U.S. patent application number 11/014822 was filed with the patent office on 2006-03-09 for jackup oil rig and similar platforms.
This patent application is currently assigned to Offshore Technology Development Pte Ltd. Invention is credited to Kok Seng Foo, Margarita Ivanova Georgieva, Chin Kau Quah.
Application Number | 20060051164 11/014822 |
Document ID | / |
Family ID | 35996403 |
Filed Date | 2006-03-09 |
United States Patent
Application |
20060051164 |
Kind Code |
A1 |
Foo; Kok Seng ; et
al. |
March 9, 2006 |
Jackup oil rig and similar platforms
Abstract
An improved jackup oil rig or similar structure that can operate
in harsher environments compared to jackup oil rigs is described.
The improved oil rigs is able to operate in harsher environments
with a worse sea state as it has a built-in capability of driving
and extracting piles without the need for dedicated pile drivers or
extractors. Further, this oil rig is able to operate in icy waters
as it has a novel, inventive and cost-effective ice breaking means.
The rig makes use of its own jackup capability to perform these
functions and can extend its productivity by being capable of
operating in harsher environments for a longer period of time.
Inventors: |
Foo; Kok Seng; (Singapore,
SG) ; Georgieva; Margarita Ivanova; (Singapore,
SG) ; Quah; Chin Kau; (Singapore, SG) |
Correspondence
Address: |
LAWRENCE Y.D. HO & ASSOCIATES PTE LTD
30 BIDEFORD ROAD, #07-01, THONGSIA BUILDING
SINGAPORE
229922
SG
|
Assignee: |
Offshore Technology Development Pte
Ltd
|
Family ID: |
35996403 |
Appl. No.: |
11/014822 |
Filed: |
December 20, 2004 |
Current U.S.
Class: |
405/228 ;
405/195.1; 405/196 |
Current CPC
Class: |
E02B 17/0021 20130101;
E02B 2017/0043 20130101; E02B 2017/0056 20130101; E02B 2017/0039
20130101; E02B 2017/0052 20130101; E02B 17/021 20130101; E02B
2017/0086 20130101 |
Class at
Publication: |
405/228 ;
405/195.1; 405/196 |
International
Class: |
E21B 17/01 20060101
E21B017/01; E02D 13/00 20060101 E02D013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 7, 2004 |
SG |
200404950-8 |
Claims
1. A method for driving piles for a jackup rig, the jackup rig
comprising a jackup hull, a mat and at least one leg, the method
comprising: b. installing a piling sub-system on the rig; the
piling sub-system comprising a plurality of piles, each pile with
at least one collars, each collar with a locking means; c. moving
the rig to a desired location; d. raising the jackup hull with the
piling sub-system unlocked; e. locking the locking means for at
least one pile; f. lowering the jackup hull a predetermined
distance, thereby driving in the at least one pile into the seabed;
g. unlocking the locking means for the at least one pile; h.
raising the jackup hull by another predetermined distance, leaving
the at least one pile unmoved; i. repeating steps d to g until the
pile is driven to a desired depth; and j. repeating steps c to h
until the desired number of piles is driven into place, thereby
utilizing the built-in jackup capability of the rig to obviate the
need for a dedicated pile driver.
2. A method according to claim 1 wherein the locking and unlocking
of the locking means is coordinated by a control sub-system.
3. A method for extracting piles for a jackup rig, the jackup rig
comprising a jackup hull, a mat and at least one leg, the method
comprising: a. installing a piling sub-system on the rig; the
piling sub-system comprising a plurality of piles, each pile with
at least one collars, each collar with a locking means; b. lowering
the jackup hull a first predetermined distance with the piling
sub-system unlocked; c. locking the locking means for at least one
pile; d. raising the jackup hull a second predetermined distance,
thereby extracting in the at least one pile from the seabed; e.
unlocking the locking means for the at least one pile; f. lowering
the jackup hull by another predetermined distance, leaving the at
least one pile unmoved; g. repeating steps c to g until the pile is
extracted; and h. repeating steps b to g until a desired number of
piles are extracted, thereby utilizing the built-in jackup
capability of the rig to obviate the need for a dedicated pile
extractor.
4. A method according to claim 3 wherein the locking and unlocking
of the locking means is coordinated by a control sub-system.
