U.S. patent application number 11/331395 was filed with the patent office on 2007-07-12 for interference-seal plunger for an artificial lift system.
Invention is credited to Danny M. Casey.
Application Number | 20070158061 11/331395 |
Document ID | / |
Family ID | 38231641 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070158061 |
Kind Code |
A1 |
Casey; Danny M. |
July 12, 2007 |
Interference-seal plunger for an artificial lift system
Abstract
A plunger for an artificial lift system and embodiment of the
plunger includes a solid body adapted to travel within a production
string positioned in a wellbore. At least one sealing ring
connected about the body. The at least one sealing ring having an
inner surface, an outer surface, a width and a thickness. The width
is sufficient such that when the body is disposed in the production
string the outer surface contacts and substantially forms a seal
between the body and an inner wall of the production string. The at
least one sealing ring having an outside diameter greater than the
inner diameter of the production tubing within which the body is
adapted to travel such that when the body is disposed within the
production string an interference fit causes the sealing rings to
roll-form into a constricted shape and diameter that exerts the
sealing contact with the production string.
Inventors: |
Casey; Danny M.;
(Huntsville, TX) |
Correspondence
Address: |
HENRY L EHRLICH
P.O. BOX 50784
DALLAS
TX
75201-0784
US
|
Family ID: |
38231641 |
Appl. No.: |
11/331395 |
Filed: |
January 12, 2006 |
Current U.S.
Class: |
166/68 ;
166/372 |
Current CPC
Class: |
E21B 43/121
20130101 |
Class at
Publication: |
166/068 ;
166/372 |
International
Class: |
E21B 43/00 20060101
E21B043/00 |
Claims
1. A plunger for an artificial lift system, the plunger comprising:
a body adapted to travel within a production string positioned in a
wellbore; and at least one sealing ring having an inner surface, an
outer surface, a width and a thickness, the sealing ring connected
about the body, wherein the width is sufficient such that when the
body is disposed in the production string the outer surface
contacts and substantially forms a seal between the body and an
inner wall of the production string.
2. The plunger of claim 1, wherein the production string is a
tubing string.
3. The plunger of claim 1, wherein the at least one sealing ring
has a width to thickness ratio within a range from about 0.02 to
about 0.2.
4. The plunger of claim 1, wherein an outer diameter of the at
least one sealing ring is between about 3% to about 6% larger than
an inner diameter of the production string within which it is
adapted to travel.
5. The plunger of claim 1, wherein an outer diameter of the at
least one sealing ring is about 5% larger than an inner diameter of
the production string within which the body is adapted to
travel.
6. The plunger of claim 1, wherein the at least one sealing ring
comprises: an inner portion proximate the inner surface formed of a
substantially rigid material; and an outer portion extending from
the inner portion to the outer surface formed of a material
substantially flexible relative to the inner portion.
7. The plunger of claim 1, wherein the body forms a recess and
wherein the at least one sealing ring is connected to the body in
the recess.
8. The plunger of claim 1, wherein the at least one sealing ring
comprises: at least one sealing ring connected about the body
proximate a top end of the body; and at least one sealing ring
connected about the body proximate a bottom end of the body.
9. The plunger of claim 1, wherein when the body is disposed within
the production string the at least one sealing ring assumes a shape
such that the sealing ring enhances movement of the body over the
drag from the sealing contact.
10. The plunger of claim 1, wherein the at least one sealing ring
has an outside diameter greater than an inner diameter of the
production tubing such that when the body is disposed within the
production string an interference fit causes the sealing ring to
roll-form into a constricted shape and diameter that exerts the
sealing contact with the inner wall of the production string.
11. A plunger for an artificial lift system, the plunger
comprising: a solid body adapted to travel within a production
string positioned in a wellbore; at least one sealing ring having
an inner surface, an outer surface, a width and a thickness, the
sealing ring connected about the body, wherein the width is
sufficient such that when the body is disposed in the production
string the outer surface contacts and substantially forms a seal
between the body and an inner wall of the production string; and
the at least one sealing ring having a width to thickness ratio
within a range from about 0.02 to 0.2 wherein when the body is
disposed within the production string the sealing ring assumes a
shape such that the sealing ring enhances movement of the body over
the drag from the sealing contact.
