Note: Descriptions are shown in the official language in which they were submitted.
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AN APPARATUS AND A METHOD FOR DEPLOYMENT OF A WELL INTER-
VENTION TOOL STRING INTO A SUBSEA WELL.
This invention relates to an apparatus and a method for
deployment of a well intervention tool string into a sub-
sea well associated with the production of hydrocarbons.
Numerous of today's wells related to the production of hy-
drocarbons are subsea wells, meaning that significant
parts of the production hardware such as wellheads, valve
arrangements, instrumentation, control systems, production
manifolds and other accessories are located on the seabed.
Subsea field developments are common in the oil industry
today. This field development philosophy enables a low
capital expense for the initial field development compared
to for example a platform solution. Hence, subsea pro-
duction systems have enabled the development of small
fields, remote locations, deep water areas and other
fields where traditional platform solutions have been non-
feasible due to high costs.
As they have matured, a significant operational expense
problem has emerged for the subsea fields: Well mainte-
nance/service is very expensive compared to platform
wells.
Well maintenance and service comprises a range of methods
for deploying relevant tool strings into live wells in or-
der to do work. Traditional methods for deploying/inter-
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vening relevant tools into live wells comprise wireline,
coil tubing, and snubbing. The downhole tools that can be
intervened and applied using such methods include perfo-
ration guns, zone isolation devices, data recording tools,
fluid samplers, a range of mechanical tools and other de-
vices.
Maintenance from a platform involves rigging up the requi-
red equipment (for instance wireline or coil tubing) on an
appropriate deck space. Hence, the costs of maintenance
are limited to renting/acquiring the equipment that is di-
rectly related to the operation of interest.
On subsea wells, a drilling rig or an intervention vessel
must be mobilised in order to do the same work. Hence,
rental costs for the rig/vessel comes on top of the cost
of renting the intervention service (wireline/coil tubing)
itself. This means that maintaining a subsea well is tre-
mendously more expensive, typically ten times or more,
than maintaining a platform well.
There has been a large industrial focus on applying tai-
lor-made vessels, typically boats, for the purpose of sub-
sea well intervention. These have a somewhat lower cost
than a drilling rig.
For intervention or maintenance operations to be performed
on a live well, lubricator systems are utilised in order
to get tools in and out of the well in a controlled man-
ner. Typically, a lubricator system comprises the follow-
ing:
= A tree connector. This is the interface between the
wellhead and the lubricator stack.
= Valve housings, so-called BOP's (blow out prevent-
ers). These include (gate-shaped) valves, that can
cut cable and coil tubing and thereupon form a seal
against the live well, as well as valves that can
close around the cable/coil tubing, without damaging
~ this, and form a seal against the well pressure.
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= Riser sections. This is simply spacer pipe. The accu-
mulated length of the riser and BOP determines the
length of tool string that can be intervened into the
well in one.run.
= Top seal assembly. In order to run a cable or a coil
tubing in and out of a well environment, a system
that seals between the high-pressurised well environ-
ment and the atmospheric (for surface operations) or
seabed pressure (for subsea operations) conditions on
the outside of the lubricator, is needed.
o For coil tubing operations, so-called stripper
rubbers, that are ring-shaped moulds of an elas-
tomer material, nylon, Teflon or similar are
used. Stripper rubbers are commonly split in two
for mounting purposes and access during the ope-
ration.
o Annular bags can also be utilised for coil tub-
ing operations. These are ring-shaped, elas-
tomer-based barrier systems. Rubber elements are
inflated around the coil in order to create a
seal against it. Annular bags are also commonly
used for heavier pipe operations, such as drill-
ing. A major difference between the stripper
rubber and the annular bag is the latter's abil-
ity to seal against objects/pipe of various di-
ameter.
o For slick wireline (slickline) analogues to the
stripper rubbers may be used, so-called stuffing
boxes, which is a stack of elastomer packers
that seal around the wire.
o In order to intervene with a braided cable into
a well, a so-called grease injection head (GIH)
is required. By means of long, narrow pipes
(flow tubes) and an injection system using vis-
cous grease, the pressure differential between
the well and the atmosphere is overcome and a
braided cable intervention can be performed.
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A lubricator ensures that barrier requirements are com-
plied with during all stages of the well intervention op-
eration. This means that new barriers (between the high-
pressurised well fluid and the open environment) are es-
tablished before old barriers are removed. As an example,
a typical well intervention operation involves the follow-
ing steps:
= Assembly of the lubricator system and mounting of this
onto the welihead;
= Mounting of the tool string inside the lubricator;
= Closing of the lubricator with the tool string inside of
it;
= Filling the lubricator with a liquid, for example gly-
col;
= Pressure testing the lubricator (upon doing this a new
barrier has been established and verified);
= Alignment of the lubricator pressure to equal the well-
head pressure;
= Opening of the wellhead valves (i.e. the original bar-
rier is removed);
= Intervene the tool string into the well to do the re-
quired operation;
When bringing tools out of the well, reversed procedures
similar to the one above are used to ensure that the
original barriers (the wellhead valves) are re-established
(closed) before opening the lubricator to take out/replace
the tool string.
