Note: Descriptions are shown in the official language in which they were submitted.
CA 02659528 2009-03-20
This application claims priority on U.S. patent application No. 12/403,576
filed
March 13, 2009, incorporated herein by reference.
TITLE OF THE INVENTION
Plug For A Perforated Liner And Method Of Using Same
FIELD OF THE INVENTION
[0001] This invention relates generally to an apparatus and its use in
plugging
perforated liners such as those that may be used in wellbores and other
installations.
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BACKGROUND OF THE INVENTION
[0002] In conventional drilling operations it is often common to line the
interior walls of a well with a liner (which is often a steel or other alloy
pipe or
tubular) in order to stabilize the wellbore and prevent collapse, particularly
in loose
or fractured formations. The space or annulus between the face of the
formation
and the liner may be packed with sand, gravel or other material. In other
instances
the liner is cemented in place through pumping cement or a cementatous-type
material into the annulus. Upon setting, the cement serves to stabilize the
position
of the liner within the wellbore, helps to prevent a collapse, sloughing and
cracking
of the exposed formation face and can further help to prevent the escape of
fluids
from the formation. Where the wellbore passes through a formation that is
saturated with water, cementing the liner in place can help to prevent the
release
of water from the formation into the well. In other instances cementing of the
liner
will help prevent the release of gas where the well passes through formations
that
harbour pressurized gas. Where there are multiple zones that are targeted for
the
production of fluid, in some instances it may be desirable to seal off
particular
zones through cementing the liner in place to permit the controlled and
systematic
release of fluid from particular zones in a particular sequence.
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[0003] Typically where a liner has been cemented within a production zone
once the cement has hardened and cured the well is re-entered in order to
perforate the liner and to allow for the extraction of production fluid. A
variety of
mechanisms and techniques have been developed in order to perforate a liner,
most of which involve the lowering of a perforating gun into the tubular and
using
the gun to perforate the liner or well casing. Such guns typically utilize
shaped
charges that produce holes within the side of the liner having a relatively
consistent
size and shape. Others have proposed various other mechanical devices to punch
or drill holes in liners once they are in place. Still others have devised
liners
themselves that are pre-fitted with small explosive charges that can be
detonated
after the liner has been connected in place in order to perforate a particular
zone or
section of the liner.
[0004] In other applications liners are pre-drilled at the surface with solid
aluminium or similar plugs inserted into the holes, following which the liner
is
lowered and placed into position within the well. Once in the well the liner
can be
cemented in place, with the plugs retaining the cement slurry within the
annulus
formed between the formation face and the exterior surface of the liner. After
the
cement has set the plugs can then be removed, effectively creating a
perforated
liner. Removal of the plugs can be achieved mechanically, ultrasonically, or
through packing off the section of the liner in question and introducing an
acid to
dissolve the material from which the plugs are made.
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[0005] While the above described methods and devices have met with varying
degrees of success, they all suffer from their own inherent limitations and
difficulties. The formation of holes or perforations within a liner through
the use of
an explosive raises obvious concerns in the case of an oil or gas well where
flammable or explosive materials may be present. Many of the currently
employed
methods require the lowering of relatively complex and expensive equipment
into
the well in order to mechanically, explosively or otherwise perforate the
liner.
Further, where the liner is cemented in place the mechanism used to perforate
the
liner or remove a plug that was previously inserted into a perforation is
often
incapable of removing or otherwise displacing the cement that has set up and
hardened between the liner and the face of the formation. In such cases
extracting
fluid from the formation through the perforated liner can be difficult or
inefficient.
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SUMMARY OF THE INVENTION
[0006] The invention therefore provides a plug for a perforated liner and a
method of using such a plug that addresses a number of the deficiencies in the
structures and methods that are currently in use.
[0007] Accordingly, in one of its aspects the invention provides a plug for
insertion into a perforation in a liner or tubular, the plug comprising a base
portion
and one or more extendible portions, said base portion securable to and
receivable
within said perforation said base portion and said one or more extendible
portions
sealing the perforation in said liner, said one or more extendible portions
having a
retracted position and an extended position such that when in said extended
position said one or more extendible portions extend outwardly from said base
portion and outwardly from the exterior surface of said liner.
[0008] In a further aspect the invention provides a plug for insertion into a
perforation in a liner or tubular, the plug comprising a base portion
securable to
and received within a perforation in said liner, the plug further comprising
one or
more extendible portions having a retracted position and an extended position,
when in said extended position said one or more extendible portions extending
outwardly from said base portion and outwardly from the exterior surface of
said
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liner, said base portion and said one or more extendible portions together
sealing
the perforation in said liner.
