Note: Descriptions are shown in the official language in which they were submitted.
CA 2853642 2017-03-06
RISER WITH INTERNAL ROTATING FLOW CONTROL DEVICE
Field of the Invention
100011 The present invention relates to devices for managing downhole fluid
pressures in
offshore drilling, and more particularly to a riser pipe section with an
internal rotating flow
control device.
Background to the Invention
[0002] Oil and gas offshore drilling operations require the use of a "riser",
or "riser string" as
it is also known. The riser consists of a string of pipe that extends from a
floating drilling
platform down to the sea floor. The riser is comprised of riser components
that are attached
end-to-end by means of flanged or custom connections. Drilling mud, cuttings
and
hydrocarbon products from the borehole in the seafloor are returned to the
drilling platform
through the riser. The top of the riser is attached to the drilling platform
while its lower end is
secured to the wellhead on the seafloor. Immediately below the drilling
platform, the riser has
a "slip joint", or "tension joint" as it is also known, that is configured to
telescope to
compensate for the heave and swell that the floating drilling platform
experiences in the sea.
[0003] It is conventional to use a subsurface blowout preventer (a "BOP")
placed between the
wellhead and the riser to provide protection against the sudden release of
gas,
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which can arise if the drilling operations encounter pressurized formations.
To promote
safety and control, a surface BOP is also frequently placed at the top of the
riser
proximate to the drilling platform.
[0004] It is also conventional to use a surface rotating flow control device
(a "RFCD") at
the level of the drilling platform in conjunction with the surface BOP. The
surface RFCD
serves multiple purposes including the provision of a pressure seal around
drill pipe that
is being moved in and out of the riser and the wellbore while allowing
rotation of same.
Conventional diverters are also placed at the head of the riser above the slip
joint to divert
wellbore returns to the surface separation and storage equipment.
[0005] While the use of a surface BOP and a surface RFCD provides a pressure
seal and
a barrier between the external environment and the wellbore returns, such a
configuration
can be problematic. If the subsurface BOP fails, or if there is a sudden
release of gas or
pressurized fluid into the riser for any other reason (for example, solution
gas assuming
gaseous form as it ascends the riser), control of the pressurized gas or fluid
in the riser
occurs at the level of the drilling platform using the surface BOP stack, the
surface RFCD
and the diverter. This can result in exposure of the drilling platform to
dangerous risk if
the pressure and volume of the wellbore return within the riser exceeds the
pressure rating
of the riser, or if the capacity of the surface equipment to deal with this
type of event is
not adequate.
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[0006] These problems may be mitigated by positioning the RFCD in the riser
below the
slip joint, which is the weakest pressure rated assembly in the riser string.
In this manner,
the RFCD creates a pressure seal that isolates the pressurized wellbore
returns in the riser
below the drilling platform so that they can be contained and diverted if
required at a
subsurface level thereby substantially eliminating the exposure of the
drilling platform to
danger, and giving the riser greater than typical pressure integrity.
[0007] U.S. 2006/0102387 to Bourgoyne et al. describes a RFCD releasably
positioned in
a riser by a holding member that is threadably connected to the RFCD. In use,
the
assembled holding member and RFCD are run down the riser together, until their
movement is resisted either by lugs on the holding member that engage an
internal
1.5 shoulder of the riser, or a passive latching mechanism between the
holding member and
an internal formation of the riser. However, the holding member adds weight to
the drill
string, and a retractable seal is required between the holding member and the
interior of
the riser to permit passage of the holding member.
[0008] WO 2013006963 to Boyd et al. describes a RFCD integrated into the riser
by a
stationary housing having a flanged connector that is, in use, sandwiched
between the
flanges of two adjacent riser pipe sections. However, the flange connection of
the
stationary housing must be made complementary to the flanges of the adjacent
riser pipe
sections.
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[0009] Accordingly, there is a need for a system to secure a RFCD in a riser
to create an
additional pressure seal between the wellbore and the external environment. It
would also be
preferable if the system avoided the need for components that added to the
weight of the drill
string, retractable seals, and extensive modification to standard riser pipe
sections. Further, it
would be preferable if the system allowed the RFCD to be remotely secured and
released.
