CA2040324A1 - Downhole reciprocating pump and components therefor - Google Patents
Downhole reciprocating pump and components thereforInfo
- Publication number
- CA2040324A1 CA2040324A1 CA 2040324 CA2040324A CA2040324A1 CA 2040324 A1 CA2040324 A1 CA 2040324A1 CA 2040324 CA2040324 CA 2040324 CA 2040324 A CA2040324 A CA 2040324A CA 2040324 A1 CA2040324 A1 CA 2040324A1
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- bore
- plunger
- valve member
- vanes
- cage
- Prior art date
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Abstract
"DOWNHOLE RECIPROCATING PUMP AND COMPONENTS THEREFOR"
ABSTRACT OF THE DISCLOSURE
A downhole reciprocating pump is provided having novel check valves and a novel plunger. Each check valve has a generally cylindrical valve member having a smooth-surfaced tapered lower end adapted to seat in a tapered seat. The upper portion of the valve member carries outwardly protruding, spaced apart vanes disposed at an acute angle relative to the axis of the valve member. Fluid can move past the valve member through the channels between the vanes. Interaction between the fluid and vanes causes the valve member to spin. By combining the downwardly tapered sealing surfaces with the spinning valve member, sand is kept clear of the sealing surfaces and erosion, arising from the surfaces being propped apart, is reduced. The plunger is equipped with oppositely directed, upper and lower pressure-driven metal seal rings. Each seal ring has a thin, axially extending, annular lip that is flexed by downhole pressure into sealing contact with the inside surface of the pump barrel. The seal rings provide the plunger with effectively an interference fit, thereby eliminating the problems that characterize plungers having a clearance fit with the barrel.
ABSTRACT OF THE DISCLOSURE
A downhole reciprocating pump is provided having novel check valves and a novel plunger. Each check valve has a generally cylindrical valve member having a smooth-surfaced tapered lower end adapted to seat in a tapered seat. The upper portion of the valve member carries outwardly protruding, spaced apart vanes disposed at an acute angle relative to the axis of the valve member. Fluid can move past the valve member through the channels between the vanes. Interaction between the fluid and vanes causes the valve member to spin. By combining the downwardly tapered sealing surfaces with the spinning valve member, sand is kept clear of the sealing surfaces and erosion, arising from the surfaces being propped apart, is reduced. The plunger is equipped with oppositely directed, upper and lower pressure-driven metal seal rings. Each seal ring has a thin, axially extending, annular lip that is flexed by downhole pressure into sealing contact with the inside surface of the pump barrel. The seal rings provide the plunger with effectively an interference fit, thereby eliminating the problems that characterize plungers having a clearance fit with the barrel.
Description
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1 BAÇKÇRO~ND OF THE INVENTION
1 BAÇKÇRO~ND OF THE INVENTION
3 ~his inventio11 relates to a novel form of check valve 4 which finds application i~ a downhole reciprocating pump of the type used in oilwells and the like. It further relates to a 6 novel plunger for use in such a pump. And finally, it relates ~ to a novel downhole reciprocating pump that incorporates one or 8 both of the novel valve and plunger.
Downhole reciprocating pumps have long been used for 11 moving fluid from the bottom of a wellbore up to ground surface.
12 In general, a conventional pump of this kind comprises:
13 - an elongate cyllndrical tubular barrel open at its 14 bottom end and closed at its top end. The barrel is attached to a seating mandrel which seats in 16 a seating nipple forming part of a tubing string 17 that extends up to ground surface. The bore of 18 the barrel communicates with the bore of the 19 tubing through suitable ports formed in the closed upper end of the barrel;
21 - a gensrally cylindrical tubular plunger, which is 22 connected at its upper end with the bottom end of 23 a sucker rod string extending to ground surface.
24 ~he rod string may ba reciprocated from ground surface by a pump jack to thus reciprocate the 26 plunger up and down within the bore of the barrel;
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1 - the plunger forms a longitudinal bore extending 2 there through which communicates with the barrel ~ bore. The plunger also has an internal 4 "travelling" ball-and-seat type check valve at its S lower end - this valve closes on the plungar up 6 stroke and opens on the down stroke;
7 - the outside cylindrical surface of the plunger has 8 sufficient clearance relative to the inside 9 cylindrical surface of the barrel so that it can slide easily up and down therein. However the 11 clearance is sufficiently small so that the 12 plunger is still able to effectively seal with 13 the barrel and lift fluid on the up stroke, 14 although there is some limited "slippage" of fluid past the plunger through the clearance; and 16 - the barrel has an internal "standing~' or 17 ~tationary ball-and-seat type check valve at its 18 lower end, which opens on th~ plunger up stroke 19 and closes on its down stroke.
In operation, when the plunger is on the down stroke, 21 the ball of the travelling valve unseats and the hydro~tatic 22 head, arising from the column of fluid in the tubing, keeps the 23 ball of the standing valve seated. Thu~ the travelling valve is 24 open and the standing valve is closed. As the plunger descends, fluid in the barrel chamber moves through the travelling valve 26 and plunger and reaches that portion of the barrel bore above the 27 plunger. When the plunger reaches the bottom of its downward 28 travel and reverses into the up stroke, the ball of the 29 travelling valve seats, thereby trapping the fluid standing above 2al~32~
1 it. As the plunger rlses, fluid is swabbed from the barrel bore 2 and through the top ports of the barrel into the tubing bore.
3 At the same time, the low pressure created by the upward stroke 4 unseats the ball of the standing valve and d.raws in oil from the wellbore and reservoir. Fluid from the wellbore thus follows the 6 rising plunger by passing through the standing valve and entering 7 the barrel bore. ~his stroking sequence is repeated again and 8 again to gradually lift a fluid column, made up of separately 9 accumulated slugs of fluid, to ground surface.
A downhole reciprocating pump as described is 11 periodically subjsct to failure. When the pump fails, it is 12 necessary to move a service rig onto the well, pull the rod 13 string and pump, and run the rod string back into the well with 14 a replacement pump. The frequency of failure is usually worsened lS in the case where the oil-producing formation is an 16 unconsolidated sand, so that the produced fluid contains 17 entrained sand.
18 The various reasons for pump failure include:
19 - partial loss of the absolute seal at ona or both of the ~tanding and travelling valves; and 21 - deterioration of the seal between the plunger and 22 barral.
23 In both cases, there is a loss in pump efficiency 24 arising from leakage at the defective seal.
For purposes of discussion, a conventional ball-and-26 seat type check valve is shown in Figure 1. The valve comprises:
27 - a tubular cage a;
28 - a ring b, forming a seat c, positioned in the cage 29 bore d;
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1 - a ball e positioned in the cage bore and operative 2 to seat on the seat and provide an annular seal;
3 - the bore of the cage having a diameter greater 4 than that of the ball, so that fluid may move past S the ball when it is unseated; and 6 - a lock ring f locking the ring in place.
7 Now, one reason that the seal of a ball-and-seat valve 8 can be damaged has to do with sand grains occasionally getting 9 trapped between the ball and the annular seat. Complete closure is not achieved when this occurs and a narrow gap is temporarily 11 left open between the two sealing surfaces. Fluid under pressure 12 then can forcefully be driven through the gap and some erosion 13 or "wash-out" of the sealing surfaces may take place. With 14 repetition, the extent of damage may become severe.
Al~ernatively, when the ball is seating it may impact 16 forcefully against sand grains trappecl against the seat. On 17 being so impacted, the abrasive sand may score the seat or ball 18 surfaces. Once scored, pressurized fluid erosion can quickly 19 enlarge the breach.
From the foregoing, the desirability of a valva design 21 that reduces the likelihood of sand grains remaining between the 22 sealing surface6 as they close, becomes apparent.
23 Another factor, which affects the speed with which the 24 sealing surfaces of the valve lose their ef~ective seal, has to do with the width of their contact area. In a conventional 26' valve, the surface of the annular seat is curved, as shown ln 27 Figure 1, so as to have the same radius of curvature as the ball.
28 This is done to ensure a contlnuous annular contact area between 29 the two parts. It is inharent in a ball and curved seat design 2~32~
1 that the width of the contact area will be small, typically belng 2 .010 - .015 thousandths of an inch.
3 It follows that it would be desirable to significantly 4 increase the width of the annular seal contact area. This would S extend the time that it takes to sufficiently damage the seal to 6 such an extent that the pump needs to be replaced.
7 Let us turn now to the steel-on-steel plunger/barrel 8 seal system used in most oilwell pumps. Ai previously stated, 9 an effective seal needs to be maintained between the outsr cylindrical surface of the plunger and the inside cylindrical 11 surface of the barrel. Yet it is also necessary to provide a 12 clearance between the parts, in the order of .00~ - .004 13 thou~andths of an inch, so that the plunger can still slide in 14 the barrel. This order of clearance can be referred to as a sliding fit. Be~ause of this clearance, minute sand particles 16 can penetrate between the two surfaces and may score one or both 17 of the cylindrical surfaces. The pressurized fluid moving 18 through the clearance will soon enlarge the scored area and the 19 seal will deteriorate.