12. The plunger of claim 11, wherein the outer diameter of the at
least one sealing ring is between about 3% to about 6% larger than
the inner diameter of the production string within which it is
adapted to travel.
13. The plunger of claim 11, wherein the at least one sealing ring
comprises: at least one sealing ring connected about the body
proximate a top end of the body; and at least one sealing ring
connected about the body proximate a bottom end of the body.
14. The plunger of claim 11, wherein the at least one sealing ring
comprises: an inner portion proximate the inner surface formed of a
substantially rigid material; and an outer portion extending from
the inner portion to the outer surface formed of a material
substantially flexible relative to the inner portion.
15. The plunger of claim 11, wherein the at least one sealing ring
comprises: an inner portion proximate the inner surface formed of a
substantially rigid material; an outer portion extending from the
inner portion to the outer surface formed of a material
substantially flexible relative to the inner portion; at least one
of the at least one sealing rings being connected about the body
within a recess formed proximate a top end of the body; at least
one of the at least one sealing rings being connected about the
body within a recess formed proximate a bottom end of the body: and
the sealing rings having an outside diameter greater than an inner
diameter of the production tubing within which the body is adapted
to travel such that when the body is disposed within the production
string an interference fit causes the sealing rings to roll-form
into a constricted shape and diameter that exerts the sealing
contact with the production string.
16. A plunger for an artificial lift system, the plunger
comprising: a solid body adapted to travel within a production
string positioned in a wellbore; at least one sealing ring having
an inner surface, an outer surface, a width and a thickness, the
sealing ring connected about the body, wherein the width is
sufficient such that when the body is disposed in the production
string the outer surface contacts and substantially forms a seal
between the body and an inner wall of the production string; and
the at least one sealing ring having an outer diameter that is
between about 3% to about 6% larger than an inner diameter of the
production string within which it is adapted to travel.
17. The plunger of claim 16, wherein the at least one sealing ring
has a width to thickness ratio within a range from about 0.02 to
about 0.2.
18. The plunger of claim 16, wherein the at least one sealing ring
comprises: an inner portion proximate the inner surface formed of a
substantially rigid material; and an outer portion extending from
the inner portion to the outer surface formed of a material
substantially flexible relative to the inner portion.
19. The plunger of claim 16, wherein the at least one sealing ring
comprises: at least one of the at least one sealing rings being
connected about the body within a recess formed proximate a top end
of the body; and at least one of the at least one sealing rings
being connected about the body within a recess formed proximate a
bottom end of the body.
20. The plunger of claim 16, wherein the at least one sealing ring
comprises: an inner portion proximate the inner surface formed of a
substantially rigid material; an outer portion extending from the
inner portion to the outer surface formed of a material
substantially flexible relative to the inner portion; at least one
of the at least one sealing rings being connected about the body
within a recess formed proximate a top end of the body; at least
one of the at least one sealing rings being connected about the
body within a recess formed proximate a bottom end of the body: and
the sealing rings having an outside diameter greater than an inner
diameter of the production tubing within which the body is adapted
to travel such that wherein when the body is disposed within the
production string the interference fit causes the sealing rings to
roll-form into a constricted shape and diameter that exerts the
sealing contact with the production string.
Description
FIELD OF THE INVENTION
[0001] The present invention relates in general to producing fluids
from a well and more specifically to an interference-seal plunger
for a plunger lift system.
BACKGROUND
[0002] In the life of most wells the reservoir pressure decreases
over time resulting in the failure of the well to produce fluids
utilizing the formation pressure solely. As the formation pressure
decreases, the well tends to fill up with liquids, such as oil and
water, which inhibits the flow of gas into the wellbore and may
prevent the production of liquids. It is common to remove this
accumulation of liquid by artificial lift systems such as plunger
lift, gas lift, pump lifting and surfactant lift wherein the liquid
column is blown out of the well utilizing the reaction between
surfactants and the liquid.
