U.S. patent application number 12/357736 was filed with the patent office on 2009-07-23 for intervention system with dynamic seal.
Invention is credited to Andrea SBORDONE.
Application Number | 20090183881 12/357736 |
Document ID | / |
Family ID | 39166146 |
Filed Date | 2009-07-23 |
United States Patent
Application |
20090183881 |
Kind Code |
A1 |
SBORDONE; Andrea |
July 23, 2009 |
INTERVENTION SYSTEM WITH DYNAMIC SEAL
Abstract
A technique for subsea intervention operations incorporates use
of a compliant guide that extends between a surface location and a
subsea installation. The technique facilitates deployment of tool
strings into a subsea well. A dynamic seal can be conveyed through
the compliant guide to a desired subsea location. At this location,
the dynamic seal is locked into place to provide a subsea dynamic
seal that can be used to facilitate the intervention
operations.
Inventors: |
SBORDONE; Andrea;
(Singapore, SG) |
Correspondence
Address: |
SCHLUMBERGER OILFIELD SERVICES
200 GILLINGHAM LANE, MD 200-9
SUGAR LAND
TX
77478
US
|
Family ID: |
39166146 |
Appl. No.: |
12/357736 |
Filed: |
January 22, 2009 |
Current U.S.
Class: |
166/335 |
Current CPC
Class: |
E21B 33/076 20130101;
E21B 17/015 20130101 |
Class at
Publication: |
166/335 |
International
Class: |
E21B 43/01 20060101
E21B043/01; E21B 33/00 20060101 E21B033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 22, 2008 |
GB |
0801124.9 |
Claims
1. A system for use with a subsea well, comprising: a tubular
member extending between a surface location and a subsea
installation; a dynamic seal sized for movement through the tubular
member to a desired location; and a locking mechanism to lock the
dynamic seal at a desired location.
2. A system as claimed in claim 1, wherein dynamic seal comprises
the locking mechanism.
3. A system as claimed in claim 1, wherein the tubular member is a
compliant guide extending between a surface location and a subsea
installation.
4. A system as claimed in claims 1, which further comprises a
conveyance on which the dynamic seal is transported through the
tubular member.
5. A system as claimed in claim 4, which further comprises an
attachment mechanism for attaching the dynamic seal to the
conveyance.
6. A system as claimed in claim 4, wherein the dynamic seal seals
against the conveyance during movement of the conveyance through
the dynamic seal.
7. A system as claimed in claim 6, wherein the dynamic seal seals
against the conveyance by means of at least one dynamic seal
member, the dynamic seal member being hydraulically operable.
8. A system as claimed in claim 7, wherein the dynamic seal member
is operable through a hydraulic activation system.
9. A system as claimed in claim 8, wherein the hydraulic activation
system is used in combination with a hydraulic ram system.
10. A system as claimed in any one of claim 7, wherein the dynamic
seal includes two dynamic seal members.
11. A system as claimed in claim 10, wherein the two dynamic seal
members each have their own hydraulic activation systems.
12. A system as claimed in claim 10 wherein the two dynamic seal
members use the same hydraulic activation system.
13. A system as claimed in claim 1, wherein the dynamic seal is
positionable within a lower end of the tubular member so as to form
a sealing contact with the tubular member when positioned at the
desired location.
14. A system as claimed in claim 1 wherein the dynamic seal is
positionable proximate the lower end of the tubular member.
15. A method for intervening in a subsea installation, comprising:
coupling a tubular member between a surface location and a subsea
installation; moving a dynamic seal down through the compliant
guide to a desired subsea location; and locking the dynamic seal
into an operative position at the desired subsea location.
16. A method as claimed in claim 15, which further comprises
releasing the dynamic seal and then retrieving it through the
tubular member following an intervention operation.
17. A method as claimed in claim 15, wherein moving of the dynamic
seal down through the tubular member to a desired subsea location
is accomplished by moving the dynamic seal through the tubular
member on a conveyance.
18. A method as claimed in claim 17, wherein the conveyance is
moved through the dynamic seal in sealing engagement with the
dynamic seal.
19. A method as claimed in claim 17, wherein the sealing engagement
is provided by at least one dynamic seal member in the dynamic
seal.
20. A method as claimed in claim 15, wherein the locking is
obtained by locking the dynamic seal within a lower end of the
tubular member.
21. A method as claimed in claim 15, which further comprises
activating the dynamic seal to seal against the conveyance, opening
the subsea well, and delivering an intervention tool into the
subsea well via the conveyance.
22. A method as claimed in claim 15 wherein the seal is adjusted
between the conveyance and the dynamic seal by adjusting the
differential pressure above and below the dynamic seal.
23. A method as claimed in claim 15 wherein the seal is adjusted
between the conveyance and the dynamic seal by adjusting the
hydraulic pressure that controls the activation of the dynamic
seal.