5. A jackup oil rig possessing a pile driving and extracting
capability, the pile driving and extracting capability comprising a
piling sub-system; the piling sub-system further comprising: at
least one collar; at least one locking means; at least one pile;
wherein the at least one collar, the at least one locking means and
the at least one pile work in conjunction with the jackup oil rig
to drive and extract the at least one pile without the need for a
dedicated pile driver or extractor.
6. The jackup oil rig according to claim 5, the pile driving and
extracting capability further comprising a control sub-system to
coordinate the operation of the piling sub-system.
7. A jackup rig comprising an upper hull and a mat, the jackup rig
further possessing at least one ice-breaking means wherein the at
least one ice breaking means breaks ice only by being moved against
ice by the operation of the jackup rig.
8. The jackup rig of claim 7, the ice breaking means located at the
underside of the upper hull.
9. The jackup rig of claim 7, the ice breaking means located at the
upper surface of the mat.
10. The jackup rig of claim 7, the ice breaking means suspended
from the upper hull.
11. The jackup rig of claim 7, the ice breaking means comprising a
heavy metal structure sloped on both upper and lower surfaces for
ice breakage.
12. The jackup rig of claim 7, the upper hull further comprising
recesses to house the ice breaking means.
13. The jackup rig of claim 7, the mat further comprising recesses
to house the ice breaking means.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to self-elevating or jackup
oil rigs and similar platforms.
[0002] In particular, this invention relates to a method and system
for jackup oil rigs and similar platforms to allow them to be used
in more severe environments than prior art oil rigs, such as bodies
of water with thin surface ice.
[0003] More particularly, this invention relates to a method and
system utilizing the built-in jackup capabilities of such platforms
to drive piles into the seabed to anchor the jackup oil rig or
similar platforms without the need for dedicated pile drivers. This
will reduce the initial and recurrent costs of operating such
rigs.
[0004] Another aspect of the present invention extends the built-in
jackup capability of such rigs in the breakup of ice formation
around the rig in cold operating environments.
BACKGROUND OF THE INVENTION
[0005] Oil rigs are offshore structures that are used to extract
petroleum and other naturally-formed hydrocarbon deposits (e.g.,
natural gas) from the seabed. However, many oil fields are found in
inhospitable locations. These locations may have extreme
environmental conditions such as storms and ice at certain times of
the year.
[0006] To maximize their output or productivity, oil rigs are
operated for as long as possible in the window of opportunity
afforded by the milder months. This window may be as short as three
months in the higher latitudes. When the environmental conditions
change for the worse, these rigs may be temporarily abandoned or if
they are mobile, displaced to another safer location.
[0007] To enable such mobility, oil rigs may be self-propelled or
may be towed to the desired site, and anchored. The means of
anchoring are well known in the art. These may include legs that
reach to the seabed enabled by jacking systems such as in U.S. Pat.
No. 6,076,996 and in the oil rigs designed and built by the
applicant of the present invention (U.S. Pat. No. 6,030,149).
Alternatively, oil rigs may be submersible or semi-submersible by
having ballast tanks that may be flooded to anchor the oil rig as
exemplified by U.S. Pat. No. 5,292,207.
[0008] Besides having to be securely anchored during use, there is
the danger posed by ice formations to oil rigs in arctic
conditions. Currently, icebreaker ships may be employed to break up
ice formation around an oil rig to prevent the ice build-up from
damaging the rig. In the case of U.S. Pat. No. 5,292,207 or U.S.
Pat. No. 6,371,695, the rigs may possess built-in means or provide
a crush-resistant structure against encroaching ice, obviating the
need for icebreaker ships.
[0009] These built-in ice breaking means are usually heavily sloped
plates or plates installed around the support legs of a rig. The
idea behind such inventions is that by flexing the ice will cause
it to fracture. Thus, as the ice sheet is formed and moves against
the rig, the ice sheets slide up the slope of the plate. As the
angle of the slope is sharp, the rigid ice sheet does not bend and
instead fractures. As such, damage from ice sheets building up
around the supporting leg is prevented. In another invention, U.S.
Pat. No. 4,102,144, the ice breaking means is raised along the
supporting leg to break the ice. The shield may be heated to melt
ice pieces adhering to it, dislodging them.
[0010] These inventions show that means to anchor an oil rig or
similar structure are important, as are means to prevent damage
from ice build-up.
