FIELD OF THE INVENTION
[0001] The present invention relates generally to oil and gas exploration and production,
and in a specific, non-limiting embodiment, to a system and method of installing and
maintaining an offshore exploration and production system having an adjustable buoyancy
chamber.
BACKGROUND OF THE INVENTION
[0002] Innumerable systems and methods have been employed in efforts to find and recover
hydrocarbon reserves around the world. At first, such efforts were limited to land
operations involving simple but effective drilling methods that satisfactorily recovered
reserves from large, productive fields. As the number of known producing fields dwindled,
however, it became necessary to search in ever more remote locales, and to move offshore,
in the search for new resources. Eventually, sophisticated drilling systems and advanced
signal processing techniques enabled oil and gas companies to search virtually anywhere
in the world for recoverable hydrocarbons.
[0003] Initially, deepwater exploration and production efforts consisted of expensive, large
scale drilling operations supported by tanker storage and transportation systems,
due primarily to the fact that most offshore drilling sites are associated with difficult
and hazardous sea conditions, and thus large scale operations provided the most stable
and cost-effective manner in which to search for and recover hydrocarbon reserves.
A major drawback to the large-scale paradigm, however, is that explorers and producers
have little financial incentive to work smaller reserves, since potential financial
recovery is generally offset by the lengthy delay between exploration and production
(approximately 3 to 7 years) and the large capital investment required for conventional
platforms and related drilling and production equipment. Moreover, complex regulatory
controls and industry-wide risk aversion have led to standardization, leaving operators
with few opportunities to significantly alter the prevailing paradigm. As a result,
offshore drilling operations have traditionally been burdened with long delays between
investment and profit, excessive cost overruns, and slow, inflexible recovery strategies
dictated by the operational environment.
[0004] More recently, deepwater sites have been found in which much of the danger and instability
present in such operations is avoided. For example, off the coast of West Africa,
Indonesia and Brazil, potential drilling sites have been identified where surrounding
seas and weather conditions are relatively mild and calm in comparison to other, more
volatile sites such as the Gulf of Mexico and the North Sea. These recently discovered
sites tend to have favorable producing characteristics, yield positive exploration
success rates, and admit to production using simple drilling techniques similar to
those employed in dry land or near-shore operations.
[0005] However, since lognormal distributions of recoverable reserves tend to be spread
over a large number of small fields, each of which yield less than would normally
be required in order to justify the expense of a conventional large-scale operation,
these regions have to date been underexplored and underproduced relative to its potential.
Consequently, many potentially productive smaller fields have already been discovered,
but remain undeveloped due to economic considerations. In response, explorers and
producers have adapted their technologies in an attempt to achieve greater profitability
by downsizing the scale of operations and otherwise reducing expense, so that recovery
from smaller fields makes more financial sense, and the delay between investment and
profitability is reduced.
[0006] For example, in published Patent Application No.
US 2001/0047869 A1 and a number of related pending applications and patents issued to Hopper et al.,
various methods of drilling deepwater wells are provided in which adjustments to the
drilling system can be made so as to ensure a better recovery rate than would otherwise
be possible with traditional fixed-well technologies. However, the Hopper system cannot
be adjusted during completion, testing and production of the well, and is especially
ineffective in instances where the well bore starts at a mud line in a vertical position.
The Hopper system also fails to support a variety of different surface loads, and
is therefore self-limiting with respect to the flexibility drillers desire during
actual operations.
[0007] In
U.S. Letters Patent No. 4,223,737 to O'Reilly, a method is disclosed in which the problems associated with traditional, vertically
oriented operations are addressed. The method of O'Reilly involves laying out a number
of interconnected, horizontally disposed pipes in a string just above the sea floor
(along with a blow out preventer and other necessary equipment), and then using a
drive or a remote operated vehicle to force the string horizontally into the drilling
medium. The O'Reilly system, however, is inflexible in that it fails to admit to practice
while the well is being completed and tested. Moreover, the method utterly fails to
contemplate functionality during production and workover operations. In short, the
O'Reilly reference is helpful only during the initial stages of drilling a well, and
would therefore not be looked to as a systemic solution for establishing and maintaining
a deepwater exploration and production operation.
