Note: Descriptions are shown in the official language in which they were submitted.
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SEALING INSERT AND METHOD
FIELD OF THE INVENTION
The present invention relates to a method for sealing a side pocket in a
downhole mandrel, such as a downhole gas-lift mandrel. The present invention
also
relates to a sealing insert for use in sealing a side pocket in a downhole
mandrel.
BACKGROUND TO THE INVENTION
In the oil and gas industry wellbores are drilled from surface to intercept
subterranean reservoirs, and used to provide a communication path for
reservoir fluids,
such as oil and gas, to flow to surface. The natural reservoir pressure may
allow
unaided production of the reservoir fluids to surface. However, in some cases
the
reservoir pressure may be insufficient to support natural production of
reservoir fluids,
for example where the pressure is naturally low, or where pressure has
diminished
over a period of time. To address such cases it is has become known for
operators to
utilise artificial lift techniques.
There are many known artificial lift techniques in common use, such as gas
lift.
Gas lift involves introducing a gas at one or more points along the wellbore
production
tubing to reduce the density of the well fluids and thus allow the reservoir
pressure to
lift the fluids out of the production tubing. Gas lift may be used in either
liquid (e.g., oil)
or gas wells.
To facilitate gas lift an operator will include a gas lift mandrel within the
production tubing string, which thus forms a permanent component of the
completion.
The gas lift mandrel includes a side port which provides fluid communication
between
the production tubing and the surrounding annulus. The gas lift mandrel
typically also
includes a side pocket which receives a gas lift valve, wherein the gas lift
valve is
sealingly engaged within the side pocket, for example via chevron seals, and
provides
selective control of fluid through the side port. Normally, the gas lift valve
is provided in
the form of a one way valve, in that fluid communication is only permitted
into the
production tubing, with outflow from the production tubing into the
surrounding annulus
prevented.
In use, whenever gas lift is required an operator will inject pressurised gas
into
the wellbore annulus, and into the production tubing via the gas lift mandrel
and valve
arrangement.
US 2005/0061369 discloses a mandrel for a gas lift valve.
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There is a risk that the gas lift mandrel could become damaged or corroded,
for
example particularly in the region of the side port. In some cases such damage
or
corrosion could compromise the ability of the gas lift valve to prevent
outflow of fluids
from the production fluid and into the annulus, resulting in possible
uncontrolled
pressurisation of the annulus, leading to a well control failure. In such
cases it may be
necessary to temporarily kill the well, and undertake a complete workover
program to
pull the entire completion and replace the faulty gas lift mandrel. The costs
of such a
workover program can be prohibitive, such that in many cases an operator may
decide
to abandon the well altogether.
Many other downhole components may include a form of side pocket mandrel
(for example, WO 2013/138896 discloses a cementing stage tool with a side
pocket),
which may also suffer from similar problems with damage or corrosion leading
to a well
control issues. For example, a downhole chemical injection valve will
typically include
a side pocket for accommodating a chemical injection valve. Further, some
downhole
valves, such as a downhole tubing valve, include a side pocket for
accommodating a
control valve which is used to operate the downhole valve.
SUMMARY OF THE INVENTION
An aspect of the present invention relates to a method for sealing a side
pocket
of a downhole mandrel in a tubing string, comprising:
retrieving a cartridge component from the side pocket of the downhole mandrel;
deploying a sealing insert into the side pocket of the downhole mandrel,
wherein the sealing insert comprises a swellable sealing element on an outer
surface
thereof; and
swelling the swellable sealing element to provide a seal within the side
pocket.
The seal within the side pocket achieved by the sealing insert may function to
substantially prevent any fluid communication outwardly or inwardly of the
downhole
mandrel via said side pocket. Such an arrangement may be used to prevent
undesired
fluid transfer between the downhole mandrel and surrounding environment.
The sealing insert may be used to address any damage to one or both of the
mandrel side pocket and the cartridge component. Such damage may otherwise
prevent the side pocket and/or cartridge component from providing a necessary
fluid
control when said cartridge component is in place. For example, damage to one
or
both of the side pocket and cartridge component may define or create a leak
path
which may establish uncontrolled fluid communication to/from the downhole
mandrel.