24. A method for intervening in a subsea well comprising deploying
a dynamic seal through a tubular member with a conveyance,
positioning the dynamic seal at a desired subsea location and
releasing the conveyance to enable movement of the conveyance
through the dynamic seal while retaining a seal between the
conveyance and the dynamic seal.
25. A method as claimed in claim 24, wherein the deployment step is
done by using a cable-type conveyance.
26. A method as claimed in claim 24, wherein positioning includes
positioning the dynamic seal above a subsea installation.
27. A method as claimed in claim 24, wherein positioning includes
positioning the dynamic seal in a lower portion of the tubular
member.
28. A method as claimed in claim 24, which further comprises
sealing the dynamic seal to the tubular member.
29. A method as claimed in claim 24, which further comprises
adjusting a differential pressure acting on the dynamic seal.
30. A method as claimed in claim 24, which further comprises
opening the subsea well, delivering an intervention tool into the
subsea well, conducting an intervention operation and retrieving
the intervention tool to a surface location.
31. A method for intervening in a subsea well comprising: coupling
a spoolable compliant guide between a surface location and a subsea
installation; delivering a dynamic seal through the spoolable
compliant guide via a conveyance; and adjusting the seal formed
between the conveyance and the dynamic seal.
32. A method as claimed in claim 31, which comprises changing the
pressure acting on the dynamic seal for adjusting the seal formed
between the conveyance and the dynamic seal.
33. A method as claimed in claim 32, wherein the pressure changing
is accomplished remotely from a surface location.
34. A method as claimed in claim 31, wherein the coupling step
includes coupling the spoolable compliant guide between a surface
vessel and the subsea installation.
35. A method as claimed claim 31, wherein delivering the dynamic
seal through the spoolable guide via the conveyance includes the
use of a cable-type conveyance that delivers the dynamic seal
through the spoolable compliant guide.
Description
TECHNICAL FIELD
[0001] This invention relates to a system for use with a subsea
well. More particularly, the invention relates to a system for use
with a subsea well which includes a dynamic seal used in a
compliant guide or other riser system.
BACKGROUND ART
[0002] The retrieval of desired fluids, such as hydrocarbon based
fluids, is pursued in subsea environments. Production and transfer
of fluids from subsea wells relies on subsea installations, subsea
flow lines and other equipment. Additionally, preparation and
servicing of the subsea well relies on the ability to conduct
subsea intervention work. A big challenge in subsea intervention
work is controlling pressure so that pressurized borehole fluids in
the subsea well are contained within the borehole during
intervention operations.
[0003] Subsea intervention work involves numerous challenges not
normally faced when working on land wells or offshore platforms. In
most cases, intervention in subsea wells is performed from a
floating platform or ship by extending the borehole to a surface
location by a tensioned riser. This approach allows pressurized
borehole fluids to move upwardly to the surface through the riser
which can span hundreds or thousands of feet of sea water. The cost
of such platforms is high, however, and the availability of vessels
capable of adequately performing this type of intervention work is
limited.
[0004] In shallow waters, subsea intervention work can be performed
with a specially equipped vessel having subsea lubricators, subsea
pressure control equipment, and wave motion compensating systems.
In most cases, guide wires extending from a wellhead all the way to
the vessel combined with the aid of professional divers is
required. Additionally, this approach requires that equipment is
conveyed and guided from the vessel to the subsea installation
through open waters. Once the subsea lubricator is connected to the
subsea installation and the tools are inside, the conveyance cable
remains exposed to open waters. Additionally, pressure control must
be exercised at the seabed. Because existing non-rig intervention
capability is limited to shallow water wireline and slickline
operations, most intervention on subsea wells is currently
performed with expensive and scarce heavy drilling units.
[0005] When performing intervention operations in subsea wells or
other installations borehole fluids are maintained in the well by
different types of pressure tight seals. It is convenient in many
cases to be able to provide a pressure tight, dynamic seal in the
vicinity of the seabed, such that a conveyance member, for example,
wireline, slickline, coiled tubing or other applicable conveyance,
can be moved up and down inside the well or flowline to perform
intervention operations. The subsea installation contains
pressurized fluids within and must prevent them from moving either
into the environment (in the case of riserless operations) or into
a tubular conveyance member connected to the subsea installation,
such as a rigid riser, a flexible riser, or a spoolable compliant
guide.
[0006] In U.S. Pat. No. 4,905,763, for example, separation of
borehole fluids is maintained during logging operations by a
sealing nipple and a stuffing box assembly. The assembly is lowered
down through a riser extending between a platform and a blowout
preventer stack. In another application described in U.S. Pat. No.
4,951,745, a hydraulically actuated stuffing box is mounted on top
of an underwater lubricator assembly to seal against a line during
well service operations.
