Note: Descriptions are shown in the official language in which they were submitted.
CA 2926387 2017-05-31
Swellable Seal with Undulating Backup
BACKGROUND
[0001] The present disclosure relates to well tools that utilize swellable
seals.
[0002] Downhole conditions in a well present numerous sealing challenges.
For example, seals in a well must often withstand extended exposure to high
pressures
and temperature. In such conditions, commonly used clastomer seals tend to
extrude
into the gap between the component carrying the seal and the surface sealed
against,
and ultimately fail. Complex backup ring designs have been developed to
address this
problem, by bridging the gap and supporting the extrusion against extrusion.
However, the backup ring designs are actuated only when the seals are
pressurized.
Also, in the context of a stinger or stab, where one well component is sealed
in a bore
of another well component, multiple seals and thus multiple backup rings are
used.
To accommodate the multiple seals in a small space, 0-rings or chevron seals
are
used. However, the effectiveness of such seals is dependent to the cleanliness
and
surface finish of the surface sealed against.
DESCRIPTION OF DRAWINGS
[0003] FIG. 1 is a schematic side view of a well incorporating a tubing
string.
[0004] FIG. 2 is an side cross-sectional view of an example of two well
components incorporating a sealing assembly.
[0005] FIG. 3A and 3B are detail views of the example well components,
showing an end of the sealing assembly prior to the seal swelling and after
the seal
has swelled.
[0006] FIG. 4 is a perspective view of an example backup member showing
the undulations.
[0007] Like reference symbols in the various drawings indicate like elements.
DETAILED DESCRIPTION
[0008] Referring first to FIG. 1, a well includes a substantially cylindrical
wellbore 10 that extends from a wellhead 22 at the surface 12 downward into
the
Earth into one or more subterranean zones of interest 14 (one shown). The
subterranean zone 14 can corresponding to a single formation, a portion of a
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formation, or more than one formulation accessed by the well, and a given well
can
access one or more than one subterranean zone 14. In certain instances, the
formations of the subterranean zone are hydrocarbon bearing, such as oil
and/or gas
deposits, and the well will be used in producing the hydrocarbons and/or used
in
aiding production of the hydrocarbons from another well (e.g., as an injection
or
observation well). The concepts herein, however, are applicable to virtually
any type
of well. A portion of the wellbore 10 extending from the wellhead 22 to the
subterranean zone 14 is lined with lengths of tubing, called casing 16.
[0009] The depicted well is a vertical well, extending substantially
vertically
from the surface 12 to the subterranean zone 14. The concepts herein, however,
are
applicable to many other different configurations of wells, including
horizontal,
slanted or otherwise deviated wells, and multilateral wells.
[0010] A tubing string 18 is shown as having been lowered from the surface
12 into the wellbore 10. The tubing string 18 is a series of jointed lengths
of tubing
coupled together end-to-end and/or a continuous (i.e., not jointed) coiled
tubing, and
includes one or more well tools (e.g., one shown, well tool 20). The string 18
has an
interior, center bore that enables communication of fluid between the wellhead
22 and
locations downhole (e.g., the subterranean zone 14 and/or other locations), in
other
instances, the string 18 can be arranged such that it does not extend from the
surface
12, but rather depends into the well on a wire, such as a slickline, wireline,
c-line
and/or other wire.
[0011] The concepts herein apply to a sealing arrangement that can be used in
a number of different contexts to seal between well components in a well. For
example, the sealing arrangement can be used in the well tool 20. In certain
instances,
the well tool 20 is of a type having an inner tubing component nested in an
outer
tubing component, with the sealing arrangement described herein configured to
seal
between the tubings. The sealing arrangement, however, need not be limited to
sealing components of the sam.e tool or device. For example, in certain
instances, the
well tool 20 is a packer type tool (e.g., packer, bridge plug, frac plug
and/or other) that
has the sealing arrangement configured to seal the tool 20 to the inner
surface of the
easing 16, a liner or other component in the well to seal the annulus around
the tubing
string 18. In another example, the tubing string 18 can be placed in the well
in two
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parts, with an uphole component that has a stab or stinger that is received
into a
corresponding bore of the downhole component. In this instance, the sealing
arrangement is configured to seal to the bore of the other component, and thus
seal
between the two -likings. In yet another example, a running tool or actuating
tool can
be used to operate the well tool 20 or another component in the well. In this
instances, the running or actuating tool has a stinger or stab that is
received into a
corresponding bore of the tool or device being actuated, and the sealing
arrangement
is configured to seal between the stinger/stab and bore. Other examples exist
and are
within the concepts herein.
[0012] Referring to FIG 2, two well components 30, 32 are shown in a half
side cross-sectional view in the present example, the well components 30, 32
are two
elongate tubings (e.g., tubings of a well tool, a packer and casing, a stinger
and bore,
or other), concentrically nested within each other. The inner tubing
(component 32)
includes a seal groove 24 sized to receive an elongate swellable elastomer
seal 26 and
backup members 28. Each of the seal groove 24, swellable seal 26 and backup
members 28 are annular or ring shaped to encircle the tubular well components
30,
32. An annular gap 34 is formed between the well components 30, 32. Although
described herein in connection with tubular well components, the same concepts
could be applied to non-cylindrical, flat or other shapes. Thus, the seal 26,
backup
members 28 and other aspects need not be annular.