In relation to the development of subsea intervention ves-
sels (boats), associated subsea lubricator assemblies are
developed.
As of current, such subsea lubricator systems have been
analogues to lubricator systems for surface/platform op-
erations, as described in the previous section. Hence, a
subsea lubricator system, common of today, is simply a
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"marinated" surface lubricator system, by means of adding
features that compensate for the fact that there is a ma-
rine environment on the outside of the lubricator rather
that atmospheric air.
Subsea lubricators as of today are limited by several fac-
tors.
There are height limitations in that the lubricator can
not exceed a certain height. This is related to technical
as well as economical considerations. For instance, in-
creaseing height means increasing bending momentum at the
base of the subsea stack where the lubricator is anchored
to the subsea wellhead. The latter has been a significant
challenge and limitation with today's lubricators. Also,
should the lubricator become too high, big and bulky, this
would impose additional requirements to the vessel, which
again could make the operation exceed accepted economical
limits.
The height restriction imposes direct limitations to tool
string length. With current subsea lubricator systems and
methods, the wellhead valves can not be opened prior to
having connected, closed, performed fluid displacement,
and pressure tested the lubricator itself. Hence, the cur-
rent lubricator technology becomes the limiting factor
with respect to tool string length. This again means that
operations requiring long tool strings must be performed
in several smaller steps. Such steps may drag the opera-
tion out in time and increase the costs dramatically. In
worst case, operations are not initiated as they become
non-economical.
As of today, the length of tool string that can be inter-
vened in one run is limited to approximately 20 metres.
There exist lubricator concepts that apply telescopic
joints in order to lengthen the lubricator. Typically,
such telescopic joints are elongated downwards through the
open wellhead, hence a lengthening of lubricator space by
a factor close to 100%, compared to standard subsea lubri-
cator systems, can be achieved.
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For platform operations, there exists a deployment system
that allows a tool string to be deployed through an open
wellhead, and where the downhole safety valve (DHSV) is
the only barrier when bringing tools in and out of the top
section of the well. The aim with this technology has been
to:
= Run (very) long tool strings into a live well
= Reduce the height of the traditional lubricator stack
= Enable operations in wellhead areas with height re-
strictions
When using this technology, pressure is bled down above a
closed down hole safety valve, DHSV, and the tools are
brought into the well through a "wide open wellhead". Upon
getting the tools in place, the top seal assembly (for ex-
ample a grease injection head) is mounted on top of the
lubricator stack, before the DHSV is opened and the tools
are run to the lower sections of the well to do the work.
Here, the lubricator stack and its functions are not re-
moved, but the riser section is, and thereby the main com-
ponent that contributes to height. By means of system fea-
tures that guarantee that no object can fall into the well
and damage the DHSV during rig-up, it is allowed to oper-
ate against only one barrier in certain stages of the op-
eration.
Such platform deployment systems are not applicable on
subsea wells as they cannot handle the pollution problem-
atic: Well fluids that are present above the downhole
safety valve would tend to segregate upwards and pollute
the sea because the well fluids are lighter than the sea
water.
The invention has as its object to remedy, or at least re-
duce, one or more drawbacks of the prior art.
The object is realized through features which are speci-
fied in the description below and in the following Claims.
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Tt is an object of the present invention to provide an ap-
paratus for subsea intervention that reduce costs and op-
erational complexity.
A further object of the present invention is to provide a
method for utilising the apparatus according to the inven-
tion.
The invention aims at reducing lubricator height and, at
the same time, dramatically increasing the length of tool
string that can be intervened in one operational step.
The invention comprises a subsea deployment system and a
method for conducting intervention. The subsea deployment
system comprises two main modules, a first module that at-
taches to the subsea wellhead and/or lubricator assembly,
and a second module that attaches to the tool string to be
intervened. More specifically, the first module of the in-
vention comprises a subsea deployment lubricator module
hereinafter denoted as "SDLM", which is a system com-
ponent, or stack of system components, that forms part of
a subsea lubricator. The second module of the invention
comprises a subsea deployment intervention module herein-
after denoted as "SDIM" which attaches to the tool string
to be intervened. The two system modules interface and in-
teract in a manner that enables deployment of long tool
strings into wells, with a minimal height subsea lubrica-
tor stack.
The main consequential differences between the invention
and existing subsea lubricator systems are:
= Eliminated/reduced need for riser joints in the lu-
bricator section, as the tool string is deployed
"through the open subsea wellhead" by means of a
unique subsea deployment technique.