Summary of the Invention
[0010] In one aspect, there is described a system for securing and sealing a
rotating flow
control device ("RFCD") within a riser pipe section, the system comprising: a
seal element
which releasably seals against the RFCD; a seal piston which actuates the seal
element; a
latch which releasably secures the RFCD in the riser pipe section; and a latch
piston which
actuates the latch, wherein a first pressure applied to the latch piston
causes the latch piston to
displace, and wherein displacement of the latch piston applies a second
pressure to the seal
piston, thereby concurrently actuating the latch and the seal element.
[0011] In another aspect, there is described a system for releasing a rotating
flow control
device ("RFCD") from a riser pipe section, the system comprising: a latch
which releasably
secures the RFCD in the riser pipe section; a latch piston which actuates the
latch; a seal
element which releasably seals against the RFCD; and a seal piston which
actuates the seal
element, wherein a first pressure applied to the seal piston causes the seal
piston to displace,
and wherein displacement of the seal piston applies a second pressure to the
latch piston, and
thereby concurrently releases the seal element and the latch from the RFCD.
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[0011a1 In another aspect, there is described a method of securing a rotating
flow control
device ("RFCD") in a riser pipe section, the method comprising: lowering the
RFCD into the
riser pipe section, the riser pipe section comprising a latch which releasably
secures the RFCD
in the riser pipe section, and the riser pipe section further comprising a
seal element which
releasably seals against the RFCD; applying a first pressure to a first port
of the riser pipe
section, thereby displacing a latch piston and actuating the latch; and
applying a second
pressure to a seal piston in response to displacement of the latch piston,
thereby displacing the
seal piston and actuating the seal element.
[0011b] In another aspect, there is described a method of releasing a rotating
flow control
device ("RFCD") from a riser pipe section, the method comprising: applying a
first pressure
to a first port of the riser pipe section, thereby displacing a seal piston
and expanding a seal
element configured to releasably seal against the RFCD; and applying a second
pressure to a
latch piston in response to displacement of the seal piston, thereby
displacing the latch piston
and releasing a latch configured to releasably secure the RFCD in the riser
pipe section.
Brief Description of the Drawings
[0012] In the drawings, like elements are assigned like reference numerals.
The drawings are
not necessarily to scale, with the emphasis instead placed upon the principles
of the present
invention. Additionally, each of the embodiments depicted are but one of a
number of
possible arrangements utilizing the fundamental concepts of the present
invention. Any
dimensions shown in the accompanying are intended to be illustrative only, and
not limiting
of the claimed invention. The drawings are briefly described as follows:
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[0013] Figure 1 is a diagrammatic depiction of one embodiment of an offshore
drilling
operation including a system of the present invention.
[0014] Figure 2 is a three-dimensional perspective view through a vertical
half-section one
embodiment of the system of the present invention installed within a riser
string, with a
RFCD and drill pipe secured therein.
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[0015] Figure 3 is a three-dimensional perspective view through a vertical
three-quarter
section of the embodiment of the system shown in Figure 2, with a flow outlet
attached,
[0016] Figure 4 is a three-dimensional perspective view through a vertical
half-section of
a portion of the embodiment of the system shown in Figure 2,
[0017] Figure 5 is a side elevation view through a vertical half-section of a
portion of the
embodiment of the system shown in Figure 2.
[0018] Figures 6A, 6B and 6C are side elevation views through a vertical half-
section of
a portion of the system shown in Figure 2, with an RFCD secured therein. In
Figure 6A,
the latch piston and seal piston are in a raised position. In Figure 6B, the
latch piston is a
lowered position and the seal piston in a raised position, In Figure 6C, the
latch piston
and the seal piston are in a lowered position.
[0019] Figure 7 is a three-dimensional perspective view through a vertical
half-section of
the embodiment of the RFCD shown in Figure 2,
Detailed Description of Embodiments of the Invention
[0020] The invention relates to a system for securing a rotating flow control
device
("RFCD") in a riser of an offshore drilling operation. When describing the
present
invention, all terms not defined herein have their common art-recognized
meanings. To
the extent that the following description is of a specific embodiment or a
particular use of
the invention, it is intended to be illustrative only, and not limiting of the
claimed
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invention. The following description is intended to cover all alternatives,
modifications
and equivalents that are included in the spirit and scope of the invention, as
defined in the
appended claims.