[0003] One method of producing fluids from a declining well having
gas production is by utilizing a plunger lift system. A well is
shut-in allowing a plunger to fall through the fluid column to the
bottom of the well. When gas pressure from the formation is
sufficient, the well may be opened allowing the gas to lift the
plunger and the fluid above the plunger to the surface for
production. The plunger acts as an interface between the gas and
liquid in the well. However, when gas pressure is overcome by the
hydrostatic head in the well, well production will cease.
[0004] Prior art plunger systems include spiral, brush, pad and cup
plungers. The plungers may also be bypass plungers or solid or
non-bypass plungers. Bypass plungers include a pathway formed
through the plunger to facilitate the plunger's descent in the
wellbore. A detachable plug is captured and seals the pathway for
ascent in the wellbore. The plug is then dislodged at the top of
the well allowing the plunger to again descend. Bypass plungers
allow for a more efficient seal to be formed between the plunger
and the production string. Bypass plungers allow fluid to bypass
the plunger in its descent, thus, allowing liquid to accumulate on
top of the plunger prior to its ascent.
[0005] Prior art solid or non-bypass plungers on the other hand
typically sacrifice sealing efficiency between the production
string and the plunger to facilitate operation. Prior art cup
plungers, casing plungers, are utilized that include a stiff
sealing element between the plunger and the casing to increase
sealing efficiency. These casing plungers require sufficient weight
to overcome the friction between the plunger and the production
string and thus are limited to use in casing. Casing plungers also
tend to get stuck requiring fishing operations.
[0006] It is thus a desire to provide a plunger that addresses the
drawbacks of the prior art plungers. It is a still further desire
to provide a plunger that provides efficient sealing between the
plunger and the production string. It is a still further desire to
provide an interference-seal between a plunger and the production
string.
SUMMARY OF THE INVENTION
[0007] Accordingly, an embodiment of a plunger for an artificial
lift system includes a solid body adapted to travel within a
production string positioned in a wellbore and at least one sealing
ring having an inner surface, an outer surface, a width and a
thickness, the sealing ring connected about the body. When the body
is positioned within the production string, the outer surface
contacts and substantially forms a seal between the body and the
production string.
[0008] The at least one sealing ring may include an inner portion
proximate the inner surface formed of a substantially rigid
material and an outer portion extending from the inner portion to
the outer surface formed of a material substantially flexible
relative to the inner portion. The at least one sealing ring may be
connected about the body within a recess formed proximate a top end
of the body. The at least one sealing ring may be connected about
the body within a recess formed proximate a bottom end of the body.
The plunger may include a plurality of plunger sealing rings.
[0009] The sealing rings may have an outside diameter greater than
the inner diameter of the production tubing within which the body
is adapted to travel such that when the body is disposed within the
production string, an interference fit causes the sealing rings to
roll-form into a constricted shape and diameter that exerts the
sealing contact with the production string.
[0010] In another embodiment the plunger may include a solid body
adapted to travel within a production string positioned in a
wellbore. At least one sealing ring is connected about the body.
The at least one sealing ring having an inner surface, an outer
surface, a width and a thickness. The width is sufficient such that
when the body is disposed in the production string, the outer
surface contacts and substantially forms a seal between the body
and an inner wall of the production string. The at least one
sealing ring has a width to thickness ratio within a range from
about 0.02 to 0.2 wherein when the body is disposed within the
production string, the sealing ring assumes a shape such that the
sealing ring enhances movement of the body over the drag from the
sealing contact.
[0011] In another embodiment the plunger may include a solid body
adapted to travel within a production string positioned in a
wellbore. At least one sealing ring connected about the body. The
at least one sealing ring having an inner surface, an outer
surface, a width and a thickness. The width is sufficient such that
when the body is disposed in the production string, the outer
surface contacts and substantially forms a seal between the body
and an inner wall of the production string. The at least one
sealing ring having an outer diameter that is between about 3% to
about 6% larger than an inner diameter of the production string
within which it is adapted to travel.
[0012] The foregoing has outlined the features and technical
advantages of the present invention in order that the detailed
description of the invention that follows may be better understood.