[0013] The elongate swellable elastomer seal 26 is made from a swellable
elastomer that swells or expands on contact with a specified fluid, e.g., oil,
water,
and/or other. Notably, the swellable elastomer swells in all directions
uniformly,
unless constrained. Therefore, in the example with the annular swellable
elastomer
seal 26 in the seal groove 24, the seal 26 swells radially outward, as well as
axially
within the groove 24, parallel to centerline of the well components 30, 32.
The seal 26
is elongate in that it axial dimension is longer than its radial dimension,
but other
configurations of seal 26 could be provided. In certain instances, the radial
dimension
of the seal 26 is selected to provide a gap with the component 30 to allow the
seal 26
(and component 32) to be inserted and withdrawn from component 30.
[0014] A backup member 28 is provided at each end of the seal 26, axially
between the seal 26 and opposing axial ends of the seal groove 24. In other
instances,
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only one backup member 28 is provided. The backup member 28 is a wave backup
member made as a wave spring, or configured similarly to a wave spring, with
one or
more axial undulations 36 distributed around the backup member 28. In certain
instances, the undulations can be distributed evenly around the backup member
28,
for example, as in FIG. 4 showing four undulations 36 distributed at 90' from
each
other. Although shown as smooth, curving sine wave like undulations 36, the
undulations could be more abrupt and/or a different shape. The backup member
28 is
constructed of a thin, flat material with parallel sidewall surfaces, and the
undulations
36 are configured so that when the member 28 is axially compressed toward
flat, they
expand the backup member 28 circumferentially, and correspondingly radially
outward. In certain instances, the backup member 28 can be sized to lightly
contact or
provide a gap with the component 30 in an unexpanded (not axially compressed)
free
state. Such a configuration allows the backup member 28 to slide axially
through the
component 30 without much or any resistance, allowing the component 32 to be
inserted and withdrawn into the component 30. The number and amplitude A of
the
undulations 36 can be selected so that when the backup member 28 is
compressed, it
bridges the gap 34 and abuts and presses on the component 30. The number of
undulations 36 and the amplitude A of the undulations can be selected to
provide a.
contact pressure against the component 30 to provide an adequate degree of
backup
that prevents the swellable seal 26 from extruding through gap 34. In certain
instances, the backup member 28 is provided with a chamfer 38 on its inner
diameter
oriented toward the seal 26 to facilitate the member 28 expanding and
centering- on
the seal 26.
[0015] The backup member 28 can be constructed of a number of different
materials. In certain instances, the member 28 can be constructed of a
material having
a higher hardness and/or yield strength than the elastomer of the swellable
seal 26 to
facilitate the backup member 28 providing an effective backup. In certain
instances,
the material is selected based. on its ability to survive the high, downhole
temperatures. Some example materials for the backup member include metal,
polymer, composite and/or other materials or mixes of materials.
[0016] In operation, with the components 30, 32 residing in the well and the
backup members 28 and seal 26 residing in the seal groove 24, the swellable
seal 26 is
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contacted with the specified fluid. The seal 26 responds by swelling into
contact and
sealing to the component 30. In certain instances, the seal formed by the seal
26 is
gas tight. FIG 3A is a detail view about the axial end of the seal groove 24,
showing
the meltable elastomer seal 26 prior to swelling and the backup 28 unexpanded.
When the swellable elastomer seal 26 is in contact with the specified fluid,
it swells
and expands both radially and axially. In axially expanding, the swellable
elastomer
seal 26 compresses the backup members 28 against the axial end wall of the
seal
groove 24. The undulations of the backup members 28 axially compress, and
cause
the backup members 28 to expand radially into abutting contact with the
component
30, as shown in FIG, 313. Then, as the seal 26 begins to hold a pressure
differential,
the seal 26 is supported against extrusion through the gap 34 by the low
pressure side
backup member 28 pressing against the component 30. By providing two backup
members 28, the pressure differential can be reversed and the opposing backup
member 28 will support the seal 26 against extrusion through the gap 34.
[0017] Notably, by using a swellable elastomer seal 26, the surface finish of
the surface sealed against on the component 30 need not be tightly controlled,
as the
swellable seal 26 provides a contact pressure that facilitates sealing rougher
surfaces
than non-swelling seals. In the context of a stinger or stab, the component 30
need
not be provided with a polished bore receptacle. Also, the seal 26 can provie
more
surface area for sealing than a conventional 0-ring or chevron seal. In
certain
instances, the greater surface area and/or the contact pressure from swelling
will allow
the swellable seal 26 to seal, even if damaged. Because the seal 26 swells in
contact
with fluid, a pressure differential is not necessary to achieve a seal or to
actuate the
backup members 28 into supporting the seal 26. The swelling also facilitates
insertion
of the component 32 into component 30, because the seal 26 need not contact
component 30 until in contact with the specified fluid. Once sealing, the seal
26
resists withdrawal of the component 32 from component 30. In certain
instances,
because of the simplicity of the backup members 28, the cost to manufacture
can be
less than other more complex backups and chevron seals.
[0018] A number of embodiments have been described. Nevertheless, it will
be understood that various modifications may be made. Accordingly, other
embodiments are within the scope of the following claims.