= Capability to deploy almost unlimited length of tool
strings in one run (the upper theoretical limit is
given by the distance from the wellhead to the down-
hole safety valve).
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The main difference from deployment systems for sur-
face/platform applications is a set of novel system compo-
nents and techniques that ensure a seal to be present be-
tween the well and the outer environment (the sea) during
deployment, hence well fluids cannot escape during the de-
ployment operation.
The SDLM is the "lubricator part" of the subsea deployment
system. In one embodiment of the invention, the lower end
of the SDLM is attached to the wellhead and the upper end
attached to a BOP (Blow Out Preventer) module. In another
embodiment of the invention, the lower end of the SDLM is
attached to the wellhead indirectly, by means of an inter-
face module, a LRP (Lower Riser Package) or other similar
equipment.
The SDLM comprises a main bore, preferably provided in the
centre region, and normally of similar or larger inner di-
ameter than the wellbore itself.
The SDLM comprises a seal arrangement. In one aspect of
the invention the seal is a dynamic seal. In one embodi-
ment, this is a stripper rubber made of elastomer, nylon,
Teflon or similar material. By applying radial or axial
forces, the seal arrangement according to said aspect is
forced radial inwards to seal around any matching object
that is inserted in the bore of the SDLM. In another em-
bodiment of the invention, the seal arrangement is an an-
nular bag or similar system that inflates around objects
in the centre of the SDLM.
In one embodiment of the invention, the seal arrangement
comprises one of said two sealing elements. In another em-
bodiment of the invention, the seal arrangement comprises
a stack of multiple amounts and/or types of sealing ele-
ments. In one embodiment of the invention, some of the
seals in a stack serve the purpose as a well barrier,
whereas other serves the purpose as "vipers" in order to
prevent pollution to the sea. In one embodiment of the in-
vention, only the "vipers" are fully active during normal
operation, whereas the other sealing arrangements are ac-
tivated in the case of emergency.
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The SDLM also comprises a valve assembly. This serves the
purpose to prevent upward segregating fluids from the well
to pollute the marine environment in parts of the opera-
tional sequence. Also, the valve assembly serves the pur-
pose of providing a barrier against the well during cer-
tain operational stages, and to provide means for pressure
testing against, in order to verify seal integrity.
In a preferred embodiment of the invention, the valve as-
sembly includes a double set of flapper type valves, where
the upper is a tri-arm flapper and the lower is a con-
ventional flapper valve. In one embodiment of the invent-
ion, the upper tri-arm flapper valve opens by means of
forcing the intervention string assembly into it whereupon
the lower flapper automatically opens as the two valves
are mechanically hinged. Hence, the lower valve may be
able to contain elastomer seals, sealing surfaces and
other features that should not be exposed to mechanical
contact with the intervention string. In summary, for this
embodiment, the upper tri-arm flapper is to be considered
a mechanical activation mechanism for the lower flapper
that is the real barrier/sealing mechanism towards the
wellbore. In one embodiment of the invention, the valve/
valve assembly is spring-loaded and biases towards a
closed position. In this case, should the intervention
string be retrieved out of the valve assembly, the valves
will automatically close.
In one embodiment of the invention, the above described
valves are complemented with another valve, typically a
ball- or a gate valve, located below the other valves.
This valve enables pressure testing of seal integrity at
the time of stinging the tool string assembly into the
SDLM. In another embodiment of the invention, this latter
valve fully replaces the need for one or both of the de-
scribed flapper valves and is the only valve that is re-
quired for the described purposes.
In other embodiments of the invention, the valve assembly
includes or comprises alternative valve types, such as
ball valves, gate valves and other valves as well as a
combination of such type valves. These valves could be op-
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erated mechanically, electrically, hydraulically or by
means of other relevant forces, using intervention tools
or surface operated electrical, hydraulic or other surface
operation mechanisms connected to the subsea mounted
equipment. Also, wireless activation signals could be ap-
plied to activate the valves.
In one embodiment of the invention, the SDLM comprises an
anti-blowout system. In one embodiment of the invention,
this is a device that is pre-installed and is centered in
the bore of the SDLM, an anti-blowout sub, which attaches
to the intervention string assembly during deployment. The
anti-blowout sub has an OD that is larger than the ID of
the SDLM above the hang-off point of the anti-blowout sub.
Hence, the intervention string can not be blown out of the
well.
In one embodiment of the invention, the anti-blowout sub
and the matching anti-blowout profile in the SDLM have the
shape and characteristics of a dampener. In one embodiment
of the invention, the two components form the male and fe-
male of a hydraulic dampener, where fluid becomes trapped
between the anti-blowout sub and the anti-blowout profile
of the SDLM, and the said fluid only can escape via narrow
channels that reduce in size or number the more fluid that
is displaced. Hence, a gradual dampening pattern is
achieved in order to avoid system damage due to hard im-
pacts between the anti-blow-out sub and the SDLM. In other
embodiments of the invention, the dampener mechanism is
based on other known dampener principles such as springs,
friction dampeners and other.