Additional features and advantages of the invention will be
described hereinafter which form the subject of the claims of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The foregoing and other features and aspects of the present
invention will be best understood with reference to the following
detailed description of a specific embodiment of the invention,
when read in conjunction with the accompanying drawings,
wherein:
[0014] FIG. 1 is a schematic drawing of an embodiment of a plunger
lift system utilizing an interference-seal plunger of the present
invention;
[0015] FIG. 2 is a side view of an embodiment of an
interference-seal plunger of the present invention;
[0016] FIG. 3 is a partial cross-sectional view of an
interference-seal plunger ascending in the production string;
and
[0017] FIG. 4 is a partial cross-sectional view of an
interference-seal plunger descending in the production string.
DETAILED DESCRIPTION
[0018] Refer now to the drawings wherein depicted elements are not
necessarily shown to scale and wherein like or similar elements are
designated by the same reference numeral through the several
views.
[0019] As used herein, the terms "up" and "down"; "upper" and
"lower"; and other like terms indicating relative positions to a
given point or element are utilized to more clearly describe some
elements of the embodiments of the invention. Commonly, these terms
relate to a reference point as the surface from which drilling
operations are initiated as being the top point and the total depth
of the well being the lowest point.
[0020] FIG. 1 is a schematic drawing of an embodiment of a plunger
lift system 5 utilizing an interference-seal plunger of the present
invention, generally denoted by the numeral 10. The well includes a
wellbore 12 extending from the surface 14 of the earth to a
producing formation 16. Wellbore 12 may be lined with a casing 18
including perforations 20 proximate producing formation 16. The
surface end of casing 18 is closed at surface 14 by a wellhead
generally denoted by the numeral 24. A casing pressure transducer
26 is mounted at wellhead 24 for monitoring the pressure within
casing 18.
[0021] A tubing string 22 (production string) supported by wellhead
24 is disposed within casing 18 and in fluid connection with a
production "T" 28. Production "T" 28 includes a lubricator 30, also
referred to as a catcher, a flow line 32 and a flow-control valve
34 connected to a controller 36. Production "T" 28 typically
further includes a tubing pressure transducer 38 for monitoring the
pressure in tubing 22. Positioned proximate the bottom of the well
and in connection with production string 22 is a standing valve 44
and spring 46.
[0022] Wellbore 12 is filled with fluid from formation 16. The
fluid includes liquid 40 and gas 42. As is well known in the art of
lift systems, the fluid in the well includes liquid 40, gas 42,
condensate and mixed phases. Plunger 10 is illustrated in the
middle of a stroke and best described as descending in production
string 22.
[0023] Interference-seal plunger 10 includes a plurality of sealing
elements 48. Sealing elements 48 substantially form a seal between
production string 22 and body 50 of plunger 10. A further
description of plunger 10 is provided with reference to FIGS.
2-4.
[0024] FIG. 2 is a side view of an embodiment of an
interference-seal plunger 10. Plunger 10 includes body 50 having a
top end 52 having a fishing neck connection, middle section 58, a
bottom end or shoe 60 and at least one sealing member 48. In the
embodiment illustrated, body 50 is solid and does not include a
bypass. It should further be understood that plunger 10 may include
elements not illustrated such as, but not limited to, pads or
brushes.
[0025] In the illustrated embodiment, plunger 10 includes two sets
of sealing members 62a, 62b. Each set includes at least one sealing
member 48 and may include a plurality of sealing members 48. First
set 62a of sealing members 48 is positioned proximate the top end
52 and separated from second set 62b of sealing members 48 that are
positioned proximate bottom end 60 by middle section 58.
[0026] Inner surface 64 is connected about outer surface 68 of body
50 such that it circumscribes body 50 and extends beyond the
outside diameter of body 50. The outside diameter is defined as the
largest diameter portion of plunger 50. Sealing members 48 may be
connected about body 50 in a cavity 61 or along a reduced diameter
section of body 50. It should be understood that sealing member 48
may be removably connected to body 50 to permit replacement or
formed as part of a one-piece molded plunger 10.