[0011] Therefore, there is a continued need for means to allow an
oil rig or similar structure to operate in harsher environments
such as rough seas or icy conditions to tap the hydrocarbon
reservoirs in these regions. An invention that can withstand such
conditions will extend the window of operation for oil rigs,
increase the production capacity while reducing costs, and hence
improve the profitability of the rig. Such an invention will be
welcomed in the industry.
SUMMARY OF THE INVENTION
[0012] The present invention discloses, in a first aspect, a method
for driving piles for a jackup rig, the jackup rig comprising a
jackup hull, a mat and at least one leg, the method comprising:
[0013] a. installing a piling sub-system on the rig; the piling
sub-system comprising a plurality of piles, each pile with at least
one collars, each collar with a locking means; [0014] b. moving the
rig to a desired location; [0015] c. raising the jackup hull with
the piling sub-system unlocked; [0016] d. locking the locking means
for at least one pile; [0017] e. lowering the jackup hull a
predetermined distance, thereby driving in the at least one pile
into the seabed; [0018] f. unlocking the locking means for the at
least one pile; [0019] g. raising the jackup hull by another
predetermined distance, leaving the at least one pile unmoved;
[0020] h. repeating steps d to g until the pile is driven to a
desired depth; and [0021] i. repeating steps c to h until the
desired number of piles is driven into place, [0022] thereby
utilizing the built-in jackup capability of the rig to obviate the
need for a dedicated pile driver.
[0023] The invention also discloses, in a second aspect, a method
for extracting piles for a jackup rig, the jackup rig comprising a
jackup hull, a mat and at least one leg, the method comprising:
[0024] a. installing a piling sub-system on the rig; the piling
sub-system comprising a plurality of piles, each pile with at least
one collars, each collar with a locking means; [0025] b. lowering
the jackup hull a first predetermined distance with the piling
sub-system unlocked; [0026] c. locking the locking means for at
least one pile; [0027] d. raising the jackup hull a second
predetermined distance, thereby extracting in the at least one pile
from the seabed; [0028] e. unlocking the locking means for the at
least one pile; [0029] f. lowering the jackup hull by another
predetermined distance, leaving the at least one pile unmoved;
[0030] g. repeating steps c to g until the pile is extracted; and
[0031] h. repeating steps b to g until a desired number of piles
are extracted, [0032] thereby utilizing the built-in jackup
capability of the rig to obviate the need for a dedicated pile
extractor.
[0033] The present invention also discloses, in a third aspect, a
jackup oil rig possessing a pile driving and extracting capability,
the pile driving and extracting capability comprising a piling
sub-system; the piling sub-system further comprising: [0034] at
least one collar; [0035] at least one locking means; [0036] at
least one pile; [0037] wherein the at least one collar, the at
least one locking means and the at least one pile work in
conjunction with the jackup oil rig to drive and extract the at
least one pile without the need for a dedicated pile driver or
extractor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] A preferred embodiment of the present invention will now be
more fully described, by way of example, with reference to the
drawings of which:
[0039] FIG. 1 illustrates the method by which the legs and piles of
a jackup oil rig of the prior art are put into place;
[0040] FIG. 2A illustrates the collar and locking means for the
piles while FIG. 2B is the plan view of an oil rig showing the
disposition of the piles around the perimeter of an oil rig with a
triangular configuration;
[0041] FIG. 3 illustrates the sequence by which piles are driven by
the method of the present invention.
[0042] FIG. 4 illustrates the sequence by which the piles are
extracted by the method of the present invention; and
[0043] FIGS. 5 to 8 are embodiments of the present invention for
breaking ice utilizing the built-in jackup capability of jackup
rigs and similar platforms.
DETAILED DESCRIPTION OF THE DRAWINGS
[0044] In accordance with the detailed descriptions, a preferred
embodiment of the invention is described, together with a few
variations to illustrate the versatility of the invention. In the
following description, details are provided to describe the
preferred embodiment. It shall be apparent to one skilled in the
art, however, that the invention may be practiced without such
details. Some of these details may not be described at length so as
not to obscure the invention.
[0045] There are many advantages of the preferred embodiment of the
invention. One advantage of the preferred embodiment is that it is
resistant against the impact of ice. Another advantage is that
additional supports for a jackup oil rig in the form of piles may
be driven in place and subsequently extracted without the need for
a dedicated pile driver or winch.
