U.S. patent application number 15/992027 was filed with the patent office on 2019-03-14 for mini-riser for scr coiled tubing and wireline interventions.
The applicant listed for this patent is Krzysztof Jan Wajnikonis. Invention is credited to Krzysztof Jan Wajnikonis.
Application Number | 20190078396 15/992027 |
Document ID | / |
Family ID | 57393157 |
Filed Date | 2019-03-14 |
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United States Patent
Application |
20190078396 |
Kind Code |
A1 |
Wajnikonis; Krzysztof Jan |
March 14, 2019 |
MINI-RISER FOR SCR COILED TUBING AND WIRELINE INTERVENTIONS
Abstract
A novel configuration of lightly tensioned or substantially
untensioned, i.e. substantially compliant mini-riser is provided to
facilitate coiled tubing and/or wireline interventions in rigid
catenary riser installations. Those can include in particular
clearing hydrates that may accidentally plug risers or subsea
pipelines connected to those risers. Existing Intervention Y units
can be used, or they can be modified to suit design condition of
particular installations. The mini-riser can be used with flexible
joint hang-offs, Titanium Stress Joint hang-offs or with novel
Spoolflex hang-offs.
Inventors: |
Wajnikonis; Krzysztof Jan;
(Rosharon, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wajnikonis; Krzysztof Jan |
Fresno |
TX |
US |
|
|
Family ID: |
57393157 |
Appl. No.: |
15/992027 |
Filed: |
May 29, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15575598 |
Nov 20, 2017 |
10024121 |
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PCT/US16/34532 |
May 27, 2016 |
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15992027 |
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62166838 |
May 27, 2015 |
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62168861 |
May 31, 2015 |
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62185749 |
Jun 29, 2015 |
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62189437 |
Jul 7, 2015 |
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62201157 |
Aug 5, 2015 |
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62214265 |
Sep 4, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 19/004 20130101;
E21B 19/006 20130101; E21B 17/01 20130101; E21B 43/0107 20130101;
E21B 17/015 20130101 |
International
Class: |
E21B 17/01 20060101
E21B017/01; E21B 19/00 20060101 E21B019/00; E21B 43/01 20060101
E21B043/01 |
Claims
1. A riser assembly comprising: an Intervention `Y` fitting
designed for coiled tubing or wireline operations, a mini-riser
connected by a lower end of said mini-riser to a service flange of
said Intervention `Y` fitting designed for said coiled tubing or
said wireline operations, said Intervention `Y` fitting designed
for said coiled tubing or said wireline operations being installed
in a general area of and connected to a top of a riser including at
least one of a rigid catenary riser, or a metallic catenary riser,
or a steel catenary riser, or a steel lazy wave riser, or a
titanium catenary riser, or a Chinese lantern riser, or a bottom
weighed riser, or a fiber reinforced plastic catenary riser, or a
fiber reinforced plastic lazy wave riser; wherein said mini-riser
is connected above a water surface by an upper end of said
mini-riser to a servicing deck attached to at least one of a
platform, or a spread moored vessel, or a turret moored vessel, or
a disconnectable turret vessel, or an offshore support vessel, or a
diving support vessel, or a multipurpose support vessel, or a
barge, or a floating buoy, or a submerged buoy, and wherein said
mini-riser is substantially compliant between said upper end of
said mini-riser and said lower end of said mini-riser.
2. The riser assembly according to claim 1, wherein the
Intervention `Y` fitting designed for the coiled tubing or the
wireline operations is installed on a steel catenary riser type
flexible joint.
3. The riser assembly according to claim 1, wherein the
Intervention `Y` fitting designed for the coiled tubing or the
wireline operations is installed on a tapered transition joint.
4. The riser assembly according to claim 1, wherein the
Intervention `Y` fitting designed for the coiled tubing or the
wireline operations is installed on a Titanium Stress Joint.
5. The riser assembly according to claim 1, wherein the
Intervention `Y` fitting designed for the coiled tubing or the
wireline operations is used with a Spoolflex jumper.
6. The riser assembly according to claim 1, wherein the
Intervention `Y` fitting designed for the coiled tubing or the
wireline operations is incorporated in a hang-off clamp of a
Spoolflex jumper.
7. The riser assembly according to claim 1, wherein the mini-riser
utilizes rigid joints, including metallic joints made of titanium,
or steel, or nickel based alloys, or aluminum.
8. The riser assembly according to claim 1, wherein the mini-riser
utilizes fiber reinforced plastics that utilize carbon fiber, or
graphite fiber, or aramid fiber, or glass fiber.