[0008] Other offshore operators have attempted to solve the problems associated with deepwater
drilling by effectively "raising the floor" of an underwater well by disposing a submerged
wellhead above a self-contained, rigid framework of pipe casing that is tensioned
by means of a gas filled, buoyant chamber. For example, as seen in prior
U.S. Letters Patent No. 6,196,322 B1 to Magnussen, the Atlantis Deepwater Technology Holding Group has developed an artificial buoyant
seabed (ABS) system, which is essentially a gas filled buoyancy chamber deployed in
conjunction with one or more segments of pipe casing disposed at a depth of between
600 and 900 feet beneath the surface of a body of water. After the ABS wellhead is
fitted with a blowout preventer during drilling, or with a production tree during
production, buoyancy and tension are imparted by the ABS to a lower connecting member
and all internal casings. The BOP and riser (during drilling) and production tree
(during production), are supported by the lifting force of the buoyancy chamber. Offset
of the wellhead is reasonably controlled by means of vertical tension resulting from
the buoyancy of the ABS.
[0009] The Atlantis ABS system is deficient, however, in several practical respects. For
example, the '322 Magnussen patent specifically limits deployment of the buoyancy
chamber to environments where the influence of surface waves is effectively negligible,
i.e., at a depth of more than about 500 feet beneath the surface. Those of ordinary
skill in the art will appreciate that deployment at such depths is an expensive and
relatively risk-laden solution, given that installation and maintenance can only be
carried out by deep sea divers or remotely operated vehicles, and the fact that a
relatively extensive transport system must still be installed between the top of the
buoyancy chamber and the bottom of an associated recovery vessel in order to initiate
production from the well.
[0010] The Magnussen system also fails to contemplate multiple anchoring systems, even in
instances where problematic drilling environments are likely to be encountered. Moreover,
the system lacks any control means for controlling adjustment of either vertical tension
or wellhead depth during production and workover operations, and expressly teaches
away from the use of lateral stabilizers that could enable the wellhead to be deployed
in shallower waters subject to stronger tidal and wave forces.
[0011] Thus, there is plainly a widespread need for a system and method of disposing an
offshore wellhead in a manner such that drillers can adjust both the depth of a wellhead
and the vertical tension applied to associated pipe casing throughout the duration
of exploration and production operations. There is also a need for an adjustable buoyancy
chamber system capable of maintaining approximately constant vertical tension on an
associated drilling or production string, and adjusting either the height of a wellhead
at any time during exploration and production by releasing additional lengths of tension
line from a buoyancy chamber height adjustment member. There is also a need for an
offshore exploration and production system that flexibly admits to use in connection
with both deepwater and shallow target horizons, without necessarily being configured
to conform to any particular operational depth.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012]
Figure 1 is a side view of an offshore exploration and production system in which
an adjustable buoyancy chamber is employed to adjust the height or depth of an associated
well terminal member.
Figures 2A and 2B are side views of an offshore exploration and production system,
in which lateral and vertical forces on an adjustable buoyancy chamber are held approximately
constant while the height of an associated well terminal member is adjusted by releasing
additional lengths of tension line.
SUMMARY OF THE INVENTION
[0013] A system and method of establishing an offshore exploration and production system
is provided, in which a well casing is disposed in communication with an adjustable
buoyancy chamber and a well hole bored into the floor of a body of water. A lower
connecting member joins the well casing and the chamber, and an upper connecting member
joins the adjustable buoyancy chamber and a well terminal member. The chamber's adjustable
buoyancy enables an operator to vary the height or depth of the well terminal member,
and to vary the vertical tension imparted to drilling and production strings throughout
exploration and production operations. Also provided is a system and method of adjusting
the height or depth of a wellhead while associated vertical and lateral forces remain
approximately constant. A variety of well isolation members, lateral stabilizers and
anchoring means, as well as several methods of practicing the invention, are also
disclosed.
DETAILED DESCRIPTION
[0014] Referring now to the specific, non-limiting embodiment of the invention depicted
in Figure 1, an offshore exploration and production system is provided, comprising
a well casing 2 installed in communication with a submerged well 1 and an adjustable
buoyancy chamber 9, wherein a lower connecting member 5 is disposed between the well
casing and the adjustable buoyancy chamber. In a presently preferred embodiment, the
well 1 is accessed from above by means of a well hole 3 that has been bored into an
associated sea floor surface. In a typical embodiment, a well casing 2 is set into
the hole in a firm and secure manner, and then cemented into place using known downhole
technology. In other embodiments, a well casing is securely set into the well hole
3, and a fluid transport member, such as a smaller-diameter pipe or pipe casing, is
inserted into well casing 2. Once a desired fit has been achieved, the outer surface
of the fluid transport member is cemented or set with a packer to the inner surface
of the well casing. Those of ordinary skill in the art will appreciate that while
the embodiment described above refers to but a single well, the offshore exploration
and production system disclosed herein can be readily adapted to simultaneously work
multiple neighboring wells without departing from the scope or spirit of the invention.