There are other problemæ arising from the clearance 21 between plunger and barrel. These have to do with "gyp" build-22 up, silt penetration into the clearance, and "gas locking". In 23 some wells, scale or gyp will accumulate on the inner surface of 24 the barrel. ~his scale can accumulate and cause the plunger and rod string to hang up. Alternatively silt may penetrate into the 26 clearance and cause the plunger to hang up. Or alternativel~, 27 if the well is producing gas, ths travelling valve can fail to 28 open, due in part to gas escaping past the plunger through the 29 clearance on the down stroke. Insufficient pressure is developsd 2~32~
1 in the barrel bore beneath the descending plunger to move the 2 ball off its seat. Thus the pump can fail to move fluid.
3 To combat the scoring problem in the past, the sealing 4 surfaces of the barrel and plunger have usually been hardened.
In addition, the clearance has been kept as small as possible.
6 This has required machining the surfaces to very fine tolerances, 7 which is difficult to do and affects cost. And finally, the 8 lengths of the plunger and barrel have been increased, to provide 9 a greater sealing area. A typical rule of thumb is that the plunger length should be 1 foot for each 1000 feet of well depth, 11 up to a maximum of ahout 5 - 6 feet. However, while very 12 helpful, these improvements have not eliminated the problems 13 inherent in the steel-on-steel plunger/barrel seal assembly.
14 As an alternative to the steel-on-steel seal assembly, it has been known to provide a greater clearance and mount 16 elastomer packing ring~ in grooves formed on the outer surface 17 of the plunger, to contact and seal against the barral. However, 18 the sand grains tend to embed in the packing rings and act to 19 score the barrel. Fluid erosion soon follows.
From the foregoing, it becomes apparent that it would 21 he desirable to provide a plunger that i5 equipped with annular 22 protruding seals which contact the barrel surface and are better 23 resistive to sand damage than the conventional elastomer rings.
24 If this could be achieved, slippage would be reduced or eliminated, pumping efficiency would improve, gas locking and gyp 26 seizure would be reduced, and the plunger could be 3horter ~n 27 length.
2 ~
1 Still another problem relating to ball-and-seat type 2 standing and travelling check valves arises when they are used 3 in heavy oil. The rate at which the pump can be stroked is 4 affected by ~he time taken for the ball (or valve member) of a check valve to move from the open (unseated) position to the 6 closed position. If the oll through which the ball is dropping is viscous, the ball can be slow to close. In the past, this 8 problem has been attacked by making the balls from heavy alloy 9 material. It will be appreciated that the weight of the ball cannot be increased by increasing the size of the ball, as its 11 dia~e~er ls dictated by the bore hole diameter and the tubular 12 parts used in conjunction with the ball.
13 Therefore it would be desirable to design a check valve 14 which would permit greater flexibility and range in the choice of weight of the valve member to be attained.
16 The present invention is directed toward providing some 17 resolution of these problems.
18 SUMMARY QF ~E INVE~Q~
19 In accordance with one aspect of the present invention, a novel check valva for downhole reciprocating pumps is provided, 21 comprising:
22 - a conventional tubular cage having a riny seat 23 member locked therein and providing an annular 24 seat; and - a valve member that is adapted to spin about its 26 longitudinal axi~ as it drops thxough fluid in the 27 bore of the cage, in the course of moving toward 28 the seat during the act of closing.
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1 More particularly, the valve me~ber has an elongated, 2 generally cylindrical body having upper and lower body sections.
3 The upper body section carries outwardly protruding, spaced apart 4 vanes extending longitudinally of the body portion at an acute angle relative to the longitudinal axis of the body. These vanes 6 form open-ended channels for enabling fluid to move past the 7 valve member as it drops through the fluid-filled bore of the 8 cage. Interaction between the angled YaneS and the fluid imparts 9 a spinning motion to the valve member as it drops. Thz lower body section is smooth-surfaced and is adapted to seal against 11 the annular seat when in the closed position.
12 The spinning valve member acts to clear at least some 13 of the sand grains away from the seat during closing. This has 14 the effect of reducing the scoring and eroæion of the sealing surfaces that would otherwise occur.
16 It will be noted that the novel valve member is 17 generally cylindrical in form. Its length (and tha length of the 18 cage) can therefore be extended as desired to achieve an increase 19 in valve member weight when the valve is to be used in a well producing viscous oil.
21 In a preferred feature, the sealing surfa~e of the 22 lower body section of the valve member is conical in form and 23 thus straight-sided and inwardly tapered. The annular seat of 24 the cage is also straight-surfaced and inwardly tapered, so as ~o conform with the sealing surface of the valve member. The 26 advantages of this design are that: ;
27 - the ssat is now downwardly sloped, to assist in 28 shedding sand grains seeking to settle thereon;
29 and 1 _ the width of the area of contact of the sea~ Q~ 3 ~ 4 2 surfaces can be significantly extended, relative 3 to what was possible with the ball and seat 4 assembly.
In another aspect of the invention, a novel plunger is 6 provided for use in a downhole reciprocating pump. The plunger 7 is equipped with a pair of novel pressure-driven ring seals and, 8 preferably, a travelling valve of the type just described. Each 9 ring seal is formed of a hard, non-elastomeric material, such as mild steel.
11 More particularly, each ring seal comprises a base ring 12 that seals against the cylindrical plunger body. This may be 13 accomplishea by shrinking the base ring to the plunger body so 14 that the ring seals are, in effect, integral with the plunger body and reciprocate with it. The plunger body iq preferably 16 recessed adjacent each of its ends, to form upper and lower 17 annular shoulders. Each ring seal is seated on and supported by 18 one of the annular shoulders. The ring seal is thus positioned 19 along the recsssed area. At one outer rim, each base ring has an axially extendiny annular lip. The lip is suficiently thin 21 so that whsn tha pressure, to which the plunger is subjected, 22 acts against the inside ~urface of the lip, it will flex the lip 23 outwardly into sealing engagement with the inside cylindrical 24 surface of the pump barrsl. As previously stated, the ring seal is formed of relatively hard material, ~uch as mild steel. The 26 outer axial side surface of the ring seal may be coated with a 27 material such as ceramic, to harden it, and the steel may be 28 nickel-coated, to impxove its corrosion resistance. The outer 29 side surface of the lip seal is straight-sided and cylindrical 1 in form and has a close sliding fit, typically about .0002~ 3~4 2 .0006 tenths of an inch, with the inside cylindrical surface of 3 the barrel. Alternatively, the outer side surface of the lip 4 seal could have an interference fit with the barrel - however the base ring would ~hen have to have an undercut of .001 to .002 6 thousandths of an inch clearance to the barrel, in order to 7 permit of assembly. The two ring seals carried by the plunger 8 are oppositely directed, so that the upper ring seal has its lip 9 directed upwardly and the lower ring seal has its lip directed downwardly.
11 This design of ring seal, when incorporated into the 12 plunger, has the following advantages:
13 - because it is hard and formed of high temp0rature 14 resistant materials, it is not as susceptible to scoring and thermal degradation as is the casa 16 with elastomer 0-rings and the like; and 17 - because the lip flexes into sealing contact with 18 the barrel, there is little, if any, fluid 19 slippage past the plunger.
Now described are the results of some tests conducted 21 on pumps equipped with the novel components.
22 In one test, a conventional pump having a steel-on-23 steel plunger~barrel seal assembly was run in a well known to 24 cause pump failure by "silting" (wherein silt penetrates into the clearance between the plunger and barrel and packs in until the 26 plunger begins to hang up on the down stroke and eventually 27 seizes up). The pump began to hang up within 4 days of 28 installation and failed within 3 months. The maximum pumping 29 rate with the pump was 6-1/2 strokes per minute ("S.P.~."). The 3 ~ ~
1 same model of pump, modified by the insertion of a plunger ln 2 accordance with the present invention~ was then run in the same 3 well. There was no indication of hang-up from silt after 4 4 months of use and the stroking rate was successfully increased from 6-1/2 to 10 S.P.M.
6 In another test, conducted under shop conditions, a 7 conventional ball-and-seat valve was used in a transparent 8 plastic standing valve cage in a pump. A suspension of 50% sand 9 in oil was continually pumped for 3 weeks through a loop with a valve on the line to create a backpressure of 3000 psi. It was 11 visually noted repeatedly that sand would be trapped between the 12 ball and seat, typically every 5-6 strokes, allowing fluid to 13 leak past the seal. A check valve in accordance with the present 14 invention, having a spinning valve member disposed in a similar transparent plastic standing cage, was then substituted and used 16 for 3 weeks under the same conditions. Only occasionally, 17 typically every 25 - 30 strokes, was it noted that the valve 18 member would not seat perfectly due to sand propping.