9. The riser assembly according to claim 1, wherein the mini-riser
utilizes steel, or duplex, or super-duplex, or nickel based alloys,
or corrosion resistant alloys.
10. The riser assembly according to claim 1, wherein the mini-riser
can be lined, or clad, or weld-overlaid with steel, or with duplex,
or with super-duplex, or with nickel based alloys, or with
corrosion resistant alloys.
11. The riser assembly according to claim 1, wherein an effective
tension is essentially designed to be close to zero essentially in
a region of the lower end of the mini-riser.
12. The riser assembly according to claim 1, wherein a maximum
effective tension along the mini-riser does not exceed 15 times a
submerged weight of said mini-riser.
13. The riser assembly according to claim 1, wherein a pre-bend
segment is used in a region of the lower end of the mini-riser.
14. The riser assembly according to claim 1, wherein one or more
clamping devices are used on the mini-riser.
15. The riser assembly according to claim 1, wherein one or more
vortex suppression devices are used on the mini-riser.
16. The riser assembly according to claim 1, wherein the mini-riser
is at least partly sheltered from actions of waves and
currents.
17. The riser assembly according to claim 1, wherein the upper end
of the mini-riser is supported from a vessel on which the
Intervention `Y` fitting designed for the coiled tubing or the
wireline operations is installed.
18. The riser assembly according to claim 1, wherein the upper end
of the mini-riser is supported from a different vessel than a
vessel on which the Intervention `Y` fitting designed for the
coiled tubing or the wireline operations is installed.
Description
[0001] This application is a continuation in part application of
U.S. Utility patent application Ser. No. 15/575,598 filed on Nov.
20, 2017, pending. This specification claims the benefit of
priority related to PCT Patent Application PCT/US16/34532 filed May
27, 2016, U.S. Provisional Patent Applications No. 62/166,838 filed
on May 27, 2015 No. 62/168,861 filed on May 31, 2015, 62/185,749 of
Jun. 29, 2015, No. 62/189,437 filed on Jul. 7, 2015, No. 62/201,157
filed on Aug. 5, 2015, 62/214,265 of Sep. 4, 2015, and of U.S.
Utility patent application Ser. No. 15/575,598 filed on Nov. 20,
2017.
TECHNICAL FIELD
[0002] This invention relates to a novel configuration of a
mini-riser that can be used for servicing catenary risers fitted
with intervention-Y devices mounted in hang-off regions of various
types of catenary risers.
BACKGROUND ART
[0003] Rigid risers are important devices used in offshore
engineering to transfer fluids in both directions between the
seabed and the vicinity of the sea surface. In particular
production risers are used to transport hydro-carbons from the
seabed to fixed and/or floating platforms or vessels.
[0004] During the life of production risers the flow of
hydrocarbons can be accidentally stopped by formation of hydrate
plugs that can be difficult to clear--it may take several months to
clear a hydrate plug. Considerable costs can be incurred during the
efforts to restore the production that add to the losses caused by
the interruptions in the production.
[0005] Intervention-Y units are occasionally installed on catenary
production risers in order to facilitate coiled tubing and/or
wireline operations. Coiled tubing and/or wirelines can be used to
clear hydrate plugs for example by dissolving them with methanol.
The Intervention-Y installations are generally regarded as optional
and are rare. They are however missed when they become necessary
and are not installed. The reasons for the above mentioned rare use
are two-fold: [0006] additional investment costs, [0007] there is
at present no easy, established way of utilizing the
intervention-Ys. Steel catenary riser hang-offs tend to be located
near the keel depths of floating platforms (approximately 100 ft to
300 ft below the sea surface), and Intervention Ys are difficult to
access from the surface through the layers of the water column
typically featuring the strongest wave and current actions. Adding
intervention-Ys to existing risers later during the life of the
field may be difficult and costly, even if feasible.
[0008] At this time two known approaches tend to be considered
while adding a servicing riser between an Intervention Y unit and
installations on the surface: [0009] A provisional multi-span riser
installation, [0010] A provisional tensioned riser/jumper
installation (for example approximately 200 kip top tension).
Neither of the about provisional methods are straightforward. It
may be difficult to provide provisional locations for supporting
clamps. Also Steel Catenary Risers (SCRs) tend to be inclined
around 10.degree. to the vertical in the regions of their hang-offs
and the change of direction between that tangent to the SCR pipe
and the service flange of an Intervention Y and the vertical
direction required for access to the servicing equipment above the
sea surface. Often the proximity of essentially vertical platform
column, truss structure, pontoon or side wall often come in the
way. The above listed types of difficulties often arise when either
of the above listed provisional riser installations are considered.