In another embodiment of the invention, the anti-blowout
function is handled by means of a gripping/locking system
that prevents upward movement of the intervention string
assembly. In one embodiment of the invention, upward move-
ment of the intervention string assembly directly mechani-
cally activates the gripping/locking system. In another
embodiment of the invention, the gripping/locking system
is activated by means of sensors detecting unwanted situ-
ations (leakage, kick, blowout, unexpected upward movement
of the intervention string assembly). Such sensors could
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include detection devices for motion, position, pressure,
fluid flowrate, fluid composition, volumetric changes and
other. In one embodiment of the invention, the grip-
ping/locking system is operator activated. In another em-
bodiment of the invention, the gripping/locking system
comprises a combination of some or all of the herein men-
tioned activation features.
In one embodiment of the invention, the gripping/locking
system includes slips that slide gently along the inter-
vention string assembly while this is being deployed into
the well, but makes a firm grip at the instant this starts
to move upwards. For deploying out of the well, the slips
are foreseen retrieved/removed radial to some distance
away from the intervention string assembly in order to de-
ploy this out of the well (i.e. upward movement), but
linked, in a fail-safe mode, to a release mechanism that
activate the slips and make them grip the intervention
string assembly in case an un-wanted event (e.g. a blow-
out, a kick or similar) should take place. Such an un-
wanted event could be indicated by means of monitoring the
speed of the upward movement of the intervention string
assembly, the fluid displacement into the well during de-
ployment out, acceleration or other indicators of unwanted
events, or a combination of such.
In one embodiment of the invention, the gripping/locking
feature is ensured by means of operator activation of the
annular bag that in one embodiment forms part of the seal
arrangement of the SDLM. Here, the annular bag is not
fully inflated against the intervention string assembly
during normal operations, but only so in the case of an
emergency.
In a preferred embodiment of the invention, the SDLM com-
prises flushing systems in order to remove unwanted fluids
from contained spaces before opening access to the well,
to the open environment, to flowlines or similar. zn one
embodiment of the invention, flushing lines are run and
operated from the vessel used for the subsea intervention
operation. In another embodiment of the invention, dedi-
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cated vessels/tanks and pump systems are used for flushing
purposes.
In one embodiment of the invention, the SDLM and acces-
sories comprises design and system to avoid fluids being
trapped in contained spaces, which can prevent system
functionality.
In a preferred embodiment of the invention, the SDLM and
accessories comprises means for pressure testing and moni-
toring of such during all relevant operational stages.
In a preferred embodiment of the invention, the SDLM and
accessories comprises means for monitoring of operational
parameters such as pressure, temperature, fluid flow rate,
volume displacement and fluid properties during all stages
of the operation. In a preferred embodiment of the inven-
tion, the SDLM comprise a position indicator system that
corresponds with the intervention string assembly.
In a preferred embodiment of the invention, the SDLM com-
prises a stop arrangement for preventing further insertion
of the intervention string assembly into the SDLM. Also,
the SDLM comprises means for locking parts of the inter-
vention string assembly in place during certain operation-
al stages.
In one embodiment of the invention, the SDLM comprises ac-
cess for a kill line to be attached, should there occur a
need to kill the well. In one embodiment of the invention,
the kill line is run and operated from the vessel used for
the subsea intervention operation.
In one embodiment of the invention, the whole or parts of
the SDLM is incorporated as a part of a permanent subsea
wellhead system. Typically, the valve assemblies could
form part of such a permanent system.
The SDIM is a device that, together with the intervention
tools themselves, forms an intervention string assembly of
the subsea deployment system.
The SDIM comprises a tubular element, hereinafter denoted
as "flush pipe" and inner seal/latch subs to be mounted on
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the intervention tool string of interest. In one embodi-
ment of the intervention, the tool string is mounted in-
side the flush pipe with at least one seal/latch sub pro-
vided in each endportion of the intervention tool string.
In a preferred embodiment of the invention, the outer sur-
face of the flush pipe is uniform and smooth and forms a
seal against the SDLM's seal arrangement. Hence, when the
SDIM is stung into the dynamic seal of the SDLM, this
forms a seal in the annular space between the well and the
open environment. Preferably, another seal of similar pur-
pose is provided on the inside of the flush pipe present
in the annular space defined by the flush pipe and the
seal/latch subs attached to the tool string.
In one embodiment of the invention, in the bottom of the
tool string, there is a connector sub for connecting the
tool string to the anti-blowout sub of the SDLM. In one
embodiment of the invention, the connector mechanism com-
prises a standard latch system, such as a GS type latch.
In another embodiment of the invention, the anti-blowout
sub latches onto the flush pipe of the SDIM (and not the
tool string). In this embodiment, the anti-blowout sub is
hollow and allows the intervention tool string to be run
through it.