[0007] It is also convenient to deploy the dynamic seal from a
surface vessel to a seabed installation together with the
intervention toolstring and conveyance member, as well as being
able to retrieve the dynamic seal back to the surface again with
the intervention tools and conveyance member. Having a retrievable
dynamic seal enables easy and frequent maintenance of the seal
itself, while still allowing efficient operations.
[0008] Advantages of the current invention are that it describes a
retrievable dynamic seal which locks itself to the intervention
toolstring or conveyance, then lands into its seat near the bottom
of the compliant guide or riser, and locks itself in place,
releases the conveyance member and toolstring, and then enables the
activation of a dynamic seal, in order to provide a valid pressure
barrier able to withstand differential pressure either from above
or below. Once the intervention operation is concluded, the device
is able to again capture the intervention toolstring, and then
release itself to be retrieved to the surface together with the
toolstring.
DISCLOSURE OF INVENTION
[0009] According to one aspect of the present invention there is
provided a system for use with a subsea installation, comprising:
[0010] a tubular guide extending between a surface location and a
subsea installation; [0011] a dynamic seal sized for movement
through the tubular guide to a desired location, and a locking
mechanism to lock the dynamic seal at a desired location.
[0012] The locking mechanism may form part of the dynamic seal,
alternatively the locking mechanism may be an external system which
when activated locks the seal at the desired location. Preferably
the tubular member is a compliant guide or riser although the use
of other tubular members connecting the subsea installation to the
surface is also contemplated. The system may further comprise a
conveyance on which the dynamic seal is transported through the
tubular member. The dynamic seal may comprise an attachment
mechanism for attaching the dynamic seal to the conveyance. Also,
the dynamic seal may seal against the conveyance during movement of
the conveyance through the dynamic seal.
[0013] In one form of the invention the dynamic seal may seal
against the conveyance by means of at least one dynamic seal
member, the dynamic seal member being hydraulically operable. The
dynamic seal member is operable through a hydraulic activation
system. The hydraulic activation system may be used in combination
with a hydraulic ram system.
[0014] The dynamic seal may include two dynamic seal members. In
one form of the invention the two dynamic seal members each have
their own hydraulic activation systems and in another form of the
invention the two dynamic seal members use the same hydraulic
activation systems.
[0015] The desired location of the dynamic seal may vary but
preferably is poistionable within the lower part of the compliant
guide or riser system, and is designed to be positioned in such a
manner as to form a sealing contact with the compliant guide or
riser system when positioned at the desired location or the dynamic
seal may be positionable proximate the lower end of the compliant
guide. It should be understood that the tubular member may vary
depending on the particular needs of the application but for
instance the compliant guide may be a spoolable compliant
guide.
[0016] According to a second aspect of the invention there is
provided a method for intervening in a subsea installation,
comprising: [0017] coupling a tubular member between a surface
location and a subsea installation; [0018] moving a dynamic seal
down through the tubular member to a desired subsea location; and
[0019] locking the dynamic seal into an operative position at the
desired subsea location.
[0020] The method may further comprise releasing the dynamic seal
and then retrieving it through the tubular member following an
intervention operation. Moving of the dynamic seal down through the
tubular member to a desired subsea location may be accomplished by
various means such as for example moving the dynamic seal through
the tubular member on a conveyance. Preferably, the conveyance is
moved through the dynamic seal in sealing engagement with the
dynamic seal. The sealing engagement may be provided by at least
one dynamic seal member in the dynamic seal. The locking may be
obtained in various ways as well such as by locking the dynamic
seal within a lower end of the tubular member. The method may
further comprise activating the dynamic seal to seal against the
conveyance, opening the subsea well, and delivering an intervention
tool into the subsea well via the conveyance. The seal may be
adjusted between the conveyance and the dynamic seal by adjusting
the differential pressure above and below the dynamic seal, or by
adjusting the hydraulic pressure that controls the activation of
the dynamic seal.
[0021] According to a third aspect of the invention there is
provided a method is for intervening in a subsea well comprising
deploying a dynamic seal through a tubular member with a
conveyance, positioning the dynamic seal at a desired subsea
location and releasing the conveyance to enable movement of the
conveyance through the dynamic seal while retaining a seal between
the conveyance and the dynamic seal.
[0022] The deployment step may be done by using a cable-type
conveyance. Also positioning may include positioning the dynamic
seal above a subsea installation or preferably in a lower portion
of the compliant guide or riser, or in proximity of the lower
portion. The method may further comprise sealing the dynamic seal
to the compliant guide, and/or adjusting a differential pressure
acting on the dynamic seal. The method also may be practiced under
many different possible variations such as including opening the
subsea well, delivering an intervention tool into the subsea well,
conducting an intervention operation and retrieving the
intervention tool to a surface location.