[0015] According to a one embodiment, a well isolation member 4 is disposed between well
casing 2 and a lower connecting member 5. In some embodiments, well isolation member
4 comprises one or more ball valves, which, if lower connecting member 5 is removed,
can be closed so that the well is effectively shut in. In further embodiments, well
isolation member 4 comprises a blowout preventer or a shear ram that can be maintained
in either an open or closed position in order to provide access to, or to instead
shut in, the contents of well 1.
[0016] In other embodiments, lower connecting member 5 further comprises one or more receiving
members disposed to receive an attachment member disposed on well isolation member
4. In an alternative embodiment, lower connecting member 5 comprises an attachment
member for attaching said lower connecting member 5 to a receiving member disposed
on well isolation member 4. Methods and means of securely fastening lower connecting
member 5 to well isolation member 4 are known to those of ordinary skill in the art,
and may comprise one or more of a wide variety of fastening techniques, e.g., hydraulic
couplers, various nut and bolt assemblies, welded joints, pressure fittings (either
with or without gaskets), swaging, etc., without departing from the scope or spirit
of the present invention.
[0017] Likewise, lower connecting member 5 may comprise any known connecting means appropriate
for the specific application contemplated by operators. For example, in various embodiments,
lower connecting member 5 comprises one or more of segments of riser, riser pipe,
and/or pipe casing. In some embodiments, lower connecting member 5 comprises a concentric
arrangement, for example, a fluid transport member having a smaller outer diameter
than the inner diameter of a pipe casing in which the fluid transport member is housed.
[0018] In further embodiments, lower connecting member 5 is disposed in communication with
one or more lateral stabilizers 6, which, when deployed in conjunction a plurality
of tension lines 7, effectively controls horizontal offset of the system. By utilizing
the buoyant forces of adjustable buoyancy chamber 9, lower connecting member 5 is
drawn taut and held in a stable position.
[0019] In an alternative embodiment, one or more stabilizers 6 control horizontal offset
of lower connecting member 5, and the height or depth of an associated well terminal
member 14 is adjusted by varying the length of upper connecting member 12. In some
embodiments, the vertical tension of lower connecting member 5 is held approximately
constant while the height or depth of well terminal member 14 is adjusted. In further
embodiments, the height or depth of well terminal member 14 is held approximately
constant, while the vertical tension imparted by adjustable buoyancy chamber 9 on
lower connecting member 5 is adjusted. In still further embodiments, the height or
depth of well terminal member 14 and the vertical tension applied to lower connecting
member 5 are held approximately constant, while lateral adjustments are performed
using lateral stabilizer 6 and one or more of tension lines 7.
[0020] In certain embodiments, one or more lateral tension lines 7 are individually adjustable,
whereas in other embodiments, the tension lines 7 are collectively adjustable. In
further embodiments, one or more tension lines 7 are both individually and collectively
adjustable. In still further embodiments, the one or more lateral stabilizers 6 are
disposed in communication with a tension measuring means, so that a fixed or predetermined
amount of lateral tension can be applied to lower connecting member 5 in order to
better control system offset. In some embodiments, the tension lines 7 are anchored
to the sea floor by means of an anchoring member 8, for example, a suction type anchor,
or alternatively, a mechanical or conventional deadweight type anchor.
[0021] In a presently preferred embodiment, adjustable buoyancy chamber 9 is approximately
annular in shape, so that lower connecting member 5 can be passed through a void longitudinally
disposed in a central portion of the device. In further embodiments, adjustable buoyancy
chamber 9 further comprises a plurality of inner chambers. In still further embodiments,
each of the chambers is independently operable, and different amounts of air or gas
(or another fluid) are disposed in the chambers to provide greater adjustable buoyancy
control. In one example embodiment, adjustable buoyancy chamber 9 further comprises
a fluid ballast that can be ejected from the chamber, thereby achieving greater chamber
buoyancy and lending additional vertical tension to lower connecting member 5. Those
of ordinary skill in the art will appreciate that many appropriate fluid ballast can
be used to increase or retard buoyancy; for example, compressed air is an appropriate
fluid that is both inexpensive and readily available.