19 Another test was conducted in a well known to cause gas locking of the pump. The well would be pumped intermittently 21 and gas locking would occur on start-up. More particularly, a 22 conventional pump with ball-and-seat check valves and steel-on-23 steel plunger/barrel seal assembly would almost invariably gas 24 lock after shut-down, due to the high gas/oil ratio of the production of the well. A pump equipped with check valves and 26 plunger in accordancs with the present invention was then 27 operated in the well. Repeated shut-downs and start-ups were 28 conducted without any indication of gas locking.
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1 DE~CRIPTION OF THE DRAWING$
2 Figure 1 is a side sectional view of a conventional 3 prio~ art ball-and-seat check valve for a downhole reciprocating 4 pump;
Figures 2a-2f are side sectional views of sections of 6 a downhole reciprocating pump in accordance with the present 7 invention, said sections when connected end to end together 8 making up the complete pump, said pump being shown seated in the 9 seatlng nipple of a tubing string;
I0 Figures 3a and 3b are side sectional views of sections 11 of the plunger, said sections when connected end to end together 12 making up the complete plunger;
13 Figure 4 is a side view, partly in section, showing a 14 valve member, in accordance with the invention, seated in a ring seat in the closed position;
16 Figure 5 is a side view, partly in section, showing the 17 valve member of Figure 4 in its cage in the unseated or open 18 position; and 19 Figure 6 is a sectional side view of a plunger seal in accordance with the invention.
21 ESGRIPTIO~_OF ~ PRF~RRED EM~O~IMENT
22 Having reference to the Figures, there is shown a 23 downhole reciprocating pump 1. The pump 1 comprises a 24 cylindrical tubular barrel 2 which may be seated in the seating nipple 3 of the tubing string 4. (Note that in Figures 2a - 2f, 26 the tubing string 4 is only shown extending to th~ top of the 27 pump. However in actual practice the tubing string would 28 commonly extend the full length of the pump.) A cylindrical 2 ~
1 plunger 5 is posltioned within the barrel bore 6. The plunger 2 5 is threaded at its upper end for connection with a 3 reciprocating rod string 7. The pump 1 and tubing and rod 4 strings 4, 7 would normally be positioned in a wellbore (not shown) and would function to lift produced fluid from the lower 6 reaches of the wellbore to ground surface, where the fluid is 7 recovered.
8 The barrel 2 i5 conventional. It comprises a steel 9 tube 8 having a hardened inside surface 9. It is closed at its upper end by closure means 10, but has a port 11, whereby the 11 barrel bore 6 is in communication with the bore 12 of the tubing 12 string 4.
13 At its lower end, the barrel tube 8 is threadably 14 connected with a standing valve 13. This standing valve comprises an open-ended tubular cage 14. The cage 14 forms a 16 longitudinal bore 15. The cage bore 15 communicates at its lower 17 end with the wellbore (not shown) and at its upper end with the 18 barrel bore 6.
19 A valve member 16 is positioned within the cage bore 15. The valvs member 16 has a sliding fit in the cage 14.
21 The cage bore surface 17 is inwardly stepped at its 22 upper end to form an annular shoulder 18. This shoulder 18 acts 23 as a stop, to limit the upward travel of the valve member 16.
24 Adjacent its lower end, the cage bore surface 17 is outwardly stepped, to form a second annular shoulder 19. A ring 26 seat member 20 is positioned in the cage bore lS adjacent its 27 lower end and at its upper end abuts the shoulder 19. The ring 28 seat member 20 is locked against the shoulder 19 by a lock ring 29 21 that is threaded into the lower end of the cage 10. The ring 2 ~
1 seat member 20 forms an annular, downwardly and inwardly tapered, 2 straight-surface~ seat 22.
3 The valve member t6 is generally cylindrical in form 4 and comprises upper and lower body portions 23, 24 (see Figuxe 4). The lower body portion 24 takes the form of a smooth-6 surfaced truncated cone. Stated otherwi~e, the lower body 7 portion 24 is downwardly and inwardly tapered and is straight-8 sided. It is configured so as to conform to the tapered seat 22.
9 The upper body portion 23 has a plurality of outwardly protruding, spaced apart, parallel vanes 26 forming open-topped, 11 open-ended channels 27 between them. The vanes 26 extend 12 longitudinally of the upper body portion 23 and are slanted at 13 an acute angle relative to the longitudinal axis of the valve 14 member 16. The vanes 26 extend upwardly beyond the upper end surface of the valve member 16, to form windows 28 for flow when 16 the valve member 16 abuts the stop shoulder 18.
17 The valve member 16 has a loose fit relative to the 18 cage bore surface 17, so that it can slicle freely therein and so l9 that sand can move axially between the outer longitudinal faces of the vanes 26 and the cage bore surface 17.
21 The channel~ 27 provide a passageway means for enabling 22 fluid to bypass the valve member 16 when it is dropping through 23 fluid in the cage bore 15 in the course of closing. When the 24 valve member 16 is moving downwardly, the fluid in the bore 15 and the vanes 26 interact to cause ths valve member 16 to spin 26 about its longitudinal axis.
27 By designing the ring seat member 20 and the valve 28 member lower body portion 24 so as to provide conforming, 29 downwardly and inwardly tapered sealing surfaces, a relatively 2~3~
1 wide annular contact surface may be achieved. Typically, for a 2 15 taper, the width of the annular contact area may be 60/1,000 3 of an inch. In addition, the downwardly sloping seat 22 tends 4 to shed sand grains settling thereon. And finally, by inducing the valve member 16 to spin as it closes, the valve membex acts 6 to clear sand grains from the seat 22.
J Turning now to the plun~er 5, it comprises a 8 cylindricaL tubular body 29. ~he plunger body 29 forms a 9 longitudinal bore 30. The body is threaded at each of its ends.
A connector 31 is threaded onto the upper end of the 11 plunger body 29. A longitudinal bore 32 extends part way up into 12 the connector 31 from its lower end. The connector bore 32 13 communicates with the plunger body bore 30. A plunger port 33 14 extends through the sidewall of the connector 31 and provides communication between the plunger bores 30, 32 and that portion 16 of the barrel bore 6 which is above the plunger 5. At its upper 17 end, the connector 31 is connected with the lower end of the rod 18 string 7.
19 More particularly, the connector 31 connects with a valve rod 51 which in turn connects by means of a bushing 52 and 21 collar 53 with the lowermost sucker rod of the rod string 7.
22 The upper end of the barrel tube 8 is connected with 23 a seating mandrel bushing 54 and seating mandrel 55. The seating 24 mandrel 55 is connected with a valve rod guide 56, which has a close sliding fit with the valve rod 51. The seating mandrel 26 bushing 54, seating mandrel 55 and valve rod guide 56 27 collectively form the upper end of the barrel 2.
28 A passageway 57 (which is part of the barrel bore 6) 29 is formed between the plunger/s valve rod 51 and the barrel's 2 ~ 2 ~
1 seating mandrel bushing 54, seating mandrel 55 and lower end of 2 the valve rod guide 56. The valve rod guide 56 forms the barrel 3port 11. Thus the passageway 57 connects ~he plunger port 33 4 with the barrel port 11 and thus with the tubing bore 12.
5In summary, the plunger 5 is connectable with the rod 6 string for reciprocation and fluid may move through th~ plunger 7bores 30, 32, and port 33 into the barrel bore 6, includin~ the 8 passageway 57, and then through the barrel port 11 into the 9 tubing string bore 12.
10At its lower end, the plunger body 2~ is threadably 11 connected with a travelling valve 34. ~his plunger travelling 12 valve 34 is identical to the barrel standing valve 13 (except as 13 to dimensions) and thus requires little description. It does 14 comprise a cage 35, having an axial bore 36, a ring seat member 1537 in the bore 36, a lock ring 38 forming part of the cage 35 and 16 locking the ring seat member against a cage shoulder 39, and a 17 valve member 40 adapted to seat in the seat 41.
18The plunger body 29 carries a pair of oppositely 19directed mechanical ring seals 42 (ses Figures 2b, 2c and 6).
More particularly, the plunger body 29 is inwardly recessed at 21 each of it8 ends to form upper and lower annular shoulders 43, 22 44. A rin~ seal 42 is positioned in each of the recessed areas 2345, 46 and is supported by one of the shoulders 43, 44.
24Each ring seal 42 is formed of non-elastomeric material, such as nickel-coated mild steel. The ring seal 42 26 comprises a base ring 47 that ls shrunk-fit onto the plunger body 27 29, so as to seal against it and to ensure that they rsciprocate 28 together. A thin annular lip 48 extends axially from the outer 29 rim of the base ring 47, remote from the plunger body support 2~32~
1 shoulder 43 or 44. The outer side surface 49 of the ring seal 2 42 is inwardly recessed between two end lands 50, 51. The 3 recessed area between the end lands 50, 51 is filled with a thin 4 layer 52 of hard ma~erial, such as sprayed-on ceramic.
