Plunger Lift Apparatus

Abstract

A plunger of improved construction for reciprocating in a production string of a gas or oil well to remove fluid from the well. The plunger includes a sleeve having a through passage extending longitudinally from a first end to a second end, the second end forming a seat, a sealing means carried by the sleeve for engaging the inner surface of the production string, a detachable valve member releasably received by the seat to seal the through passage, and a catch positioned to releasably couple the detachable valve member to the sleeve within the seat. The catch retaining the detachable valve member until the detachable valve member is impacted at the surface of the well by a trip rod. The improved construction provides for the use of a heavier or more dense detachable valve member and a lighter or less dense sleeve than previously used in prior plungers, which results in a plunger having an increased efficiency and a greater cycle frequency.

Description

FIELD OF THE INVENTION

The present invention relates generally to a plunger apparatus for use in plunger lift operations of an oil or gas well to remove fluid that has accumulated within the well resulting in reduced well production. More particularly, relating to a plunger having an improve construction which increases cycle frequency and plunger performance.

BACKGROUND OF THE INVENTION

In general, plunger lift is an artificial-lift method principally used in gas wells to unload formation fluid that has accumulated in the well production string. However, plunger lift can be used in oil wells. An automated system mounted on the wellhead controls the well on an intermittent flow regime. When the well is shut-in, a plunger drops down the production string. When the control system opens the well for production, the plunger and a column of fluid are carried up the tubing string. The surface receiving mechanism detects the plunger when it arrives at surface and, through the control system, prepares for the next cycle.

There have been many different plunger apparatuses developed for use in plunger lift. Examples of such devices are described in U.S. Pat. Nos. 4,986,727; 4,531,891; 4,984,970; and 4,502,843. 6,148,923.

A particular plunger design includes a hollow sleeve and a detachable valve member that lighter than the sleeve. The sleeve includes a longitudinal through passage, sealing elements which engage the inner surface of a production string of a well and a seat or structure for receiving the detachable valve member to seal the through passage. In use, the detachable valve member is first dropped into the production string followed by the sleeve after determined time elapse. The time elapse is to allow the detachable valve member to reach the bottom of the production string. As the sleeve falls into the well, gas and fluid within the well flows through the passage. Once the detachable valve member followed by the sleeve reach the bottom of the production string they unite, the ball having enough cross sectional area and being light enough in ratio to the sleeve is lifted faster then the sleeve by gas produced by the well and pushed into the seat of the sleeve where it seals the passage, thereby preventing fluid in the well from flowing across the sleeve. As gas is continually produced, the pressure and volume of gas bellow the sleeve lifts the sleeve and fluid above the sleeve to the surface of the well. This plunger design relies on the sleeve being more dense or heavier to trap the less dense or lighter detachable valve member within the seat to seal the passage. In this design, the detachable valve member must be lighter or less dense than the sleeve, so that the detachable valve member is not easily dislodged from the sleeve during lift, which would result in opening of the passage and a loss of fluid load being lifted by the plunger. Further, it would cause the sleeve to fall back down the production string until the detachable valve member was once again reseated in the sleeve. An example of this plunger design is described in U.S. Pat. Nos. 6,148,923 and 6,719,060, which both are incorporated herein by reference in entirety.

A few drawbacks exist with this design, one being, the detachable valve member being lighter or less dense than the sleeve it needs an appreciable amount of time to reach the bottom of the well prior to dropping the sleeve. The greater amount of time needed between dropping the detachable valve member and dropping the sleeve reduces the cycle frequency of the plunger, which results in an increase in time needed to unload fluid from the well. A second drawback, is the requirement of using a less dense or light detachable valve member to ensure the valve member remains captured by the seat requires the use of a more dense or heavier sleeve. A heavy sleeve increases wear on well equipment, such as a bottom hole spring and or the surface lubricator springs, from repetitive impact by the heavy sleeve.

As such, there is a need for a plunger that increases cycle frequency, a plunger having a detachable valve member that is not easily dislodged from the sleeve, and a plunger where the density or weight of the sleeve is lowered to reduce wear on other well equipment. The plunger of present invention provides a plunger that increases cycle frequency, provides a catch that prevents the detachable valve member from becoming dislodged from the sleeve. The provision of the catch allows the use of a less dense or lighter sleeve, resulting in less wear on well equipment and a heavier or more dense detachable valve, resulting in less wait time between dropping the detachable valve member and sleeve.

SUMMARY OF THE INVENTION

In accordance with the present invention, an a plunger for reciprocating in a production string of a gas or oil well to remove fluid from the well, the well including a trip rod at the surface.

In general, in one aspect, the plunger includes a sleeve having a through passage extending longitudinally from a first end to a second end thereof, the second end forming a seat; a sealing means carried by the sleeve for engaging the inner surface of the production string; a detachable valve member releasably received by the seat to seal the through passage; and a catch positioned to releasably couple the detachable valve member to the sleeve within the seat. The catch retaining the detachable valve member until the detachable valve member is impacted at the surface of the well by the trip rod.

There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated.

Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof Such description makes reference to the annexed drawings wherein:

FIG. 1 is a longitudinal cross sectional view a plunger showing one embodiment of a catch constructed in accordance with the principles of the present invention;

FIG. 2 is a detailed longitudinal cross section of sleeve showing a detachable valve member exploded from the seat, the detachable valve member is shown as sphere;

FIG. 3 is a detailed longitudinal cross section of sleeve showing a detachable valve member exploded from the seat, the detachable valve member is shown as having a bullet shape with a spherical end;

FIG. 4 is detailed longitudinal cross sectional of the plunger sleeve showing a second embodiment of a catch in use with a detachable valve member having a spherical body;

FIG. 5 is detailed longitudinal cross sectional of the plunger sleeve showing a second embodiment of a catch in use with a detachable valve member having a bullet shaped body;

FIG. 6 is a partial longitudinal cross section of the plunger showing the engagement of a trip rod impacting and dislodging the detachable valve member from the sleeve.

The same reference numerals refer to the same parts throughout the various figures.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, the plunger 10 of this invention has an improved construction affording the plunger an increased cycle frequency and cycle efficiency in lifting fluid that has accumulated in a production string of well. The improved construction allows the use of a more dense detachable valve member and a less dense sleeve, as will be further described in detail below.

With reference now to FIG. 1, the plunger 10 includes a sleeve 12 having a through passage 14 that extends longitudinally through the sleeve from a first, bottom end, 16 to a second, top end 18. The sleeve 12 may comprises several sections coupled together as shown or can be made unitary. The second end 18 can define an internal fishing neck 58.

The sleeve 12 carries sealing elements 20 which are engagable with the inner surface 22 of a production string 24 sealing the annulus 26 between the sleeve and the inner surface of the production string from fluid flow. However, the sleeve 12 itself can be made to make sealing contact with the inner surface 22, thereby removing the need for the sealing elements 20.

The first end 16 of the sleeve defines a inwardly formed seat 30. The seat 30 removably receives a detachable valve member 32 to seal the through passage 14 from fluid flow. The detachable valve member 32 is shown received by the seat 30 and sealing the through passage 14. The opening 34 of the seat 30 is tapered or otherwise shaped to help direct the detachable valve member 32 into the seat so that it correctly engages the seat and seals the through passage 14.

With reference to FIGS. 2 and 3, the seat 30 can include a concaved spherical surface 36 formed such that the apex 38 is aligned axially with the longitudinal axis of the sleeve 12. FIG. 2, shows the detachable valve member 32 having a spherical body 40 of dimensions to be received by the spherical surface 36. FIG. 3, shows the detachable valve member 32 having a bullet shaped body 42 with a spherical end 44 of dimensions to be received by the spherical surface 36. The bullet shaped body 42 can also include centralizing fins to help centralize the body in the production string 24. The detachable valve member 32 as shown in FIGS. 2 and 3 as having a spherical body 40 and a bullet shaped body 42 is for exemplary purposes as the detachable valve member and seat 30 may take any shape so long the detachable valve member seals the through passage 14 when received by the seat.

With further reference to the Figures the sleeve 12 includes a catch 46 positioned to releasably couple the detachable valve member 32 to the sleeve within the seat 30, until the detachable valve member is impacted at the surface of the well by the trip rod 56 as shown in FIG. 6. The provision of the catch 46 allows the use of a more dense or heavier detachable valve member 32 and a less dense or lighter sleeve 12 than what has been previously used in prior art plungers. A heavier detachable valve member 32 falls more quickly in the production string allowing the sleeve 12 to be dropped at a short time after the detachable valve member has been released. Reducing the time between dropping the detachable valve member 32 and the sleeve 12 increases the cycle frequency of the plunger 10. Further, now that a lighter sleeve 12 can be employed, wear on well equipment from impact with the sleeve is reduced.

In FIGS. 1, 2 and 3, one embodiment of a catch 46 is shown which includes at least one magnet 48 positioned to attract and retain the detachable valve member 32, made of at least partially a ferrous material, within the seat 30. The magnet 48 can be wholly encapsulated by the sleeve 12 or can have a surface formed flush with a surface of the seat 30. In the embodiment shown, the magnet 48 is formed flush with the surface of the seat 30 and can include a coating 50 covering the magnet. The coating 50 can also at least partially cover seat surfaces adjacent the magnet 48. The magnet 50 as shown can be ring shaped and positioned to at least partially encircle the detachable valve member 32.

With reference now to FIGS. 4 and 5, the catch 46 can be resiliently biased and for exemplary purposes may include a spring loaded detent 52. The catch 46 could also include numerous other resiliently or spring biased mechanism which act to releasably couple the detachable valve member 32 and retain the detachable valve member until the detachable valve member is impacted at the surface of the well by a trip rod, as shown in FIG. 6. In FIG. 4, the plunger is shown with the catch 46 including spring loaded detents 52 in use with the detachable valve member 32 having a spherical body 40. In FIG. 5, the plunger is shown with the catch 46 including spring loaded dents 52 in use with the detachable valve member 32 having a bullet shaped body 42. Again, the catch 46 including spring load detents 52 is shown only as an example, as numerous other mechanism which total a number unreasonable to illustrate could be employed such that the catch operates to releasably couple the detachable valve member 32 and retain the detachable valve member until the detachable valve member is impacted at the surface of the well by a trip rod.