[0021] Offshore oil and gas drilling operations conducted on the sea floor
require the use
of riser. In one embodiment, as shown in Figure 1, the riser (2) extends from
the drilling
platform (4) down to the sea floor (6). The drilling platform (4) may comprise
a floating
rig or a drill ship, or any like surface platform employed by the offshore
drilling industry.
The riser (2) is comprised of a string of interconnected riser components,
including riser
pipe sections (30a, 30b, 30c, 30d), generally denoted as (30). Commonly, the
riser pipe
sections (30) have flanged ends. The flanged ends of the riser pipe sections
(30) attach in
a complementary manner and are secured by bolts passing through apertures
formed in
the flanged ends,
[0022] Once a wellbore (8) has been established in the sea floor (4) and a
casing (10) has
been cemented into place in the wellbore (8), a subsea BOP (12) is landed on
and secured
to the well head (not shown). The riser (2) connects to the subsea BOP (12)
and extends
to the drilling platform (4). In practice, the subsea BOP (12) is tested to
ensure
operational functionality following which, drilling operations commence
through the riser
(2) in an incremental manner, Drill pipe (not shown) is lowered down through
the riser
(2) and drilling mud is injected down through the drill pipe. Drilling mud,
cuttings and
hydrocarbon returns from the borehole travel up to the drilling platform (4)
through the
annular space between the drill pipe and the riser (2). Immediately below the
drilling
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platform (4), the riser (2) has a slip joint (14) that is configured to
telescope in an open
and closed fashion to compensate for the heave and swell that the floating
drilling
platform (4) experiences in the sea. The slip joint (14) prevents the riser
(2) from being
pulled or pushed off the well head as the drilling platform (4) rises and
falls with the
movement of the sea.
[0023] As further shown in Figure 1, a surface BOP (16) may be employed
proximate to
the drilling platform (4). It is also conventional to use a surface RFCD (18)
at the head on
the riser (2) on the drilling platform (4). The surface RFCD (18) serves
multiple purposes
including the provision of a pressure seal around tubular are being tripped in
and out of
the riser (2), and ultimately the wellbore (8) itself, while allowing rotation
of the drill
pipe, A conventional diverter (20) is also placed at the head of the riser (2)
beneath the
surface RFCD (16) to divert wellbore returns from the riser (2) to the surface
separation
and storage equipment (not shown).
[0024] The use of a conventional diverter (20) and a surface RFCD (18) at the
head of a
riser (2) provides a pressure seal and a barrier between the external
environment and the
wellbore returns. However, such configuration can be problematic. If the
subsurface BOP
stack (12) fails, or if there is a sudden release of gas or pressurized fluid
into the riser (2)
for any other reason (for example, solution gas assuming gaseous form as it
ascends),
control of the pressurized gas or fluid in the riser (2) occurs at the level
of the drilling
platform (4) using the surface BOP (16), the surface RFCD (18), and the
diverter (20),
This can expose of the drilling platform (4) to dangerous risk if the pressure
and volume of
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CA 02853642 2014-06-09
the wellbore return within the riser (2) exceeds the pressure rating of the
riser (2), or if the
capacity and pressure rating of the surface equipment to deal with this type
of event is
inadequate. For example, should the pressure in the riser (2) exceed the
pressure capacity
of its weakest component, which is typically a 500 psi maximum pressure rated
slip joint
(14) located immediately below the diverter (20) and drilling platform (4),
then to
preclude mechanical failure of the riser (2), the diverter (20) is usually
configured to
automatically open a control port to vent the wellbore returns to relieve
pressure. This
results in the sudden release of pressurized hydrocarbon product at surface
level that can
potentially ignite resulting in an explosion at surface, Further, if venting
using the diverter
(20) does not successfully reduce the pressure in the riser (2), mechanical
failure in the
riser (2) or the well head may occur, resulting in uncontrolled introduction
of wellbore
returns into the sea and external environment.
