Note: Descriptions are shown in the official language in which they were submitted.
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MONOBORE RISER BORE SELECTOR
' The present invention relates to a system for
coupling a monobore high pressure riser, a dual bore sub-
sea tubing hanger and a dual bore tubing hanger running
tool together. In particular, the invention relates to
a monobore riser cross-over apparatus for providing
communication between the monobore riser and the dual
bores.
A conventional sub-sea well system incorporates a
dual bore tubing hanger set within a sub-sea wellhead
system, with a dual bore sub-sea xmas tree installed onto
the wellhead thereby establishing discrete flowpaths for
the production, and annulus access bores and
communication to downhole safety equipment, the downhole
safety valve (DHSV), electrical equipment for measuring
pressure and temperature, and other well operating
functions in the case of multi-lateral completions.
During the installation procedure wireline plugs are
installed through the tubing hanger running tool into the
tubing hanger to accommodate the requirements of the
statutory authorities, to maintain well control during
the interval between the disconnection of the blow-out
preventer (BOP) stack from the wellhead and the
installation of the xmas tree. Within the production
bore a preliminary barrier is established by the
installation of a deep-set plug in the downhole
completion which is located at or below the packer
assembly. A secondary barrier is established by the
installation of a second similar plug within a suitable
profile in the tubing hanger production bore. On the
annulus side, the primary barrier is the downhole packer
assembly, and a secondary barrier is established by the
installation of a similar wireline set plug in a suitable
profile in the annulus access bore within the tubing
hanger. Thus, the statutory requirement to provide two
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barriers between the reservoir and the environment is
satisfied.
Once the dual bore xmas tree has been installed onto
the wellhead, the wireline plugs are retrieved to
facilitate production of the reservoir through the sub-
sea xmas tree.
In order to access the two discrete bores of a
conventional dual bore production system for the
installation of wireline plugs, historical practice has
been to utilise a dual bore riser system as shown in Fig.
1 of the drawings. It should be understood that the
capital cost of such a conventional dual bore riser
system is significant. The most common and economic
form of a dual bore riser is the skeletal riser in which
two separate tubular members are clamped together at
regular intervals to form discrete joints which are
usually about 50 ft. in length and which are connected
together to form the dual bore riser string. The
operational depth limit of such a riser is generally
agreed to be about 3000 ft. An alternative to the
conventional dual bore skeletal riser system is sought in
order to reduce cost, to extend the ability to make
available risers in a variety of sizes available a short
delivery notice and to extend the opportunities of using
sub-sea production systems to exploit oil reservoirs in
water depths exceeding 3000 ft. One of these
alternatives is already described in applicant's co-
pending International Patent Application PCT/GB96/00435
for a Dual Bore Riser using casing and coiled tubing.
A monobore riser system can be made for less cost
and can be made to work in greater water depth much more
economically than a dual bore riser system. However, a
single bore riser has a significant limitation in that it
cannot, on its own, access a dual bore system without
there being some means provided to permit an exclusive
selection of which of the two bores within the sub-sea
tubing hanger to access.
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Traditionally, the means by which such an exclusive
selection has been accomplished has been to arrange the
production bore (A) to be straight and vertical; with the
annulus access bore (B) being "kicked off" to one side in
the form of an inverted "Y" shape as shown in Fig. 2 of
the drawings. Access into the production bore (A) is
simply straight down the vertical path and, because the
production bore is always larger than the annulus access
bore, components which run into the production bore are
too large to fit into the annulus bore. Access into the
annulus bore is accomplished by blocking the path into
the production bore by the installation of a plug, called
a whipstock (C), using wireline techniques an example of
which is also shown in Fig. 2 of the drawings. The
whipstock (C) has a top profile (D) which shaped to
encourage components into the annulus access bore (B) to
change direction laterally to enter the "Y" branch into
the annulus access bore.
One problem of this existing arrangement is that the
whipstock has to be run-in on wireline to block the
production bore and access the annulus bore. This
requires time both to run the tool in and to withdraw the
tool which is relatively expensive. In addition, each
time there is a wireline operation run, there is a risk
of complications.
One proposed solution to overcoming the problems
associated with the wireline run whipstock is disclosed
in published U.K. Patent Application GB 2258675A to B.P.