By forming the ring seal 42 of mild steel, one can 6 ensure that it will not seriously wear or scratch the hardened .7 internal surface 9 of the barrel 2. By nickel-coating the steel, 8 corrosion damage may be reduced. By inilling the recessed outer 9 surface of the ring seal 42 with ceramic, a hard, abrasion-resistant surface 49a for sealing against the barrel surface 9 11 is provided.
12 It will be noted that the outer side surface 49a of the 13 ceramic-coated ring seal 42 is cylindrical and straight.
14 An annular space 58 is formed between the inside surface 59 of the lip 48 and the plunger outer surface 60. This 16 space 58 is in communication with the barrel bore 6. Thus the 17 inside surface 59 of the lip 48 is exposed to the fluid pressure 18 present in the barrel bore 6. More particularly, the lip inside 19 surface 59 of the lower ring seal 42 is exposed to the hydrostatic head of the column of fluid in the t~lbing bore 12 21 (i.e. the lldownhole pressure") when the plunger 5 is on the 22 downstroke. The lip inside surface 59 of the upper ring seal 42 23 i5 exposed to that downhole pressure on the upstroke.
24 The lip 48 is sufficiently thin so that it will flex into fluid-tight sealing engagement with the barrel's cylindrical 26 inside surface 9, when the lip inside surface 59 is acted on by 27 the downhole pressure.
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1 The ring seal 42 has a sufflciently close sliding fit 2 with the barrel 2, so that pressure is not equalized across the 3 lip 48.
4 By way of example, I have used the following dimensional relationships for the ring seal when using it with 6 a barrel haviny an inside diameter of 1.500 inches and a plunger 7 having an out~ide diametex of 1.460 inches:
8 - thickness of base ring - .125"
9 - height of base ring - .500 "
- thickness of lip - .030"
11 - height of lip - 1.300"
12 - clearance of lip from barrel - .0006 tenths of an 13 inch 14 - thickness of ceramic - .007 thousandths of an inch The scope of the invention is set forth in the claims 16 now following.
Downhole reciprocating pumps have long been used for 11 moving fluid from the bottom of a wellbore up to ground surface.
12 In general, a conventional pump of this kind comprises:
13 - an elongate cyllndrical tubular barrel open at its 14 bottom end and closed at its top end. The barrel is attached to a seating mandrel which seats in 16 a seating nipple forming part of a tubing string 17 that extends up to ground surface. The bore of 18 the barrel communicates with the bore of the 19 tubing through suitable ports formed in the closed upper end of the barrel;
21 - a gensrally cylindrical tubular plunger, which is 22 connected at its upper end with the bottom end of 23 a sucker rod string extending to ground surface.
24 ~he rod string may ba reciprocated from ground surface by a pump jack to thus reciprocate the 26 plunger up and down within the bore of the barrel;
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1 - the plunger forms a longitudinal bore extending 2 there through which communicates with the barrel ~ bore. The plunger also has an internal 4 "travelling" ball-and-seat type check valve at its S lower end - this valve closes on the plungar up 6 stroke and opens on the down stroke;
7 - the outside cylindrical surface of the plunger has 8 sufficient clearance relative to the inside 9 cylindrical surface of the barrel so that it can slide easily up and down therein. However the 11 clearance is sufficiently small so that the 12 plunger is still able to effectively seal with 13 the barrel and lift fluid on the up stroke, 14 although there is some limited "slippage" of fluid past the plunger through the clearance; and 16 - the barrel has an internal "standing~' or 17 ~tationary ball-and-seat type check valve at its 18 lower end, which opens on th~ plunger up stroke 19 and closes on its down stroke.
In operation, when the plunger is on the down stroke, 21 the ball of the travelling valve unseats and the hydro~tatic 22 head, arising from the column of fluid in the tubing, keeps the 23 ball of the standing valve seated. Thu~ the travelling valve is 24 open and the standing valve is closed. As the plunger descends, fluid in the barrel chamber moves through the travelling valve 26 and plunger and reaches that portion of the barrel bore above the 27 plunger. When the plunger reaches the bottom of its downward 28 travel and reverses into the up stroke, the ball of the 29 travelling valve seats, thereby trapping the fluid standing above 2al~32~
1 it. As the plunger rlses, fluid is swabbed from the barrel bore 2 and through the top ports of the barrel into the tubing bore.
3 At the same time, the low pressure created by the upward stroke 4 unseats the ball of the standing valve and d.raws in oil from the wellbore and reservoir. Fluid from the wellbore thus follows the 6 rising plunger by passing through the standing valve and entering 7 the barrel bore. ~his stroking sequence is repeated again and 8 again to gradually lift a fluid column, made up of separately 9 accumulated slugs of fluid, to ground surface.
A downhole reciprocating pump as described is 11 periodically subjsct to failure. When the pump fails, it is 12 necessary to move a service rig onto the well, pull the rod 13 string and pump, and run the rod string back into the well with 14 a replacement pump. The frequency of failure is usually worsened lS in the case where the oil-producing formation is an 16 unconsolidated sand, so that the produced fluid contains 17 entrained sand.
18 The various reasons for pump failure include:
19 - partial loss of the absolute seal at ona or both of the ~tanding and travelling valves; and 21 - deterioration of the seal between the plunger and 22 barral.
23 In both cases, there is a loss in pump efficiency 24 arising from leakage at the defective seal.
For purposes of discussion, a conventional ball-and-26 seat type check valve is shown in Figure 1. The valve comprises:
27 - a tubular cage a;
28 - a ring b, forming a seat c, positioned in the cage 29 bore d;
2~32~
1 - a ball e positioned in the cage bore and operative 2 to seat on the seat and provide an annular seal;
3 - the bore of the cage having a diameter greater 4 than that of the ball, so that fluid may move past S the ball when it is unseated; and 6 - a lock ring f locking the ring in place.
7 Now, one reason that the seal of a ball-and-seat valve 8 can be damaged has to do with sand grains occasionally getting 9 trapped between the ball and the annular seat. Complete closure is not achieved when this occurs and a narrow gap is temporarily 11 left open between the two sealing surfaces. Fluid under pressure 12 then can forcefully be driven through the gap and some erosion 13 or "wash-out" of the sealing surfaces may take place. With 14 repetition, the extent of damage may become severe.
Al~ernatively, when the ball is seating it may impact 16 forcefully against sand grains trappecl against the seat. On 17 being so impacted, the abrasive sand may score the seat or ball 18 surfaces. Once scored, pressurized fluid erosion can quickly 19 enlarge the breach.
From the foregoing, the desirability of a valva design 21 that reduces the likelihood of sand grains remaining between the 22 sealing surface6 as they close, becomes apparent.
23 Another factor, which affects the speed with which the 24 sealing surfaces of the valve lose their ef~ective seal, has to do with the width of their contact area. In a conventional 26' valve, the surface of the annular seat is curved, as shown ln 27 Figure 1, so as to have the same radius of curvature as the ball.
28 This is done to ensure a contlnuous annular contact area between 29 the two parts. It is inharent in a ball and curved seat design 2~32~
1 that the width of the contact area will be small, typically belng 2 .010 - .015 thousandths of an inch.
3 It follows that it would be desirable to significantly 4 increase the width of the annular seal contact area. This would S extend the time that it takes to sufficiently damage the seal to 6 such an extent that the pump needs to be replaced.
7 Let us turn now to the steel-on-steel plunger/barrel 8 seal system used in most oilwell pumps. Ai previously stated, 9 an effective seal needs to be maintained between the outsr cylindrical surface of the plunger and the inside cylindrical 11 surface of the barrel. Yet it is also necessary to provide a 12 clearance between the parts, in the order of .00~ - .004 13 thou~andths of an inch, so that the plunger can still slide in 14 the barrel. This order of clearance can be referred to as a sliding fit. Be~ause of this clearance, minute sand particles 16 can penetrate between the two surfaces and may score one or both 17 of the cylindrical surfaces. The pressurized fluid moving 18 through the clearance will soon enlarge the scored area and the 19 seal will deteriorate.
There are other problemæ arising from the clearance 21 between plunger and barrel. These have to do with "gyp" build-22 up, silt penetration into the clearance, and "gas locking". In 23 some wells, scale or gyp will accumulate on the inner surface of 24 the barrel. ~his scale can accumulate and cause the plunger and rod string to hang up. Alternatively silt may penetrate into the 26 clearance and cause the plunger to hang up. Or alternativel~, 27 if the well is producing gas, ths travelling valve can fail to 28 open, due in part to gas escaping past the plunger through the 29 clearance on the down stroke. Insufficient pressure is developsd 2~32~
1 in the barrel bore beneath the descending plunger to move the 2 ball off its seat. Thus the pump can fail to move fluid.
3 To combat the scoring problem in the past, the sealing 4 surfaces of the barrel and plunger have usually been hardened.
In addition, the clearance has been kept as small as possible.