The seat 30 can be fitted with a resilient seal 60 received by a groove 62 formed around the surface of the seat and sized so that it sealing abuts the detachable valve member 32 when the detachable valve member is within the seat.

Turning to FIG. 6, a partial section view of the plunger 10 is shown with a trip rod 56 extending into the through passage 14 and impacting the detachable valve member 32 to dislodge the detachable valve member from the seat 30 separating it from the sleeve 12 of the plunger. The trip rod 56 impacts the detachable valve member 32 as the plunger reaches the top of the production string 24 with enough force to over come the catch 46 and release it from the catch.

In use, it can now be understood, the plunger 10 broadly operates by first dropping the detachable valve member 32 in the production string of a liquid loaded well, shortly followed by the sleeve 12. As the sleeve 12 falls downward in the production string, fluid is caused to flow through the through passage 14. At or towards the bottom of the production string, the detachable valve member 32 is caused to enter the seat 30 sealing the through passage 14 from fluid flow. The detachable valve member is retained in the seat 30 in sealing contact therewith by the catch 46. At this point a column of fluid has collected above the plunger 10 and gas produced by the well is accumulating below the plunger. The produced gas pressurizes the production string below the plunger 10 and lifts the sleeve 12 and detachable valve member 32 as one along with the column of fluid to the surface of the well. As the plunger 10 is lifted, the column of fluid is unloaded from the production string. As the sleeve 12 of the plunger 10 approaches the surface of the well, the sleeve passes over a stationary trip rod inserting the trip rod into the passage 14 and impact the detachable valve member 32 with enough force to overcome the catch 46 and releasing the detachable valve member from the catch separating the detachable valve member from the sleeve. Then detachable valve member 32 once again falls downward into the production string followed shortly by the sleeve 12, restarting the entire cycle once again.

A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. A plunger for reciprocating in a production string of a gas or oil well to remove fluid from the well, the well including a trip rod at the surface, the plunger comprising:

a sleeve having a through passage extending longitudinally from a first end to a second end thereof, said second end forming a seat;

sealing means carried by said sleeve for engaging the inner surface of the production string;

a detachable valve member releasably received by said seat to seal said passage; and

a catch positioned to releasably couple said detachable valve member to said sleeve within said seat, said catch retaining said detachable valve member until said detachable valve member is impacted at the surface of the well by the trip rod.

2. The plunger of claim 1, wherein said catch is a magnetic catch positioned to attract and retain said detachable valve member within said seat.

3. The plunger of claim 2, wherein said magnet encircles said detachable valve member when said detachable valve member is within said seat.

4. The plunger of claim 2, wherein said magnet is flush with the surface of said seat.

5. The plunger of claim 4, wherein said plunger further comprises:

a coating applied over said magnet and a least partially over the surface of said seat.

6. The plunger of claim 1, wherein said catch is resiliently biased.

7. The plunger of claim 6, wherein said catch includes spring loaded detents.

8. The plunger of claim 1, wherein said first end defines an internal fishing neck.

9. The plunger of claim 1, further comprising:

a resilient seal received by a groove formed around the surface of said seat and sized so that it sealing abuts said detachable valve member when said detachable valve member is within said seat.

10. The plunger of claim 1, wherein said detachable valve member is a sphere.

11. The plunger of claim 10, wherein said seat defines a spherical surface for at least partially receiving said detachable valve member.

12. The plunger of claim 1, wherein said detachable valve member comprises a bullet shaped body having a spherical end.

13. The plunger of claim 12, wherein said seat defines a spherical surface for at least partially receiving said spherical end of said bullet shaped body.

14. A plunger for reciprocating in a production string of a gas or oil well to remove fluid from the well, the plunger comprising:

a sleeve having a through passage extending longitudinally from a first end to a second end thereof, said second end forming a seat having a spherical surface;

sealing means carried by said sleeve for engaging the inner surface of the production string;

a detachable valve member releasably received by said seat to seal said passage;

a catch positioned to releasably couple said detachable valve member to said sleeve within said seat; and

an resilient seal received by a groove formed around the surface of said seat and sized so that it sealing abuts said detachable valve member when said detachable valve member is within said seat.

15. The plunger of claim 14, wherein said catch is a magnetic catch positioned to attract and retain said detachable valve member within said seat.

16. The plunger of claim 2, wherein said magnet encircles said detachable valve member when said detachable valve member is within said seat.

17. The plunger of claim 1, wherein said catch is resiliently biased.

18. The plunger of claim 6, wherein said catch includes spring loaded detents.

19. The plunger of claim 1, wherein said detachable valve member is a sphere.

20. The plunger of claim 1, wherein said detachable valve member comprises a bullet shaped body having a spherical end.