[0022] In some embodiments, adjustable buoyancy chamber 9 further comprises a ballast input
valve, so that a fluid ballast can be injected into the chamber from an external source,
for example, through an umbilical line run to the surface or a remote operated vehicle,
so that an operator can deliver a supply of compressed gas to the chamber via the
umbilical, thereby adjusting buoyancy characteristics as desired. In other embodiments,
the fluid input valve is disposed in communication with one or more pumps or compressors,
so that the fluid ballast is delivered to the chamber under greater pressure, thereby
effecting the desired change in buoyancy more quickly and reliably.
[0023] In other embodiments, adjustable buoyancy chamber 9 further comprises a ballast output
valve, so that ballast can be discharged from the chamber. In instances where air
or another light fluid is injected into the chamber while water or another heavy liquid
is discharged, the chamber will become more buoyant and increase vertical tension
on lower connecting member 5. Conversely, if water or another heavy liquid is injected
into the chamber while air is bled out, the chamber will lose buoyancy, thereby lessening
vertical tension on lower connecting member 5.
[0024] In alternative embodiments, the ballast output valve is disposed in communication
with one or more pumps or compressors, so that ballast is ejected from the chamber
in a more reliable and controlled manner. In some embodiments, the ballast output
valve is disposed in communication with an umbilical, so that ballast ejected from
the chamber can be recovered or recycled at the surface. In any event, a principle
advantage of the present invention is that adjustments to the chamber's buoyancy and
tensioning properties, and the ability to control the height of the well terminal
member 14, can be performed at any time during either exploration or production, due
to the various ballast input and output control means disposed about the body of the
chamber.
[0025] In further embodiments, adjustable buoyancy chamber 9 is further disposed in communication
with one or more tension lines 10 provided to anchor the adjustable buoyancy chamber
to the sea floor. As before, tension lines 10 are anchored to the sea floor using
known anchoring technology, for example, suction anchors or dead weight type anchors,
etc. The one or more tension lines 10 can also provide additional lateral stability
for the system, especially during operations in which more than one well is being
worked. In one embodiment, the one or more tension lines 10 are run from the adjustable
buoyancy chamber 9 to the surface, and then moored to other buoys or a surface vessel,
etc., so that even greater lateral tension and system stability are achieved. In further
embodiments, the tension lines 10 are individually adjustable, whereas in other embodiments,
the tension lines 10 are collectively controlled. In still further embodiments, the
one or more tension lines 10 are both individually and collectively adjustable.
[0026] In one example embodiment, adjustable buoyancy chamber 9 is disposed in communication
with a vertical tension receiving member 11. In another embodiment, the vertical tension
receiving member 11 is equipped with a tension measuring means (e.g., a load cell,
strain gauge, etc.), so that vertical tension applied to lower connecting member 5
is imparted in a more controlled and efficient manner. In another embodiment, the
buoyant force applied to tension receiving member 11 is adjusted by varying the lengths
of tension lines 10, while the buoyancy of adjustable buoyancy chamber 9 is held approximately
constant. In a further embodiment, the buoyancy of adjustable buoyancy chamber 9 is
controlled by means of one or more individually selectable ballast exhaust ports disposed
about the body of the chamber, which vent excess ballast fluid to the surrounding
sea. In still further embodiments, the open or closed state of the ballast exhaust
ports are individually controlled using port controllers known to those of ordinary
skill in the art (e.g., plugs, seacocks, etc.).
[0027] In a presently preferred embodiment, the system is disposed so that a well terminal
member 14 installed above buoyancy chamber 9 is submerged to a depth at which maintenance
and testing can be carried out by SCUBA divers using lightweight, flexible diving
equipment, for example, at a depth of about 100 to 300 feet beneath the surface. In
some embodiments, the well terminal member 14 is submerged only to the minimum depth
necessary to provide topside access to the hulls of various surface vessels servicing
the well, meaning that well terminal member 14 could also be disposed at a much shallower
depth, for example, a depth of about 50 to 100 feet. In alternative embodiments, well
terminal member 14 is disposed at depths of less than 50 feet, or greater than 300
feet, depending upon the actual conditions surrounding operations. In still further
embodiments, well terminal member 14 is disposed either at the surface or above the
surface of the water, and a blowout preventer or a production tree is installed by
workers operating aboard a service platform or surface vessel. This "damp tree" model
avoids the need to assemble long subsurface riser stacks, as would generally be required
during deepwater operations. Moreover, disposing the well terminal member at or near
the surface also permits testing and maintenance to be carried out by SCUBA divers
or surface crews, without the need for expensive and time-consuming remote operated
vehicle operations.