For a provisional tensioned riser/jumper an additional difficulty
may be on the side of the structural strength limitations of an
Intervention Y already installed.
[0011] The mini-riser configurations suggested herein are designed
to overcome the above highlighted difficulties.
[0012] Intervention Ys considered herein are those suitable to be
installed on rigid catenary risers, or metallic catenary risers,
SCRs, Lazy Wave SCRs or Steel Lazy Wave Risers (SLWRs), or a
titanium catenary risers, or a Chinese lantern risers, or a bottom
weighed risers, or a fiber reinforced plastic catenary risers, or a
fiber reinforced plastic lazy wave risers.
[0013] Rigid catenary risers, or metallic catenary risers, SCRs,
Lazy Wave SCRs or SLWRs, or a titanium catenary risers, or a
Chinese lantern risers, or a bottom weighed risers, or a fiber
reinforced plastic catenary risers, or a fiber reinforced plastic
lazy wave risers are essentially variations of SCRs and without a
use of Intervention Ys like those described herein coiled tubing
or/and wireline operations would not be possible in those risers.
It is known to anybody skilled in the art that all the above
highlighted risers generally connect to subsea pipelines provided
on their other ends with Pipeline End Manifolds (PLEMs), Pipeline
End Terminations (PLETs) or skids used to connect subsea pipelines
to continuing subsea pipelines. Those in turn are usually connected
to subsea wells using jumpers.
[0014] It is also known to anybody skilled in the art that subsea
wells can be accessed from the surface using tensioned or
freestanding drilling, completion or workover risers that allow
direct drilling, coiled tubing, wireline operations and tool access
essentially vertically from the surface using standard intervention
equipment. However, accessing subsea pipelines from the side of
subsea wells is even more difficult than it is from the tops of
rigid catenary risers, or a metallic catenary risers, SCRs, Lazy
Wave SCRs or SLWRs, or a titanium catenary risers, or a Chinese
lantern risers, or a bottom weighed risers, or a fiber reinforced
plastic catenary risers, or a fiber reinforced plastic lazy wave
risers, and that provides an option for utilizing mini-risers
according to this invention.
[0015] It immediately follows for anybody skilled in the art that
intervention operations using top tensioned or freestanding risers
in subsea wells or in surface wells are not of a concern with
regard to the use of this invention.
DISCLOSURE OF INVENTION
[0016] This invention involves a mini-riser connected by a lower
end of said mini-riser to a service flange of an Intervention `Y`
fitting designed for coiled tubing or wireline operations, said
Intervention `Y` fitting designed for said coiled tubing or said
wireline operations installed in a general area of and connected to
a top of a riser including at least one of a rigid catenary riser,
or a metallic catenary riser, or a steel catenary riser, or a or a
steel lazy wave riser, or a titanium catenary riser, or a Chinese
lantern riser, or a bottom weighed riser, or a fiber reinforced
plastic catenary riser, or a fiber reinforced plastic lazy wave
riser and said mini-riser is connected above a water surface by an
upper end of said mini-riser to a servicing deck attached to at
least one of a platform, or a spread moored vessel, or a turret
moored vessel, or a disconnectable turret vessel, or an offshore
support vessel, or a diving support vessel, or a multipurpose
support vessel, or a barge, or a floating buoy, or a submerged
buoy, whereas said mini-riser is substantially compliant between
said upper end of said mini-riser and said lower end of said
mini-riser.
[0017] Novel mini-risers can be built out of steel, duplex,
super-duplex, nickel based alloys, Corrosion Resistant Alloys
(CRAs), etc. or from other high elastic modulus high strength
materials. They can be lined, clad or weld-overlaid with other
materials like the above listed materials, including the CRAs.
[0018] Optional Intervention `Y` fittings (`Ys`) used with this
invention need to be able to sustain static and dynamic loads in
the mini-risers, platform piping or in novel Spoolflex hang-off
jumpers, see U.S. Utility patent application Ser. No. 15/575,598
filed Nov. 20, 2017 and herein. An alternative name also used
herein (and previously) to describe novel Spoolflex hang-offs is
Short Jumper Spool (SJS) hang-offs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] A selection of multiple implementations of this invention is
illustrated on FIGS. 1 and 2.