[0025] In one embodiment, the system (1) of the present invention seeks to
mitigate these
problems by securing a RFCD in the riser (2) at a position below both the
drill platform
(4) and the weakest pressure rated assembly in the riser string, namely the
slip joint (14),
thus giving the riser (2) a much greater typical pressure integrity. In one
embodiment, a
riser (2) employing the system (1) of the present invention may have a
pressure integrity
of up to 2000 psi. When so secured, the combination of the system (1) and the
RFCD
create a pressure seal that isolates the pressurized wellbore returns in the
riser (2) below
the drilling platform (4) such that it can be contained and diverted if
required at a
subsurface level thereby substantially eliminating the exposure of the
drilling platform to
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danger, In this manner, the system and the RFCD provide an effective
additional safety
system to complement the surface level conventional diverter (20), surface BOP
(16), and
the surface RFCD (18).
[0026] One embodiment of the system (1) of the present invention is now
described with
reference to Figures 2 to 7. Referring to Figure 2, the system (1) secures a
RFCD (100)
that in conjunction with stripper elements (120, 122) form a pressure seal
around a drill
pipe (200) in a riser (2). In general, the system (1) includes a riser pipe
section (30), a
lower retaining member (40), an upper retaining member (50), and a removable
fastener
assembly (60), In the embodiment shown in the Figures, the system (1) also
includes a
collet locating member (130). As used herein, in describing the orientation of
parts of the
system (1), the term "axial" means a direction substantially parallel to the
lengthwise
direction of the drill pipe (200), and the term "radial" means a direction
substantially
perpendicular to the axial direction,
[0027] The riser pipe section (30) allows the system (1) to be installed
axially within the
riser string (2). Referring to Figure 2, in one embodiment, the riser pipe
section (30) has
an inner wall (32) that defines a bore, which de-fines an annular space
between the riser
(2) and the drill pipe (200). The lower end (34) of the riser pipe section
(30) is formed
into a flange with bolt holes, which are complementary to the bolt holes
formed in the
upper flange of adjacent lower riser pipe section (30b). Similarly, the upper
end (36) of
the riser pipe section (30) is formed into a flange with bolt holes, which are
complementary to the bolt holes formed in the lower flange of adjacent upper
riser pipe
CA 02853642 2014-06-09
section (30d). The flanges can be standard American Petroleum Institute (API)
flanges or
custom-sized to match flanges of riser components, In other embodiments (not
shown),
the lower and upper ends (34, 36) may comprise other types of connection
systems
employed in the art for rigidly connecting riser pipe components, Referring to
Figure 3, in
one embodiment, the riser pipe section (30) also defines one or more ports
(38) which can
be used to relieve pressure downhole of the RECD (100) in to an attached flow
outlet
(140), which is positioned axially between the RFCD (100) and the wellbore
(8),
[0028] The lower and upper retaining members (40, 50) axially restrain the
fastening
member (60) therebetween within the riser pipe section (30). In one
embodiment, as
shown in Figure 3, the lower and upper retaining members (40, 50) also axially
restrain
the collet locating member (130) therebetween within the riser pipe section
(30). At least
one of the retaining members (40, 50) is removably attached to the inner wall
of the riser
pipe section (30) to allow for removal of the fastener assembly (60) and, if
present, the
collet locating member (130), from the riser pipe section (30). The other
retaining
member may also be removably attached to the inner wall of the riser pipe
section (30), or
may be permanently affixed or integrally formed with the riser pipe section
(30). In one
embodiment, the lower and upper retaining members (40, 50) have an inner
diameter that
is substantially equal to the drift (i.e., internal diameter) (D) of the riser
pipe section (30),
[0029] Referring to Figure 4, in one embodiment, the lower retaining member
(40)
comprises a continuous annular ring. The ring is attached to the bottom of
fastener
assembly (60) by bolts. Each of four quarter snap rings (42) are received in a
groove
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formed in the inner wall of the riser pipe section (30) to define a gap
therebetween. The
ring of the lower retaining member (40) has arms (41) that are received in one
of the gaps
and form a friction-fit with one of the snap rings (42) and the inner wall of
the riser pipe
section (30). When so assembled, the snap rings (42) resist downward axial
movement of
the ring and attached fastener assembly (60). In other embodiments (not
shown), the
lower retaining member (40) may have a different shape, such as a plurality of
projections
such as lugs. The lower retaining member (40) may also be attached to the
inner wall of
the riser pipe section (30) by other suitable means known in the art such as a
threaded
connection, or may be formed integrally with the inner wall of the riser pipe
section (30).