In a preferred embodiment of the invention, at least one
of the seal/latch subs comprises a latch that attaches the
intervention string to the flush pipe.
In one embodiment of the invention, the flush pipe does
not cover parts of the tool string during installation.
Typically, this involves cases where the tool string can
be made of similar uniform shape and outer diameter as the
flush pipe, and/or cases where said non-covered parts of
the tool string are going to be permanently left in the
well, such as for zone isolation devices. In one embodi-
ment of the invention, the flush pipe is omitted. This
would typically apply for cases where the entire tool
string can be made of similar uniform shape and outer di-
ameter as the flush pipe.
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In a preferred embodiment of the invention, the flush pipe
includes a so-called "no-go profile" in the top portion
that matches a similar profile in the SDLM. This feature
physically prevents the flush tube from being deployed
lower than the no-go profile permits. One intention with
the no-go feature is to ease exact depth determination.
Also, the no-go feature is a very important system feature
in case of an emergency. Should there occur a need to drop
the SDIM, this will stop in a controlled manner in the no-
go profile. Otherwise, a falling SDIM could drop through
the downhole safety valve and create a severe situation.
In one embodiment of the invention, the no-go system in-
cludes one or more dampening functions to enable a smooth
landing of the SDIM into the SDLM, said functions could be
hydraulic-, spring-, friction-based or other damper prin-
ciples.
In some situations, for example in the case of tool
strings of varying outer diameter and shape, like pro-
duction logging strings, it might not be feasible to use
solid, large size seal/latch subs. In particular, such
seal/latch subs could conflict with the operational scope
if placed in the bottom of such tool strings. In one em-
bodiment of the invention, hollow, fluted, expandable or
similar feature seal/latch subs are used. In another em-
bodiment of the invention, instead of a seal/latch sub,
the bottom and/or other parts of the flush pipe is provid-
ed with a valve system. This could comprise one or more
ball valves, gate valves, flapper valves, or other types
and/or combination of valves. The operation of the valve
system could be by means of a shifting tool located in the
bottom of the tool string, or by means of surface operator
controls that are mechanical, hydraulic, electrical, fi-
bre-optical and/or wireless activation based. Remote acti-
vation techniques, such as wireless signals based on
acoustic, electromagnetic, pressure pulse or other methods
known per se, could be applied to activate the valve sys-
tem.
In one embodiment of the invention, the SDIM comprises a
system for fluid displacement. Typically, in order to
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avoid pollution when deploying out of the hole, this fea-
ture could be applied in cases where it is not possible to
obtain a good seal between the flush pipe and the seal/
latch subs after the tool string has been in the well.
In a preferred embodiment of the invention, the SDIM com-
prises passive modules of a position indicator system.
This could be magnets, weak radioactive sources and other
types of passive system components known per se. In anot-
her embodiment of the invention, the SDIM comprises active
position indicator modules.
In the event of loosing the tool string in the well and
the flush pipe needs to be withdrawn from the hole "on its
own", a plug would normally be run in the bottom of the
flush pipe. In a preferred embodiment of the invention,
the bottom section of the flush pipe is compatible.with
plugs, by means of having necessary reinforcements and/or
plug setting profiles.
In most relevant subsea well intervention cases, the sub-
sea well of interest will produce into a manifold that re-
ceives flow from a number of wells. Hence, the manifold
will be pressurised during the entire subsea intervention
operation. This prohibits displaced fluids from the de-
ployment operation to be routed into the manifold. Also,
in most cases, the downhole safety valve (typically a
flapper valve) will be closed and have a significant pres-
sure under it, hence displaced fluids can not be routed
into the well neither. To avoid fluids being*trapped,
hence preventing the subsea deployment operation from be-
coming feasible, a volume monitoring and storage module
(VMSM) is introduced.
In a preferred embodiment of the invention, the VMSM com-
prises components for monitoring in- and out-flux of flu-
ids from the well as well as other relevant data when de-
ploying in and out of the well. In one embodiment of the
invention, the instrumentation of the VMSM includes sen-
sors for measuring pressure, temperature, flow rate, fluid
composition, volumetric changes, density and other rele-
vant parameters in order to gain sufficient control of
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what fluids goes in and out of the well during the various
operational steps.
In one embodiment of the invention, the VMSM also com-
prises a system for handling and/or storing fluids that
are displaced and replaced during the operational sequen-
ces. In one embodiment of the invention, the VMSM com-
prises a tank, located at the seabed or at the vessel it-
self, that fluids are routed to while deploying into the
well and returned from when deploying out of the well.
In another embodiment of the invention, rather than using
a tank, available lines that are permanently connected to
the well of interest, are used for displacement and re-
placement of fluids. In one embodiment of the invention,
such line could be a so-called "annulus line".