[0020] FIG. 1 depicts schematically examples of uses of
Intervention Ys with multiple novel Spoolflex hang-off
configurations used on various offshore structures. Intervention Ys
are depicted as installed and/or as options for possible
installations. The uses of Intervention Ys with known SCR Hang-offs
like SCR type flexible joints or Titanium Stress Joints (TSJs) in
general on a tapered transition joint are analogous and they are
not depicted herein, because they are well known to those skilled
in the art.
[0021] FIG. 2 depicts schematically a configuration of a novel
mini-riser system suggested for coiled tubing or wireline
interventions into risers for use with Intervention `Ys`.
MODES OF CARRYING OUT THE INVENTION
[0022] This invention is explained further by reference to FIGS. 1
and 2.
[0023] FIG. 1 depicts schematically Spoolflex (SJS) 655 through 659
and 6155 through 6160 used in riser hang-off configurations on
various types of floaters. SJSs shown can be used on any kind of
floaters discussed herein, and on turrets, disconnectable buoys,
floating buoys or submerged buoys 630.
[0024] SJSs 655, 656 and 659 use very short straight segments
between bends, just long enough to use connectors. Non-descending
SJSs 655, 656 differ with the number of 90.degree. bends
incorporated in their partial loops--one for SJS 655 and two for
SJS 656. SJSs 655, 656, 657, 658, 6155, 6156 and 6157 are
ascending. SJS 659 features an ascending/descending configuration
with a part of its entry spool, the one bend partial loop and a
part of its exit spool having negative slope angle in the floater
system of coordinates. SJSs 6158, 6159 and 6160 feature
ascending/descending geometries, whereas the top parts of exit
spools shown are arranged along lines tangent to their risers
corresponding at the pivot locations. Such configurations can be
rotated around the common riser--end of exit spool axes to
arbitrary azimuth angles for more convenient design. In fact the
essentially ascending/descending designs of SJS 6158 and 6159
feature considerable reductions of the absolute values of the
negative slopes and of the lengths of the negatively sloped
segments because of such rotations in comparison with their
original design orientation (not shown) that was similar to the
entry spool orientation of SJS 6160. SJSs 6156 and 6157 demonstrate
that all the SJSs shown on FIG. 1 can be optionally suspended with
help of hang-off clamps 650. SJS 6160 features considerably larger
footprint than do the other SJSs featured on FIG. 1.
[0025] SJSs 657, 658, 6155, 6156, 6157, 6158 and 6159 feature the
minimum footprints feasible while utilizing 5 OD bends--they have
no straight segments in the partial loops, where applicable or
between the entry spool, the partial loop and the exit spool, where
applicable. SJSs 6158 and 6159 use slightly bigger outside diameter
than do all the other SJSs featured herein and their dimensions are
proportionally bigger. Exit spool 695 shows an alternative exit
spool configuration that is one of exit spool configurations
feasible with most SJSs shown on FIG. 1.
[0026] Optional Intervention `Ys` 6270, 6271, 6272, 6273, 6274 and
6275 depicted demonstrate that the use of Intervention `Ys` may be
feasible for all the configurations herein that do not utilize
hang-off clamps 650. For the latter configurations it can be in
some cases feasible to incorporate a part of Intervention `Y`
fittings with the diverter inside hang-off clamps 650 and to place
service valve unit 6175, 6176 on top of the pivot arrangements.
Ball joint pivots 640, flex joint pivots 641, gimbal pivots 142,
242, 342, 442 and many other pivot arrangements can be used to
replace the pivot arrangements depicted on FIG. 1. All SJSs shown
on FIG. 1 can optionally utilize hang-off clamps 550 and most can
utilize optional Intervention `Ys` 6270, 6271, 6272, 6273, 6274
subject to the availability of essentially straight access above
the `Ys`.
[0027] FIG. 2 shows schematically an optional configuration of
rigid catenary riser or SCR servicing equipment that can be used
during coiled tubing or wireline interventions.
[0028] Optional Intervention `Y` fitting 9270 is shown
schematically on FIG. 2, the SCR, the riser porch and the platform
piping or SJS are omitted for clarity. Sea Water Level (SWL) 4500
is shown schematically on FIG. 2.
[0029] Catenary riser (SCR, SLWR, etc.) intervention service unit
4505 is mounted directly or indirectly in a region of deck 4515 or
on deck 4515 of vessel 4520 and it is optionally supported on the
vessel side or on other structure structurally associated with
vessel 4520. The vessel can be the production platform supporting
the catenary riser to be serviced, like a semisubmersible, TLP,
Spar, etc., an FPSO, etc., an auxiliary support/servicing vessel or
a barge stationary in the vicinity of the production vessel. The
production and the auxiliary/servicing vessel may or may not be
moored to each other. Dynamic positioning can be used.