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The method may comprise sealing a side pocket of a downhole mandrel which
has become damaged, for example by corrosion, by other wellbore operations or
the
like. In such an arrangement the sealing insert may function to seal any
regions of
damage, such as corroded regions, within the side pocket of the mandrel. This
may
therefore prevent such damaged regions providing or continuing to provide any
potential leak paths.
The ability to address any damage to the downhole mandrel in accordance with
the present invention may provide significant advantages in that any
requirement to
retrieve the entire downhole mandrel, and the associated tubing string, may be
prevented.
However, although the present invention has application in addressing
situations where the downhole mandrel has become damaged, the method may
nevertheless be used in other occasions, such as when an operator may wish to
disable an existing and normally functioning downhole mandrel.
The downhole mandrel may comprise a side port which communicates with the
side pocket. The cartridge component, during normal use and prior to being
retrieved,
may be configured to cooperate with the side pocket of the downhole mandrel to
control fluid communication through the side port. In the event of failure or
damage of
one or both of the cartridge component and side pocket of the mandrel, such
fluid
control may be compromised. In such an arrangement the sealing insert may
function
to seal said side port, and thus prevent any subsequent communication with the
side
pocket and the tubing string associated with the downhole mandrel.
The method may comprise sealing a side pocket which has become damaged
in the region proximate or adjacent to the side port.
The side port of the downhole mandrel may be arranged to communicate with
an annulus surrounding the downhole mandrel. Such an annulus may be defined
between the mandrel and a bore wall, such as a wall of a casing string, liner
string,
open hole or the like. In such an arrangement the sealing insert may function
to
substantially prevent any fluid communication between the annulus and the
downhole
mandrel.
The side port of the downhole mandrel may be arranged to communicate with a
fluid conduit, such as an injection conduit or line which may extend from the
downhole
mandrel to surface level. In such an arrangement the sealing insert may
function to
substantially prevent any fluid communication between the fluid conduit and
the
downhole mandrel.
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The sealing element may extend along a desired length of the side pocket to
established sealing therein. The sealing element may extend along a sufficient
length
to span the side port. The sealing element may extend along a sufficient
length to
span damaged or corroded areas within the side pocket.
The downhole mandrel may comprise any downhole mandrel comprising a side
pocket. In such an arrangement the cartridge may comprise any cartridge which
may
be utilised within the side pocket of any downhole mandrel
In one embodiment the downhole mandrel may comprise or define a gas lift
mandrel. In such an arrangement the cartridge component may comprise or define
a
gas lift valve.
In one embodiment the downhole mandrel may comprise or define a chemical
injection mandrel. In such an arrangement the cartridge component may comprise
or
define a chemical injection valve.
In one embodiment the downhole mandrel may comprise or define a downhole
valve mandrel, such as a tubing safety valve mandrel, downhole safety valve
mandrel
or the like. In such an arrangement the cartridge component may comprise or
define a
control cartridge for use in providing control to the associated downhole
valve. For
example, in such an arrangement the cartridge component may comprise or define
a
control valve.
The sealing insert may be of the same general geometrical form as the
cartridge component being retrieved. Such an arrangement may permit the
sealing
insert to be readily received within the side pocket of the downhole mandrel.
The downhole mandrel may be connected in-line with the tubing string. The
downhole mandrel may comprise connectors, such as threaded connectors, at
opposing ends to facilitate in-line connection with the tubing string.
The tubing string may define a production tubing string. The tubing string may
be arranged for the production of fluids from a subterranean reservoir. The
tubing
string may be arranged for the production of a gas from a subterranean
reservoir. The
tubing string may be arranged for the production of liquids, such as oil, from
a
subterranean reservoir.
The tubing string may define an injection tubing string. The tubing string may
be
arranged for the injection of fluids, such as a liquid (e.g., water) or gas
into a
subterranean reservoir.
The method may comprise retrieving the cartridge component through the
tubing string. The method may comprise retrieving the cartridge component to
surface.
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The method may comprise retrieving the cartridge component via a conveyance
arrangement. The conveyance arrangement may comprise an elongate line, such as
wireline, slickline or the like. The conveyance arrangement may comprise
coiled
tubing.