Exploration Operating Company Limited. This
specification discloses a workover system for sub-sea oil
and/or gas wells which has a converter to allow the
system to be used to access any of the bores of a
parallel multiple bore well. A movable bored inner
portion can be rotated or swung in pendulum fashion to
connect a single bore to one of two parallel bores. In
the rotatable embodiment, rotation may be effected using
a rack and pinion arrangement and in the pendulum
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embodiment this may be achieved using hydraulically
operated rams or pistons. In both embodiments actuation
may be achieved by using electric motors or mechanically
by an ROV and they may be controlled from a surface rig
or vessel using the hydraulic control system of the
workover BOP. However, this prior art reference is
intended to couple a single bore to any one of a number
of parallel bores in an oil or gas well and in particular
one of a number of parallel wells. There is no specific
disclosure of the mechanism being used to couple between
a single bore and a production or annulus bore and to
allow access between the single bore and the production
bore and/or the annulus bore.
An object of an aspect of the present invention is
to provide an improved mechanism for facilitating access
from a monobore riser to a production bore or annulus
bore.
A further object of an aspect of the present
invention is to provide improved access to a production
bore or annulus bore in a dual bore system from a
monobore riser without using a whip stock run in on a
wireline.
A further object of an aspect of the present
invention is to facilitate communication between a
monobore riser and dual bores within a dual bore sub-sea
tubing hanger which can be readily controlled from the
surf ace .
This is achieved by providing a bore selector
apparatus disposed within the bore of a HOP stack and
which can be coupled between casing or tubing and a sub-
sea test tree. The bore selector apparatus can be
actuated from the surface or from an ROV to provide a
coupling exclusively between the tubing bore and the
production bore or between the tubing bore and the
smaller annulus bore.
In a preferred embodiment this is achieved by using
a rotatable ball valve element located in a housing
disposed between the casing/tubing and a sub-sea test
tree, the ball valve element being apertured and being
rotatable between a first position whereby the aperture
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connects the production tubing to the production tubing
bore and in a second position is rotated whereby the
aperture connects the annulus bore to the tubing or
casing bore. When one of the production or annulus
bores is connected to the tubing bore, then the other
bore is isolated or disconnected.
In yet another embodiment of the invention the bore
selector mechanism is implemented by a flapper plate
mechanism which is moveable by a cylindrical sleeve
between a first open position whereby access to the
production is blocked and there is communication between
the casing or tubing and the annulus access bore and a
second position whereby a sleeve is actuated to move
within the housing forcing the flapper plate to an open
position whereby there is communication via the sleeve
between the production bore and the casing and the sleeve
isolates the annulus access bore from the production
bore.
According to a first aspect of the present
invention, there is provided bore selection apparatus for
use in coupling a monobore high pressure riser with a
dual bore sub-sea tubing hanger and a dual bore tubing
hanger running tool, said bore selection apparatus
comprising .
a housing carrying a bore selection means, said bore
selection means being moveable between a first position
and a second position, whereby in said first position of
said bore selection element, communication is provided
between tubing and a main production bore and in said
second position, communication is provided between said
tubing and said annulus access bore, said bore selection
apparatus including means for moving such selection means
between said first and said second positions.
Preferably, said selection means is provided by an
apertured ball valve element, said apertured ball valve
element being moveable between said first and second
positions and rotatable as it is moved between said first
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and second position to provide communication to a
respective production bore or annulus access bore,
whereby when one of said annulus access bores and
production bores is coupled to the main production bore,
the other bore is isolated. Conveniently, the
apertured ball valve element is arranged to rotate about
a horizontal~axis through an angle to allow equipment to
be run through the monobore into either the production or
annulus bores below the ball valve element. The ball
valve element is caused to rotate by camming mechanism
which comprises an eccentrically mounted pin which is
constrained to move vertically and which engages a slot
or hole in the rotatable ball element whereby vertical
movement of the pin imparts a torque to the rotatable
element, thereby causing the ball valve element to
rotate.
The bore selector means may be coupled directly to
the sub-sea test tree or via a separate coupling sub.
In a further alternative arrangement, the bore
selector means is provided by means of a moveable flapper
valve which is moveable between a first position where it
is arranged to block one of the production and annular
access bores and a second out-of-use position whereby it
is moved to a position whereby there is communication
through either the annulus access bore or the production
bore.
Preferably, the bore selector means comprises a
housing which carries a pivotably mounted flapper plate,
a moveable sleeve is disposed within the production bore
and is moveable between a first downstream position and a
second upstream position, the sleeve, when in the
upstream position, is located such that the flapper valve
closes off the production bore and allows communication
from the monobore riser only to the annulus access bore,
and when the sleeve is actuated to be disposed in said
downstream position it urges the flapper valve to an out-
of-use position providing communication from the monobore
~ CA 02250228 2003-07-08
7
riser through the bore selector mechanism to the
production bore only and isolates access to the annulus
bore.
Conveniently, the sleeve is actuated hydraulically
and this is achieved from surface, using the BOP stack
pipework arrangement or via an ROV. Alternatively, the
sleeve is actuated mechanically using an ROV.
In yet a further alternative arrangement the bore
selector means is provided with a slotted caroming
mechanism, said caroming mechanism having a pair of spaced
apart cam plates with slots disposed therein, said
flapper plate being pivotably connected to the housing at
one end carrying a pin for engagement with said slots,
the spaced cam plates being moveable in the longitudinal
axis of the housing such that the interaction of the pin
and slots causes the flapper plate to move between a
first position allowing communication through the
production bore and preventing communication through the
annulus bore, and a second position allowing
communication through the annulus bore and preventing
communication through the production bore.
It will be understood the bore selector means may be
actuated from surface or via an ROV using hydraulic,
mechanical or electrical means.
According to an aspect of the present invention,
there is provided a bore selection apparatus for use in
coupling a monobore riser to a dual bore sub-sea tubing
hanger and a dual bore tubing hanger running tool, said
bore selection apparatus comprising:
a housing carrying an apertured ball valve, said
apertured ball valve being moveable between a first
position and a second position and rotatable as it is
moved between said first and second positions, whereby in
said first position of said apertured ball valve,
communication is provided between tubing and a main
production bore and in said second position,
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communication is provided between said tubing and an
annulus access bore, said bore selection apparatus
including means for moving said apertured ball valve
between said first and said second positions, whereby
when one of said annulus access bore and said production
bore is coupled to the main production bore, the other
bore is isolated.
According to another aspect of the present
invention, there is provided a bore selection apparatus
for use in coupling a monobore riser to a dual bore sub-
sea tubing hanger and a dual bore tubing hanger running
tool, said bore selection apparatus comprising:
a housing carrying a moveable flapper valve which is
moveable between a first position where it is arranged to
block one of a production bore and an annulus access bore
and a second out-of-use position whereby it is moved to a
position whereby there is communication with one of the
annulus access bore and the production bore, said
moveable flapper valve including means for moving said
flapper valve between said first and said second
positions.
These and other aspects of the present invention
will become apparent from the following description when
taken in combination with the accompanying drawings in
which: -
Fig. 1 is a schematic and exploded view of a dual
bore riser system which is typical of a prior art
arrangement;
Fig. 2 is a diagrammatic view through a sub-sea
wellhead assembly showing a prior arrangement for
selecting an annulus bore instead of a production bore
using a whipstock run in on wireline;
Fig. 3 is a schematic view of a wellhead arrangement
similar to that shown in Fig. 2 but incorporating a bore
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selector apparatus in accordance with a first embodiment
of the present invention;
Fig. 4 depicts a schematic view similar to that
shown in Fig. 3 and shows an intervention system and a
second embodiment of a bore selector apparatus in
accordance with the present invention;
Figs. 5a and 5b depict enlarged and more detailed
drawings of the embodiment shown in Fig. 4 with the
flapper valve in an open and a closed position
respectively;
Figs. 6a and 6b are longitudinal sectional and
cross-sectional views through a bore selector apparatus
in accordance with an alternative embodiment of the
invention with a flapper-plate arranged to provide access
to a 6" production bore, and
Figs. 7a and 7b are view similar to Figs. 6a and 6b
with the flapper plate arranged to provide access to a 2"
annulus bore.
Reference is first made to Fig. 3 of the drawings
which depicts a sub-sea wellhead assembly, generally
indicated by reference numeral 10, consists of an annular
BOP 12 coupled to a shear ram housing 13 containing BOP
shear rams 14 (shown in broken outline) and two pairs of
BOP rams 16 and 18 disposed beneath the shear rams 14.
The housing 13 of the shear rams 14 is coupled via flange
22 to a BOP connector 24 which connects to the sub-sea
wellhead 26.
Within the wellhead 26 is located a proprietary 7" x
2" tubing hanger 28 with two wireline plugs 30 and 32
shown installed in the production bore 34 and the annulus
bore 36 respectively. It will be appreciated that the
production and annulus bores 34,36 are coupled to similar
bores 34a,36a in the bore selector apparatus, generally
indicated by reference numeral 38, via a 7" x 2" sub-sea
test tree 39 of the same type as shown in Fig. 2 of the
drawings and as disclosed in applicant's co-pending U.K.
Patent Application No. 9509547.7 and via a proprietary 7"
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x 2" tubing hanger running tool (THRT) 40 (shown in
broken outline).
The bore selector apparatus 38, has an outer housing
42 defining a top bore 44. Disposed within the housing
42 is a rotatable ball-like valve element, generally
indicated by reference numeral 46. Beneath the
rotatable element 46 is disposed the main bore 34a and
the smaller diameter bore 36a. These bores register
with the production and annulus bores in the 7" x 2" sub-
sea test tree as seen in Fig. 3. It will be seen that
the bores 34a and 36a are separated by a barrier 50 which
terminates just beneath the ball valve element creating,
in the view shown, a hollow profile within the apparatus
38 which is shaped like the inverted "Y". This "Y"
profile (44,34a,36a) incorporates the rotatable element
46 to select either the branch bores. It will be
appreciated that the rotatable element 46 is made to
rotate about a horizontal axis through an angle to suit
the ability to let equipment run through the monobore 44
into either of the production or annulus bores 34a,36b
below the rotary element 46. The rotatable element can
be implemented by an apertured ball valve as described
above in which the element 46 is caused to rotate by a
camming mechanism as disclosed in applicant's co-pending
application published as W093/03255 comprising an
eccentrically mounted pin which is constrained to move
vertically and which engages a slot or hole in the
rotatable element 46 so that the vertical movement of the
pin imparts a torque to the rotatable element 46, thus
causing the element to rotate. The element 46 has a
through-aperture, generally indicated by reference
numeral 48, and the element 46 is rotatable within the
housing 42 so that the aperture can be rotated to align
only with the main bore 36a or with the secondary annulus
access bore 36a as shown in Fig. 3 of the drawings, thus
providing a selection from the main riser bore to either
the production bore 34 or to the annulus bore 36.
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Rotation of the ball valve element is effected from the
surface as disclosed in WO 93/03255, the disclosure of
which is incorporated herein.
It will also be understood that other apparatus may
be provided in which relative vertical movement between
an eccentric and a rotatable element or a cage containing
and restraining a rotating element causes rotation of a
rotary element.
In the case of intervention with the tubing hanger
28, the location of the "Y" branch (44,34a,36a) and the
bore selector apparatus 38 is above the dual bore sub-sea
test tree 39 which provides suitable barriers in the
production and annulus access bores 34,36. The "Y"
branch and the bore selector 38 may also be accommodated
within the tubing hanger orientation joint (not shown).
In the case of intervention with a sub-sea xmas
tree, the "Y" branch (44,34a,36a) and the bore selector
apparatus 38 are accommodated within the lower end of the
riser system. This allows the employment of existing
dual bore lower riser package safety blocks (LRP) and/or
emergency disconnect packages (EDP? of the workover riser
system. It will also be understood that the bore
selector apparatus may be incorporated into a monobore
system, located below the safety valves in the LRP/EDP,
so that the selection of the bore occurs immediately
above the sub-sea xmas tree.
Reference is now made to Fig. 4 of the drawings
which depicts a further embodiment of a bore selector
apparatus in accordance with the present invention with
like numerals also referring to like parts in Fig. 3.
In this case, the bore selector apparatus, generally
indicated by reference numeral 70, includes a hinged oval
flapper plate 72 located at a downward facing angle 74
within the production bore 34a. The plate 72 is
rotatable between an open and a shut position by the
axial travel of a tubular sleeve 76 located below the
oval plate 72. The bore selector apparatus 70 has a
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production bore 34a coupled to the bore 75 of 7" casing
77 and annulus bore 34a is coupled to the top of the
housing 78 by a control line 79 (shown in broken outline)
to allow annulus monitoring.