[0023] According to a fourth aspect of the invention there is
provided a method for intervening in a subsea well is provided the
method comprising: [0024] coupling a spoolable compliant guide
between a surface location and a subsea installation; [0025]
delivering a dynamic seal through the spoolable compliant guide via
a conveyance; and [0026] adjusting the seal formed between the
conveyance and the dynamic seal.
[0027] The method may comprise changing the pressure acting on the
dynamic seal for adjusting the seal formed between the conveyance
and the dynamic seal. The pressure changing may be accomplished in
a couple different ways preferably remotely from a surface
location. The coupling step may include coupling the spoolable
compliant guide between a surface vessel and the subsea
installation. Delivering the dynamic seal through the spoolable
guide via the conveyance may include the use of a cable-type
conveyance that delivers the dynamic seal through the spoolable
compliant guide.
BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS
[0028] Certain embodiments of the invention will hereafter be
described with reference to the accompanying drawings, wherein like
reference numerals denote like elements, and:
[0029] FIG. 1 shows a schematic front elevation view of a subsea
intervention system, according to a first embodiment of the present
invention;
[0030] FIG. 2 shows a schematic side view of a portion of the
subsea intervention system illustrating a dynamic seal, according
to the first embodiment of the present invention;
[0031] FIG. 3 shows a schematic side view similar to that of FIG. 2
but showing the intervention tool string conveyance released from
the dynamic seal, according to the first embodiment of the present
invention;
[0032] FIG. 4 shows a schematic side view similar to that of FIG. 2
but showing the intervention tool string entering a subsea
wellbore, according to the first embodiment of the present
invention;
[0033] FIG. 5 shows a schematic side view similar to that of FIG. 2
but showing the intervention tool string exiting the subsea
wellbore, according to the first embodiment of the present
invention; and
[0034] FIG. 6 shows a schematic side view similar to that of FIG. 2
but showing the dynamic seal being retrieved, according to the
first embodiment of the present invention.
[0035] FIG. 7 shows a schematic side view of a portion of the
subsea intervention system illustrating a dynamic seal, according
to a second embodiment of the present invention;
[0036] FIG. 8 shows a schematic side view similar to that of FIG. 7
but showing the sealing member integrated in the lower portion of
the dynamic seal, according to the second embodiment of the present
invention;
[0037] FIG. 9 shows a schematic side view similar to that of FIG. 7
but showing two sealing members, one integrated in the upper
portion of the dynamic seal and one integrated in the lower portion
of the dynamic seal, each with its own activation device according
to the second embodiment of the present invention;
[0038] FIG. 10 shows a schematic side view similar to that of FIG.
7 but showing two sealing members, one integrated in the upper
portion of the dynamic seal and one integrated in the lower portion
of the dynamic seal, both sharing an activation device according to
the second embodiment of the present invention; and
[0039] FIG. 11 shows a schematic side view similar to that of FIG.
7 but showing one sealing member having hydraulic rams in
combination with an activation device, according to the second
embodiment of the present invention.
MODE(S) FOR CARRYING OUT THE INVENTION
[0040] A first embodiment of the invention for a subsea
intervention system is illustrated in FIGS. 1 to 6.
[0041] Referring generally to FIG. 1, an intervention system 20 is
illustrated according to an embodiment of the present invention. In
this embodiment, system 20 comprises a compliant guide 22, e.g a
spoolable compliant guide, and a dynamic seal assembly 24, which
also can be referred to as a dynamic stuffing box. Compliant guide
22 is coupled between a subsea installation 26 and a surface vessel
28, such as an intervention vessel located at a surface 30 of the
sea. Subsea installation 26 may be located on or at a seabed floor
32. The pressure in the compliant guide 22 can be selectively
adjusted to assist intervention operations involving, for example,
pulling out of the well or running into the well.
[0042] Compliant guide 22 is flexible, and dynamic seal 24 is sized
for deployment and retrieval along the interior of compliant guide
22. Depending on the specific intervention application, compliant
guide 22 may be arranged in a variety of curvilinear shapes
extending between a surface location, e.g. intervention vessel 28,
and subsea installation 26. Compliant guide 22 also may be
constructed as a tubular member formed from a variety of materials
that are sufficiently flexible, including metal materials of
appropriate cross-section and composite materials. While the system
is described with reference to the tubular member being a compliant
guide, the system of the invention can encompass any type of riser
or guide which can be deployed to connect a surface vessel to a
subsea installation. Such tubular guides can include tensioned
risers, flexible riser, jointed drillpipe, flowline, and coiled
tubing for example.
[0043] To control the pressure differential acting on dynamic seal
24, compliant guide 22 may be filled with a buffer fluid 34, such
as seawater, introduced into the interior of compliant guide 22. In
some applications, other buffer fluids 34 can be used, e.g.
environmentally friendly greases for friction reduction or for
pressure sealing; fluids designed for hydrate prevention; weighted
mud; and other appropriate buffer fluids. The level and pressure of
buffer fluid 34 can be controlled from the surface by, for example,
standard pressure control equipment 36 that may be mounted on
intervention vessel 28.