6 This has required machining the surfaces to very fine tolerances, 7 which is difficult to do and affects cost. And finally, the 8 lengths of the plunger and barrel have been increased, to provide 9 a greater sealing area. A typical rule of thumb is that the plunger length should be 1 foot for each 1000 feet of well depth, 11 up to a maximum of ahout 5 - 6 feet. However, while very 12 helpful, these improvements have not eliminated the problems 13 inherent in the steel-on-steel plunger/barrel seal assembly.
14 As an alternative to the steel-on-steel seal assembly, it has been known to provide a greater clearance and mount 16 elastomer packing ring~ in grooves formed on the outer surface 17 of the plunger, to contact and seal against the barral. However, 18 the sand grains tend to embed in the packing rings and act to 19 score the barrel. Fluid erosion soon follows.
From the foregoing, it becomes apparent that it would 21 he desirable to provide a plunger that i5 equipped with annular 22 protruding seals which contact the barrel surface and are better 23 resistive to sand damage than the conventional elastomer rings.
24 If this could be achieved, slippage would be reduced or eliminated, pumping efficiency would improve, gas locking and gyp 26 seizure would be reduced, and the plunger could be 3horter ~n 27 length.
2 ~
1 Still another problem relating to ball-and-seat type 2 standing and travelling check valves arises when they are used 3 in heavy oil. The rate at which the pump can be stroked is 4 affected by ~he time taken for the ball (or valve member) of a check valve to move from the open (unseated) position to the 6 closed position. If the oll through which the ball is dropping is viscous, the ball can be slow to close. In the past, this 8 problem has been attacked by making the balls from heavy alloy 9 material. It will be appreciated that the weight of the ball cannot be increased by increasing the size of the ball, as its 11 dia~e~er ls dictated by the bore hole diameter and the tubular 12 parts used in conjunction with the ball.
13 Therefore it would be desirable to design a check valve 14 which would permit greater flexibility and range in the choice of weight of the valve member to be attained.
16 The present invention is directed toward providing some 17 resolution of these problems.
18 SUMMARY QF ~E INVE~Q~
19 In accordance with one aspect of the present invention, a novel check valva for downhole reciprocating pumps is provided, 21 comprising:
22 - a conventional tubular cage having a riny seat 23 member locked therein and providing an annular 24 seat; and - a valve member that is adapted to spin about its 26 longitudinal axi~ as it drops thxough fluid in the 27 bore of the cage, in the course of moving toward 28 the seat during the act of closing.
2~32~
1 More particularly, the valve me~ber has an elongated, 2 generally cylindrical body having upper and lower body sections.
3 The upper body section carries outwardly protruding, spaced apart 4 vanes extending longitudinally of the body portion at an acute angle relative to the longitudinal axis of the body. These vanes 6 form open-ended channels for enabling fluid to move past the 7 valve member as it drops through the fluid-filled bore of the 8 cage. Interaction between the angled YaneS and the fluid imparts 9 a spinning motion to the valve member as it drops. Thz lower body section is smooth-surfaced and is adapted to seal against 11 the annular seat when in the closed position.
12 The spinning valve member acts to clear at least some 13 of the sand grains away from the seat during closing. This has 14 the effect of reducing the scoring and eroæion of the sealing surfaces that would otherwise occur.
16 It will be noted that the novel valve member is 17 generally cylindrical in form. Its length (and tha length of the 18 cage) can therefore be extended as desired to achieve an increase 19 in valve member weight when the valve is to be used in a well producing viscous oil.
21 In a preferred feature, the sealing surfa~e of the 22 lower body section of the valve member is conical in form and 23 thus straight-sided and inwardly tapered. The annular seat of 24 the cage is also straight-surfaced and inwardly tapered, so as ~o conform with the sealing surface of the valve member. The 26 advantages of this design are that: ;
27 - the ssat is now downwardly sloped, to assist in 28 shedding sand grains seeking to settle thereon;
29 and 1 _ the width of the area of contact of the sea~ Q~ 3 ~ 4 2 surfaces can be significantly extended, relative 3 to what was possible with the ball and seat 4 assembly.
In another aspect of the invention, a novel plunger is 6 provided for use in a downhole reciprocating pump. The plunger 7 is equipped with a pair of novel pressure-driven ring seals and, 8 preferably, a travelling valve of the type just described. Each 9 ring seal is formed of a hard, non-elastomeric material, such as mild steel.
11 More particularly, each ring seal comprises a base ring 12 that seals against the cylindrical plunger body. This may be 13 accomplishea by shrinking the base ring to the plunger body so 14 that the ring seals are, in effect, integral with the plunger body and reciprocate with it. The plunger body iq preferably 16 recessed adjacent each of its ends, to form upper and lower 17 annular shoulders. Each ring seal is seated on and supported by 18 one of the annular shoulders. The ring seal is thus positioned 19 along the recsssed area. At one outer rim, each base ring has an axially extendiny annular lip. The lip is suficiently thin 21 so that whsn tha pressure, to which the plunger is subjected, 22 acts against the inside ~urface of the lip, it will flex the lip 23 outwardly into sealing engagement with the inside cylindrical 24 surface of the pump barrsl. As previously stated, the ring seal is formed of relatively hard material, ~uch as mild steel. The 26 outer axial side surface of the ring seal may be coated with a 27 material such as ceramic, to harden it, and the steel may be 28 nickel-coated, to impxove its corrosion resistance. The outer 29 side surface of the lip seal is straight-sided and cylindrical 1 in form and has a close sliding fit, typically about .0002~ 3~4 2 .0006 tenths of an inch, with the inside cylindrical surface of 3 the barrel. Alternatively, the outer side surface of the lip 4 seal could have an interference fit with the barrel - however the base ring would ~hen have to have an undercut of .001 to .002 6 thousandths of an inch clearance to the barrel, in order to 7 permit of assembly. The two ring seals carried by the plunger 8 are oppositely directed, so that the upper ring seal has its lip 9 directed upwardly and the lower ring seal has its lip directed downwardly.
11 This design of ring seal, when incorporated into the 12 plunger, has the following advantages:
13 - because it is hard and formed of high temp0rature 14 resistant materials, it is not as susceptible to scoring and thermal degradation as is the casa 16 with elastomer 0-rings and the like; and 17 - because the lip flexes into sealing contact with 18 the barrel, there is little, if any, fluid 19 slippage past the plunger.
Now described are the results of some tests conducted 21 on pumps equipped with the novel components.
22 In one test, a conventional pump having a steel-on-23 steel plunger~barrel seal assembly was run in a well known to 24 cause pump failure by "silting" (wherein silt penetrates into the clearance between the plunger and barrel and packs in until the 26 plunger begins to hang up on the down stroke and eventually 27 seizes up). The pump began to hang up within 4 days of 28 installation and failed within 3 months. The maximum pumping 29 rate with the pump was 6-1/2 strokes per minute ("S.P.~."). The 3 ~ ~
1 same model of pump, modified by the insertion of a plunger ln 2 accordance with the present invention~ was then run in the same 3 well. There was no indication of hang-up from silt after 4 4 months of use and the stroking rate was successfully increased from 6-1/2 to 10 S.P.M.
6 In another test, conducted under shop conditions, a 7 conventional ball-and-seat valve was used in a transparent 8 plastic standing valve cage in a pump. A suspension of 50% sand 9 in oil was continually pumped for 3 weeks through a loop with a valve on the line to create a backpressure of 3000 psi. It was 11 visually noted repeatedly that sand would be trapped between the 12 ball and seat, typically every 5-6 strokes, allowing fluid to 13 leak past the seal. A check valve in accordance with the present 14 invention, having a spinning valve member disposed in a similar transparent plastic standing cage, was then substituted and used 16 for 3 weeks under the same conditions. Only occasionally, 17 typically every 25 - 30 strokes, was it noted that the valve 18 member would not seat perfectly due to sand propping.
19 Another test was conducted in a well known to cause gas locking of the pump. The well would be pumped intermittently 21 and gas locking would occur on start-up. More particularly, a 22 conventional pump with ball-and-seat check valves and steel-on-23 steel plunger/barrel seal assembly would almost invariably gas 24 lock after shut-down, due to the high gas/oil ratio of the production of the well. A pump equipped with check valves and 26 plunger in accordancs with the present invention was then 27 operated in the well. Repeated shut-downs and start-ups were 28 conducted without any indication of gas locking.
3 2 ~
1 DE~CRIPTION OF THE DRAWING$
2 Figure 1 is a side sectional view of a conventional 3 prio~ art ball-and-seat check valve for a downhole reciprocating 4 pump;
Figures 2a-2f are side sectional views of sections of 6 a downhole reciprocating pump in accordance with the present 7 invention, said sections when connected end to end together 8 making up the complete pump, said pump being shown seated in the 9 seatlng nipple of a tubing string;
I0 Figures 3a and 3b are side sectional views of sections 11 of the plunger, said sections when connected end to end together 12 making up the complete plunger;
13 Figure 4 is a side view, partly in section, showing a 14 valve member, in accordance with the invention, seated in a ring seat in the closed position;
16 Figure 5 is a side view, partly in section, showing the 17 valve member of Figure 4 in its cage in the unseated or open 18 position; and 19 Figure 6 is a sectional side view of a plunger seal in accordance with the invention.