5 The
method may comprise establishing a connection between the conveyance
arrangement and the cartridge component.
The method may comprise releasing the cartridge component from the side
pocket, for example by disabling a latch mechanism, overcoming an interference
force
or the like.
The method may comprise deploying the sealing insert through the tubing
string. The method may comprise deploying the sealing insert from surface.
The method may comprise deploying the sealing insert via a conveyance
arrangement. The conveyance arrangement may be the same or similar to the
conveyance arrangement used to retrieve the cartridge component. The
conveyance
arrangement may comprise an elongate line, such as wireline, slickline or the
like. The
conveyance arrangement may comprise coiled tubing.
The method may comprise releasing a connection between the conveyance
arrangement and the sealing insert when said sealing insert is located within
the side
pocket of the mandrel.
The method may comprise securing the sealing insert within the side pocket of
the downhole mandrel. The method may comprise mechanically latching the
sealing
insert within the side pocket of the mandrel. The method may comprise securing
the
sealing insert within the side pocket of the mandrel via the swelling element
after
sealing has been established. For example, the sealing element may provide an
interference force within the side pocket of the mandrel.
The method may comprise preventing or restricting flow along the tubing string
prior to retrieving the cartridge component. For example, the method may
comprise
ceasing production or injection along the tubing string. This may be achieved
via well
control equipment, such as a production or injection tree, sub surface valve,
well kill
fluid or the like, or any suitable combination.
The method may comprise setting a barrier downhole of the mandrel.
The method may comprise setting a barrier within the tubing string downhole of
the mandrel. Such a barrier may be set by closing a valve within the tubing
string. The
barrier may be set by installing a plug within the tubing string. The plug may
be
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deployed on a conveyance arrangement, such as on wireline, slickline, coiled
tubing or
the like.
The method may comprise removing the barrier set within the tubing string, for
example after the sealing insert has established a seal within the side pocket
of the
mandrel. Such an arrangement may permit subsequent production and/or injection
operations to be achieved using the tubing string which now incorporates a
sealed
mandrel.
The method may comprise flowing or placing a fluid into the tubing string.
Such
a fluid may be placed above a barrier set within the tubing string. Such a
fluid may be
placed in the tubing string before or after the sealing insert is located
within the side
pocket of the mandrel.
A fluid placed within the tubing string may be utilised to establish a desired
hydrostatic pressure therein. Such hydrostatic pressure may be used to contain
well
pressure. Such an arrangement may have particular application where the tubing
string has previously been used to produce a gas from or inject gas into a
subterranean
formation.
A fluid placed within the tubing string may be utilised to provide a desired
swelling activator for the swellable sealing element.
The method may comprise setting a barrier within an annulus surrounding at
least a portion of the tubing. Such an annulus barrier may be set via one or
more
packers or the like. The method may comprise subsequently removing the barrier
from
the annulus, for example after the sealing insert has provided a seal within
the side
pocket of the mandrel.
The method may comprise flowing or placing a fluid into the annulus. Such a
fluid may be placed above a barrier set within the annulus.
A fluid placed within the annulus may be utilised to establish a desired
hydrostatic pressure therein. Such hydrostatic pressure may be used to provide
a
degree of pressure control within the annulus.
A fluid placed within the annulus may be utilised to provide a desired
swelling
activator for the swellable sealing element.
The sealing element may be generally annular in form.
The sealing element may be formed of or comprise a swellable material, such
as a swellable elastomer material. The sealing element may be configured to
swell
when exposed to a swelling activator. The sealing element may be configured to
swell
when exposed to water. The sealing element may be configured to swell when
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exposed to a hydrocarbon fluid, such as hydrocarbon gas, oil or the like. The
sealing
element may be configured to swell when exposed to different swelling
activators. For
example, the sealing insert may be composed of or comprise different swellable
materials.
The sealing element may be configured to provide a sufficient delayed
activation period upon exposure to a swelling activator. This may allow
sufficient time
for an operator to deploy the sealing insert in position within the side
pocket of a gas lift
mandrel without interference by premature swelling.