[0044] Once compliant guide 22 is coupled between subsea
installation 26 and intervention vessel 28, the dynamic seal
assembly 24 may be run down through compliant guide 22 with an
intervention tool string 38. The intervention tool string 38 is
deployed by a conveyance 40, and dynamic seal 24 is coupled to
conveyance 40 for movement to a desired subsea location 42. The
dynamic seal 24 is coupled to conveyance 40 until locked into
position at the desired subsea location 42. Subsequently, the
dynamic seal 24 is released from conveyance 40 but remains sealed
against conveyance 40 as the conveyance is moved to deploy and/or
retrieve intervention tool string 38. In some applications, the
conveyance of dynamic seal 24 down through compliant guide 22 can
be assisted by pumping a fluid into the compliant guide so the
pumped fluid pushes the dynamic seal down through the compliant
guide. A port can be provided at the bottom of the compliant guide
for expulsion of displaced fluid. The retrieval of dynamic seal 24
also can be assisted by pumping fluid out of the compliant guide
from the surface. In this latter case, fluid can enter through the
port and apply hydrostatic pressure against the bottom of the
dynamic seal 24. The maximum force applied against the dynamic seal
can be controlled by setting a limit on the pressure of the fluid
pumped at the surface with hydraulic pressure control equipment 36,
for example.
[0045] The dynamic seal 24 and compliant guide 22 can accommodate
many different types of conveyances 40. For example, conveyance 40
may be a flexible, cable-type conveyance, such as a wireline or
slickline. However conveyance 40 also may comprise stiffer
mechanisms including coiled tubing and coiled rod. When a
cable-type conveyance 40 is used to convey intervention tool string
38, compliant guide 22 can be arranged to facilitate passage of the
intervention tool string 38, in some applications, without
requiring a pushing force. In other words, the curvilinear
configuration of compliant guide 22 is readily adjustable via, for
example, locating intervention vessel 28 so as to avoid bends or
deviated sections that could interfere with the passage of
intervention tool string 38. Thus, in addition to enabling pressure
control within the compliant guide 22, the flexibility of compliant
guide 22 enables its configuration to be adjusted as necessary by
simply moving intervention vessel 28. Dynamic changes can
temporarily be made to compliant guide 22 to change the shape of
the compliant guide for facilitating the passage of a tool string.
By way of further example, the intervention vessel can be turned to
orient itself with its bow against the wind, waves, and currents.
Furthermore, the desired orientation of the compliant guide may
change from one intervention operation to another or during a given
intervention operation depending on parameters, such as current,
subsea obstacles, surface obstacles and other environmental
factors.
[0046] Although a variety of subsea installations 26 can be
utilized depending on the particular environment and type of
intervention operation, one example is illustrated in FIG. 1. In
this example, the subsea installation 26 comprises a subsea
wellhead 44, which may include a Christmas tree, coupled to a
subsea well 46. Dynamic seal 24 may be positioned generally at the
bottom of compliant guide 22 to help block incursion of well fluids
into an interior 48 of the compliant guide. In other embodiments,
dynamic seal 24 may be positioned proximate compliant guide 22 in,
for example, subsea installation 26.
[0047] In the embodiment illustrated, dynamic seal 24 is generally
positioned above a subsea lubricator 50 of subsea installation 26.
As illustrated, subsea installation 26 also may comprise a variety
of other components. For example, subsea installation 26 comprises
a lubricating valve 52 that may be deployed directly above subsea
wellhead 44. Lubricating valve 52 can be used to close the borehole
of subsea well 46 during certain intervention operations, such as
tool change outs. A blowout preventer 54 may be positioned above
lubricating valve 52 and may comprise one or more cut-and-seal rams
56 able to cut through the interior of the subsea installation and
seal off the subsea installation during an emergency disconnect.
The subsea installation 26 also may comprise a second blowout
preventer 58 positioned above blowout preventer 54 and comprising
one or more sealing rams 60 able to seal against the conveyance 40.
Many other components, e.g. an emergency disconnect device 62, also
can be incorporated into intervention system 20 depending on the
specific intervention application.
[0048] In operation, the subsea dynamic seal 24 is designed to
prevent the escape of borehole fluids from subsea well 46. This
prevents the mixing of the borehole fluids with buffer fluid 34
within compliant guide 22. The dynamic seal 24 seals against
conveyance 40, and may be designed to seal against a variety of
conveyances, such as those listed above. The dynamic seal 24 can
also be designed with an active system that can be controlled to
selectively open and close its sealing element to accommodate the
passage of larger tools through the dynamic seal.