21 ESGRIPTIO~_OF ~ PRF~RRED EM~O~IMENT
22 Having reference to the Figures, there is shown a 23 downhole reciprocating pump 1. The pump 1 comprises a 24 cylindrical tubular barrel 2 which may be seated in the seating nipple 3 of the tubing string 4. (Note that in Figures 2a - 2f, 26 the tubing string 4 is only shown extending to th~ top of the 27 pump. However in actual practice the tubing string would 28 commonly extend the full length of the pump.) A cylindrical 2 ~
1 plunger 5 is posltioned within the barrel bore 6. The plunger 2 5 is threaded at its upper end for connection with a 3 reciprocating rod string 7. The pump 1 and tubing and rod 4 strings 4, 7 would normally be positioned in a wellbore (not shown) and would function to lift produced fluid from the lower 6 reaches of the wellbore to ground surface, where the fluid is 7 recovered.
8 The barrel 2 i5 conventional. It comprises a steel 9 tube 8 having a hardened inside surface 9. It is closed at its upper end by closure means 10, but has a port 11, whereby the 11 barrel bore 6 is in communication with the bore 12 of the tubing 12 string 4.
13 At its lower end, the barrel tube 8 is threadably 14 connected with a standing valve 13. This standing valve comprises an open-ended tubular cage 14. The cage 14 forms a 16 longitudinal bore 15. The cage bore 15 communicates at its lower 17 end with the wellbore (not shown) and at its upper end with the 18 barrel bore 6.
19 A valve member 16 is positioned within the cage bore 15. The valvs member 16 has a sliding fit in the cage 14.
21 The cage bore surface 17 is inwardly stepped at its 22 upper end to form an annular shoulder 18. This shoulder 18 acts 23 as a stop, to limit the upward travel of the valve member 16.
24 Adjacent its lower end, the cage bore surface 17 is outwardly stepped, to form a second annular shoulder 19. A ring 26 seat member 20 is positioned in the cage bore lS adjacent its 27 lower end and at its upper end abuts the shoulder 19. The ring 28 seat member 20 is locked against the shoulder 19 by a lock ring 29 21 that is threaded into the lower end of the cage 10. The ring 2 ~
1 seat member 20 forms an annular, downwardly and inwardly tapered, 2 straight-surface~ seat 22.
3 The valve member t6 is generally cylindrical in form 4 and comprises upper and lower body portions 23, 24 (see Figuxe 4). The lower body portion 24 takes the form of a smooth-6 surfaced truncated cone. Stated otherwi~e, the lower body 7 portion 24 is downwardly and inwardly tapered and is straight-8 sided. It is configured so as to conform to the tapered seat 22.
9 The upper body portion 23 has a plurality of outwardly protruding, spaced apart, parallel vanes 26 forming open-topped, 11 open-ended channels 27 between them. The vanes 26 extend 12 longitudinally of the upper body portion 23 and are slanted at 13 an acute angle relative to the longitudinal axis of the valve 14 member 16. The vanes 26 extend upwardly beyond the upper end surface of the valve member 16, to form windows 28 for flow when 16 the valve member 16 abuts the stop shoulder 18.
17 The valve member 16 has a loose fit relative to the 18 cage bore surface 17, so that it can slicle freely therein and so l9 that sand can move axially between the outer longitudinal faces of the vanes 26 and the cage bore surface 17.
21 The channel~ 27 provide a passageway means for enabling 22 fluid to bypass the valve member 16 when it is dropping through 23 fluid in the cage bore 15 in the course of closing. When the 24 valve member 16 is moving downwardly, the fluid in the bore 15 and the vanes 26 interact to cause ths valve member 16 to spin 26 about its longitudinal axis.
27 By designing the ring seat member 20 and the valve 28 member lower body portion 24 so as to provide conforming, 29 downwardly and inwardly tapered sealing surfaces, a relatively 2~3~
1 wide annular contact surface may be achieved. Typically, for a 2 15 taper, the width of the annular contact area may be 60/1,000 3 of an inch. In addition, the downwardly sloping seat 22 tends 4 to shed sand grains settling thereon. And finally, by inducing the valve member 16 to spin as it closes, the valve membex acts 6 to clear sand grains from the seat 22.
J Turning now to the plun~er 5, it comprises a 8 cylindricaL tubular body 29. ~he plunger body 29 forms a 9 longitudinal bore 30. The body is threaded at each of its ends.
A connector 31 is threaded onto the upper end of the 11 plunger body 29. A longitudinal bore 32 extends part way up into 12 the connector 31 from its lower end. The connector bore 32 13 communicates with the plunger body bore 30. A plunger port 33 14 extends through the sidewall of the connector 31 and provides communication between the plunger bores 30, 32 and that portion 16 of the barrel bore 6 which is above the plunger 5. At its upper 17 end, the connector 31 is connected with the lower end of the rod 18 string 7.
19 More particularly, the connector 31 connects with a valve rod 51 which in turn connects by means of a bushing 52 and 21 collar 53 with the lowermost sucker rod of the rod string 7.
22 The upper end of the barrel tube 8 is connected with 23 a seating mandrel bushing 54 and seating mandrel 55. The seating 24 mandrel 55 is connected with a valve rod guide 56, which has a close sliding fit with the valve rod 51. The seating mandrel 26 bushing 54, seating mandrel 55 and valve rod guide 56 27 collectively form the upper end of the barrel 2.
28 A passageway 57 (which is part of the barrel bore 6) 29 is formed between the plunger/s valve rod 51 and the barrel's 2 ~ 2 ~
1 seating mandrel bushing 54, seating mandrel 55 and lower end of 2 the valve rod guide 56. The valve rod guide 56 forms the barrel 3port 11. Thus the passageway 57 connects ~he plunger port 33 4 with the barrel port 11 and thus with the tubing bore 12.
5In summary, the plunger 5 is connectable with the rod 6 string for reciprocation and fluid may move through th~ plunger 7bores 30, 32, and port 33 into the barrel bore 6, includin~ the 8 passageway 57, and then through the barrel port 11 into the 9 tubing string bore 12.
10At its lower end, the plunger body 2~ is threadably 11 connected with a travelling valve 34. ~his plunger travelling 12 valve 34 is identical to the barrel standing valve 13 (except as 13 to dimensions) and thus requires little description. It does 14 comprise a cage 35, having an axial bore 36, a ring seat member 1537 in the bore 36, a lock ring 38 forming part of the cage 35 and 16 locking the ring seat member against a cage shoulder 39, and a 17 valve member 40 adapted to seat in the seat 41.
18The plunger body 29 carries a pair of oppositely 19directed mechanical ring seals 42 (ses Figures 2b, 2c and 6).
More particularly, the plunger body 29 is inwardly recessed at 21 each of it8 ends to form upper and lower annular shoulders 43, 22 44. A rin~ seal 42 is positioned in each of the recessed areas 2345, 46 and is supported by one of the shoulders 43, 44.
24Each ring seal 42 is formed of non-elastomeric material, such as nickel-coated mild steel. The ring seal 42 26 comprises a base ring 47 that ls shrunk-fit onto the plunger body 27 29, so as to seal against it and to ensure that they rsciprocate 28 together. A thin annular lip 48 extends axially from the outer 29 rim of the base ring 47, remote from the plunger body support 2~32~
1 shoulder 43 or 44. The outer side surface 49 of the ring seal 2 42 is inwardly recessed between two end lands 50, 51. The 3 recessed area between the end lands 50, 51 is filled with a thin 4 layer 52 of hard ma~erial, such as sprayed-on ceramic.
By forming the ring seal 42 of mild steel, one can 6 ensure that it will not seriously wear or scratch the hardened .7 internal surface 9 of the barrel 2. By nickel-coating the steel, 8 corrosion damage may be reduced. By inilling the recessed outer 9 surface of the ring seal 42 with ceramic, a hard, abrasion-resistant surface 49a for sealing against the barrel surface 9 11 is provided.
12 It will be noted that the outer side surface 49a of the 13 ceramic-coated ring seal 42 is cylindrical and straight.
14 An annular space 58 is formed between the inside surface 59 of the lip 48 and the plunger outer surface 60. This 16 space 58 is in communication with the barrel bore 6. Thus the 17 inside surface 59 of the lip 48 is exposed to the fluid pressure 18 present in the barrel bore 6. More particularly, the lip inside 19 surface 59 of the lower ring seal 42 is exposed to the hydrostatic head of the column of fluid in the t~lbing bore 12 21 (i.e. the lldownhole pressure") when the plunger 5 is on the 22 downstroke. The lip inside surface 59 of the upper ring seal 42 23 i5 exposed to that downhole pressure on the upstroke.