[0030] Referring to Figure 4, in one embodiment, the upper retaining member
(50) also
comprises a continuous annular ring. A bolted connection removably secures the
upper
retaining member (50) to an annular shoulder (39) formed monolithically with
the inner
wall of the riser pipe section (30). The lower surface (52) of the upper
retaining member
(50) provides a downward facing bearing surface for the collet locating member
(130).
An upper surface (54) of the upper retaining member (50) bears against the
internal
annular shoulder (39) of the riser pipe section (30). In other embodiments
(not shown),
the upper retaining member (50) may have a different shape. Also, the upper
retaining
member (50) may be removably attached to the inner wall of the riser pipe
section (30) by
other suitable means known in the art such as a threaded connection, or may be
formed
integrally with the inner wall of the riser pipe section (30).
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[0031] The fastener assembly (60) releasably secures the RFCD (100) within the
riser
pipe section (30). Referring to Figure 4, in one embodiment, the fastener
assembly (60) is
retained within the riser pipe section (30) by direct engagement with the
lower retaining
member (40) and indirect engagement with the upper retaining member (50) via
the collet
locating member (130). In one embodiment, the fastener assembly (60) has an
inner
diameter that is substantially the same as the drift (D) of the riser pipe
section (30).
However, the fastener assembly (60) includes a plurality of latches (62) which
extend
radially inward to engage the RFCD (100) when installed in the fastener
assembly (60),
and which retract to disengage from the RFCD (100) to allow for removal of the
RFCD
(100). In one embodiment, springs (not shown) bias the latches (62) in the
radial inward
direction, but yield when compressed to allow the RFCD (100) to slide into the
annulus
(64) of the fastener assembly (60). The fastener assembly (60) also has a seal
assembly
(84) to sealingly engage the RFCD (100) and resist axial rotation of the RFCD
(100) as
the drill pipe (200) rotates within the RFCD (100). Referring to Figure 6A, in
one
embodiment, the seal element (84) is attached to the inner surface of the
inner member
(70). The seal element (84) may be made of a compressible material so that
when the
RFCD (100) slides axially into the annulus (64) of the fastener assembly (60),
the seal
element (84) compresses radially to allow axial passage of the RFCD (100).
[0032] Referring to Figure 4, in one embodiment, the fastener assembly (60)
comprises
an annular outer member (66), intermediate member (68), inner member (70) and
ring
(72). The wall of the outer member (66) has a substantially L-shape cross-
section in the
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axial plane, with a horizontal leg that is adjacent and attached to the lower
retaining
member (40), and a vertical leg that is complementary to the inner wall of the
riser pipe
section (30) so as to create a fluid-tight seal therebetween. The wall of the
intermediate
member (68) has a substantially T-shape cross-section in the axial plane. The
wall of the
'inner member (70) has a substantially linear cross-section in the axial plane
and is
disposed between the horizontal leg of the outer member (66) and the
horizontal arm of
the intermediate member (68). The inner member (70) retains the latches (62)
and defines
apertures for radial extension and retraction of the latches (62). The ring
(72) engages the
vertical leg of the outer member (66), the top of the intermediate member (68)
and the
bottom of the collet locating member (130) so as to create a fluid-tight seal
therebetween.
The ring (72) is secured to the vertical leg of the outer member (66) by bolts
(not shown)
through aligned screw holes (73).