[0049] Referring generally to FIG. 2, one embodiment of dynamic
seal assembly 24 is illustrated as being deployed down through
compliant guide 22. In this embodiment, dynamic seal 24 is
illustrated as having an upper region 64, a central region 66 and a
lower region 68, however the dynamic seal can be formed in a
variety of shapes and configurations. Furthermore, dynamic seal 24
can be formed with a variety of features and components that
facilitate its deployment, retrieval and use in the intervention
operations. For example, dynamic seal 24 may comprise a sealing
element 70, such as a compressible rubber element, that can be
compressed to form a seal around conveyance 40. A squeezing element
72 may be positioned proximate sealing element 70 to enable
selective compression of the sealing element which, in turn, allows
control to be excised over the force with which sealing element 70
engages conveyance 40. The squeezing element 72 may be controlled
via pressures established in compliant guide 22, differential
pressures across dynamic seal 24, by direct hydraulic control via a
dedicated control line, or by other appropriate control mechanisms.
By way of example, sealing element 70 and squeezing element 72 may
be positioned in upper dynamic seal region 64. Upper region 64 also
may comprise a fishing neck 74 to allow engagement of a fishing
tool if necessary. The upper region 64 also may comprise other
elements, such as a grease injection system to provide a more
efficient seal against conveyance 40 in case of high differential
pressures across dynamic seal 24.
[0050] Dynamic seal 24 also may comprise a variety of other
components, such as an external sealing device 76 that enables
formation of a seal between dynamic seal 24 and compliant guide 22,
or other surrounding structure, once the dynamic seal 24 reaches
its desired subsea location 42. The combination of sealing against
the conveyance and sealing against the internal surface of the
compliant guide helps prevents well fluids from escaping the well
during an intervention operation. External sealing device 76 may
comprise a variety of seal technologies, including those used in
swab cups, traveling pigs, and other seal technologies able to form
a sufficient seal. The dynamic sealing assembly 24 and external
sealing device 76 also can be designed to seal against specifically
designed surfaces separate from the internal surfaces of the
compliant guide 22.
[0051] A locking mechanism 78 is designed to lock dynamic seal 24
in position once it reaches desired subsea location 42. A variety
of locking mechanisms can be utilized. However, one embodiment of
locking mechanism 78 comprises one or more locking dogs or pins 80
that are spring biased via one or more springs 82 for engagement
with corresponding receptacles 84 once dynamic seal 24 reaches
desired subsea location 42. The dynamic seal 24 also may be
designed with a weak point for releasing the dynamic seal when a
predefined differential pressure or pulling force is applied.
Additionally, a central sealing device 86 may be provided to
automatically seal off the opening through which conveyance 40
normally extends in the event conveyance 40 is removed. By way of
example, sealing device 76, locking mechanism 78 and central
sealing device 86 may be generally positioned in central region
66.
[0052] Other dynamic seal features may comprise an appropriate
attachment mechanism 88 by which dynamic seal 24 is selectively
attached to conveyance 40 during deployment and the retrieval of
the dynamic seal. Attachment mechanism 88 may be a clamping member
designed to clamp onto conveyance 40 with sufficient force to
secure dynamic seal 24 to the conveyance during transfer. The
engagement of attachment mechanism 88 as well as the disengagement
of locking mechanism 78 may be initiated mechanically by, for
example, movement of intervention tool string 38 into engagement
with a tool catcher 90 of dynamic seal 24, as illustrated in FIG.
2. However, a variety of mechanical, hydraulic, electrical or other
control mechanisms can be used to engage and disengage both
attachment mechanism 88 and locking mechanism 78. By way of
example, attachment mechanism 88 may be positioned in lower dynamic
seal region 68. However, the position, configuration and
arrangement of the dynamic seal components can change depending on
the dynamic seal design parameters, environment and intervention
operations anticipated.
[0053] The dynamic seal may also comprise a check valve system. The
check valve system is designed to seal the cavity through which the
conveyance passes in the event of the conveyance breaking and being
forced out of the dynamic seal, such that the conveyance is no
longer presence the cavity. The check valve system seals the
passage when the conveyance is not presence and against
differential pressure in both directions.
[0054] In FIG. 2, the dynamic seal assembly 24 is illustrated as
attached to conveyance 40 as it is moved down through compliant
guide 22 to the desired subsea location 42. Movement of dynamic
seal 24 can be aided by pumping a fluid, e.g. water, into compliant
guide 22 above dynamic seal 24 and applying downward pressure as
indicated by arrows 92. Pumping fluid into compliant guide 22 and
applying pressure to an upper side of dynamic seal 24 also can
facilitate movement of the dynamic seal 24 through the bends and
deviated sections of compliant guide 22. Fluid in the lower dynamic
seal 24 can escape through an exit port 94 and is released to the
sea, brought back to the surface, or injected into the well.