24 The lip 48 is sufficiently thin so that it will flex into fluid-tight sealing engagement with the barrel's cylindrical 26 inside surface 9, when the lip inside surface 59 is acted on by 27 the downhole pressure.
3 ~ ~
1 The ring seal 42 has a sufflciently close sliding fit 2 with the barrel 2, so that pressure is not equalized across the 3 lip 48.
4 By way of example, I have used the following dimensional relationships for the ring seal when using it with 6 a barrel haviny an inside diameter of 1.500 inches and a plunger 7 having an out~ide diametex of 1.460 inches:
8 - thickness of base ring - .125"
9 - height of base ring - .500 "
- thickness of lip - .030"
11 - height of lip - 1.300"
12 - clearance of lip from barrel - .0006 tenths of an 13 inch 14 - thickness of ceramic - .007 thousandths of an inch The scope of the invention is set forth in the claims 16 now following.
Claims (16)
1. A check valve adapted for use as a standing or travelling valve in a downhole reciprocating pump, comprising:
an upright tubular cage forming an internal bore and having an internal annular seat adjacent its lower end; and a generally cylindrical valve member positioned in the cage bore and having upper and lower body portions, said upper body portion having a plurality of outwardly protruding, spaced apart vanes extending longitudinally thereof to form a plurality of channels, said vanes extending at an acute angle relative to the longitudinal axis of the valve member, said lower body portion being smooth-surfaced and adapted to seal against the seat;
said valve member having a sufficiently loose fit in the cage bore whereby it is adapted to slide freely therein;
whereby the valve member, when closing, may drop through fluid in the cage bore and interaction between the fluid and vanes will cause the valve member to spin about its longitudinal axis.
an upright tubular cage forming an internal bore and having an internal annular seat adjacent its lower end; and a generally cylindrical valve member positioned in the cage bore and having upper and lower body portions, said upper body portion having a plurality of outwardly protruding, spaced apart vanes extending longitudinally thereof to form a plurality of channels, said vanes extending at an acute angle relative to the longitudinal axis of the valve member, said lower body portion being smooth-surfaced and adapted to seal against the seat;
said valve member having a sufficiently loose fit in the cage bore whereby it is adapted to slide freely therein;
whereby the valve member, when closing, may drop through fluid in the cage bore and interaction between the fluid and vanes will cause the valve member to spin about its longitudinal axis.
2. The check valve set forth in claim 1 wherein:
the annular seat is downwardly and inwardly tapered, and the lower body portion is downwardly and inwardly tapered and adapted to conform with the seat.
the annular seat is downwardly and inwardly tapered, and the lower body portion is downwardly and inwardly tapered and adapted to conform with the seat.
3. The check valve set forth in claim 1 wherein:
the cage bore surface is inwardly stepped at its upper end to form a stop shoulder for limiting upward travel of the valve member; and the vanes extend longitudinally above the upper end of the upper body portion, whereby flow windows are formed when the vanes contact the stop shoulder.
the cage bore surface is inwardly stepped at its upper end to form a stop shoulder for limiting upward travel of the valve member; and the vanes extend longitudinally above the upper end of the upper body portion, whereby flow windows are formed when the vanes contact the stop shoulder.
4. The check valve set forth in claim 2 wherein:
the cage bore surface is inwardly stepped at its upper end to form a stop shoulder for limiting upward travel of the valve member; and the vanes extend longitudinally above the upper end of the upper body portion, whereby flow windows are formed when the vanes contact the stop shoulder.
the cage bore surface is inwardly stepped at its upper end to form a stop shoulder for limiting upward travel of the valve member; and the vanes extend longitudinally above the upper end of the upper body portion, whereby flow windows are formed when the vanes contact the stop shoulder.
5. A downhole reciprocating pump plunger comprising:
a cylindrical plunger body having means at its upper end for attachment to a rod string, the outer surface of said plunger body being inwardly recessed axially adjacent each end to provide seal ring - mounting recesses, said plunger body being generally tubular, so as to form a longitudinal bore extending therethrough;
a pair of pressure-driven seal rings, one mounted on each of the recessed portions of the plunger body, each seal ring comprising an annular base ring engaging the outer surface of the plunger body and being sealed thereto, said base ring having a relatively thin annular lip extending axially from its outer rim, said lip having a straight cylindrical outer side surface, said lip being sufficiently thin so that, in use, it may be flexed outwardly by downhole pressure acting against its inner surface, the upper ring seal having its lip extending upwardly, the lower ring seal having its lip extending downwardly; and said plunger body being connected with a travelling check valve at its lower end, for controlling fluid movement through the plunger body bore.
a cylindrical plunger body having means at its upper end for attachment to a rod string, the outer surface of said plunger body being inwardly recessed axially adjacent each end to provide seal ring - mounting recesses, said plunger body being generally tubular, so as to form a longitudinal bore extending therethrough;
a pair of pressure-driven seal rings, one mounted on each of the recessed portions of the plunger body, each seal ring comprising an annular base ring engaging the outer surface of the plunger body and being sealed thereto, said base ring having a relatively thin annular lip extending axially from its outer rim, said lip having a straight cylindrical outer side surface, said lip being sufficiently thin so that, in use, it may be flexed outwardly by downhole pressure acting against its inner surface, the upper ring seal having its lip extending upwardly, the lower ring seal having its lip extending downwardly; and said plunger body being connected with a travelling check valve at its lower end, for controlling fluid movement through the plunger body bore.
6. The plunger as set forth in claim 5 wherein the check valve comprises:
a tubular cage forming an internal bore in communication with the internal bore of the plunger body, said cage having an internal annular seat adjacent its lower end, and a generally cylindrical valve member positioned in the cage bore and having upper and lower body portions, said upper body portion having a plurality of outwardly protruding, spaced apart vanes extending longitudinally thereof at an acute angle relative to the longitudinal axis of the valve member, said vanes forming a plurality of channels, said lower body portion being smooth-surfaced and adapted to seal against the seat;
said valve member having a sufficiently loose fit in the cage bore whereby it is adapted to slide freely therein;
whereby the valve member, when closing, may drop through fluid in the cage bore and interaction between the fluid and vanes will cause the valve member to spin about its longitudinal axis.
a tubular cage forming an internal bore in communication with the internal bore of the plunger body, said cage having an internal annular seat adjacent its lower end, and a generally cylindrical valve member positioned in the cage bore and having upper and lower body portions, said upper body portion having a plurality of outwardly protruding, spaced apart vanes extending longitudinally thereof at an acute angle relative to the longitudinal axis of the valve member, said vanes forming a plurality of channels, said lower body portion being smooth-surfaced and adapted to seal against the seat;
said valve member having a sufficiently loose fit in the cage bore whereby it is adapted to slide freely therein;
whereby the valve member, when closing, may drop through fluid in the cage bore and interaction between the fluid and vanes will cause the valve member to spin about its longitudinal axis.
7. The plunger as set forth in claim 6 wherein:
the annular seat is downwardly and inwardly tapered, and the lower body portion is downwardly and inwardly tapered and adapted to conform with the seat.
the annular seat is downwardly and inwardly tapered, and the lower body portion is downwardly and inwardly tapered and adapted to conform with the seat.
8. The check valve set forth in claim 6 wherein:
the cage bore surface is inwardly stepped at its upper end to form a stop shoulder for limiting upward travel of the valve member; and the vanes extend longitudinally above the upper end of the upper body portion, whereby flow windows are formed when the vanes contact the stop shoulder.
the cage bore surface is inwardly stepped at its upper end to form a stop shoulder for limiting upward travel of the valve member; and the vanes extend longitudinally above the upper end of the upper body portion, whereby flow windows are formed when the vanes contact the stop shoulder.
9. The check valve set forth in claim 7 wherein:
the cage bore surface is inwardly stepped at its upper end to form a stop shoulder for limiting upward travel of the valve member; and the vanes extend longitudinally above the upper end of the upper body portion, whereby flow windows are formed when the vanes contact the stop shoulder.
the cage bore surface is inwardly stepped at its upper end to form a stop shoulder for limiting upward travel of the valve member; and the vanes extend longitudinally above the upper end of the upper body portion, whereby flow windows are formed when the vanes contact the stop shoulder.
