Note: Descriptions are shown in the official language in which they were submitted.
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ROTATING CONTROL DEVICE HAVING SEAL RESPONSIVE TO
OUTER DIAMETER CHANGES
TECHNICAL FIELD
This disclosure relates generally to equipment utilized
and operations performed in conjunction with a subterranean
well and, in one example described below, more particularly
provides a rotating control device with a seal which is
responsive to outer diameter changes of a drill string.
BACKGROUND
Rotating control devices generally include one or more
seals for sealing about drill pipe while the drill pipe
rotates therein. These seals can be damaged by repeated
displacement of drill pipe connections (e.g., collars or
tool joints) or other outer diameter changes through the
seals. One reason is that the seals deform to allow the
drill pipe diameter changes to pass through them.
The seals are already compressed against the drill pipe
(in order to seal), so further compression of the seals when
diameter changes pass through them further strains the
seals. In addition, drill pipe connections are typically not
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perfectly smooth, so the seals can also be scraped, cut,
abraded, etc., when the connections pass through the
already-strained seals.
Therefore, it will be appreciated that improvements are
continually needed in rotating control devices and the seals
therein.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a representative partially cross-sectional
view of a well drilling system and associated method which
can embody principles of this disclosure.
FIG. 2 is a representative enlarged scale partially
cross-sectional view of a rotating control device which may
be used in the system and method of FIG. 1, and which can
embody the principles of this disclosure.
FIG. 3 is a representative further enlarged scale
cross-sectional view of a seal which may be used in the
rotating control device of FIG. 2, and which can embody the
principles of this disclosure.
FIG. 4 is a representative cross-sectional view of the
seal, with an outer diameter change of a drill string being
inserted into the seal.
FIG. 5 is a representative cross-sectional view of the
seal, with the outer diameter change being displaced in the
seal.
FIG. 6 is a representative cross-sectional view of the
seal, with the outer diameter change being displaced out of
the seal.
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DETAILED DESCRIPTION
Representatively illustrated in FIG. 1 is a system 10
for use with a subterranean well, and an associated method,
which system and method can embody principles of this
disclosure. However, it should be clearly understood that
the system 10 and method are merely one example of an
application of the principles of this disclosure in
practice, and a wide variety of other examples are possible.
Therefore, the scope of this disclosure is not limited at
all to the details of the system 10 and method described
herein and/or depicted in the drawings.
In the FIG. 1 example, a wellbore 12 is drilled by
rotating a drill pipe 14, such as, by utilizing a drilling
rig (not shown) at or near the earth's surface. The drill
pipe 14 can be rotated by any means, e.g., a rotary table, a
top drive, a positive displacement or turbine drilling
motor, etc. Thus, it should be understood that the scope of
this disclosure is not limited to any particular way of
rotating the drill pipe 14.
The drill pipe 14 is part of an overall drill string
16, which can include a variety of different components.
Preferably, a drill bit 18 is connected at a distal end of
the drill string 16, so that the drill bit cuts into the
earth when the drill string rotates and weight is applied to
the drill bit.
An annulus 20 is formed radially between the drill
string 16 and the wellbore 12. A drilling fluid 22 (commonly
known as "mud," although other fluids, such as brine water,
may be used) is circulated downward through the drill string
16, exits the drill bit 18, and flows back to the surface
via the annulus 20.
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The drilling fluid 22 serves several purposes,
including cooling and lubricating the drill bit 18, removing
cuttings, maintaining a desired balance of pressures between
the wellbore 12 and the surrounding earth, etc. In some
situations (e.g., in managed pressure drilling or
underbalanced drilling, or even in conventional overbalanced
drilling), it may be desirable to seal off the annulus 20 at
or near the earth's surface (for example, at a land or sea-
based drilling rig, a subsea facility, a jack-up rig, etc.),
so that communication between the annulus 20 and the earth's
atmosphere or sea is prevented.
For this purpose, a rotating control device 24 can be
used to seal about the drill string 16 during a drilling
operation. In the example depicted in FIG. 1, the rotating
control device 24 is connected to a blowout preventer stack
26 on a wellhead 28, but in other examples the rotating
control device could be positioned in or on a riser string,
in a subsea wellhead, in a wellbore, etc. The scope of this
disclosure is not limited to any particular location of the
rotating control device 24.
Referring additionally now to FIG. 2, an enlarged scale
partially cross-sectional view of one example of the
rotating control device 24 is representatively illustrated.