[0046] Another advantage is that ice formation around such rigs or
similar platforms may be broken up using novel and inventive means
based on the built-in jackup capability of such rigs and
platforms.
[0047] Referring now to FIG. 1, the method of putting an oil rig of
the prior art into operation is described. Such an oil rig is
exemplified by a model designed and built by the applicant of the
present invention.
[0048] Such an oil rig is first moved into position by one or more
barges (FIG. 1A). The oil rig comprises an jackup hull 100
connected to a lower structure, a buoyant watertight mat 200, by
one or more legs 300. When in position, ballast tanks in the mat
are flooded and the mat sinks until it reaches the seabed 400 (FIG.
1B).
[0049] Thereafter, the rig's built-in jacking system, itself
comprising of complementary jackup modules 500 of elevating units
of jacks and locks working in unison, is used to raise the jackup
hull 100 above sea level for a predetermined distance (FIG. 1C).
This may be done in one continuous operation or a series of
operations until an air gap 410 is achieved. The air gap is the
height or distance of the bottom of the jackup hull above sea
level.
[0050] The oil rig is now largely ready to begin actual drilling
operations with the volume of water in the mat acting as ballast to
anchor and stabilize the rig. However, it may be desirable, for
example, in rough seas, to have additional supports comprising
piles 600 driven into the seabed to further anchor the oil rig
(FIG. 1D). In the prior art, this is done by erecting a dedicated
pile driver 700 to drive the piles into the seabed 400. When it is
time to displace the oil rig, a winch or vibratory pile extractor
(such as those manufactured by the International Construction
Equipment company) is needed to remove the piles from the
seabed.
[0051] Under the present invention, a novel and inventive method is
taught whereby use of a dedicated pile driver and pile extractor is
obviated. The system of the present invention is a jackup oil rig
or similar structure possessing the capability and means described
and practicing the invention according to the methods as taught
below.
[0052] In the present invention, the mass and jacking system of the
oil rig are used to drive the piles. To extract the piles, the
jacking system and the buoyancy of the rig is used. As the jacking
system is already part of a jackup rig's built-in machinery, no
additional cost for a dedicated pile driver or extractor are
needed. This cuts costs significantly as, in the prior art, the
dedicated pile driver and extractor are only needed at the
beginning and end of a rig's operational period at any particular
site. While such rig is in operation, the pile driver and extractor
remain essentially idle and does not contribute to productivity
while contributing to the cost of the rig.
[0053] The only additional features required to practice the
invention are the installation of a piling sub-system 800
comprising collars 810 (FIG. 2A) that align and guide the piles and
locking means that work in conjunction with the collars to engage
and grip the piles during insertion and extraction, and the piles
700 to be driven in. These features are in addition to the
supporting legs 300 and jackup modules 500 already present in a
jackup rig. At least one such collar 810 with its accompanying
locking means, here shown as a pin 820 as an example, is used for
each pile 700 to be driven in (FIG. 2A). The locking means
comprises as least one pin driven to engage or withdraw from a
complementary recess in the pile. These complementary recesses are
found at intervals along each pile.
[0054] By way of example, for an oil rig of a triangular
configuration of 240 ft length by 220 ft width, eight to 10 piles
700 evenly disposed around the perimeter of the oil rig is
recommended (FIG. 2B). This is only an illustration and the number
and disposition of the collars and piles may be varied according to
the configuration of the rig and the conditions under which they
operate.
[0055] The collars and locking means may be readily retrofitted
into existing oil rigs or included in the constructions of new
ones. If desired, the piles may also be further supported by guides
or bores 210 built into the mat such that the alignment of the pile
is substantially perpendicular to the horizontal plane of the mat
200 or jackup hull 100 (FIG. 1D).
[0056] FIG. 3 shows how piles are driven in by the method of the
present invention. The oil rig of the present invention is first
moved into position (FIG. 3A). On the rig are elements of the
piling sub-system 800 (comprising a plurality of the collars and
locking means) and piles 700 previously described. The lower ends
of the piles are substantially flushed with the bottom of the
mat.