[0027] Sealing members 48 are ring shaped members having an inner
surface 64 and an outer surface 66. Sealing ring 48 is constructed
substantially of a readily pliable elastomeric material. It should
be understood that portions of sealing ring 48 may be formed of
different materials or material having different physical
characteristics. For example, the inner portion 47 (FIGS. 3 and 4)
of sealing ring 48, proximate inner surface 64, may be formed of a
substantially rigid material such as plastic or a metal to
facilitate connection to the outer surface 68 of body 50 and to
provide form and shape. The outer portion 49 (FIGS. 3 and 4) of
sealing ring 48 may be formed of a more pliable and/or flexible
material than inner portion 47. Description of features and
characteristics of outer portion 49 are described at times herein
with reference generally to sealing ring 48.
[0028] Sealing ring 48 (outer portion 49) is flexible in that its
shape can be distorted then returned to it natural shape without
substantial damage. Outer surface 66 is adapted for sealing contact
with the internal wall 70 of production string 22 (shown in FIGS. 3
and 4). Sealing ring 48, portion 49, has the ability to readily
abandon its natural shape and bend in the presence of a limited
applied force. Ring 48 is desirably thin for flexibility and to
counteract the effects of gas entrainment. In an embodiment of the
invention sealing ring 48 has a width 72 to thickness 74 ratio
within a range of from about 0.02 to about 0.20.
[0029] Reference is now made to FIGS. 3 and 4, wherein FIG. 3 is a
partial cross-sectional view of plunger 10 ascending in production
string 22 and FIG. 4 is a partial cross-sectional view of plunger
10 descending in production string 22. In use, sealing rings 48
form a barrier membrane separating the fluid above plunger 10 from
the fluid below plunger 10. The outer ring diameter (outer surface
66) of sealing ring 48 is from about 3% to about 6%, desirably 5%,
larger than the inner diameter (inner wall 70) of production string
22. This dimension produces an interference fit between sealing
ring 48 and inner production string wall 70. The interference fit
causes the outer portion 49 of sealing ring 48 to roll-form into a
constricted shape and diameter that exerts a sealing contact 76
with the inner production tubing wall 70.
[0030] A desired shape of sealing ring 48 is planer in construction
with a width to thickness ratio that allows sealing ring 48 to form
in use to an optimized shape. The shape assumed by sealing ring 48
balances the pressure differential across plunger 10 with the drag
created by the seal contact area 76. The shape assumed by sealing
ring 48 balances the pressure differential by allowing and urging
plunger 10 to move in the direction that reduces the pressure
differential. The size and interference fit of the seal produces a
shape of sealing ring 48 that enhances lift over drag. Wherein
"lift" describes movement either ascending or descending in
production string 22.
[0031] FIG. 3 illustrates the shape of sealing ring 48 (outer
portion 49) during the upward travel of plunger 10. The domed
shaped is caused by a pressure differential typically of
approximately three psi. FIG. 4 illustrates the shape of plunger 10
as it descends in production string. The oversizing of sealing ring
48 causes sealing ring 48 to partially curl. The pressure is
substantially equalized above and below sealing ring 48 and the
friction (drag) at seal contact 76 causes sealing ring 48 to
curl.
[0032] The number of sealing rings 48 is a variable dependent on
the well applications. Some wells have varying diameter sections.
Thus, varying sealing ring 48 dimensions may be utilized. The width
to thickness ratio of sealing ring 48 needs to be sufficient to
withstand the pressure differential and maintain sealing contact 76
and thin enough to permit sealing ring 48 to change shape and roll
into a new shape during reciprocation of travel of plunger 10.
[0033] From the foregoing detailed description of specific
embodiments of the invention, it should be apparent that an
interference-seal plunger for an artificial lift system that is
novel and unobvious has been disclosed. Although specific
embodiments of the invention have been disclosed herein in some
detail, this has been done solely for the purposes of describing
various features and aspects of the invention and is not intended
to be limiting with respect to the scope of the invention. It is
contemplated that various substitutions, alterations, and/or
modifications, including but not limited to those implementation
variations which may have been suggested herein, may be made to the
disclosed embodiments without departing from the spirit and scope
of the invention as defined by the appended claims which
follow.
* * * * *