In this view, it may be clearly seen that the rotating
control device 24 includes two annular seals 30, 32 which
seal against an exterior surface of the drill pipe 14 as the
drill pipe rotates within an outer housing assembly 34 of
the rotating control device. The FIG. 2 rotating control
device 24 may be used with the system 10 and method of FIG.
1, or it may be used with other systems and methods.
In the FIG. 2 example, the outer housing assembly 34 is
provided with a flange 36 at a lower end thereof for
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connection to the blowout preventer stack 26. However, in
other examples, the outer housing assembly 34 could be
provided with suitable connectors for installing the
rotating control device 24 in or on a riser string, to a
subsea wellhead, or at any other location.
As depicted in FIG. 2, the lower seal 30 is positioned
in the outer housing assembly 34, whereas the upper seal 32
is positioned in an upper "pot" or enclosure 38. In other
examples, either or both of the seals 30, 32 could be
positioned inside or outside of the outer housing assembly
34, and other numbers of seals (including one) may be used.
The scope of this disclosure is not limited to any
particular number or positions of seals.
The seals 30, 32 are in one sense "passive," in that
they sealingly engage the drill pipe 14 whenever the drill
pipe is positioned in the rotating control device 24,
without any need of actuating the seals to effect such
sealing. However, the seals 30, 32 can also be considered
"active" seals, because they are responsive to change their
sealing characteristics when acted upon by a stimulus, as
described more fully below.
In the FIG. 2 example, the seals 30, 32 are mounted to
a bearing assembly 40, which is secured to the outer housing
assembly 34 by a clamp 42. The bearing assembly 40 includes
bearings 44, which permit an inner generally tubular mandrel
46 to rotate relative to the outer housing assembly 34.
In other examples, a latch mechanism or other device
could be used in place of the clamp 42. The bearing assembly
40 and both seals 30, 32 could be positioned entirely within
the outer housing assembly 34. Thus, the scope of this
disclosure is not limited to any particular arrangement or
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configuration of the various components of the rotating
control device 24.
Note that, as depicted in FIG. 2, the seals 30, 32
rotate with the enclosure 38 and mandrel 46 relative to the
outer housing assembly 34 when the drill pipe 14 rotates in
the rotating control device 24. Preferably, the drill pipe
14 is both sealingly and grippingly engaged by the seals 30,
32.
Referring additionally now to FIG. 3, the seal 30 is
representatively illustrated apart from the remainder of the
rotating control device 24. The seal 30 may be used in the
FIG. 2 rotating control device 24, or it may be used in
other types of rotating control devices, in keeping with the
principles of this disclosure.
In the FIG. 3 example, the drill string 16 includes an
outer diameter change 48. The outer diameter change 48 may
be in the form of a tool joint, a collar, another type of
drill pipe connection, a drilling tool, etc. Any type of
outer diameter change can be included in the drill string
16, within the scope of this disclosure.
In this example, the outer diameter change 48 comprises
an increased outer diameter of the drill pipe 14. It is
desired for the seal 30 to continue sealing against the
outer diameter change 48 and the adjacent drill pipe 14 as
the outer diameter change passes through the seal, without
incurring any damage to the seal, shortening its useful
life, etc.
For this purpose, the seal 30 includes fluid-filled
chambers 50, 52 in a resilient material 54 of the seal. The
material 54 may comprise, for example, an elastomer (such
as, a nitrile, fluoro-elastomer, EPDM, etc.).
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The chambers 50, 52 are preferably formed by molding
them into the seal 30 when the seal is fabricated. However,
the scope of this disclosure is not limited to any
particular method of forming the chambers 50, 52.
An annular-shaped passage 56 connects the chambers 50,
52. The passage 56 may also be formed in resilient material
54, or it may be formed in a rigid or other non-resilient
material if desired.
It will be appreciated that fluid 58 can flow between
the chambers 50, 52 via the passage 56. Thus, if one of the
chambers 50, 52 is compressed or reduced in volume, the
fluid 58 can flow to the other chamber via the passage,
thereby enlarging a volume of the other chamber.
The fluid 58 is preferably a compressible fluid (e.g.,
a liquid or gas, such as, silicone fluid, nitrogen gas,
etc.). In this manner, compression of the fluid 58 will
function to resiliently bias the seal 30 into sealing
contact with the drill pipe 14 and any outer diameter change
48.
Referring additionally now to FIG. 4, the seal 30 is
representatively illustrated after the diameter change 48
has entered an upper portion of the seal. The increased
outer diameter of the drill pipe 14 has caused a volume of
the upper chamber 50 to decrease, thereby forcing some or
all of the fluid 58 in the chamber 50 to flow via the
passage 56 to the other chamber 52.