[0057] The mat 200 is then lowered (FIG. 3B) by blowing its ballast
tanks and letting in water until the mat rests on the seabed. The
jackup hull 100 remains at the level of the water surface as it is
buoyant. As the locking means are not engaged, friction with the
bores 110, 210 and their own mass allow the piles 700 to be brought
down with the lowering of the mat to the seabed 400. The arrows in
the figures indicate the movement of the piles.
[0058] The rig or structure's jacking system is then engaged to
raise the jackup hull 100 (FIG. 3C) to a predetermined height above
the level of the water. It may be seen that the lower ends of the
piles remain in contact with the seabed 400 during this operation
as the piles are not being gripped or engaged by the locking means
800. As such, they slide freely within the collars 810, and the
bores 110, 220 as the jackup hull is raised.
[0059] Thereafter, depending on capability of the jacking system,
the number of piles present, and the type and condition of soil in
the seabed, one or more piles may be locked by their respective
locking means 800 in preparation for being driven into the
seabed.
[0060] The jacking system is then engaged in the reverse direction
to lower the jackup hull 100 (FIG. 3D), driving any piles 700 that
are locked into the seabed 400 a predetermined distance. A person
skilled in the art will appreciate that in this driving operation,
both the jacking force generated by the jacking system and the mass
of the jackup hull are harnessed to drive in the pile. This total
force of the jackup system alone may be as high as 46,800 kips for
the rig example cited and is considerably greater than that
generated by most pile marine pile drivers in use. A person skilled
in the art will appreciate that the number of piles that may be
driven in simultaneously depends on a variety of factors such as
the mass of the jackup hull, the power of the jacking system, and
the seabed conditions.
[0061] Once a pile is driven in, the jackup hull 100 is then jacked
up again with the locking means 800 released or disengaged,
allowing the collars to freely slide up the piles, leaving the
piles that were just driven in position, unmoved (FIG. 3E).
[0062] The locking means for the pile just driven in may be
reengaged and the hull lowered again to further drive in the pile
until the appropriate depth is desired. A person skilled in the art
of pile driving will appreciate that this operation may be repeated
as many times as necessary until the pile has been driven to the
desired depth. A person skilled in the art will also appreciate
that, with the present invention, a number of piles may be
simultaneously driven in to save time and cost. This is a huge
increase in efficiency over the use of a pile driver to
sequentially drive in the piles one by one. When driving in
multiple piles at the same time, it is apparent to one skilled in
the art that it will be best to drive in the piles such that the
total force generated Backing force and mass of the hull) be evenly
and symmetrically distributed to the piles being driven. For
example, piles at the apices of an oil rig with a triangular
configuration may be driven in at the same time.
[0063] Once the last pile has been driven in, the hull is then
raised to the desired height above the sea level (air gap 410) and
the oil rig can then begin its drilling and extraction operations
(FIG. 3F).
[0064] When it is time to displace the rig to avoid extreme
conditions, or when the location has been exhausted of its
hydrocarbon deposits, the present invention may be used to extract
the piles without the need for a dedicated extractor or winch. It
will be apparent to one skilled in the art that reversing the
process of driving in the piles will extract the piles, except that
now, it is the buoyancy, not the mass, of the jackup hull, that
work in conjunction with the jackup system in this extraction
operation.
[0065] As shown in FIG. 4A, the locking means 800 for all the piles
700 are released. The jackup system is then engaged in reverse to
lower the jackup hull 100, preferentially until part of it is below
the waterline. In most rigs, the jackup hull is watertight and is
thus positively buoyant. Thereafter, the locking means for one or
more piles to be extracted are engaged and the hull jacked up to a
predetermined height (FIG. 4B). The raising of the hull will pull
up any engaged piles and the buoyancy of the hull is tapped to
assist in the extraction of the piles.
[0066] The locking means that were engaged are now released and the
hull lowered again (FIG. 4C). Then the locking means for the
partially extracted piles 700 are reengaged and the hull raised.
This operation is repeated until the all the piles are extracted.
Even if the hull is not buoyant, the considerable force generated
by the jacking system itself is greater than that of a winch or
vibratory extractor. As such, multiple piles may be extracted
simultaneously instead of sequentially as with technology of the
prior art. This saves time and cost for the installation or rental
of a dedicated extractor.