[0030] Catenary riser intervention service unit 4505 is represented
on FIG. 2 schematically, structural details of its construction are
typical and they can be specified for any particular sets of
functional requirements and design loads by anybody skilled in the
art.
[0031] Vessel (platform) side 4520 is also represented
schematically on FIG. 2. Catenary riser intervention service unit
4505 has its geometrical configuration, structural design and
structural supports customized in each installation case to be
compatible with that of vessel 4520. In case of `portable` generic
intervention service unit 4505, specific shape and structural
support modifications would typically be made in order to customize
the design and the geometry of intervention service unit 4505 for
specific catenary risers (SCRs, flexible risers, etc.) and for use
at any specific installation location on a vessel. Structural
details of such modifications are typical and they can be specified
for any particular sets of functional requirements and design loads
by anybody skilled in the art. Engineering standards, like for
example API RP 2A, and specifications used must be complied with at
all times.
[0032] Catenary riser intervention service unit 4505 can be
dedicated to servicing a particular SCR or a group of SCRs, or it
can be generic, portable, designed for general use with various
catenary risers. The SCRs serviced can be provided with flexible
SJS hang-offs according to this invention, they can be used on
traditional SCRs supported with flex joints or TSJs, or they can be
flexible risers (bonded or unbonded).
[0033] Catenary riser intervention service unit 4505 depicted
schematically on FIG. 2 is mounted on a vessel using supporting
structure 4525 of arbitrary design and welded or otherwise attached
directly or indirectly to a deck of vessel 4515 and to vessel side
4520 or to other structure associated structurally with vessel 4520
using optional brackets 4530. Instead of a side of the vessel, the
servicing equipment can be also located in a moonpool of vessel
4520 or in its general area. Supporting structures such as 4525 and
welding brackets such as 4530 are typical items used offshore and
principles of their design are well known to those skilled in the
art. Optional bearing pad(s) 4531 can be used. Supporting
structures such as 4525 and welding brackets such as 4530 are
designed to adequately interact with the vessel structure,
including its frames, stiffeners, plating, etc. If necessary
optional strengthening plates, etc. (including gusset plates) can
be welded to the vessel deck and/or side and/or inside the vessel
structure. Additional, optional strengthening members can be added
as well. Supporting structure 4525 can be attached to any vessel
deck, at a general area of any vessel deck or to any part of the
vessel structure, as convenient for the intervention operations.
The design needs to take into account the safety of all operations,
the shape to be assumed by mini-riser 4545 during the intervention
operations, the ease of installation of all intervention equipment,
crane access, handling equipment and functional considerations,
etc.
[0034] Coiled tubing 4537 or wireline (also 4537, not shown) is
stored and deployed from storage/deployment package 4535. Package
4535 incorporates all the necessary servicing equipment that is not
represented in detail on FIG. 2. That equipment may involve an
injector, a lubricator (whether or not deployed above or below the
sea surface), the coiled tubing reel, all the electrical,
mechanical, hydraulic, etc. power units, measuring, monitoring and
control equipment, etc. Those will be deployed on decks of vessel
4520 or on other barges or vessels as practicable. Mini servicing
riser 4545 used for interventions is suspended from servicing deck
or servicing table 4510. Mini-riser 4545 can be made up and run
using connectors 4550 or it can be made of flexible pipe and
deployed from a reel, in cases where the design conditions allow
that. The mini-riser joint making up equipment (if installed at
all, it may be optional), optional flexible deployment reel
equipment and all other hardware required are omitted from this
schematic drawing for simplicity. The running of the mini-riser can
be also carried out from a platform dry tree moonpool and
`keel-hauled` outboard in an essentially vertical configuration for
installation in place. If available it can be also run from a
drilling vessel, a J-lay tower or a portable drilling rig. Whether
or not the installation opportunities highlighted above are or are
not readily available, other and often more economical mini-riser
installation arrangements (see further below) can be used
instead.
[0035] Intervention operation described herein can be carried out
using existing Intervention `Y` fitting 9270, or Intervention `Y`
can be retrofitted on any installation originally constructed
without it. Retrofitting of Intervention ` Y` fitting 9270 must be
carried out consistently with widely used repair or/and equipment
upgrade good practice and procedures that are obvious to anybody
skilled in the art.