The sealing insert may comprise a base member upon which the sealing
element is mounted. The sealing element may be bonded to the base member.
Alternatively, the sealing element may be formed as or on a sleeve which may
be
mounted over the base member.
The base member may be elongate. The base member may be generally
cylindrical in form, for example the base member may be provided in the form
of a rod.
The base member may comprise a metal or metal alloy material. The base member
may be substantially solid.
The base member may comprise at least one annular recess, wherein the
sealing element is received within said annular recess. When the sealing
element is
received within the recess and in an unswollen state, the sealing element may
define
an outer diameter which is less than or equal to the outer diameter of the
base
member. Such an arrangement may assist with easier deployment of the sealing
insert.
In some embodiments a single annular recess is provided within the base
member. Such a single annular recess may accommodate one or more sealing
elements.
In alternative embodiments the base member may define multiple annular
recesses, axially separated from each other, wherein each annular recess
accommodates at least one sealing element.
The base member may comprise or define a connection region, to facilitate
connection with a conveyance arrangement.
The base member may comprise a generally conical nose portion. Such an
arrangement may assist with deployment and insertion of the sealing element
into the
side pocket of the mandrel.
The base member may comprise a unitary component.
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A further aspect of the present invention relates to a sealing insert for use
in
performing the method of any other aspect.
A further aspect of the present invention relates to a sealing insert for use
in
sealing a side pocket of a downhole mandrel, comprising:
a base member; and
a swellable sealing element mounted on the outer surface of the base member
and configured to swell when exposed to an activator,
wherein the sealing insert is geometrically configured to permit insertion
within a
side pocket of a downhole mandrel such that when the sealing element is
swollen said
sealing element provides a seal within said side pocket.
The sealing insert may comprise a connector portion to permit connection to a
conveyance arrangement. Such a conveyance arrangement may be used to deploy
the sealing arrangement downhole and into a side pocket of a mandrel. The
conveyance arrangement may comprise wireline, slickline, coiled tubing or the
like.
The base member may define a connector portion to permit connection to the
conveyance arrangement.
The sealing element may be generally annular in form.
The sealing element may be formed or comprise a swellable material, such as a
swellable elastomer material. The sealing element may be configured to swell
when
exposed to a swelling activator. The sealing element may be configured to
swell when
exposed to water. The sealing element may be configured to swell when exposed
to a
hydrocarbon fluid, such as hydrocarbon gas, oil or the like. The sealing
element may
be configured to swell when exposed to different swelling activators. For
example, the
sealing insert may be composed of or comprise different swellable materials.
The sealing element may be configured to provide a sufficient delayed
activation period upon exposure to a swelling activator. This may allow
sufficient time
for an operator to deploy the sealing insert in position within the side
pocket of a gas lift
mandrel without interference by premature swelling.
The sealing element may be bonded to the base member. Alternatively, the
sealing element may be formed as or on a sleeve which may be mounted over the
base member.
The base member may be elongate. The base member may be generally
cylindrical in form, for example the base member may be provided in the form
of a rod.
The base member may comprise a metal or metal alloy material. The base member
may be substantially solid.
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The base member may comprise at least one annular recess, wherein the
sealing element is received within said annular recess. When the sealing
element is
received within the recess and in an unswollen state, the sealing element may
define
an outer diameter which is less than or equal to the outer diameter of the
base
member. Such an arrangement may assist with easier deployment of the sealing
insert.
In some embodiments a single annular recess may be provided within the base
member. Such a single annular recess may accommodate one or more sealing
elements.
In alternative embodiments the base member may define multiple annular
recesses, axially separated from each other, wherein each annular recess
accommodates at least one sealing element.
The base member may comprise a generally conical nose portion. Such an
arrangement may assist with deployment and insertion of the sealing element
into the
side pocket of the mandrel.
The base member may comprise a unitary component.
Another aspect of the present invention relates to a sealing insert for
sealing a
side pocket of a downhole mandrel, the sealing insert comprising:
a core and a swellable material positioned on the periphery of the core; and
an upper sub connected to the core and having a conveyance connector for
allowing connection to a conveyance running tool.