[0067] It will be appreciated that the sequence of operations
(locking and unlocking the piles, raising and lowering the jackup
hull, etc) may be done manually or automatically. The degree of
automation desired may be obtained by installing a suitable control
sub-system to coordinate the locking and unlocking of the locking
means with the jackup operation. A person skilled in the art will
appreciate that such a control sub-system may be readily
implemented and as such, details of this control sub-system is not
described so as not to obscure the invention.
[0068] Also, the operation of the locking means may be powered by
any suitable means of motive force, such as those supplied by
electrical, mechanical, electromechanical, hydraulic or pneumatic
means. Such motive means and control sub-systems come under the
scope of the present invention.
[0069] It will be apparent to a person skilled in the art that
variations to the guiding of the piles may be done while keeping
within the scope and spirit of the invention. For example, we have
described and illustrated that the piles are already in place in
their collars at the start of the driving operation. It is clear
that the piles need not be pre-positioned and may also be inserted
into place after the rig has arrived and the mat lowered into
position. Such preparatory details are not essential in this
invention. What is essential is the idea to use the built-in
capabilities of the jacking system of a jackup rig to replace a
dedicated pile driver and extractor. This extended use of the
jackup system and capability of jackup rigs and similar structures
are hitherto untapped in rigs of the prior art.
[0070] The present invention also provides for a method and system
to break up ice formation around the rig using the jackup system of
the rig; it maximizes the capabilities of the jackup system and
thereby extending the useful operating window of the rig in icy or
arctic conditions.
[0071] The ice breaking means of the present invention is a heavy
three-dimensional metal structure, preferably resembling a
three-dimensional heavily-sloped trapezoidal or pyramidal structure
900 with sharp corners (FIGS. 5, 6, 7 and 8). The ice breaking
means is also preferentially disposed circumferentially around, or
near the legs 300 of the jackup rig. This is because ice sheets 420
pose great risk to the legs of an oil rig.
[0072] The ice breaking means may be located on the underside of
the jackup hull 100 (FIG. 5) or on the upper surface of the mat 200
(FIG. 6), depending on the depth of water the rig is operating in.
In very shallow water, the ice breaking means may be arranged on
the mat such that the ice breaking means is at or near the surface
of the water where the ice sheets will form.
[0073] To break up forming ice sheets 420, the jackup system of the
present invention is engaged to lower the upper hull 100 until the
lower surface of the upper hull forces against the ice sheets.
Regardless of whether the ice breaking means 900 is located on the
underside of the upper hull (FIG. 5) or on the upper surface of the
mat (FIG. 6), the mass and shape of the ice breaking means, the
mass of the upper hull and the power of the jackup system, provide
sufficient force to fracture the ice 430 (FIGS. 5B and 6B; arrows
indicate the direction of movement of the jackup hull).
[0074] It is clear that an ice breaking means with sharp corners
will be better at fracturing the ice although smooth rounded shapes
will also work. To facilitate the housing of the ice breaking means
while the rig is in transit, corresponding recesses 960 and 970 may
be constructed in the opposing surface to contain the ice breaking
means.
[0075] It can be seen that the breaking of ice in the present
invention is to use the jackup system of the oil rig to move the
jackup hull 100 against a fixed structure such as the mat 200 or
the ice breaking means 900. As such, in another embodiment (FIG.
7), the ice breaking means 910 may be fixed around each supporting
leg of the rig, at the surface of the water. As the jackup hull 100
is lowered, ice 430 is broken by being sandwiched between the
jackup hull 100 and the ice breaking means 910 (FIG. 7B).
[0076] Unlike the ice breaking method of U.S. Pat. No. 4,102,144,
wherein the ice breaking shield is raised to break ice, the ice
breaking means in yet another embodiment (FIG. 8) of the present
invention can break ice when it is both raised or lowered, as it is
sloped on both the upper 930 and lower 940 surfaces, making it more
efficient than that of the prior art.
[0077] In this embodiment, the ice breaking means 910 is heavy and
held by a suspension means 950 such as chains or ropes to the
underside of the upper hull, and is preferentially disposed around
or near each supporting leg 300 of the rig (FIG. 8A).
[0078] Referring again to FIG. 8A, the length of the suspension
means 800 supporting the ice breaking means is adjusted after the
oil rig is deployed and operational so that the ice breaking means
is held at a "resting" position. This resting position is near
(above or below), or at the waterline. As ice sheets build up,
raising or lowering the ice breaking structure 910 will break the
ice sheets 430.