[0033] In one embodiment, the latches (62) and seal element (84) are
hydraulically or
pneumatically actuated together to extend and retract radially to engage with
or disengage
from the RFCD (100). Referring to Figure 6A, in one embodiment, the outer
member
(66) and intermediate member (68) cooperate to form an annular chamber (74). A
sliding
annular latch piston (76) divides the chamber (74) into a lower portion and an
upper
portion and scalingly isolates the portions from each other. A linear cam (82)
tbnned on
the latch piston (72) translates axial movement of the latch piston (76) into
radial
movement of the latches (62). The intermediate member (68) and the inner
member (70)
of the fastener assembly (60) cooperate to form an annular chamber (86). A
sliding
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CA 2853642 2017-03-06
annular seal piston (88) divides the chamber (86) into a lower portion and an
upper portion by
and sealingly isolates the lower portion from the upper portion. An upper port
(61) in the
intermediate member (68) allows fluid communication between the lower portion
of the
chamber (74) and the upper portion of chamber (86). A linear cam (90) formed
on the seal
piston (88) translates axial movement of the seal piston (88) into radial
movement of the seal
element (84) to engage with or disengage from the RFCD (100). A lower port
(35) of the
riser pipe section (30) is aligned with a lower port (63) of the outer member
(66) and a
port (65) of the intermediate member (68), which is in fluid communication
with the lower
portion of chamber (86). An upper port (33) of the riser pipe section (30) is
aligned with
an upper port (80) of the outer member (66) which is in fluid communication
with the
upper portion of chamber (74). The latches (62) and seal element (84) may be
disengaged
from the RFCD (100) remotely by pumping fluid through a line connected to the
lower port
(35) of the riser pipe section (30), while relieving fluid through a line
connected to the upper
port (33) of the riser pipe section (30). As shown in Figure 6A, when the
fluid pressure at the
lower port (35) is greater than the fluid pressure at the upper port (33), the
fluid urges the
seal piston (88) to move upwardly in the fluid chamber (86), thus allowing the
seal element
(84) to retract radially and disengage from the RFCD (100). As the seal piston
(88) moves
upwards in the chamber (86), it forces the fluid in the upper portion of
chamber (86) through
port (61) into the lower portion of chamber (74). This urges the latch piston
(76) to move
upwardly in the fluid chamber (74), thus allowing the latches (62) to retract
radially and
disengage from the RFCD (100). Conversely, the latches (62) and seal element
(84) may be
CA 2853642 2017-03-06
engaged with the RFCD (100) remotely by pumping hydraulic fluid through a line
connected
to the upper port (33) of the riser pipe section (30), while relieving
hydraulic through a line
connected to the lower port (35) of the riser pipe section (30). As shown in
Figure 6B, a
greater fluid pressure at the upper port (33) than at the lower port (35)
urges the latch piston
(76) to move downwardly in the fluid chamber (74), thus allowing the latches
to extend
radially and engage the RFCD (100). As shown in Figure 6C, when the latch
piston (76)
moves axially downward, it forces hydraulic fluid from the lower portion of
chamber (74)
through the port (61) and into the upper portion of chamber (86). This urges
the seal piston
(88) to move axially downward in chamber (86), thus driving the seal element
(84) to extend
radially and engage the RFCD (100). In this manner, the latches (62) and seal
element (84)
can, in unison, be selectively engaged with the RFCD (100) or disengaged from
the RFCD
(100) as a result of fluid communication between chamber (74) and chamber
(86).
[0034] An intermediate port (31) of the riser pipe section (30) allows the
latches (62) to be
disengaged, independently of the seal element (84), from the RFCD (100). The
intermediate
port (31) is connected to a high flow line of hydraulic or pneumatic fluid and
is in fluid
communication with the lower portion of the chamber (74) via intermediate port
(78) of outer
member (66). In the event of seal failure of the latch piston (76) wherein the
latches (62)
remains engaged with the RFCD (100), hydraulic or pneumatic fluid can be
pumped through
the intermediate port (31) at high volume flow rate to drive the latch piston
(76) upwards, and
thereby allow the latches (62) to sufficiently disengage from the RFCD (100)
so that the
RFCD (100) can
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be pulled upwards and out of the fastener assembly (60). Although the seal
element (84)
may remain engaged with the RFCD (100), the seal element (84) may be
configured so
that there is insufficient friction between the seal element (84) and the RFCD
(100) to
prevent deliberate removal of the RFCD (100) when the latches (62) are
disengaged from
the RFCD (100).
[0035] The removable RFCD (100) permits the drill pipe (200) to rotate within
the riser
pipe section (30). Referring to Figure 7, in one embodiment, the RFCD (100) is
=
configured for a dual stripper arrangement. The RFCD (100) includes a robust
lower
housing (102) and a lower inner tubular shaft (104) for axial rotation
therein. An
intermediate housing (106) connects the lower outer housing (102) to a robust
upper outer
housing (108), which houses an upper inner tubular shaft (110) for axial
rotation therein.
The housings (102, 106, 108), and the tubular shafts (104, 110) may be
constructed from
any suitable metallic material including, without limit, 41/30 alloy steel.