A further aspect of the present invention relates to a sealed downhole
mandrel,
comprising:
a side pocket including a side port; and
a sealing insert sealingly mounted within the side pocket, wherein the sealing
insert includes a swollen sealing element which extends at least over the side
port of
the side pocket.
A further aspect of the present invention relates to a method for sealing a
side
pocket of a downhole mandrel in a tubing string, comprising:
deploying a sealing insert into the side pocket of the downhole mandrel,
wherein the sealing insert comprises a swellable sealing element on an outer
surface
thereof; and
swelling the swellable sealing element to provide a seal within the side
pocket.
Another aspect of the present invention relates to a method for performing a
downhole intervention, comprising:
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retrieving a cartridge from a side pocket of a downhole mandrel, wherein the
retrieved cartridge comprises at least one seal arrangement for providing a
seal
between the cartridge and the side pocket of the mandrel when located therein;
deploying a new cartridge which comprises at least one swellable seal
5 arrangement into the side pocket mandrel of the downhole mandrel; and
swelling the at least one swellable seal arrangement to establish a seal
between the new cartridge and the side pocket mandrel.
In such a method the new cartridge, once in place, may perform substantially
the same function as the retrieved cartridge prior to retrieval. However, the
presence
10 of at least one swellable seal element on the new cartridge may assist
to address any
loss of sealing integrity suffered by the retrieved cartridge when originally
in place.
The method may comprise replacing the at least one seal arrangement of the
retrieved cartridge with at least one swellable seal element, and then
deploying the
retrieved cartridge as the new cartridge. In such an arrangement, the
retrieved
cartridge may be reused.
The method may comprise deploying a new cartridge which is different from the
retrieved cartridge.
The retrieved cartridge may comprise at least one non-swelling seal
arrangement.
The retrieved cartridge may comprise at least one chevron seal arrangement.
A further aspect of the present invention relates to a downhole side pocket
cartridge for installing within a side pocket of a downhole mandrel,
comprising at least
one swellable sealing arrangement mounted on an outer surface thereof for
establishing sealing engagement within a side pocket of a downhole mandrel.
It should be understood that features described or presented in relation to
one
aspect may be used in combination with any other aspect.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other aspects of the present invention will now be described, by way
of non-limiting examples only, with reference to the accompanying drawings, in
which:
Figure 1 is a diagrammatic illustration of a portion of a wellbore which
includes
a conventional gas lift mandrel during normal operation;
Figure 2 is a diagrammatic illustration of the gas lift mandrel of Figure 1
following loss in sealing integrity;
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Figures 3, 4 and 6 to 8 illustrate sequential stages of a method according to
an
embodiment of the present invention for sealing the gas lift mandrel of Figure
1;
Figure 5 is a longitudinal cross sectional view of a sealing insert in
accordance
with an embodiment of the present invention for use in a method for sealing
the gas lift
mandrel of Figure 1; and
Figures 9 and 10 diagrammatically illustrate sequences in a method according
to an alternative embodiment of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
A wellbore system, generally indicated by reference 10, is shown in Figure 1,
wherein said wellbore system 10 is provided to support the production of a gas
from a
subterranean reservoir (not shown). The wellbore system 10 includes a drilled
bore 12
within which is located a casing string 14, wherein the casing string 14 may
be
cemented or packed-off within the drilled bore 12. In the embodiment
illustrated a
production tubing string 16 extends through the casing string 14 to intercept
a gas
production zone (not shown) of the subterranean reservoir, wherein the
production
tubing 16 defines an annulus 17 with the casing string 14. A gas lift mandrel
18 is
installed in-line with the production tubing 16, via threaded end connectors
20, 22.
The gas lift mandrel 18 includes a primary bore section 24 which is aligned
with
the fluid communication path along the production tubing 16, and a side pocket
26
laterally off-set from the primary bore section 24. The side pocket may define
an
internal diameter of, for example, around 20 to 40mm. For example in some
embodiments the side pocket mandrel may define an internal diameter of, for
example,
25.4 mm (1"). In other embodiments the side pocket mandrel may define an
internal
diameter of, for example, 38.1mm (1.5"). The primary bore section 24 and side
pocket
26 are in fluid communication with each other. A side port 28 is formed in the
side wall
of the mandrel 18 and provides fluid communication between the side pocket 26
and
the annulus 17.