In one embodiment of the invention, the VMSM comprises a
pump system that enables displacement of fluids to the
production header while deploying in, and retrieval of
fluids, from the same header or an alternative location,
when deploying out of the well.
In one embodiment of the invention, a line from a dedi-
cated tank at the seabed or the surface vessel supplies a
hydrate inhibitor that is routed into the wellbore when
deploying out of the well. In that way, excessive handling
of wellbore fluids is avoided.
In one embodiment of the invention, access to the wellbore
fluid is achieved by mounting the VMSM onto the choke
bridge of a subsea wellhead. In another embodiment of the
invention, the same access is achieved by means of dedi-
cated ports in the SDLM or an alternative location on the
subsea stack and/or flowline system.
The subsea deployment system according to the present in-
vention will typically be applied for all subsea well in-
tervention operations. In general, by means of eliminating
or at least reducing the riser of a standard subsea inter-
vention stack as well as providing a mean for intervening
very long tool strings in one operational step, the subsea
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deployment system could be a valuable system component in
each and every subsea intervention operation.
The subsea deployment system enables operations, that oth-
erwise would require several runs in the hole, to be per-
formed in only one run. Typically, such operations involve
deploying long perforation guns, zonal isolation strings
or data logging strings.
In the case of a horizontal x-mas tree, a typical subsea
deployment and intervention method according to the in-
vention would include the following steps:
= Pull the debris cap off the tree.
= Mount the SDLM on top of the wellhead or equivalent,
using an appropriate connector sub.
= Mount the BOP on top of the subsea lubricator module.
= Pull the tree plugs of the horizontal x-mas tree. A
small riser section on top of the SDLM and BOP might
be required to get sufficient space. Upon pulling the
tree plugs, the DHSV and the SDLM valve assembly
forms the remaining barriers.
= Mount the tool string inside the flush pipe, assem-
bling component by component, whilst the lower seg-
ments are lowered into the sea. Inside the flush
pipe, seal/latch joints are attached to the top and
bottom of the tool string in order to form seals be-
tween the inside of the flush pipe and the outer en-
vironment. Typically, the assembly operation is con-
ducted some horizontal distance away from the well-
head in case of accidentally dropped objects.
= Prior to building the cable head and mounting this on
top of the tool string, the cable is tread through
the grease injection head.
= When the SDIM is assembled: The vessel is positioned
above the well and the SDIM lowered into the sea with
the grease injection head following closely behind
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(above), both held by their respective wires and
guiding systems.
= The bottom of the SDIM/flush pipe is guided into the
BOP and the SDLM. Now, the SDIM forms a seal against
the SDLM dynamic seal, whereupon it latches onto the
anti-blowout sub.
= A pressure test is conducted to confirm seal inte-
grity across the dynamic seal of the SDLM. For hori-
zontal x-mas trees, this pressure test is conducted
against a valve in the SDLM valve assembly. For ver-
tical x-mas trees, this pressure test could be con-
ducted against one of the valves in the tree itself.
= Sea water that is trapped between the bottom of the
SDIM and the SDLM valve assembly is removed by means
of the SDLM flushing systems. This is done to avoid
hydrate and similar problems that might occur when
sea water becomes mixed with well fluids.
= The anti-blowout sub is released from the SDLM and
the SDIM is continued lowered into the hole.
= The SDLM valve assembly is opened and the SDIM is
lowered further, until the top of the SDIM is inside
the SDLM and the no-go profiles meet.
= The SDIM is anchored to the SDLM top section.
= The grease injection head is lowered on top of and
attached to the BOP. Now, the total "lubricator" is
in place.
= Sea water that is trapped between the top of the SDIM
and the grease injection head is removed by means of
the SDLM flushing systems.
= The tool string is released from the flush pipe. This
can be achieved by means of applying forces to the
wireline cable or coil tubing, or by means of apply-
ing hydraulic, electrical, mechanical or other forces
and/or impulses to the flush pipe through the wire-
line, coil tubing or directly from the vessel to the
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SDLM itself. Also, wireless communication methods
could be applied for this purpose.
= The tool string is run to the well section of inter-
est, whereupon it performs the relevant operation,
before it is retrieved out of the well.
= The tool string is pulled into the flush pipe and
latches onto the flush pipe's seal/latch sub pro-
files. The seals in the seal/latch subs in the top
and bottom of the tool string ensures that pollutants
from the well that might have attached to the tool
string are now contained inside the flush pipe while
deploying this out of the well and through open wa-
ter.
= Prior to disconnecting the grease injection head
(GIH) and pulling the flush pipe with the tool string
out of the BOP, the volume between the grease injec-
tion head and the flush pipe is flushed with a fluid
that replaces all well fluids and other contaminants.
Typically, the replacement fluid is characterised by
being harmless to the environment as well as being of
a hydrate preventive nature.