[0028] In some embodiments, well terminal member 14 further comprises either a blowout preventer
or a production tree. In a presently preferred embodiment, however, well terminal
member 14 further comprises a combined blowout preventer and production tree assembly
configured so as to facilitate simplified well intervention operations.
[0029] In some embodiments, lower connecting member 5 terminates within the void formed
in a center portion of the annular chamber 9, at which point an upper connecting member
12 becomes the means by which fluids are transported up to the wellhead. In other
embodiments, lower connecting member 5 does not terminate within the void formed in
a center portion of the annular chamber, but instead runs through the void and is
subsequently employed as an upper connecting member 12 disposed between the chamber
and the wellhead. In other embodiments, a vertical tension receiving member 11 is
disposed between the buoyancy chamber 9 and upper connecting member 12, so that the
chamber's buoyant forces are transferred to the vertical tension receiving means 11,
thereby applying vertical tension to the drilling or production string extended below
the chamber.
[0030] In further embodiments, upper connecting member 12 further comprises a well isolation
member 13, e.g., one or more ball valves or blowout preventers, used to halt fluid
flow in the event that well terminal member 14 is either removed or disabled, for
example, during testing and maintenance operations. Those of ordinary skill in the
art will appreciate that the precise types and exact locations of isolation valves
13 employed in the system are variable and flexible, the only real requirement being
that the valves are capable of allowing or preventing fluid flow from the well 1 during
periods in which testing or maintenance, or even an emergency safety condition, are
present.
[0031] For example, well terminal member 14 can be equipped with a production tree so that
a production hose disposed on a surface vessel can be attached to the system and production
can commence. Alternatively, well terminal member 14 can terminate in a blowout preventer,
so that the well will not blow out during drilling operations. In other embodiments,
well terminal member 14 terminates in a combined production tree and blowout preventer
assembly to facilitate simplified well intervention operations.
[0032] Turning now to the specific, non-limiting embodiments of the invention depicted in
Figures 2A and 2B, a system and method of establishing a height-variable well terminal
member is provided, comprising a lower fluid transport pipe 21, an inner well casing
22, an outer well casing 23, and a wellhead 24. In some embodiments, a well isolation
member 25 is disposed above the wellhead 24, so that the well can be closed off or
shut in if desired.
[0033] In the example embodiment depicted in Figure 2A, well isolation member 25 further
comprises one or more ball valves that can be adjustably opened or closed as desired
by an operator. A lower connecting member 26 having one or more interior seals 27
and an interior polished bore 28 houses a fluid transport member 29 such that the
height of fluid transport member 29 is variably adjustable within a body portion of
lower connecting member 26 in response to vertical lifting forces imparted by adjustable
buoyancy chamber 30. Various lengths of pipe define the height of an upper connecting
member disposed between the buoyancy chamber 30 and a well terminal member 36. In
some embodiments, an upper well isolation member 35, such as a ball valve or a blowout
preventer, is disposed in communication with the upper connecting member between buoyancy
chamber 30 and well terminal member 36.
[0034] In some embodiments, the system is moored to the sea floor using one or more mooring
lines 31 connected to a first vertical tension receiving means 32a, while buoyancy
chamber 30 is raised or lowered by either spooling-out or reeling-in lengths of one
or more tension lines 37 disposed between a second vertical tension receiving means
32b and a chamber height adjustment means 33. As adjustable buoyancy chamber 30 rises,
vertical tension is applied to vertical tension receiving member 34, which in turn
lifts well terminal member 36 up toward the surface.
[0035] As seen in the example embodiment depicted in Figure 2B, the height of both the well
terminal member 36 and fluid transport member 29 are vertically adjusted by increasing
the length of tension lines 37 using chamber height adjustment means 33, even as vertical
and lateral tension on mooring lines 31 and tension lines 37 remains approximately
constant. In one embodiment, vertical tension on lower connecting member 26 is also
kept approximately constant during this process, since fluid transport member 29 is
moved vertically within a body portion of lower connecting member 26. In another embodiment,
a second, lower adjustable buoyancy chamber is added to the system to maintain tension
on lower connecting member 26, while the height of the well terminal member is adjusted
as described above.
[0036] The foregoing specification is provided for illustrative purposes only, and is not
intended to describe all possible aspects of the present invention. Moreover, while
the invention has been shown and described in detail with respect to several exemplary
embodiments, those of ordinary skill in the pertinent arts will appreciate that minor
changes to the description, and various other modifications, omissions and additions
may also be made without departing from either the spirit or scope thereof.