A gas lift valve cartridge 30 is mounted within the mandrel side pocket 26,
and
includes upper and lower seals 32, 34, such as chevron seals, positioned on
either side
of the port 28. The seals 32, 34 provide sealing between the valve cartridge
20 and the
side walls of the side pocket 26. As will be described in further detail
below, the valve
cartridge 30 functions to control fluid communication between the production
tubing 16
and the annulus 17 via the port 28.
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During normal use, an operator will inject gas 38 at high pressure into the
annulus 17 from surface. When the annulus gas pressure at least exceeds the
gas
pressure within the production tubing 16, the gas lift valve cartridge 30 will
open and
permit inflow of the injected gas 38 into the gas lift mandrel 18. The
injected gas 38 will
intimately mix with the gas 40 being produced from the subterranean reservoir,
with the
resulting gas mixture 42 having a lower density than the produced gas 40,
allowing the
reservoir pressure to then drive the gas upwardly through the production
tubing string
16 to surface. An operator may continuously inject gas 38, or may provide
intermittent
injection. The gas lift valve 30 will function as a one way valve, such that
outflow of
gas from the gas lift mandrel 18 into the annulus 17 should normally be
prevented.
There are occasions, however, where the gas lift valve 30, side pocket 26
and/or side port 28 of the mandrel 18 may become damaged, for example by
corrosion,
such that fluid sealing and control may become lost. For example, as shown in
Figure
2 the seals 34, 36 between the valve cartridge 30 and the side pocket 26 may
become
compromised by corrosion in this region such that gas within the production
tubing 16
may leak past the valve 30 and ultimately into the annulus 17. This may result
in
possible uncontrolled pressurisation of the annulus 17, leading to a well
control failure.
In some instances the fault may lie with the gas lift valve cartridge 30. In
such
cases it might be possible to perform a wireline based intervention operation
to retrieve
and replace the valve cartridge 30. However, where the fault lies with the
mandrel side
pocket 26, either initially or through damage during a valve replacement
operation, the
options to the operator were heretofore either to perform a complete workover
to pull
and replace the entire production string 16, or abandon the wellbore 10, which
will be
understood by those of skill in the art to both be undesirable. The present
invention
provides a heretofore unknown alternative to an operator, which will allow the
wellbore
to continue to operate.
Accordingly, if an operator discovers that a gas lift mandrel has become
compromised, he may utilise an embodiment of the present invention, as will
now be
described, initially with reference to Figure 3. An operator will initially
set a plug 50
within the tubing string 16 below the gas lift mandrel 18, for example using a
wireline
deployed plug. Following this the valve cartridge 30 is picked up by wireline
52, for
example via a suitable connector and running tool (not shown), and retrieved
from the
side pocket 26 of the mandrel 18 and towards surface.
Subsequent to this, as shown in Figure 4, a sealing insert 60 according to an
embodiment of the present invention is deployed from surface through the
production
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tubing 16. Also, as illustrated in Figure 4, the production tubing 16 above
the plug 50,
and the annulus 17, are filled with a fluid 54, in this example water. It
should be
understood that this water may be placed into the wellbore 10 immediately
following
setting of the plug, and before the valve cartridge 30 is removed. The water
provides a
column of fluid which establishes a hydrostatic pressure within the wellbore
to assist in
containing the lower wellbore and reservoir pressure. The water will also
function to
operate the sealing insert 60, as will be described in more detail below.
Reference is now made to Figure 5 in which there is shown a longitudinal cross-
sectional view of the sealing insert 60 of Figure 4. The insert 60 includes a
cylindrical
solid base member 62 which has a conical tip 64 at one end and a connection
profile
66 at an opposite end. The connection profile 66 facilitates connection to the
wireline
52 via an appropriate connector 68 and running tool 70 (all shown in broken
outline).
The insert 60 further comprises an annular sealing element 72 which is
mounted within an annular recess 74 formed in the base member 62. The sealing
element comprises a swellable elastomer material which in the present
exemplary
embodiment is caused to swell upon exposure to water. When the sealing element
74
is in its unswollen state, the outer diameter of said sealing insert may be
less than or
equal to the largest outer diameter of the base member.
