump-seating nipple.

12. A pump assembly comprising: (a) a pump-seating nipple adapted for mounting to a lower end of the tubing string; (b) a seating assembly having a cylindrical bore, said seating assembly being in seating engagement with the pump-seating nipple; (c) a plunger assembly comprising: c.1 an upper plunger having a cylindrical wall, an upper end, and a lower end, said upper plunger defining an upper plunger chamber and having a fluid port extending through the wall and located proximal to the upper end of the upper plunger and adapted for allowing fluid entry from the tubing string into the upper plunger chamber, and said upper plunger being reciprocatingly and sealingly movable within the bore of the seating assembly; c.2 a lower plunger having a cylindrical wall, an upper end, and a lower end, with the outer diameter of the cylindrical wall of the lower plunger being larger than the outer diameter of the cylindrical wall of the upper plunger, said lower plunger being reciprocatingly and sealingly movable within a pump barrel; and c.3 a transition section contiguously disposed between the lower end of the upper plunger and the upper end of the lower plunger, said transition section housing an upper valve proximal to the lower end of the upper plunger, and a lower valve proximal to the upper end of the lower plunger; said transition section having a wall having at least one fluid port therethrough, and defining a valve chamber bounded by the wall and the upper and lower valves; wherein: (d) the upper valve regulates fluid flow from the valve chamber into the upper plunger chamber.

13. The pump assembly as in claim 12 wherein the transition is of frustoconical configuration.

14. The pump assembly as in claim 12 wherein the upper and lower valves comprise ball-type valves.

15. The pump assembly as in claim 12, further comprising stop means for limiting the downstroke of the plunger assembly.

16. The pump assembly as in claim 12, further comprising an elastomeric packing element disposed within a seal-receiving groove formed in the bore of the seating assembly.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of pumps in accordance with the present disclosure will now be described with reference to the accompanying figures, in which numerical references denote like parts, and in which:

(2) FIG. 1A is a vertical cross-section through a prior art sucker rod pump disposed within a production tubing string in a wellbore, shown with both the standing valve and the travelling valve closed;

(3) FIG. 1B is a vertical cross-section through the prior art pump in FIG. 1A, shown with the sucker rod string and plunger on the upstroke, with the travelling valve closed, and with the standing valve open to allow wellbore fluids into the pump barrel;

(4) FIG. 1C is a vertical cross-section through the prior art pump in FIG. 1A, shown with the sucker rod string and plunger on the downstroke, with the travelling valve open to allow fluid flow into the production string, and with the standing valve closed to prevent backflow into the formation;

(5) FIG. 2A is a vertical cross-section through one embodiment of a pump in accordance with the present disclosure, shown with the plunger at the beginning of its downstroke in accordance with certain embodiments of the present disclosure;

(6) FIG. 2B is a vertical cross-section through the pump in FIG. 2A, shown with the plunger shown at the bottom of its downstroke in accordance with certain embodiments of the present disclosure;

(7) FIG. 2C is a vertical cross-section through the pump in FIG. 2A, shown with the plunger at the beginning of its upstroke in accordance with certain embodiments of the present disclosure; and

(8) FIG. 2D is a vertical cross-section through the pump in FIG. 2A, shown with the plunger in the flush-by position in accordance with certain embodiments of the present disclosure.

NOTATION AND NOMENCLATURE

(9) As used herein, any form of the word comprise is to be understood in its non-limiting sense to mean that any item following such word is 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 such element is present, unless the context clearly requires that there be one and only one such element. Any use of any form of the terms connect, engage, attach, mount, or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the subject elements, and may also include indirect interaction between the elements such as through secondary or intermediary structure. Relational terms such as (but not limited to) concentric are not intended to denote or require absolute mathematical or geometrical precision. Accordingly, such terms are to be understood as denoting or requiring substantial precision only (e.g., substantially concentric) unless the context clearly requires otherwise. As used in this patent document, the term fluid may denote a liquid, a gas, or a liquid-gas mixture, as the context may suggest or require.

DETAILED DESCRIPTION

(10) FIGS. 1A, 1B, and 1C illustrate a typical prior art sucker rod pump, the construction and operation of which was generally described in the Background section of this document. The arrows in FIGS. 1A, 1B, and 1C indicate the direction of both fluid flow and sucker rod movement, with reference characters in accordance with the following legend:

(11) AFluid level in well

(12) BSucker rod string

(13) CTraveling valve

(14) DPlunger

(15) EPump barrel

(16) FStanding valve

(17) FIGS. 2A, 2B, 2C, and 2D illustrate one embodiment of a subsurface pump 10 in accordance with the present disclosure, in various stages of operation. Pump 10 comprises a pump barrel 20 mounted to the lower end of a suitable pump-seating nipple 30, the upper end of which is mounted to the lower end of a string of production tubing 12. Pump-seating nipple 30 is depicted in FIGS. 2A-2D as being a very short component, but this is schematic only; typical pump-seating nipples are 12 to 18 inches in length.

(18) Pump barrel 20 has an open lower end 20L through which wellbore fluids can flow into a barrel chamber 22 in a lower region of pump barrel 20. Preferably (but not necessarily), at least one flush port (or barrel chamber flush port) 24 is provided through the wall of the pump barrel 20 within barrel chamber 22. In cases where flush port(s) 24 are provided, pump barrel 20 may alternatively be referred to as a ported fluid entry sub.