Each of the
housings (102, 108) and their respective inner tubular shafts (104, 110)
define
therebetween an annular chamber (not shown) that contains bearing elements
(not shown)
and lubricating fluid. The annular chambers are sealed with respect to the
lubricating
fluid, thus avoiding the need for an external source of lubricating fluid and
lubricating
fluid lines. The bearing elements may comprise any suitable type used for like
purposes
by those skilled in the art, and may be arranged in any manner in the annular
chambers to
provide appropriate axial and radial support to the inner tubular shafts (104,
110). Any
suitable lubricating fluid may be utilized in the annular chamber to cool and
lubricate the
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CA 02853642 2014-06-09
bearing elements. Rotation of the inner tubular shafts (104, 110) within their
respective
outer housings (102, 108) is made possible by the bearing elements engaging an
outer
race that remains stationary with the housings (102, 108) and an inner race
that rotates
with the inner tubular shafts (104, 110).
[0036] Referring to Figure 7, in one embodiment, the lower outer housing (102)
defines a
circumferential lower recess (112) and upper recess (114). The lower recess
(112)
provides an engagement surface that is complementary in shape to the seal
element (84)
of the fastener assembly (60) to create a fluid-tight seal barrier between the
lower outer
housing (102) of the RFCD (100) and the inner member (70) of the fastener
assembly
(60). The upper recess (114) provides an engagement surface that is
complementary in
shape to the latches (62) of the fastener assembly (60).
10037] The stripper elements (120, 122) sealingly grip the drill pipe (200) to
create a fluid
tight seal with the drill pipe (200) and transfer axial rotation of the drill
pipe (200) into
axial rotation of the inner tubular shafts (104, 106) of the RFCD (100).
Referring to
Figure 7, in one embodiment, a lower stripper element (120) is attached to the
lower inner
tubular shaft (104) and an upper stripper element (122) is attached to the
upper inner
tubular shaft (110) for a RFCD (100) with a dual stripper configuration. The
stripper
elements (120, 122) may be constructed from any suitable rubber, elastomer, or
polymer
substance.
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CA 02853642 2014-06-09
[0038] The collet locating member (130) cooperates with a collet (116)
attached to the
RFCD (100) to properly position the RFCD (100) within the fastener assembly
(60) for
engagement by the latches (62) and seal element (84). Referring to Figure 4,
in one
embodiment, the collet locating member (130) is an annular member formed
separately
and retained axially within the riser pipe section (30) by engagement with the
upper
retaining member (50) and the fastener assembly (60). In other embodiments,
the collet
locating member (130) may have different shapes and may be positioned
elsewhere
within the riser pipe section (30). The collet locating member (130) may also
be formed
integrally with the inner wall of the riser pipe section (30), the lower
retaining member
(40), or the upper retaining member (50).
[0039] Referring to Figure 4, in one embodiment, the inner wall of the collet
locating
member (130) includes a vertical frustum-shaped surface (132) that terminates
at the
lower end with a horizontal annular land (134). The collet locating member
(130) defines
an inner diameter that is equal to the drift (i.e., internal diameter) (D) of
the riser pipe
section (30). Referring to Figure 7, in one embodiment, the collet (116)
attached to the
RFCD (100) is made of spring steel, and is a generally tubular member with a
plurality of
kerfs (not shown) cut in the axial direction to define a plurality, of
fingers. The fingers
have a lower chamfer (117) that is similar to an upper chamfer (56) of the
upper retaining
member (50). When the lower chamfer (70) of the fingers is forced downwardly
against
the upper chamfer (56) of the upper retaining member (50), the upper chamfer
(56)
squeezes together the fingers to allow the collet (116) and attached RFCD
(100) to pass
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CA 02853642 2014-06-09
through the upper retaining member (50) and the annulus (64) of the fastener
assembly
(60). As the collet (116) continues to move downwards through the frustum-
shaped
surface (132) of the collet locating member (130), the fingers of the collet
(116) expand
radially outwardly and engage the land (134), thus preventing further downward
movement of the RFCD (100) as shown in Figure 6A. The collet (116) is
dimensioned so
that when it engages the land (134), the recesses (112, 114) of the RFCD (100)
are axially
aligned with the seal element (84) and the latches (62), respectively, of the
fastener
assembly (60). The fingers also have an upper chamfer (118) that is similar to
the
frustum-shaped surface (132) of the riser collet locating member (130). When
the RFCD
(100) is pulled upwards, the frustum-shaped surface (132) engages the upper
chamfer
(118) of the collet (130), thereby squeezing them together and allowing the
collet (116) to
pass through the annulus (64) of the fastener assembly (60) and the upper
retaining
member (50).