[0055] In some applications of the present invention the
retrievable dynamic seal does not present a seal between it's body
and the internal surfaces of the compliant guide, and it moves
attached to the conveyance without the need to apply pressure and
to have a way of escape for the fluid in the compliant guide below
the retrievable dynamic seal.
[0056] Regardless of whether pressure is applied via fluid above
dynamic seal 24, the dynamic seal 24 is ultimately moved to desired
subsea location 42 where it is landed on a landing mechanism 96 and
locked into position by locking mechanism 78, is best illustrated
in FIG. 3.
[0057] Once dynamic seal 24 is landed, conveyance 40 is released by
releasing attachment mechanism 88. This allows conveyance 40 to
move down and/or up with respect to dynamic seal 24. In some
embodiments, control over the differential pressure above and below
dynamic seal 24 can be used to apply a greater or lesser squeezing
force against conveyance 40 via sealing element 70. For example,
the pressure of buffer fluid 34 in compliant guide 22 can be
increased to activate sealing element 70 via squeezing element 72.
When sealing element 70 of dynamic seal 24 is appropriately
activated to form a sufficient seal against conveyance 40, the
pressure of the buffer fluid 34 can be substantially equalized with
the pressure of borehole fluid 98 and the well can be opened.
[0058] When the well is opened, tool string 38 can be deployed into
the subsea well 46 for performance of the desired intervention
work, as illustrated in FIG. 4. Pressure of the borehole fluid 98
can be monitored from the surface, and the pressure of buffer fluid
34 in compliant guide 22 can be adjusted from the surface via
pressure control equipment 36 to maintain the desired differential
pressure. The subsea well 46 is opened by opening an appropriate
wellbore seal 100 which may be part of existing subsea installation
components or combinations of components. For example, the subsea
well 46 can be opened for deployment of intervention tool string 38
by opening lubricating valve 52, opening blowout preventer rams, or
opening other wellbore seal components or combinations of
components.
[0059] Upon completion of the intervention operation, the
intervention tool string 38 is pulled back to a position above
wellbore seal 100, as illustrated in FIG. 5. The wellbore seal 100
is then closed to isolate compliant guide 22 from subsea well 46.
Borehole fluid may be replaced by clean fluid between dynamic seal
24 and wellbore seal 100. The buffer fluid pressure in compliant
guide 22 is then released so that dynamic seal 24 can be retrieved
to the surface. Intervention tool string 38 is pulled up against
dynamic seal assembly 24 and into engagement with tool catcher 90,
as illustrated in FIG. 6. In this embodiment, the top or head of
intervention tool string 38 mechanically releases locking mechanism
78 and engages attachment mechanism 88. Conveyance 40 is then
pulled upwardly to retrieve dynamic seal 24 and intervention tool
string 38 to the surface. In some applications, fluid is pumped
from the interior of compliant guide 22, and clean fluid is allowed
to enter beneath dynamic seal 24 through a port, such as port 94.
While retrieving dynamic seal assembly 24, buffer fluid 34 can be
flushed to the surface for recovery and reconditioning if
necessary.
[0060] The use of compliant guide 22 and retrievable dynamic seal
assembly 24 facilitates deployment and retrieval of intervention
tool string 38. This system and methodology simplifies and
increases the efficiency with which intervention tool strings can
be interchanged. Additionally, the ability to quickly and
efficiently retrieve dynamic seal enables its easy maintenance and
replacement of the dynamic sealing elements, which are subject to
wear when the conveyance moves up and down in the well.
[0061] Intervention system 20 also may include or be combined with
other components and features. For example, the dynamic seal 24 may
comprise an automatic sealing release that can be actuated by, for
example, a pre-defined differential pressure to enable fluid to be
pumped through the dynamic seal. The system 20 also can be designed
to provide a grease injection sealing system having a grease
reservoir to enable grease injection under a specified differential
pressure. The grease injection system can be designed for use when
pressure control is lost at the surface. For example, if pressure
in the compliant guide drops and the differential pressure across
dynamic seal 24 become too great, it may become desirable or
necessary to inject grease to maintain the seal. The (automatic)
grease injection can be triggered by, for example, relatively
higher pressure above dynamic seal 24, relatively higher pressure
below dynamic seal 24, or a specific differential pressure in
either direction.
[0062] Intervention system 20 facilitates deployment of many types
of tool strings in a dependable and efficient manner. The compliant
guide 22 provides a protected environment through which dynamic
seal 24 is readily transported to an operative position. The
overall design enables use of a relatively simple dynamic seal
while maintaining great system adaptability and providing an
efficient way of deploying and retrieving intervention tool
strings, while minimizing the size and weight of the sealing
equipment to be deployed.
[0063] A second embodiment of the invention for a subsea
intervention system is illustrated in FIGS. 7 to 11. Similar
numbering to those used to illustrate the first embodiment has been
used to illustrate similar parts in the second embodiment shown
FIGS. 7 to 11.