The increased volume of fluid 58 in the lower chamber
52 is beneficial, in that it causes the lower portion of the
seal 30 to be increasingly biased into sealing contact with
the drill pipe 14 below the diameter change 48. This is due
in part to the volume of the lower chamber 52 increasing as
a result of the additional fluid 58 therein.
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Referring additionally now to FIG. 5, the seal 30 is
representatively illustrated after the diameter change 48
has been displaced further downward in the seal 30. The
diameter change 48 in this view is now positioned opposite
the lower chamber 52.
The lower chamber 52 is radially compressed by the
presence of the diameter change 48 in the seal 30, thereby
forcing the fluid 58 from the lower chamber to the upper
chamber 50 via the passage 56. Thus, the volume of the lower
chamber 52 decreases, while the volume of the upper chamber
50 increases.
The increased volume of fluid 58 in the upper chamber
50 is beneficial, in that it causes the upper portion of the
seal 30 to be increasingly biased into sealing contact with
the drill pipe 14 above the diameter change 48. This is due
in part to the volume of the upper chamber 50 increasing as
a result of the additional fluid 58 therein.
Referring additionally now to FIG. 6, the seal 30 is
representatively illustrated after the diameter change 48
has been displaced downwardly out of the seal. The upper and
lower chambers 50, 52 have now returned to their respective
FIG. 3 volumes, with some of the fluid 58 having flowed from
the upper chamber 50 back to the lower chamber 52.
The transfer of the fluid 58 between the chambers 50,
52 during the passage of the diameter change 48 through the
seal 30 allows the seal to enlarge as needed, and where
needed, to prevent over-straining the seal, as well as
abrasions and cuts, due to the diameter change. However,
instead of decreasing the sealing capability of the seal 30,
the transfer of the fluid 58 to a particular chamber 50 or
52 allows a respective portion of the seal to be
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increasingly biased into sealing contact with the drill pipe
14, thereby enhancing the sealing capability of the seal.
Note that these benefits can be obtained, even without
applying any external pressure to the chambers 50, 52. Thus,
it is preferably not necessary to connect any external
pressure source (e.g., a pump, bottles of compressed gas,
etc.) to the seal 30. This simplifies the construction and
operation of the rotating control device 24, thereby
reducing manufacturing, operating and maintenance costs,
while enhancing the rotating control device's reliability
and sealing capability. However, in some examples, an
external pressure source could be connected to the seal 30.
Although the diameter change 48 is depicted in FIGS. 3-
6 as displacing downwardly through the seal 30, similar
benefits are obtained when the diameter change displaces
upwardly through the seal. In that case, the fluid 58 would
travel in opposite directions, and the chambers 50, 52 would
expand and contract, in reverse order to that described
above for FIGS. 3-6.
Although the diameter change 48 is depicted in FIGS. 3-
6 as comprising a diameter increase, similar benefits can be
obtained when the diameter change comprises a diameter
decrease. In that case, the fluid 58 would travel in
opposite directions, and the chambers 50, 52 would expand
and contract, in reverse order to that described above for
FIGS. 3-6.
The diameter change 48 could comprise a combination of
diameter increases and decreases. Thus, the scope of this
disclosure is not limited to any of the specific details of
the diameter change 48, the seal 30 (or any other elements
of the rotating control device 24) or the method described
above and/or depicted in the drawings.
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It may now be fully appreciated that an improved
rotating control device 24 is provided to the art by the
above disclosure. In one example described above, the
rotating control device 24 seals about a drill string 16
having a change in outer diameter 48. The rotating control
device 24 can comprise a seal 30 which rotates with the
drill string 16. The seal 30 can include at least first and
second chambers 50, 52 connected by at least one passage 56,
and a fluid 58 which flows between the first and second
chambers 50, 52 via the passage 56 in response to
displacement of the outer diameter change 48 through the
seal 30.
One of the first and second chambers 50, 52 can
decrease in volume in response to an increase in volume of
the other of the first and second chambers 50, 52. Each of
the first and second chambers 50, 52 may increase in volume
and decrease in volume in response to displacement of the
diameter change 48 through the seal 30 in any direction.
The first and second chambers 50, 52 are preferably
free of any connection to an external pressure source. The
fluid 58 may comprise a compressible fluid.
Each of the first and second chambers 50, 52 may be
formed in a resilient material 54 of the seal 30, although
non-resilient materials may be used, if desired. The passage
56 may comprise an annular space formed in a resilient
material 54 of the seal 30. The passage 56 in other examples
could be formed in a rigid or other non-resilient material,
and is not necessarily annular in shape (for example, holes
of various shapes could be used).