[0040] The use and operation of the embodiment of the system (1) shown in
Figure 2 is
now described. The riser pipe section (30), the lower retaining member (40),
the upper
retaining member (50), the fastener assembly (60) and the collet locating
member. (130)
are assembled at the surface prior to installation in the riser string (2).
Hydraulic or
pneumatic fluid lines are connected to each of ports (31, 33, 35) of the riser
pipe section
(30). A dual valve flow outlet (140) (as shown in Figure 3) for equalizing
fill, and purge
operations is connected to one of the ports (38). The flow outlet (140) is
connected to
pipes or hoses (142) (as shown in Figure 1) which travel to the surface for
the selective
CA 02853642 2014-06-09
discharge of well fluids and gases. The valves in the flow outlet (140) may be
opened and
closed remotely using surface controls to facilitate the selective venting and
diversion of
the well bore returns. Once assembled in this manner, the riser pipe section
(30) is
installed into the riser (2) as riser pipe section (30c) between adjacent
riser pipe sections
(30b, 30cI) as shown in Figures 1 and 2.
[0041] The RFCD (100) and associated stripper elements (120, 122) are also
assembled
at the surface. When required, the drill pipe (200) is inserted through the
stripper
elements (120, 122). As shown in Figure 2, the RFCD (100) rides the drill pipe
(200) as
the drill pipe (200) is lowered into the riser (2). Eventually, the collet
(116) engages the
land (134) of the collet locating member (130) to prevent further downward
movement of
the RFCD (100) when the recesses (112, 114) of the RFCD (100) are axially
aligned with
the seal element (84) and latches (62) of the fastener assembly (60). When the
RFCD
(100) is so positioned, hydraulic or pneumatic fluid is pumped from the
surface through
the upper port (33) of the riser pipe section (30) into the upper portion of
chamber (74)
and relieved from the lower portion of chamber (86) through lower port (35) of
the riser
pipe section (30). This urges the latches (62) into engagement with the recess
(114) of
the RFCD (100) to secure the RFCD (100) in place. As the latch piston (76)
moves
downwards and drives fluid into the upper portion of chamber (86), the seal
element (84)
is urged into sealing engagement with the recess (112) of the RFCD (100). The
RFCD
(100) may be removed by reversing the foregoing steps. If the stripper
elements (120,
122) are not too compromised, the RIVE) (100) may be removed by pulling the
drill pipe
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CA 02853642 2014-06-09
(200) upwards. However, if the stripper elements (120, 122) are unable to form
an
adequate seal on the drill pipe (200), then a recovery tool may be used for
removal of the
RFCD (100).
[0042] Once secured in the riser (2), the system (1) in conjunction with the
RFCD (100)
provides a seal on drill pipe (200) that is being run into or out of the
wellbore (8) and
provides an additional pressure barrier between the external environment and
the
wellbore (8) at a subsea level below the drilling platform (4). It also
isolates the slip joint
(14) from pressurized well bore returns. In the event of failure of the lower
BOP stack
(12) or the introduction of pressurized gas or fluid into the riser (2), the
system (1) and
RFCD (100) form a pressure seal thus precluding exposure of the slip joint
(14) and the
drilling platform (4) components to the pressurized fluid or gas. If venting
is required to
reduce the pressure in the riser (2) beneath the system (1), ports in the flow
outlet (140)
may be opened and the associated hose or pipe (142) will conduct the vented
substances
to a location that is a safe distance from the drilling platform. As such, the
system (1) and
RFCD (100) may be employed for well control operations, to promote safety and
to
mitigate environmental concerns and to manage high pressure drilling
activities.
[0043] As will be apparent to those skilled in the art, various modifications,
adaptations
and variations of the foregoing specific disclosure can be made without
departing from
the scope of the invention claimed herein.
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