Note: Descriptions are shown in the official language in which they were submitted.
CA 02568434 2006-11-20
Plunger Lift Apparatus
FIELD OF THE INVENTION
[001] 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
[002] 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.
[003] There have been many different plunger apparatuses developed for use in
plunger lift.
Examples of such devices are described in US patents 4,986,727; 4,531,891;
4,984,970;
and 4,502,843. 6,148,923.
10041 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
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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 US Patents 6,148,923 and 6,719,060, which both
are
incorporated herein by reference in entirety.
[005] 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.
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[006] 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
[007] 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.
[008] 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.
[009] 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.
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[0010] 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.
[0011] 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.
[0012] 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
[0013] 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:
[0014] Figure 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;
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[0015] Figure 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;
[0016] Figure 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;
[0017] Figure 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;
[0018] Figure 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;
[0019] Figure 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.
[0020] The same reference numerals refer to the same parts throughout the
various figures.
DETAILED DESCRIPTION OF THE INVENTION
[00211 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.
100221 With reference now to Figure 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
CA 02568434 2006-11-20
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.
[0023] 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.
100241 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.
[0025) With reference to Figure 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.
Figure 2, shows the detachable valve member 32 having a spherical body 40 of
dimensions to be received by the spherical surface 36. Figure 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 Figures 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.
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[0026] 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 Figure 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.
[0027] In Figures 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.
[0028] With reference now to Figures 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
Figure 6. In Figure 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
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Figure 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.
[0029] 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.
[0030] Turning to Figure 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.
[0031] 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
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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.
[0032] 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.
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