[0064] In FIG. 7 a retrievable dynamic seal 24 is located in
compliant guide 22 and is shown to include a dynamic sealing member
102 integrated into the upper portion 104 of dynamic seal 24. In
FIG. 8 dynamic sealing member 102 is shown integrated into the
lower portion 105 of dynamic seal 24. It is possible to convey the
retrievable dynamic seal 24 together with the intervention
toolstring 38, through open waters in the case of riserless
operations, or through a rigid riser, flexible riser, drillpipe,
tubing, spoolable compliant guide or any other suitable tubular
conduit connecting the subsea installation to a surface moving
vessel.
[0065] The retrievable dynamic seal 24 can be temporarily locked to
the top of the intervention toolstring 38 by means of a mechanical
locking system 106 in the form of tool catching fingers, which
prevents the body of the retrievable dynamic seal 24 from sliding
up on the conveyance 40 during the descent towards the subsea
installation.
[0066] The retrievable dynamic seal 24 can land into a dedicated
sealing surface and lock itself in place by means of a mechanical
locking system 108, or it can be locked in place by activating an
external system, like for example the rams 110 shown in FIG. 11,
which can both hold the dynamic seal 24 in place and seal against
its body at the same time.
[0067] Once the retrievable dynamic seal 24 is locked in place, an
automatic system well known to the person skilled in the art will
release the locking system 106 holding the toolstring 38, and the
toolstring 38 attached to the conveyance 40 will be able to move up
and down through the retrievable dynamic seal 24 to perform the
required intervention operations.
[0068] When the retrievable dynamic seal 24 lands in its seat,
communication is established between a hydraulic activation circuit
112 and the chamber 114 below an activation piston 116 of the
dynamic seal member 102. The hydraulic pressure is contained also
by the elastomeric seals 118 or by the sealing/locking rams 110.
Applying hydraulic pressure to the fluid contained in the
activation circuit 112 through the conduit 119 in the rams 110 will
push the dynamic seal activation piston 116 in the direction of
compressing the dynamic seal element 102, activating in this way
the dynamic seal 24 against the conveyance 40, and creating a valid
pressure barrier which can hold differential pressure between the
upper and lower sides of the dynamic seal element 102.
[0069] Once the intervention operation is completed and the
toolstring 38 is ready to be retrieved to surface, the intervention
toolstring 38 is pushed up against the body of the retrievable
dynamic seal 24. This action activates the mechanism 106 that locks
the head of the intervention toolstring 38 in the retrievable
dynamic seal body, activates an equalization system that equalizes
the pressure above and below the retrievable dynamic seal 24,
unlocks the locking system 108 and allows the retrievable dynamic
seal 24 to be retrieved towards the surface together with the
intervention toolstring 38.
[0070] FIG. 9 represents an alternative configuration of the second
embodiment of the invention, where two independent dynamic seal
members 102 are integrated into the same retrievable dynamic seal
24, one in the upper portion 104 and the other in the lower portion
105, each of the dynamic seal members 102 having its own hydraulic
activation circuit 112. In this configuration the two dynamic seal
members 102 can either be activated at the same time, or one can
act as a backup dynamic seal member to the other one, and be
activated only in case of failure of the other dynamic seal member
102. The dynamic seal can also have a fail-safe mode whereby in the
case of a lose of control of the activating signal, the dynamic
seal will lock into position and the dynamic seal will be activated
to create a seal around the conveyance.
[0071] FIG. 10 represents yet another alternative configuration of
the second embodiment of the invention, where two dynamic seal
members 102 are embedded into the same retrievable dynamic seal 24,
and both seal members 102 are activated by the same hydraulic
activation circuit 112. In this configuration the lower dynamic
seal 102 in the lower portion 105 has been turned upside down, and
is in this case activated from above rather than from below as it
was in the previous cases. In this configuration the two dynamic
seal member activation pistons 116 include between them a tubular
sliding link 120 which allows the variation of the distance between
the two activation pistons 116 by means of an elastomer seal
between the extremities of the sliding link 120 and the bodies of
the activation pistons 116. At the same time the tubular sliding
link 120 has the function of containing the hydraulic activation
pressurized fluid from escaping along the conveyance 40 in between
the two activation pistons 116.
[0072] In an even further configuration of the invention it is
conceivable to use viscous grease in the hydraulic activation
circuit, in order to improve the sealing performance of the dynamic
seal sealing element 102 and extend its operating range even to the
highest differential pressures and in presence of gas.
[0073] Other changes can be made while staying within the scope of
the invention. Although only a few embodiments of the present
invention have been described in detail above, those of ordinary
skill in the art will readily appreciate that many modifications
are possible without materially departing from the teachings of
this invention. Accordingly, such modifications are intended to be
included within the scope of this invention as defined in the
claims.
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