1. A method of transferring fluid flow initiated from a subsurface wellhead (24) disposed
beneath the surface of a body of water to a fluid retention vessel disposed nearer
the surface of said body of water, said method comprising:
buoyantly supporting a well control system within said body of water;
positioning said well control system through said subsurface wellhead;
initiating a fluid flow from said subsurface wellhead;
receiving said fluid flow from said subsurface wellhead using a fluid flow receiving
means;
transferring said fluid flow from said fluid flow receiving means to said well control
system; and
transferring said fluid flow from said well control system to said fluid retention
vessel.
2. The method of transferring fluid flow initiated from a subsurface wellhead of claim
1, wherein said method further comprises:
buoyantly supporting said well control system within said body of water using a buoyancy
chamber (9; 30).
3. The method of transferring fluid flow initiated from a subsurface wellhead of claim
1, wherein said method further comprises:
positioning said well control system through said subsurface wellhead (24) using a
stress joint.
4. The method of transferring fluid flow initiated from a subsurface wellhead of claim
3, wherein said method further comprises:
receiving said fluid flow from said subsurface wellhead (24) using said stress joint.
5. The method of transferring fluid flow initiated from a subsurface wellhead of claim
1, wherein said method further comprises:
transferring said fluid flow from said fluid flow receiving means to said well control
system using production casing.
6. The method of transferring fluid flow initiated from a subsurface wellhead of claim
1, wherein said method further comprises:
transferring said fluid flow from said well control system to said fluid retention
vessel using at least one of a production tree, a blowout preventer, and a wellhead
disposed nearer the surface of said body of water than said subsurface wellhead.
7. A means for transferring fluid flow initiated from a subsurface wellhead (24) disposed
beneath the surface of a body of water to a fluid retention vessel disposed nearer
the surface of said body of water, said means comprising:
means (9; 30) for buoyantly supporting a well control system within said body of water;
means for positioning said well control system through said subsurface wellhead;
means for initiating a fluid flow from said subsurface wellhead;
means for receiving said fluid flow from said subsurface wellhead;
means for transferring said fluid flow from said subsurface wellhead to said well
control system; and
means for transferring said fluid flow from said well control system to said fluid
retention vessel.
8. The means for transferring fluid flow initiated from a subsurface wellhead disposed
beneath the surface of a body of water of claim 7, wherein said means further comprises:
a buoyancy chamber (9; 30) for supporting said well control system within said body
of water.
9. The means for transferring fluid flow initiated from a subsurface wellhead disposed
beneath the surface of a body of water of claim 7, wherein said means further comprises:
a stress joint for positioning said well control system through said subsurface wellhead.
10. The means for transferring fluid flow initiated from a subsurface wellhead disposed
beneath the surface of a body of water of claim 9, wherein said stress joint is also
used for receiving said fluid flow from said subsurface wellhead.
11. The means for transferring fluid flow initiated from a subsurface wellhead disposed
beneath the surface of a body of water of claim 7, wherein said means further comprises:
a length of production casing for transferring said fluid flow from said subsurface
wellhead to said well control system.
12. The means for transferring fluid flow initiated from a subsurface wellhead disposed
beneath the surface of a body of water of claim 7, wherein said means further comprises:
at least one of a production tree, a blowout preventer, and a wellhead disposed nearer
the surface than said subsurface wellhead used for transferring said fluid flow from
said well control system to said fluid retention
vessel.
13. A system for transferring fluid flow initiated from a subsurface wellhead (24) disposed
beneath the surface of a body of water to a fluid retention vessel disposed nearer
the surface of said body of water, said system comprising:
a buoyancy chamber (9; 30) for buoyantly supporting a well control system within said
body of water;
a means for positioning said well control system through said subsurface wellhead;
a means for initiating a fluid flow from said subsurface wellhead;
a fluid flow receiving means for receiving said fluid flow from said subsurface wellhead;
a length of production casing for transferring said fluid flow from said fluid flow
receiving means to said well control system; and
at least one of a production tree, a blowout preventer and a wellhead disposed nearer
the surface of said body of water used for transferring said fluid flow from said
well control system to said fluid retention vessel.
14. The system for transferring fluid flow initiated from a subsurface wellhead disposed
beneath the surface of a body of water of claim 13, wherein said means for positioning
said well control system through said subsurface wellhead further comprises a stress
joint.
15. The system for transferring fluid flow initiated from a subsurface wellhead disposed
beneath the surface of a body of water of claim 14, wherein said stress joint is also
used to receive said fluid flow from said subsurface wellhead.