[0036] In particular, before any existing spool is removed: [0037]
the line must be depressurized, [0038] internal fluids must be
removed from the platform piping and at least the top segments of
the riser, [0039] the disassembly area must be internally separated
with effective separation plug or plugs; [0040] the piping and the
riser must be scrapped and internally cleaned; [0041] external
areas must be cleaned; [0042] etc., consistently with best
engineering and subsea operation practice, legal requirements,
engineering standards and specifications approved by the Company
and Classification Societies, as it is well known to those skilled
in the art.
[0043] After any interfering platform piping or SJS entry spool
segments are removed, the catenary riser flange (typically above a
flex joint, TSJ or flexible riser hang-off) is prepared to accept
optional Intervention `Y` fitting 9270, or in a case there is no
plan to retrofit one, bottom fitting 4560 of mini servicing riser
4545 can be installed directly on top of the catenary riser flange
(typically above a flex joint, TSJ or flexible SJS riser
(Spoolflex) hang-off, not shown).
[0044] Subsequently a new shortened piping spool can be connected
between Intervention `Y` fitting 9270 and the platform piping.
Whenever there is no plans to use an optional Intervention `Y`
fitting 9270, the coiled tubing or wireline servicing operations
can be carried out and after those are completed, and the
replacement piping spool or the original spool removed for the
servicing operation can be reinstalled.
[0045] In a case existing optional Intervention `Y` fitting 9270,
as installed, is structurally inadequate to support design loads on
the intervention equipment, an optional support clamp (not shown
for clarity) can be installed between the Intervention `Y` fitting
at the general area of the low end of the mini-riser. The optional
support clamp can be attached directly to the vessel structure, the
vessel side included, it can utilize the riser porch or riser bank
for support, etc. In cases where there may be difficulties in
designing conventional type of a support, a cradle like support can
be used. A cradle like support can utilize a configuration of one,
two, three, four or more, etc. strengthening legs resulting in
monopod, bipod, tripod, or four or more strengthening legs, etc.,
whereas the legs can be straight or curved legs, optional
strengthening members can be added, etc. Support structures like
those described above can be used on traditional installations of
catenary risers including SCR installations utilizing SCR types of
flex joints and TSJs, where Intervention `Y` fittings are designed
as fixed relative the vessel structure. Any known attachment means
can be used where acceptable as required with the supporting
structure or structures. Those may include clamping, bolting
attachments, thermite welding, helium or argon shield welding,
laser beam welding, hyperbaric welding, friction welding, etc. For
simplicity new Intervention `Y` fitting installations can be
optionally fitted with the supporting structures or they can
preferably be designed to sustain all design loads without a need
for use of optional support structure(s).
[0046] In cases where flexible SCR hang-off featuring SJS(s)
according to this invention is used Intervention `Y` fitting 9270
is fixed to the SCR and it undergoes rotational deflections
together with the top of the SCR. In such installations
Intervention `Y` fitting must be designed to sustain full design
loads imposed on the intervention equipment, or the `vessel side`
ends of the supporting cradle, including monopods, bipods, tripods,
four or more leg structures, etc. must be fixed, directly or
indirectly, to the SCR flange and rotate with the SCR tops, as the
SCR deflects relative the vessel structure.
[0047] It is obvious to anybody skilled in the art that
Intervention `Y` fitting does not need to be designed for the full
survival range of rotational deflections, for which the hang-off is
designed. In a case a tropical cyclone (hurricane) or other storm
passage, extreme loop current event passage, etc. is expected, etc.
mini servicing riser 4545 would be disconnected from the
Intervention `Y` fitting, etc., and all the equipment secured. In
such conditions mini servicing riser 4545 could be also optionally
disconnected from its service unit 4505 as required. It can be
subsequently retrieved on deck of the vessel or platform, a support
vessel, etc., it can be wet stored on the seabed, fitted with
additional floatation on one end and anchored to the seabed or
moored to other subsea equipment and stored at a safe water depth
until the tropical cyclone or other condition, etc. has passed.
[0048] The design shape for mini servicing riser 4545 to assume
should be as direct and straight as possible, but in general a
gentle `S` shape may be unavoidable, as shown on FIG. 2. The top
segments of SCRs are generally inclined at various angles to the
vertical (often close to 10.degree.), but flexible risers can be
inclined to the vertical at both larger and smaller angles. Mini
servicing riser 4545 should be as closely aligned with the riser
axis as possible, which will often favor a use of pre-bent lower
joint or joints. A use of such pre-bend joints is one of the
reasons for designing mini servicing riser 4545 for small effective
tensions, which is recommended where feasible (see further
below).