(19) Pump 10 further comprises a plunger assembly 40 having a cylindrical upper plunger section 42 and a cylindrical lower plunger section 44, with upper and lower plungers 42 and 44 being concentric, and with the outer diameter (O.D.) of upper plunger 42 being less than the O.D. of lower plunger 44. The interior of upper plunger 42 defines an upper plunger chamber 43. Upper and lower plungers 42 and 44 are interconnected by a transition section 46 housing an upper valve 50 proximal to the lower end of upper plunger 42 and a lower valve 60 proximal to the upper end of lower plunger 44. In the illustrated embodiment, transition section 46 is shown as being of frustoconical configuration, but this is not essential; transition section 46 could be of a different geometrical configuration without materially affecting the function or operation of pump 10. Upper and lower valves 50 and 60 are shown as ball-type valves, each having a ball (51 or 61) and a seat (52 or 62), but this is by way of non-limiting example only. At least one fluid port 46P is provided through the wall of transition section 46. The subassembly of transition section 46, upper valve 50, and lower valve 60 may be referred to as a double-valve ported valve cage 70, and defines a valve chamber 72 bounded by the wall of transition section 46 and valve assemblies 50 and 60.

(20) The O.D. of upper plunger 42 is sized to facilitate sealing reciprocating movement within the cylindrical bore of a seating assembly 32 adapted for engagement with pump-seating nipple 30. The seating assembly 32 is preferably provided with an elastomeric packing element 34 disposed within a seal-receiving groove formed in the bore of seating assembly 32, or other suitable sealing means for deterring entry of sand into the pump. The upper end 42U of upper plunger 42 is closed off by a cap member 41, with at least one fluid port 41P being provided through cap member 41. Optionally, and as seen in the illustrated embodiment, at least one fluid port (or upper plunger flush port) 42P may be provided through the cylindrical wall of upper plunger 42, to facilitate flushing of the pump (as will be described in greater detail later herein). The O.D. of lower plunger 44 is sized to facilitate sealing reciprocating movement within pump barrel 20.

(21) Plunger assembly 40, with seating assembly 32 disposed around upper plunger 42, is suspended from a sucker rod string 15 connected to the upper end 42U of upper plunger 42, and then lowered into the well until seating assembly 32 engages pump-seating nipple 30. Seating assembly then remains stationary in the well, while plunger assembly 40 is reciprocatingly movable within the well.

(22) Optionally, pump 10 may be provided with stop means for limiting the downward travel of the plunger. The illustrated embodiment of pump 10 features stop means in the form of an annular flange 45 fixed to an upper region of upper plunger 42, and the function of this feature is best understood with reference to FIG. 2D. Although illustrated herein as an annular flange, the plunger stop means could take any functionally suitable form, including but not limited to one or more lug members welded to upper plunger 42.

(23) Normal operation of pump 10 is illustrated in FIGS. 2A-2C. FIG. 2A shows pump 10 with plunger assembly 40 at the beginning of its downstroke. The weight of the fluid column within production tubing 12 (and upper plunger chamber 43) keeps upper valve 50 closed as shown. Barrel chamber 22 contains fluid drawn in through the open lower end 20L of pump barrel 20 (and through flush ports 24 if provided) during the preceding upstroke. The downward movement of plunger assembly 40 into the fluid in barrel chamber 22 forces lower valve 60 to open as shown, allowing fluid from barrel chamber 22 to flow (as indicated by flow arrows F.sub.1) into a production chamber 80 comprising valve chamber 72 and the annular space 73 bounded by pump barrel 22, valve cage 70, and a lower region of upper plunger 42.

(24) In FIG. 2B, plunger assembly 40 is at the bottom of its downstroke, at which stage production chamber 80 will be filled with fluid. With the downward movement of the plunger assembly having stopped, the weight of fluid in production chamber 80 causes lower valve 60 to close as shown, while upper valve 50 remains closed due to the weight of the fluid column above it.

(25) In FIG. 2C, plunger assembly 40 has begun to rise from the position shown in FIG. 2B. At this point, pump 10 is compressing the fluid in production chamber 80, with lower valve 60 in the closed position. When the fluid in production chamber 80 reaches a pressure greater than the pressure in production tubing 12, upper valve 50 will open as shown, discharging fluid from production chamber 80 into upper plunger chamber 43 (as indicated by flow arrows F.sub.2). The fluid exits upper plunger chamber 43 through fluid port(s) 41P and into production tubing 12. As plunger assembly 40 continues its upstroke, additional fluid is drawn into barrel chamber 22 through open lower end 20L of pump barrel 20 (as indicated by flow arrows F.sub.3). When plunger assembly 40 reaches the top of its upstroke, a new downstroke begins, as illustrated in FIG. 2A.

(26) FIG. 2D illustrates pump 10 in the flush-by position, with plunger assembly 40 at a position lower than the bottom of its normal operational downstroke (per FIG. 2B) such that fluid ports 42P in upper plunger 42 are below seating assembly 32, and lower plunger 44 is below flush ports 24 in pump barrel 20. With plunger assembly 40 in this position, a flushing fluid introduced into production tubing 12 can enter upper plunger chamber 43 through fluid ports 41P, then exit upper plunger chamber 43 through fluid ports 42P into annular space 73 between upper plunger 42 and pump barrel 20, and then exit annular space 73 through flush ports 24 in pump barrel 20 into the wellbore (as indicated by flow arrows F.sub.4). Upper and lower valves 50 and 60 remain closed throughout this operation due to the weight of flushing fluid in production tubing 12 and upper plunger chamber 43. Pump 10 can be set to attain this flush-by position should gas-locking be a concern.

(27) It will be readily appreciated by those skilled in the art that various modifications to embodiments in accordance with the present disclosure may be devised without departing from the scope and teaching of the present teachings, including modifications using equivalent structures or materials hereafter conceived or developed. It is to be understood that the scope of the claims appended hereto should not be limited by the preferred embodiments described and illustrated herein, but should be given the broadest interpretation consistent with the description as a whole. It is also to be understood that the substitution of a variant of a claimed element or feature, without any substantial resultant change in functionality, will not constitute a departure from the scope of the disclosure.