[0009] The invention also concerns a method of using and deploying a plug
for insertion into a perforation in a liner or tubular to be inserted into a
bore hole,
the plug comprising a base portion and one or more extendible portions, said
base
portion securable to and receivable within the perforation, said one or more
extendible portions having a retracted position and an extended position, said
one
or more extendible portions extending outwardly from said base portion and
outwardly from the exterior surface of said liner when in said extended
positions,
the method comprising:
(i) inserting said plug into a perforation in the liner or tubular and
securing said plug thereto;
(ii) positioning the liner or tubular at a desired location within a
wellbore; and,
(iii) pressurizing the interior of the liner or tubular to move said one
or more extendible portions from said retracted to said extended
positions such that they extend outwardly from the exterior
surface of said liner.
[0010] Further aspects and advantages of the invention will become apparent
from the following description taken together with the accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0011] For a better understanding of the present invention, and to show more
clearly how it may be carried into effect, reference will now be made, by way
of
example, to the accompanying drawings which show the preferred embodiments of
the present invention which:
[0012] Figure 1 is a vertical sectional view through a wellbore that has been
lined with a perforated liner wherein the perforations are enclosed with plugs
in
accordance with one of the preferred embodiments of the present invention;
[0013] Figure 2 is an enlarged sectional view of a lined borehole wherein the
liner has plugs in accordance with one of the preferred embodiments of the
invention inserted within perforations;
[0014] Figure 3 is a Figure similar to Figure 2 wherein the borehole is cased;
[0015] Figure 4 is an enlarged sectional view of a borehole having a
perforated liner with plugs in accordance with one of the preferred
embodiments of
the invention inserted within the perforations and wherein the plugs are
generally
flush with the exterior surface of the liner;
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[0016] Figure 5 is a view similar to Figure 4 wherein the plugs are in an
extended position;
[0017] Figure 6 is an enlarged sectional view of the plugs shown in Figure 4;
[0018] Figure 7 is a view of the plug shown in Figure 6 in a partially
deployed
position;
[0019] Figure 8 a view of the plug shown in Figure 6 in a fully deployed
position; and,
[0020] Figure 9 is a view similar to Figure 8 wherein the plug is in a
deployed
position.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] The present invention may be embodied in a number of different
forms. However, the specification and drawings that follow describe and
disclose
only some of the specific forms of the invention and are not intended to limit
the
scope of the invention as defined in the claims that follow herein.
[0022] With reference to Figure 1 there is shown a vertical section through a
typical borehole 1 extending from a surface rig 2 into an underground
formation 3.
It will be appreciated by those skilled in the art that the configuration and
nature of
the borehole can vary substantially from application to application. For
example, as
shown in Figure 1 the borehole may have a horizontal section. In addition, the
borehole may be cased or uncased, however, the particular configuration and
structure of the borehole does not affect the invention. In Figure 1 the
borehole is
lined with a liner 4 having perforations. The perforations have plugs 6,
constructed
in accordance with the present invention, inserted therein.
[0023] As shown more specifically in Figures 2 through 6, plug 6 is comprised
generally of a base portion 7 and one or more extendible portions S. The base
portion is securable to and receivable within the perforations in liner 4. The
base
portion, together with the one or more extendible portions, seal the
perforation. As
is also shown, the extendible portions have a retracted position and an
extended
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position such that when they are in their retracted position the outer surface
of the
plug is generally flush with the exterior surface of the liner. When the
extendible
portions are in their extended position they extend outwardly from the base
portion
and outwardly from the exterior surface of the liner.
[0024] In the embodiment of the invention shown in the attached drawings,
base portion 7 and extendible portions 8 are formed from circular, cylindrical
members that are nested and concentric such that the extendible portions are
telescopically received within the base portion. It will be appreciated that
the
precise geometric configuration and shape of both the base portion and the
extendible portions could vary while remaining within the broad scope of the
invention. For example, rather than comprising circular, cylindrical members,
the
cross-section of the extendible portions could be rectangular, hexagonal,
octagonal
or any one of a wide variety of other geometric shapes. In addition, base
portion 7
could also take on a variety of different geometric shapes.
[0025] Plug 6 further include seals 9 positioned between adjacent cylindrical
members such that when the base portion is received within a perforation the
base,
in combination with the extendible portions and seals 9, serves to seal the
perforation. In the embodiment of the invention shown in the attached drawings
seals 9 are O-rings, however, it will also be appreciated by those skilled in
the art
that various other seals could equally be utilized. In the embodiment depicted
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based portion 7 includes threads 10 to permit it to be threaded into the
perforation
within liner 4.
[0026] Figures 6 through 9 show one of the preferred structures that may
form base portion 7 and extendible portions 8. In this embodiment the
extendible
portions have an outwardly oriented flange 11 on their inner ends 12 and an
inwardly oriented shoulder 13 on their outer ends 14. In this manner the
nesting of
a plurality of extendible portions permits an outwardly telescopic movement of
the
nesting portions while preventing their separation (see Figures 7, 8 and 9).