[0049] Mini servicing riser 4545 would preferably be lead outboard
of all the vessel structure, vessel piping, etc., but exceptions
from that recommendation are by all means acceptable. For example a
part of the mini-riser can be lead inside a truss structure of a
truss Spar, inside some piping, etc. Where that is the case, the
entire mini servicing riser may be `threaded` along its
installation path required during the installation operation, or it
can be installed in segments. In the latter case some connectors
4550 may be made-up after all segments of mini-riser 4545 have been
located essentially along their desired installation path.
[0050] Connectors 4550 can be of any type convenient. Simple
threaded `drill-pipe` like connectors can be used, Merlin.TM.
connectors or their third party competitors, upgrades of the
Merlin.TM. family connectors designed to transfer high torsional
loads structurally, flanged connections, connectors with mating
sides clamped together, collet connectors, etc. can be used, as
functionally acceptable.
[0051] In a case any curved or straight segment(s) of mini-riser
4545 come into a proximity to the vessel structure, to any piping,
I-Tubes, etc. one or more clamping devices well known to those
skilled in the art can be used. In some cases a use of temporary
distance clamping may be acceptable and recommended in order to
prevent rubbing or clashing. It may be acceptable to use (a) light
weight provisional type(s) of clamp(s) for that purpose, if
acceptable according to Company guidelines and standard engineering
practice. Optionally the temporary distance clamping arrangement
may have compliant characteristics. It may be acceptable to use
elastomeric material(s), fiber reinforced or not reinforced plastic
materials to build such temporary clamp(s), wood for components
loaded in compression only, high strength webbing straps (like
those made off aramid fibers, ultra high molecular weight
polyethylene like Spectra, Amsteel, etc. for attachments, etc. It
is recommended that in cases where webbing, fiber ropes, etc. is
(are) used for attachment, such attachment provisions should
include independent components at least doubled for redundancy. For
example a temporary clamping arrangement should include at least
two independent webbing sets for the attachment to the mini-riser,
two independent webbing sets for the attachment to the vessel
structural element and two independent webbing, steel cable, etc.
sets wound around, in a `figure eight` or equivalent temporarily
clamping directly the mini-riser and the vessel structural element
in the area of the temporary clamp. The webbing or other
arrangement may be optionally designed and calibrated for automatic
disconnection or rapture in a case of an accidental overload.
Calibrated `weak link(s)` can be used for that purpose. It is
understood here, that if acceptable at all, such temporary clamp(s)
would not necessarily carry any important structural loads; they
could be essentially used as distance spacers, or similar.
[0052] In a case an intervention is carried out with a riser or a
subsea pipeline blocked internally, all the preparation operations
including pigging must be safely carried out from the top end, as
if the riser system were not piggable. For safety reasons all the
upstream pressures should be blead before the intervention
operations or extra secure safety plugs must be installed
internally in order to safely separate any possibly pressurized
segments of riser/flowline system.
[0053] An economical way to install mini-riser 4545 is to assemble
the mini-riser on deck of a small barge or support vessel.
Mini-riser 4545 can be provided with additional buoyancy, and
launched from deck in the S-lay mode. Davit-lift like assembly or
an assembly utilizing provisional outboard outriggers can be
carried out instead outboard of a small barge or a support vessel,
etc. The above or similar techniques can be used in order to
gradually launch the mini-riser to a surface or an off-surface
mode. Launching from deck can be used, or an optional ramp can be
used that can be inclined or not inclined at an acute angle to the
deck. Onshore connection and launching from a beach or from a quay
would work as well. If applicable the mini-riser can be towed from
the onshore or offshore launching location, to the field, up-ended
and connected to the Intervention `Y` fitting. All these and other
installation methods are well known to those skilled in the art and
need not be described further.
[0054] Mini-riser 4545 can utilize rigid joints, like for example
metallic joints made of titanium, steel, nickel based alloys,
aluminum, etc. Mini-riser joints can be also made of Fiber
Reinforced Plastics (FRPs) that utilize carbon fiber, graphite
fiber, aramid (including Kevlar.RTM.) fiber, glass fiber, etc. The
use of titanium, FRP joints or flexible pipe is preferred because
of their superior bending flexibilities. Achieving a suitable
bending flexibility of mini-riser 4545 is the key objective of this
design. Mini-riser 4545 is suspended from the top using connector
4570 (or flange).