A method of sealing about a drill string 16 having an
outer diameter change 48 is also described above. In one
example, the method comprises: forming at least first and
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second chambers 50, 52 in a resilient material 54 of a seal
30; displacing the outer diameter change 48 into the seal
30, thereby transferring fluid 58 from the first chamber 50
to the second chamber 52; and displacing the outer diameter
change 48 out of the seal 30, thereby transferring the fluid
58 from the first chamber 50 to the second chamber 52.
Displacing the outer diameter change 48 into the seal
30 can include flowing the fluid 58 through at least one
passage 56 which connects the first and second chambers 50,
52, and/or increasing a volume of the second chamber 52.
Displacing the outer diameter change 48 into the seal 30 may
be performed without either of the first and second chambers
50, 52 being connected to an external pressure source.
The method can include forming the passage 56 in the
resilient material 54.
Displacing the outer diameter change 48 out of the seal
30 can include flowing the fluid 58 from the second chamber
52 to the first chamber 50 via the passage 56, and/or
increasing a volume of the first chamber 50.
The passage 56 can comprise an annular space.
The method can include displacing the outer diameter
change 48 within the seal 30, thereby displacing the fluid
58 from the second chamber 52 to the first chamber 50.
Also described above is a seal 30 for sealing about a
drill string 16 in a rotating control device 24, the drill
string 16 having an outer diameter change 48. In one
example, the seal 30 can include at least first and second
chambers 50, 52. One of the first and second chambers 50, 52
increases in volume while the other of the first and second
chambers 50, 52 decreases in volume.
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The first one of the first and second chambers 50, 52
decreases in volume in response to an increase in volume of
the other of the first and second chambers 50, 52.
Each of the first and second chambers 50, 52 increases
in volume and decreases in volume in response to
displacement of the outer diameter change 48 through the
seal 30. This displacement may be in any direction. The
diameter change 48 may be an increase and/or a decrease in
diameter.
The first and second chambers 50, 52 may be free of any
connection to an external pressure source. Each of the first
and second chambers 50, 52 may be formed in a resilient
material 54 of the seal 30.
The first and second chambers 50, 52 are preferably
connected by at least one passage 56. The passage 56 may
comprise an annular space formed in a resilient material 54
of the seal 30.
The seal 30 can include a fluid 58 which flows between
the first and second chambers 50, 52 via the passage 56 in
response to displacement of the diameter change 48 through
the seal 30. The fluid 58 may comprise a compressible fluid,
although compressible fluid(s) may be used in addition to,
or in place of, compressible fluid.
Although various examples have been described above,
with each example having certain features, it should be
understood that it is not necessary for a particular feature
of one example to be used exclusively with that example.
Instead, any of the features described above and/or depicted
in the drawings can be combined with any of the examples, in
addition to or in substitution for any of the other features
of those examples. One example's features are not mutually
exclusive to another example's features. Instead, the scope
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of this disclosure encompasses any combination of any of the
features.
Although each example described above includes a
certain combination of features, it should be understood
that it is not necessary for all features of an example to
be used. Instead, any of the features described above can be
used, without any other particular feature or features also
being used.
It should be understood that the various embodiments
described herein may be utilized in various orientations,
such as inclined, inverted, horizontal, vertical, etc., and
in various configurations, without departing from the
principles of this disclosure. The embodiments are described
merely as examples of useful applications of the principles
of the disclosure, which is not limited to any specific
details of these embodiments.
In the above description of the representative
examples, directional terms (such as "above," "below,"
"upper," "lower," etc.) are used for convenience in
referring to the accompanying drawings. However, it should
be clearly understood that the scope of this disclosure is
not limited to any particular directions described herein.
The terms "including," "includes," "comprising,"
"comprises," and similar terms are used in a non-limiting
sense in this specification. For example, if a system,
method, apparatus, device, etc., is described as "including"
a certain feature or element, the system, method, apparatus,
device, etc., can include that feature or element, and can
also include other features or elements. Similarly, the term
"comprises" is considered to mean "comprises, but is not
limited to."
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Of course, a person skilled in the art would, upon a
careful consideration of the above description of
representative embodiments of the disclosure, readily
appreciate that many modifications, additions,
substitutions, deletions, and other changes may be made to
the specific embodiments, and such changes are contemplated
by the principles of this disclosure. For example,
structures disclosed as being separately formed can, in
other examples, be integrally formed and vice versa.
Accordingly, the foregoing detailed description is to be
clearly understood as being given by way of illustration and
example only, the spirit and scope of the invention being
limited solely by the appended claims and their equivalents.