= In one embodiment of the invention, the flush pipe
and the SDIM are flushed with a fluid that replaces
most of the well fluids in order to avoid excessive
exposure of such on the vessel.
= The grease injection head (GIH) is loosened from the
BOP and lifted slightly above the rest of the lubri-
cator stack.
= The SDIM is loosened from the SDLM and retrieved out
of the well. The grease injection head (GIH) is re-
trieved in the same operation.
= Upon having passed the SDLM valve housing the anti-
blowout sub connected to the SDZM lands in the anti-
blowout profile of the SDLM.
= The SDLM valve assembly is closed.
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= The volume between the SDLM valve assembly and the
bottom of the SDIM is flushed with a fluid that re-
places all well fluids and other contaminants.
= The SDIM is released from the anti-blowout sub. This
can be achieved by means of applying forces to the
wireline cable or coil tubing, or by means of apply-
ing hydraulic, electrical, mechanical or other forces
and/or impulses to the flush pipe through the wire-
line, coil tubing or directly from the vessel to the
SDLM itself. Also, wireless communication methods
could be applied for this purpose.
= The SDIM is pulled out of the lubricator stack,
whereupon the SDIM and the grease injection head are
retrieved to the intervention vessel and disassemb-
led.
= The x-mas tree plugs are reinstalled and pressure
tested.
= Thereupon the BOP module and the subsea deployment
lubricator module are retrieved.
= The debris cap is reinstalled and the operation is
finished.
In what follows is described a non-limiting exemplary embodi-
ment of a preferred embodiment which is visualized in the
following drawings, in which:
Figure 1 shows a simplified illustration of the overall
lubricator system according to the present invention as it
appears when rigged up at the seabed, with an intervention
operation in progress.
Figure 2 shows in a larger scale and partly in cross sec-
tion the Subsea Deployment Lubricator Module (SDLM) with
schematically illustrated internal features.
Figure 3 shows in smaller scale a view of the Subsea De-
ployment Intervention Module (SDIM).
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Figure 4 shows partly in cross section a view of the SDIM
in figure 3 with a wireline tool string (perforation gun)
mounted inside.
Figure 5 shows partly in cross section and in smaller
scale a view of the SDLM and SDIM in a lst step in the
process of deploying in a wireline tool string.
Figure 6 shows partly in cross section a view of the SDLM
and SDIM in a 2nd step in the process of deploying in a
wireline tool string.
Figure 7 shows partly in cross section a view of the SDLM
and SDIM in a 3rd step in the process of deploying in a
wireline tool string.
Figure 8 shows partly in cross section a view of the SDLM
and SDIM in a 4th step in the process of deploying in a
wireline tool string
Figure 9 shows partly in cross section a view of the SDLM
and SDIM in a 5th step in the process of deploying in a
wireline tool string.
Figure 1 illustrates the system overview as it appears at
the seabed with a wireline intervention in progress. The
Subsea Deployment Module (SDLM) 101 is attached to the X-
mas tree or wellhead 102. Alternatively there could be a
separate module, for example a wellhead connector, between
the SDLM 101 and the X-mas tree/wellhead 102, but that is
not illustrated here. A BOP (Blow Out Preventer) 103 is
provided on top of the SDLM 101. A Grease Injection Head
(GIH) 104 is provided on top of the BOP 103. A wireline
cable 105 enters the GIH 104 in a top portion of the GIH
104. Inside the illustrated subsea stack, the intervention
string assembly is located. However, this is not shown in
Figure 1. The Volume Monitoring and Storage Module (VMSM)
107 is connected to the production flowline 108. The VMSM
comprises a volume tank 109 as well as instrumentation
110. A kill line 111 to the vessel is shown connected to
the SDLM 101. Below the X-mas tree/wellhead 102, the well-
bore 112, i.e. the well itself is illustrated.
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Figure 2 shows in a larger scale and partly in cross sec-
tion the SDLM 101. This comprises a centre bore 201, a dy-
namic seal 202, a valve assembly 203 and an anti-blowout
system 206. The valve assembly 203 comprises an upper,
tri-arm flapper valve 204 and a lower, conventional flap-
per valve 205. Also, in this illustration, the anti-
blowout system 206 comprises an anti-blowout sub 207 and a
SDLM anti-blowout profile 208. In order to clean the sys-
tem for unwanted fluids at given operational stages, a
flushing system comprising an upper flushing bore 209 and
a lower flushing bore 210 are applied. For illustrative
purposes the flushing system is only indicated by bores
209, 210 in the SDLM 101. However, a person skilled in the
art will be familiar with such a flushing system. The SDLM
101 also comprises a dynamic seal activation system 212
for operating (activating/deactivating) the dynamic seal
202 also known to a person skilled in the art. In the up-
per portion of the SDLM 101, there is a SDIM latch 211 ar-
ranged for attaching to the intervention string assembly.