10. A downhole reciprocating pump for use in a well having tubing and rod strings, comprising:
a barrel, seatable in the tubing string, having a cylindrical longitudinal bore and a standing valve at its lower end for controlling the movement of fluid through the barrel bore, said barrel having means at its upper end for providing communication between the bore of the barrel and the bore of the tubing;
a cylindrical plunger having a longitudinal bore and positioned within the barrel bore, said plunger having external sealing means for sealing against the surface of the barrel bore, said plunger having a travelling valve at its lower end for controlling fluid movement through the plunger bore, said plunger having means at its upper end for connection with the rod string;
said standing and travelling valves each comprising a tubular cage, forming an internal bore and having an internal annular seat adjacent its lower end, and a generally cylindrical valve member positioned in the cage bore and having upper and lower body portions, said upper body portion having a plurality of outwardly protruding, spaced apart vanes extending longitudinally thereof at an acute angle relative to the longitudinal axis of the valve member, said vanes forming a plurality of channels, said lower body portion being smooth-surfaced and adapted to seal against the seat, said valve member having a sufficiently loose fit in the cage bore whereby it is adapted to slide freely therein, whereby the valve member, when closing, may drop through fluid in the cage bore and interaction between the fluid and vanes will cause the valve member to spin about its longitudinal axis.
a barrel, seatable in the tubing string, having a cylindrical longitudinal bore and a standing valve at its lower end for controlling the movement of fluid through the barrel bore, said barrel having means at its upper end for providing communication between the bore of the barrel and the bore of the tubing;
a cylindrical plunger having a longitudinal bore and positioned within the barrel bore, said plunger having external sealing means for sealing against the surface of the barrel bore, said plunger having a travelling valve at its lower end for controlling fluid movement through the plunger bore, said plunger having means at its upper end for connection with the rod string;
said standing and travelling valves each comprising a tubular cage, forming an internal bore and having an internal annular seat adjacent its lower end, and a generally cylindrical valve member positioned in the cage bore and having upper and lower body portions, said upper body portion having a plurality of outwardly protruding, spaced apart vanes extending longitudinally thereof at an acute angle relative to the longitudinal axis of the valve member, said vanes forming a plurality of channels, said lower body portion being smooth-surfaced and adapted to seal against the seat, said valve member having a sufficiently loose fit in the cage bore whereby it is adapted to slide freely therein, whereby the valve member, when closing, may drop through fluid in the cage bore and interaction between the fluid and vanes will cause the valve member to spin about its longitudinal axis.
11. The pump as set forth in claim 10 wherein:
the annular seat is downwardly and inwardly tapered, and the lower body portion is downwardly and inwardly tapered and adapted to conform with the seat.
the annular seat is downwardly and inwardly tapered, and the lower body portion is downwardly and inwardly tapered and adapted to conform with the seat.
12. The pump as set forth in claim 11 wherein:
the cage bore surface is inwardly stepped at its upper end to form a stop shoulder for limiting upward travel of the valve member; and the vanes extend longitudinally above the upper end of the upper body portion, whereby flow windows are formed when the vanes contact the stop shoulder.
the cage bore surface is inwardly stepped at its upper end to form a stop shoulder for limiting upward travel of the valve member; and the vanes extend longitudinally above the upper end of the upper body portion, whereby flow windows are formed when the vanes contact the stop shoulder.
13. A downhole reciprocating pump, for use in a well having tubing and rod strings, comprising:
a barrel, seatable in the tubing string, having a cylindrical longitudinal bore and a standing check valve at its lower end for controlling the movement of fluid through the barrel bore, said barrel having means at its upper end for providing communication between the bore of the barrel and the bore of the tubing;
a cylindrical plunger having a longitudinal bore and positioned within the barrel bore, said plunger having external sealing means for sealing against the surface of the barrel bore, said plunger having a travelling valve at its lower end for controlling fluid movement through the plunger bore, said plunger having means at its upper end for connection with the rod string;
said plunger comprising a cylindrical tubular plunger body having an outer surface which is inwardly recessed axially adjacent each end to provide seal ring-mounting recesses; and a pair of pressure-driven seal rings, one mounted on each of the recessed portions of the plunger body, each seal ring comprising an annular base ring engaging the outer surface of the plunger body and being sealed thereto, said base ring having a relatively thin annular lip extending axially from its outer rim, said lip having a straight cylindrical outer side surface, said lip being sufficiently thin 50 that, in use, it may be flexed outwardly by downhole pressure acting against its inner surface, the upper ring seal having its lip extending upwardly, the lower ring seal having its lip extending downwardly; and said plunger body being connected with a travelling check valve at its lower end, for controlling fluid movement through the plunger bore.
a barrel, seatable in the tubing string, having a cylindrical longitudinal bore and a standing check valve at its lower end for controlling the movement of fluid through the barrel bore, said barrel having means at its upper end for providing communication between the bore of the barrel and the bore of the tubing;
a cylindrical plunger having a longitudinal bore and positioned within the barrel bore, said plunger having external sealing means for sealing against the surface of the barrel bore, said plunger having a travelling valve at its lower end for controlling fluid movement through the plunger bore, said plunger having means at its upper end for connection with the rod string;
said plunger comprising a cylindrical tubular plunger body having an outer surface which is inwardly recessed axially adjacent each end to provide seal ring-mounting recesses; and a pair of pressure-driven seal rings, one mounted on each of the recessed portions of the plunger body, each seal ring comprising an annular base ring engaging the outer surface of the plunger body and being sealed thereto, said base ring having a relatively thin annular lip extending axially from its outer rim, said lip having a straight cylindrical outer side surface, said lip being sufficiently thin 50 that, in use, it may be flexed outwardly by downhole pressure acting against its inner surface, the upper ring seal having its lip extending upwardly, the lower ring seal having its lip extending downwardly; and said plunger body being connected with a travelling check valve at its lower end, for controlling fluid movement through the plunger bore.
14. The pump as set forth in claim 13 wherein:
the standing and travelling check valves each comprise a tubular cage, forming an internal bore and having an internal annular seat adjacent its lower end, and a generally cylindrical valve member positioned in the cage bore and having upper and lower body portions, said upper body portion having a plurality of outwardly protruding, spaced apart vanes extending longitudinally thereof at an acute angle relative to the longitudinal axis of the valve member, said vanes forming a plurality of channels, said lower body portion being smooth-surfaced and adapted to seal against the seat, said valve member having a sufficiently loose fit in the cage bore whereby it is adapted to slide freely therein, whereby the valve member, when closing, may drop through fluid in the cage bore and interaction between the fluid and vanes will cause the valve member to spin about its longitudinal axis.
the standing and travelling check valves each comprise a tubular cage, forming an internal bore and having an internal annular seat adjacent its lower end, and a generally cylindrical valve member positioned in the cage bore and having upper and lower body portions, said upper body portion having a plurality of outwardly protruding, spaced apart vanes extending longitudinally thereof at an acute angle relative to the longitudinal axis of the valve member, said vanes forming a plurality of channels, said lower body portion being smooth-surfaced and adapted to seal against the seat, said valve member having a sufficiently loose fit in the cage bore whereby it is adapted to slide freely therein, whereby the valve member, when closing, may drop through fluid in the cage bore and interaction between the fluid and vanes will cause the valve member to spin about its longitudinal axis.
15. The pump as set forth in claim 14 wherein:
the annular seat is downwardly and inwardly tapered, and the lower body portion is downwardly and inwardly tapered and adapted to conform with the seat.
the annular seat is downwardly and inwardly tapered, and the lower body portion is downwardly and inwardly tapered and adapted to conform with the seat.
16. The pump as set forth in claim 15 wherein:
the cage bore surface is inwardly stepped at its upper end to form a stop shoulder for limiting upward travel of the valve member; and the vanes extend longitudinally above the upper end of the upper body portion, whereby flow windows are formed when the vanes contact the stop shoulder.
the cage bore surface is inwardly stepped at its upper end to form a stop shoulder for limiting upward travel of the valve member; and the vanes extend longitudinally above the upper end of the upper body portion, whereby flow windows are formed when the vanes contact the stop shoulder.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2040324 CA2040324A1 (en) | 1991-04-12 | 1991-04-12 | Downhole reciprocating pump and components therefor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2040324 CA2040324A1 (en) | 1991-04-12 | 1991-04-12 | Downhole reciprocating pump and components therefor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2040324A1 true CA2040324A1 (en) | 1992-10-13 |
Family
ID=4147384
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2040324 Abandoned CA2040324A1 (en) | 1991-04-12 | 1991-04-12 | Downhole reciprocating pump and components therefor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2040324A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102758761A (en) * | 2012-07-18 | 2012-10-31 | 中国石油天然气股份有限公司 | Chemical compound flooding scale-deposition type antiscale oil-well pump |
| WO2016133906A1 (en) * | 2015-02-16 | 2016-08-25 | Weatherford Technology Holdings, LLC. | Diversion plunger for reciprocating rod pump |
-
1991
- 1991-04-12 CA CA 2040324 patent/CA2040324A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102758761A (en) * | 2012-07-18 | 2012-10-31 | 中国石油天然气股份有限公司 | Chemical compound flooding scale-deposition type antiscale oil-well pump |
| WO2016133906A1 (en) * | 2015-02-16 | 2016-08-25 | Weatherford Technology Holdings, LLC. | Diversion plunger for reciprocating rod pump |
| US10731446B2 (en) | 2015-02-16 | 2020-08-04 | Weatherford Technology Holdings, Llc | Diversion plunger for reciprocating rod pump |
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| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |