Note: Descriptions are shown in the official language in which they were submitted.
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SPOOLABLE RISER HANGER
FIELD OF THE INVENTION
The present invention relates to a spoolable riser hanger for supporting
spoolable media and, particularly but not exclusively, to a hanger for use
with
spoolable coil tubing. The invention is particularly suitable for use with
coil tubing
when the coil tubing is used as a riser.
BACKGROUND TO THE INVENTION
In the oil and gas industry, risers are well known and are used to couple a
wellhead to a platform work surface. When a platform is floating, vertical
movement
is compensated by well-known compensation mechanisms so that stresses on the
riser due to ocean movement do not cause the riser to break or otherwise
become
damaged. Risers can be very large, heavy and expensive. In many cases the
riser
diameter can be of the order of 36 inches or more. These risers are difficult
to
manoeuvre particularly from floating vessels because of the size and weight of
the
riser. In applicant's WO 2009/016346, there is disclosed a novel coil tubing
riser
system which obviates various problems with the traditional types of risers.
In order to be able to use a spoolable riser offshore at depths greater than
the
depth of one roll of coil tubing, the coil tubing must be joined in the riser
system,
which will typically require the deployed riser section to be suspended and
supported
while a further riser section is connected thereto.
SUMMARY OF THE INVENTION
An aspect of the present invention relates to a spoolable riser hanger which
engages the spoolable medium which passes through the riser hanger and
suspends
the medium therein.
CONFIRMATION COPY
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In one aspect the spoolable medium comprises coil tubing and the hanger
defines a coil tubing hanger which is used to suspend the coil tubing.
The coil tubing is used as a coil tubing riser and when the coil tubing riser
is
deployed from a floating vessel, the tubing hanger is supported in a
compensated
frame which is also located on the vessel.
Alternatively, the tubing hanger may be used on a land well where the coil
tubing does not need to function as a riser.
The hanger may be retrievable and may be used to permit lengths of coil
tubing to be joined to make a longer riser.
The tubing hanger may comprise actuatable gripping means which are
moveable to engage and grip the coil tubing and suspend said tubing within the
coil
tubing hanger. The actuatable gripping means may comprise slips which are
vertically and axially moveable to grip the coil tubing within the hanger.
The coil tuning riser hanger may comprise a sealing arrangement for
engaging the coiled tubing being supported by the hanger. The sealing
arrangement
may be adapted to retain fluid pressure associated with the coil tubing. The
sealing
arrangement may be adapted to retain fluid pressure within a region defined
between
the riser hanger and the coil tubing, such as an annular region. The sealing
arrangement may be adapted to retain fluid pressure within the coil tubing.
The tubing hanger may comprise seals for retaining fluid pressure within the
coil tubing, i.e., within the internal tubing bore, when the coil tubing is
being
suspended, for example when being suspended in preparation for or while being
joined to a further length of coil tubing.
The tubing hanger may comprise a bend stiffener stress joint adapted to
minimise stress points on an associated tubing, for example when the tubing is
being
deployed through the hanger or when the tubing is supported by the hanger. The
bend stiffener may be secured to the hanger via a support frame, such as a
compensated support frame.
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In another aspect of the present invention, there is provided a coil tubing
riser
hanger for use with a coil tubing riser, said coil tubing riser hanger being
adapted to
be coupled to a compensated frame and having gripping means for engaging the
coil
tubing riser to suspend and support the coil tubing in the hanger and seal
means for
retaining bore pressure on the coil tubing riser when suspended in the hanger.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other aspects of the present invention will now be described, by
way of example only, with reference to the accompanying drawings, in which:
Fig. 1 is a schematic diagram of the coil tubing riser system used with a
vessel and incorporating a coil tubing hanger, in accordance with an
embodiment of
the invention, and
Fig. 2 is an enlarged longitudinal sectional view of part of the Fig. 1
illustrating
the coil tubing hanger with a coil tubing riser suspended in the hanger.
DETAILED DESCRIPTION OF THE DRAWINGS
Reference is first made to Fig. 1 of the drawings which depicts part of a coil
tubing riser system, generally indicated by reference numeral 10, used on a
floating
vessel 12 with a moon pool 14 beneath a moveable vessel floor 16. The entire
coil
tubing riser system is not described but it includes a compensated frame 18
which is
coupled via cable 20 to a compensator (not shown) for compensating for vessel
movement. The complete coil tubing riser system is disclosed in more detail in
applicant's WO 20091016346, the description of which is not essential to the
understanding of the present invention.
The frame 18 supports an injection head 22 which is coupled by a connector
24 to a coil tubing make-up window 25 which depicts free ends 26,28 of coil
tubing
27 to be connected by a coil tubing connector (not shown) to allow longer coil
tubing
risers to be made up in deep water, i.e. water of such a depth that a single
spool of
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coil tubing cannot operate satisfactorily as a riser and requires to be joined
to another
length of coil tubing. A connector for this purpose is disclosed in
applicant's co-
pending UK patent application no. 0811638.6, but a detailed description of
this
connector is not essential for the understanding of the present invention.
The coil tubing make-up window 25 is coupled to the top 30 of the tubing
hanger 32. The tubing hanger 32 includes a hanger housing portion 34 connected
to
the frame 18 and a lower stress joint 36 for minimising the stress on the coil
tubing
riser as will be later described in detail.
The coil tubing 27 is fed through an umbilical feeding device 40 and through
the vessel floor 16 into the moon pool 14. The umbilical feeding device 40 is
rotatable about a vertical axis 42 to feed umbilicals 44 around the coil
tubing 27 as it
is injected by the injector head 22 into the ocean to provide a composite
riser 46
formed of the coil tubing 27 and the umbilicals 44.
Reference is now made to Fig. 2 of the drawings which depicts an enlarged
longitudinal sectional view of the tubing hanger 32 mounted on the compensated
frame 18. The tubing hanger main housing 34 is coupled to the frame 18 by a
flange
46, and is coupled to a top connector 48 and to the lower bend stiffener
stress joint
36. The connector 48 has two parts: a lower connecting joint 48a which is
coupled to
the housing 34 by nuts 50; and a top connecting joint 48b which is coupled to
the
lower joint 48a and which is adapted, in use, to be coupled to the bottom of
the
injector 22. Connectors 48a,48b, main housing 34 and stress joint 36 all have
separate bores which are coaxially aligned to form a common bore 52, when
assembled as shown in Fig. 2. The bore 52 receives coil tubing 27 from the
injector
head.
The main housing 34 contains a coil tubing gripping arrangement which is
provided by a pair of slips 54a,54b which are located in respect of chambers
56a,56b. One of the slips 54a is shown in the upper position in chamber 56a
and in
this position is spaced from the wall of the coil tubing 27 and the other of
the slips
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54b is shown in a lower position in chamber 56b where it is engaged with the
wall of
the coil tubing 27. The slips 54a,54b may be actuated hydraulically to move
between
the upper and lower positions.
A safety collar 58 is shown which is axially secured relative to the string 27
5 and which, in use, moves downwardly with the string 27 so that the bottom of
the
collar 58 engages the top of the slips 54a and 54b and moves the slips 54a,54b
from
the disengaged position (slip 54a) to the engaged position (slip 54b) to
suspend the
coil tubing. Thus, in the event of the slips failing to actuate to engage the
string 27,
the string 27 will begin to fall through the hanger until the safety collar 58
engages
the slips 54a,54b to initiate engagement.
Therefore, in slip position 54b the coil tubing is suspended in the coil
tubing
hanger 32. To ensure that bore pressure is retained in the bore 52 a seal
block 60
with seals 62 is located within connector 48a and seals 64 are also located
between
the upper and lower connectors 48a and 46b. Thus, it will be understood from
the
foregoing description that the coil tubing hanger can be actuated to support
the
weight of the coil tubing in the slips and the seals 62,64 retain bore
pressure while an
additional length of coil tubing is connected to the suspended portion in the
coil
tubing hanger to allow the appropriate length of coil tubing riser to be made
up.
Various modifications may be made to the embodiment hereinbefore
described without departing from the scope of the invention. For example, the
coil
tubing hanger need not be used with a compensated frame and the hanger can be
used with any spoolable medium, for example, plastic or a metal/plastic
composite,
other than coil tubing. The collar 58 can be actuated by any suitable means
other
than hydraulic means, for example electrical or mechanical means. Moreover,
the
bend stiffener stress joint 36 may be provided by a single piece or by a two-
piece
split connector as shown in Fig. 2.
Advantages of the invention are that the coil tubing hanger permits coil
tubing
to be used as a riser and made up into lengths suitable for deep water use.
The coil
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tubing hanger can support the weight of the riser and allows the riser to be
retrievable as well, the bore 50 being large enough to accommodate the width
of the
joint making up the longer riser. The spoolable riser hanger may be used with
spoolable media, other than coil tubing, for example plastic and the hanger
can be
used in other applications other than floating vessels, for example on land.
The riser
provides an efficient way of suspending the spoolable medium/coil tubing and
the
design allows for bore pressure to be suitably sealed whilst riser joints are
being
made up.