Also, a lip or "no-go profile" 213 extending from the sur-
face in the top portion of the bore 201 of the SDLM 101 is
provided for receiving a corresponding profile of the SDIM
301, thereby preventing further deployment of the SDIM 301
in the bore 201 of the SDLM 101. The kill line 111 to the
vessel is also illustrated. Accessories such as access
lines, pumps, fittings, check valves, seals and similar
are not shown. However, such accessories are known to a
person skilled in the art.
Figure 3 shows the SDIM 301 as it appears when assembled.
In the upper portion, this module has an outer latch pro-
file 312 and the SDIM no-go profile 313 as mentioned
above. In the bottom, sticking out of the SDIM 301, a GS
latch 311 is illustrated. The function, and purpose of the
components herein are explained in connection with figures
5-9. A portion of a wireline cable 105 extending to the
surface is also illustrated in the figures.
Figure 4 illustrates the internal system components of the
SDIM 301. The flush pipe 302 forms the outer body of the
SDIM 301. This is a pipe element having an outer surface
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finish that enable the dynamic seal 202 of Figure 2 to
provide a seal against it. A wireline tool string 314 is
mounted inside the flush pipe 302. Said tool string 314
comprises a cable head 303, an upper seal/latch sub 304
with its seal 305 and latch 306, the wireline tool 314 it-
self, in this example a perforation gun 307, a bottom
seal/latch sub 308 with a seal 309 (no latch included on
this sub) and a GS Latch 311. The GS latch 311 is provided
for connecting the wireline tool string 314 onto the anti-
blowout sub 207 illustrated in Figure 2. In the upper end
of the flush pipe 302, there is an outer latch profile 312
that allows the flush pipe 302 to be anchored to the SDLM
101 (cf. Figure 2 - the SDIM latch 211) after installation
and a SDIM no-go profile 313 that matches the SDLM no-go
profile 213 of Figure 2.
Figure 5 shows the lst step in the process of deploying in
a well service tool string using the Subsea Deployment
Module. In the figure, the SDIM 301 is being lowered into
the bore 201 of the SDLM 101, whereupon the GS latch 311
attaches to the anti-blowout sub 207.
Figure 6 shows the 2a step of the operation. Upon a suc-
cessful connection of the GS latch 311 onto the anti-
blowout sub 207, the anti-blowout sub 207 is released from
the SDLM 101. The connection and release mechanism between
the anti-blowout sub 207 and the SDLM 101 is not shown.
However, such a release mechanism is known to a person
skilled in the art and could for example, but not limited
to, be a latch mechanism operated by applying forces on
the wireline wire, or a release mechanism operated from
the vessel or another remote location by means of hydrau-
lic, electrical or mechanical impulses and/or activation
mechanisms, or other known attachment/release mechanisms.
Further, the SDIM 301 with the anti-blowout sub 207 is
lowered further until it contacts the tri-arm flapper
valve 204. This also forces the conventional flapper valve
205 to open, whereupon the SDIM 301 with the anti-blowout
sub 207 is further lowered towards and into the wellbore.
Figure 7 shows the 3rd step in the process. Here, the SDIM
301 with the anti-blowout sub 207 is further lowered to-
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wards and into the wellbore until the flush pipe 302 lands
inside the SDLM 101. This takes place when the SDIM no-go
profile 313 has made a physical stop in the SDLM no-go
profile 213. Now, the SDIM latch 211 of the SDLM 101 is
aligned with the Outer Latch Profile 312 of the flush pipe
302.
Figure 8 shows the 4th step of the operation. Here, the
SDIM latch 211 of the SDLM 101 is activated to attach onto
the outer latch profile 312 of the flush pipe 302, hence
the flush pipe 302 becomes attached to the SDLM 101.
Figure 9 shows the 5th step in the process. Here, the wire-
line tool 314 is released from the flush pipe 302 by means
of releasing latch 306 of the upper seal/latch sub 304.
When the latch 306 is disconnected, the wireline tool 314
is free to be intervened into the well. Prior to releasing
the latch 306, the Grease Injection Head (GIH, cf. 104 in
Figure 1) is mounted on top of the SDLM 101 in order to
ensure that all required barriers between the well and the
outer environment are in place prior to the well interven-
tion. In this example, the anti-blowout sub 207 follows
the wireline tool 314 into the well during the well inter-
vention. In a preferred embodiment of the invention, the
anti-blowout sub 207 attaches to the flush pipe 302 di-
rectly and does not follow the wireline tool 314 into the
well. When deploying out of the well, the sequence de-
scribed in figures 5-9 is mainly reversed, with some minor
variations. Flushing to displace unwanted fluids might be
required in one or more steps to avoid pollution to the
sea when pulling 'the SDIM 301 out of the SDLM 101 after
ended operation.