[0079] If the ice breaking means were "resting" above the waterline
(FIG. 8A), lowering it a short distance will fracture ice sheets
430 that are building up below it (FIG. 8B). Conversely, a person
skilled in the art will appreciate that if the ice breaking means
is suspended above the waterline, lowering it (by lowering the
entire jackup hull) will break the ice. Unlike the other ice
breaking embodiments of the present invention, the mass of the
upper hull is not used. Rather, the ice breaking means relies on
its own mass to break the ice when it is lowered with the lowering
of the jackup hull 100.
[0080] Also unlike the prior art, the suspension means 500 is not
involved in the raising or lowering of the ice breaking means but
rather, it is merely to maintain the ice breaking means at the
desired resting position.
[0081] This resting position is a matter of choice. If the ice
breaking means is held just under the surface of the water, the
raising of the ice breaking means will utilize both the power of
the jackup system and the shape of the ice breaking means to
perform this function. As such, this embodiment (FIG. 8) works when
the ice breaking means is raised or lowered. In addition, by the
ice breaking means being suspended, the distance by which the upper
hull has to be moved is reduced. This aspect of the present
invention essentially improves the efficiency of breaking ice by
over one fold over methods of the prior art in an inventive and
non-obvious way.
[0082] This method is non-obvious as prior art inventions such as
U.S. Pat. No. 4,102,144 are shaped and configured to break ice only
when the ice breaking means is raised. That invention does not
perform its function when lowered to its "resting position".
[0083] Again, as with the other embodiments, concave recesses 960,
970 in the jackup hull 100 and mat 200 respectively (see example in
FIG. 8) receive the ice breaking structure in a stowed position
during transit.
[0084] A person skilled in the art will appreciate that unlike the
first embodiment of the ice breaking means, the means do not
necessarily have to move along the supporting legs. They merely
need to be affixed to either the bottom of the jackup hull or the
top of the mat and the complementary recesses 960 and 970 are
provided to receive the ice breaking structures during transit.
[0085] It will be appreciated that the sequence of operations
(monitoring of the ice build-up and the raising and lowering the
ice breaking means, etc) may be done manually or automatically. The
degree of automation desired may be obtained by the installation of
a suitable control system.
[0086] Additionally, the driving of the various mechanical aspects
of the present invention (eg locking means, adjustment of the
suspension means of the ice breaking means, etc) may be obtained by
suitable electrical, pneumatic, hydro-pneumatic or hydraulic
actuators and devices. A person skilled in the art will appreciate
that such devices are easily implemented. As such, further
description of such devices is not provided so as not to obscure
the invention.
[0087] The present invention therefore provides, in one aspect, a
method of driving and extracting piles for a jackup rig and similar
structures without the need for dedicated pile drivers or
extractors. In another aspect, the present invention is a jackup
oil rig or similar structures possessing capability afforded by the
elements and features described for driving and extracting piles,
and practicing the methods taught.
[0088] In yet another aspect, the present invention provides a
jackup oil rig or similar structure with an ice breaking capability
exemplified by the several embodiments of a novel and innovative
built-in ice protection means taught.
[0089] It is apparent to one skilled in the art that, while the ice
breaking aspect of the present invention are described, such ice
breaking means are not necessary for practicing the invention of
driving and extracting piles in warmer waters where there is no
danger from ice sheets.
[0090] While the present description is for an oil rig, it is
apparent to one skilled in the art, that the present invention may
be applied to structures similar to jackup oil rigs such as
geological survey vessels and wreck recovery ships. Additionally,
while a marine oil rig is described, oil rigs and similar
structures used for other bodies of water (e.g., lakes, rivers
& etc) also come within the scope and spirit of the present
invention.
[0091] It will be appreciated that although only a few preferred
embodiments have been described in detail, various modifications
and improvements can be made by a person skilled in the art without
departing from the scope of the present invention.
[0092] The present invention is novel and inventive as there is
nothing in the prior art to suggest the use of jackup systems in an
oil rig or similar platforms, to drive and extract piles, or to
break up ice formation. Jackup oil rigs and similar platforms have
always used separate means such as pile drivers and extractors for
piles and separate ice-breaking means to handle ice sheets. It is
clear that, with this application, the invention is non-obvious,
even to persons skilled in the art.
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