The sealing insert 60 is deployed into the side pocket 26 of the mandrel 18,
as
illustrated in Figure 6, with the wireline detached and retrieved to surface.
Over time,
exposure to the water 54 within the production tubing 16 and annulus 17 will
cause the
sealing element 72 of the sealing insert 60 to swell thus sealing the side
pocket 26 of
the mandrel 18, as illustrated in Figure 7. As illustrated, the sealing
element is of
sufficient length to span the side port 28 in the mandrel 18. Further, the
nature of the
swelling material of the sealing element is such that it can readily comply
with the
surfaces of the side pocket 26, and will therefore also seal-off any damaged
or highly
corroded areas. Further, any further corrosion or damage may be accommodated
by
the continuous swelling, or self-healing, effect of the swelling material.
Once the sealing insert is fully swollen and the side pocket 26 of the mandrel
18 is fully sealed, the plug 50 may be removed, as shown in Figure 8. The
wellbore 10
may then recommence production, or alternatively could now be used as an
injection
well.
In some instances an operator may recognise that a fault has occurred at the
location of a gas lift mandrel 18, as illustrated in Figure 2. However, there
may be
occasions where an operator wishes to retain the operation of the particular
gas lift
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mandrel. Embodiments of an aspect of the present invention may permit an
operator
to address the fault at the mandrel 18, while still maintaining its
functionality. Such an
exemplary embodiment will now be described with additional reference to
Figures 9
and 10.
In this respect, when a fault is recognised, as illustrated in Figure 2, an
operator
may retrieve the gas lift valve cartridge 30 on wireline 52, in the same
manner as
shown in Figure 3. However, rather than deploying a sealing insert as in
previous
embodiments, the operator can, according to the present invention, deploy a
new gas
lift valve cartridge 30a, as illustrated in Figure 9, again on wireline 52. In
this case the
new valve cartridge 30a comprises upper and lower swellable seals 34a, 36a at
the
locations previously occupied by the chevron seals 34, 36 of the retrieved
cartridge 30.
In some embodiments the retrieved cartridge may be reconditioned to remove the
existing seals 34, 36 and replace these with new, swellable seals 34a, 36a.
However,
in other embodiments a different cartridge may be utilised.
Although the arrangement in Figure 9 does not show any fluids positioned in
the
tubing string 16 above the plug 50, such fluid may, nevertheless be provided,
as in
Figure 6.
Once the new cartridge 30a is positioned within the side pocket 26 of the
mandrel 18, the seals 34a, 36a may be activated to swell, thus providing
sealing
engagement between the new cartridge 30a and the side pocket mandrel, as
illustrated
in Figure 10. The use of the swelling seals 34a, 36a in this case may address
any
previous issues with losses in seal integrity with the retrieved cartridge 30,
and may
allow fluid control via the side port 28 of the mandrel 18 to be retained.
It should be understood that the embodiments described herein are merely
exemplary and that various modifications may be made thereto without departing
from
the scope of the invention. For example, in the embodiment illustrated the
wellbore 10
supports gas production. However, in other embodiments oil production may be
present, or alternatively downhole injection may be present. Further, the
sealing
element of the sealing insert in the illustrated embodiments is provided to
swell upon
exposure to water. However, in other embodiments, for example where the
wellbore
supports oil production, the sealing element may be arranged to swell when
exposed to
oil.
Also, in the exemplary embodiments a single mandrel is shown within a tubing
string. However, in other embodiments multiple mandrels may be present,
axially
distributed along the tubing string. In some cases more than one mandrel may
require
CA 02923107 2016-03-03
WO 2015/043801 PCT/EP2014/066294
remedial attention, such as described above. Where one or more of a number of
mandrels remain operational, such operational mandrels may support continued
gas lift
production, after one or more other mandrels have been sealed.
Further, in the exemplary embodiment described the mandrel is a gas lift
5 mandrel. However, embodiments of the present invention may be used in
combination
with any downhole mandrel, such as a chemical injection mandrel, downhole
valve
mandrel or the like.