Reference is now made to Figs. 5a and 5b of the
drawings where it will be seen that the sleeve 76
includes an annular piston 78 which is moveable in the
vertical plane by the application of pressurised
hydraulic fluid to actuating cylinders (not shown)
disposed at each side of the piston. From Fig. 5a it
will be seen that when the sleeve 76 is in the lower
position the flapper plate 72 is also in the lower
position closing the production bore 34a and providing
communication with the annulus access bore 36a. When
the sleeve is moved in the upper position as shown in
Fig. 5b the flapper plate 72 is in an upright position
located in a recess 80 whereby access to the production
bore 34a is open, through the sleeve and, simultaneously,
the sleeve 76 extends within the housing 70 to the top
and, as can be seen, isolates access to the smaller
annulus axis bore 36a. The area on the underside of the
sleeve 76 exposed to wellbore pressure is made
deliberately larger than a similar area on the upper side
of the sleeve so that, in the event of a failure of the
hydraulic system, the resultant force on the sleeve is
upward to ensure that the sleeve takes the position in
the upper location shown in Fig. 5b which provides access
to the production bore.
Reference is now made to Figs. 6a, 6b and 7a and 7b
of the drawings which depict longitudinal sectional and
cross-sectional views through a bore selector apparatus
82 in accordance with a further embodiment of the present
invention. In this case, the bore selector apparatus 82
can be set to allow access to a 2" annulus bore or a 6"
production bore from a single bore 44 as will now be
described.
Reference is first made to Figs. 6a and 6b which
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depicts the bore selector set for providing access to the
6" production bore 34a. In this embodiment like
numerals will refer to like parts.
With regard to Figs. 6a and 6b it will be seen that
the flapper plate 72 is pivotally mounted at one end 80
for pivotal movement. between a substantially upright
position as shown in Fig. 6a where access to the
production bore 34a is allowed and an inclined position,
as best seen in Figs. 7a and 7b, where the flapper plate
restricts access through bore 34a and allows access to
annulus bore 36a.
Still referring to Figs. 6a and 6b, it will be seen
that a pair of cam plates 86 constrained by connections
to vertical rods 88 (Figs. 6b) are moveable along the
longitudinal access of the bore selector apparatus 82
(which typically coincides with the vertical plane) by
the application of pressurised hydraulic fluid to a pair
of actuating cylinders 90 which are disposed at each side
of the cam plates as best seen in Fig. 6b.
A cam slot 92 is provided in each cam plate 86 and a
cam pin 94 is provided at each side of the flapper plate
72 and engages with the cam slot 92 in each cam plate 86.
Thus, when the cylinders 90 are actuated to cause axial
travel of the cam plates, this results in an interaction
between the cam slots 92 and cam pins 94 which cause a
change in the inclination of the flapper plate 72. The
pistons 91 of the actuating cylinders 90 are connected to
the cam plates 80 by end blocks 96 (Fig. 6b, Fig. 7b.
As shown in Figs. 6a and 6b the pistons 91 remain in
a lower position, such that the flapper plate 72 is
substantially vertical, closing the annulus bore 36a and
allowing access to the production bore 34a. When the
pistons 91 are actuated to move the cam plates 86
upwards, as shown in Fig. 7a, the engagement of the cam
pin 94 with the cam slots 92 causes the flapper plate 72
to move across the interior of the bore selector
apparatus 82 to lie in the inclined position shown in
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Fig. 7b so that it allows access to the 2~~ annulus bore
36a and, simultaneously, prevents access to the 6°
production bore 34a. Reactuation of the cylinders 90 to
move downwards will return the flapper plate to the
position shown in Figs. 6a,6b.
It will be appreciated that various modifications
may be made to the embodiments hereinbefore described
without departing from the scope of the invention.
For example, it will be appreciated that any of the
embodiments hereinabove described may be used with an
annulus bore and a production bore of different sizes.
With regard to the embodiment shown in Figs. 6a,6b,7a and
7b, it will be understood that an annular piston can
replace the dual hydraulic actuating means. In addition,
an annular piston (cylinder) may replace the cam plates,
with a groove or slot machined in the inner surface of
the piston, for receiving pins from the flapper plate so
that, as the annular piston is actuated to rise and fall,
the flapper plate moves between positions as shown in
Figs. 6a,6b and in Figs. 7a,7b.
Advantages of the invention include; the bore
selection apparatus provides improved access from a
monobore riser to either a production bore or annulus
bore without the need for a whipstock, the operation of
bore selection apparatus can be controlled from surface
and the bore selection apparatus can be used in
combination with a dual bore sub-sea test tree to provide
a well controlled system satisfying statutory
requirements.