An
inwardly extending shoulder 15 about the outer edge 16 of base portion 7
retains
the nested and telescopic extendible portions within the confines of the plug.
As
mentioned previously, the placement of O-ring seals 9 between adjacent
cylindrical
members presents a fluid tight seal between the various parts of plug 6.
Preferably
the central extendible portion 17 is in the form of a cylindrical member
having an
annular flange 18 on its inner end 19. The outer end 20 of the central
extendible
portion 17 will be enclosed and generally flat to permit it to engage the
interior
surface of borehole 1 or the interior surface of the liner if the borehole is
lined.
[0027] Through construction of plug 6 in accordance with the preferred
embodiment shown in the attached drawings and as described above, deployment
of the plug such that the extendible portions are moved from their retracted
to
extend positions can be accomplished by pressurizing the interior of liner 4.
The
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sealing of base portion 7 within the perforation and the use of seals at 9
between
adjacent cylindrical members allows the plug to retain pressurized fluid
within the
liner, forcing the telescopically nested extendible portions to be driven
outwardly
until either the annular flange 19 on the central extendible portion 17 is
driven up
against the outer shoulder 13 on the next adjacent extendible portion (see
Figure
8), or until the outer end 20 of the central extendible portion 17 comes into
contact
with either the borehole wall (see Figure 9) or the interior surface of the
casing if
the borehole is cased. Typically, deployment of the extendible portions will
be
accomplished through packing off a section of the liner and injecting
pressurized air
or gas into that section. Alternately, the extendible portions may be deployed
through pressurizing the liner with a wide variety of other fluids.
[0028] In use, a plurality of plugs 6 are inserted into perforations in a
section
of liner. As mentioned, in one of the preferred embodiments the plugs are
threaded into the perforations, however, in alternate embodiments the plugs
could
also be secured in place through the use of glues or adhesives, through
welding, or
through press fitting or any other commonly used means. Initially, the
extendible
portions 8 will be in their retracted position and held roughly in those
positions
through the interaction of the O-ring seals with adjacent cylindrical
portions. The
perforated portion of the liner can then be inserted into a well or borehole
and
positioned at its desired location. Thereafter, the interior of the liner is
pressurized
causing the extendible portions 8 to move from their retracted to their
extended
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positions, at which point the outer ends 20 of central extendible portions 17
will be
in contact with (or in close proximity to) the borehole wall. At that point
cementing
operations can commence where the annulus between the liner and the wellbore
is
filled or injected with cement or a cementatous-type material. Once the cement
or
cementatous-type material has hardened or cured, at least the extendible
portions
of the plugs are destroyed, leaving the liner cemented in place, while at the
same
time providing access to the face of the bore hole through the perforations in
the
liner.
[0029] Destruction of the extendible portions can be accomplished through a
variety of different mechanisms. In one embodiment the extendible portions are
constructed from material that dissolves when exposed to acid and the
destruction
of the extendible portions involves exposing the plugs to an acidic solution
for a
sufficient length of time to dissolve at least the extendible portions of the
plugs.
This process would typically be accomplished through packing off the liner and
delivering the acidic solution by running coiled tubing into the well. To that
end,
the extendible portions (and for that matter the base portion as well if
desired) can
be formed from an aluminium alloy which can be dissolved through subjecting to
an
acid. Alternately the extendible portions could be constructed from a variety
of
plastics or other materials. In alternate embodiments the extendible portions
can
be constructed from materials that can be destroyed or pulverized and the
destruction of the extendible portions could be accomplished through
subjecting
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them to the blast from the detonation of a charge, through drilling, through
mechanical impact, or through sonic or ultra-sonic vibration.
[0030] It will be appreciated by those of reasonable skill in the art and
having
a thorough understanding of the invention as described and shown herein that
the
use of plugs 6 within the perforations of a liner will allow for the
centralization of
the liner within the borehole and also effectively present a tunnel leading
from the
interior of the liner to the face of the formation once the liner has been
cemented in
place, and at least the extendible portions of the plug disengrated or
dissolved.
The use of such plugs removes the need for subsequently entering the well with
perforating guns or other mechanical devices that have previously been used to
perforate a liner in situ. In addition, whereas existing plugs can be used to
fill
perforations and later dissolved, the plugs of the present invention present
the
ability to maintain a tunnel or effectively a direct conduit that terminates
at the face
of the borehole, whereas standard plugs, once dissolved, still require the
dissolution
or destruction of the cement between the plug and the face of the borehole.
It is to be understood that what has been described are the preferred
embodiments
of the invention and that it may be possible to make variations to these
embodiments while staying within the broad scope of the invention. Some of
these
variations have been discussed while others will be readily apparent to those
skilled
in the art.
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