[0055] It is recommended that mini-riser 4545 be very lightly
tensioned, where acceptable, i.e. that the effective tension at the
Intervention `Y` fitting connector 4555 (or flange) be close to
zero, so that the mini-riser remains compliant in all its design
conditions. If necessary and safe from environmental protection
point of view connector 4555 should be designed for an automatic
disconnection in a case of exceeding its design parameters, like
for example maximum tension or/and the maximum deflection angle
between the min-riser and the axis of the service branch of
Intervention `Y` 9270 and any line pressure must be contained. Such
a provision may be necessary for example in a case servicing unit
4505 is supported by a different vessel than that on which the
catenary riser is installed. In such a case one or two gate
valve(s), if used, in Intervention `Y` fitting 9270 may be
customized for emergency shearing of coiled tubing or wireline
inserted into mini servicing riser 4545. Other disconnection
arrangements can also be used.
[0056] Mini-riser 4545 be also lightly tensioned, with maximum
effective tension along its length not exceeding for example 2.5
times, or between 5 and 15 times the submerged weight of mini-riser
4545 provided with all equipment it is designed to be used
with.
[0057] Covering mini-riser 4545 with positively buoyant coating
and/or floatation clamps 4565 in order to achieve the desired
tension distribution along its length, which in particular could be
essentially neutrally buoyant, or it could be tensioned by its
controlled self-weight submerged. The effective length deployed is
controlled with appropriate selection of the lengths of the joints
deployed, including pup-joints, but additional fine adjustments of
the length on mini-riser 4545 can be made by utilizing optional
spacer or spacers, optional jacking equipment (hydraulic, screw
type, etc.). Mini-riser can be optionally top tensioned, if desired
so. Optional top tensioning arrangement (not shown) can be used for
that purpose, if required.
[0058] The ends of mini-riser 4545 can be optionally provided with
stepped or tapered stress joints, bending stiffeners, bending
restrictors, etc., as required, item 4560 at the bottom end and/or
item 4575 at the top end. In a case mini-riser 4545 is designed to
service a range of different sizes of catenary risers, its low end
connection 4555 incorporates an adapter to fit any particular
flange of the equipment serviced (not shown separately). The
adapter will incorporate in its design suitable gradual transition
in its internal diameter.
[0059] Optional protection from VIVs, if required, can be provided
by strakes or 3-D dampers 4580, fairings 4585 or any other
effective VIV suppressor or protector. Mini-riser 4545 or its
segments can be also designed to be sheltered from the action of
wave and currents.
[0060] All the components of the mini-riser systems have to be
designed with care and safety in mind. Utilizing relevant sections
of industry workover riser codes, recommended practices and
specifications should be consulted and used, wherever
applicable.
[0061] Oil States Industries, Inc. (OSI) for example provide
designs of Intervention `Y` fitting and diverter plug removal
tooling. That OSI equipment, or similar equipment can be used with
this invention, or design modifications to OSI, or similar,
Intervention `Y` fittings can be included in the design. Also it
may be feasible to design coiled tubing mounted tooling for
optional removal of the diverter plug from the Intervention `Y`
fitting from the surface using mini service riser 4545 for access,
instead of using equipment that is already available commercially.
Any other suitable catenary riser intervention arrangement can be
used instead of that depicted on FIG. 2, if so desired.
[0062] This invention involves a mini-riser connected by its lower
end to a service flange of an Intervention `Y` fitting, said
Intervention `Y` fitting installed in a general area of and
connected to a top of a riser including at least one of a rigid
catenary riser, or a metallic catenary riser, or a steel catenary
riser, or a titanium catenary riser, or a Chinese lantern riser, or
a bottom weighed riser, or a fiber reinforced plastic catenary
riser, or a fiber reinforced plastic lazy wave riser, or a flexible
riser and said mini-riser is connected above a water surface by an
upper end of said mini-riser to a servicing deck attached to at
least one of a platform, or a spread moored vessel, or a turret
moored vessel, or a disconnectable turret vessel, or an offshore
support vessel, or a diving support vessel, or a multipurpose
support vessel, or a barge, or a floating buoy, or a submerged
buoy, whereas said mini-riser is compliant between its said upper
end and its said lower end.
INDUSTRIAL APPLICABILITY
[0063] Novel mini-risers can be used for any coiled tubing or
wireline applications necessary, and in particular for clearing
hydrate plugs from rigid catenary risers and from subsea pipelines
connected to those risers.
[0064] The mini-riser for riser intervention system suggested
compliments the existing intervention technology. It allows
carrying out coiled tubing and wireline interventions from above
the sea surface and it can be designed as adjustable, portable and
compatible with many types of floating production systems.
* * * * *