Note: Descriptions are shown in the official language in which they were submitted.
I
PILED OF THE INVENTION
This invention is directed to a novel method
and apparatus for constructing artificial islands in
relatively shallow waters. More particularly, this
invention it directed to a novel method and apparatus
for constructing artificial induce in relatively
shallow bodice of water such as lake r seas and ocean
for use in drilling oil and gay wells and in~tallin4
storage and production platform.
BACKGROUND OF THE INVENTION
In recent years, with mankind' 5 increasing and
continuous reliance upon hydrocarbon fuels and products,
and the depletion ox exiting oil field on land in the
western hemi~phsr~, extensive and costly efforts have
been made to locate petroleum deposits that underlay the
floor of various large bodies of water such as lakes,
seas and oceans. In North America, substantial oil and
gas well drilling activity has taken place in the
Beau fort Sea, which is in the Arctic Ocean north of
Alaska and the northern territorial of Canada.
Petroleum geologists generally believe that several of
the sedimentary geological formations located below the
floor ox the Beau fort Sea contain large deposits of
petroleum material.
I being in a polar region, drilling oil and gas
wells in the effort Sea it hazardous and extensive
ope~atlon. ambient temperatures are Qxtremoly low
during the wintertime. Moreover, tremendous pressures
are generated against the drilling station by polar ice.
One of the methods used in the effort Sea in
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preparation for drilling an oil well is to build an
artificial island at the location where the well is to
be drilled, The material for such islands is dredged
from the sea floor and piled in one location until the
surface of the island is above the water and is level.
Substantial erupt to date has been concentrated in the
Canadian sector of the Beau fort Sea where the explore-
lion procedure has followed two main patterns. In
relatively shallow water, up to about 19 eaters,
drilling has been a winter operation from artificial
sand islands formed the previous summer by dredging and
dumping from barges. In deeper water, from 25 to 68
metros, drilling has been a summer operation using
drill-shipaO
Sand deposited under water tends to take up a
very flat edgy slope of about 7 to 8 percent with the
result that artificial islands in water deeper than
about 10 Metro consume huge quantities of sand and
are hence very expensive to construct. In order to
overcome this problem, a caisson-retained island has
been developed whereby the upper portion of the sand is
retained by a ring or collar of caissons. These are
founded on an underwater pad of dredged sand about 10
meres below sea level. Dome Petroleum, a large
Canadian company which it actively searching for oil in
the Beau fort Sea, completed a concrete caisson-retained
island in the fall of 1981. Essay Resources is presently
proceeding with the construction of a tensioned-steel
Cowan retained island.
Numerous procedures and apparatus for drilling
oil wells in the formations below water bodies have been
proposed. Some of these procedures and apparatus are
disclosed in the patents listed below: -
patent No. Issue Date Inventor
US. 2,472,869 June 14, 1949 Traverse
2,589,153 March 11, 1952 Smith
2,939,290 June 7, 1960 Craze
Tao Feb. 28, 1961 McLean
104,037,424 July 26, 1977 Angers
4,080,7~B March 28, 1978 Reusswig et at.
4,118,941 Oct. 10, 1978 Bruce
Cdn.470,212 Dec. 19, 1950 Traverse
966,320 April 22, 1975 Guy
~71,758 July 29, 1975 Best
1,963,817 Oct. 9, 1979 Coachmen
1,066,900 Nov. 27, 1979 Bennett
The basic theme of most of these references is
to provide artificial islands or operation sites in
water bodies such as the Beau fort Sea or the Gulf of
Mexico for the purpose of supporting equipment such as
drilling rigs engaged in searching for petroleum
deposits below the water body floor. Current techniques
for building islands cost in the hundreds of millions of
dollars and usually consist in part of dredging solid
matter from the water body f loon and heaping it to
thereby provide a foundation of earth material upon
which can be situated various type of hardware such as
submerged barges or caissons, the tops of which
ultimately penetrate the surface of the water body. In
moms kiwi, to reduce slump, the idea of the land are
supported with a retaining member such a a wall or
caisson.
SUMMARY OF THE INVENTION
The present invention lo directed to a eddy
and apparatus for constructing an artificial island by
taking atr0noth~ned oil tanlcers, oil~bulk/ore or oil/ore
tankers, transporting them to ohs diehard sites, either
under their own power or by wowing, and partially sub-
merging the hulls, with awry and waler ballast dredged
from the Roe floor, The hulls can be used individually
or in combination. The concept of Herb the flexibility
of providing a movably drilling island, which can ha
achieved in a relatively short lima by partially
submerging the hull or hull, conducting the desired
operation such as drilling an oil well, and then when
completed, refloating the hull and transporting it to a
new site. Alternatively, the partially submerged hull
can be left in place to form a production or Tory
platform The bow(s) of the substantially submerged
hull B) would normally be pointed in the direction of
the prevailing winds, WOW and ice action for the
area.
The invention it directed to method of forming
tubule drooling production or Atari facility in a
relatively shallow hvdy of water which may be contested
with ice or other objects comprising: con~tructlng a
vessel which can float or be partially submerged by
taking on liquid or solid ballast and of sufficient ma
and strength to provide tabulate for oil well drilling,
production or storage operations, and movement
resistance against wave, ice and other objects
equipping the vessel with a drilling rig and a drill
stem and production cawing protector-rstainer located
below the drilling rig, the protector-rQtainer extending
downwardly from about the base of thy drilling rig or
produc~lon facility to the bottom of the vessel;
importing the vessel to the water or ice bound area
where thy drilling or production platform it to be
lotted and submerging the vessel with liquid or solid
ballast 80 that the buttock... of the vessel it founded on
the bottom of the water body, or on a pad formed on the
bottom of the water body, while the deck remains above
water, the protector-re~ainer protecting drill stem and
oil well production casing from interference by ice,
wave or other object and restraining any fluid
produced during drilling or operation of an oil well
from string the surrounding body of water.
The method may include drilling an oil well
into the floor of the water body while the partially
submersed hull it founded on the bottom of the water
body The hull may be refloated after being partially
merged by removing ballast from the interior of the
partially submerged hull.
I the oil jell experiences a blow-out during
the drilling thereof, the curds oil it dlrec~ed into the
$nterlor ox the partially submersed hull to prevent
contamination of the water body. The oil direction can
be automatic or by jump. A Rowley well may be drilled
prom the ~ar~lally submerged hull while the oil well it
- 5
experlenGin~ blow-out. Thy towered oil can by burnt
off or hauled away.
In the method, protective barrier may be
cons~ructad alongside By eye one wide of the partially
submerged hull by drudging solid material from the water
body floor and heaping it alongside thy partially
submerged hull. Thy artificial island may be formed by
two partially ~ubmarged ship hulls. The two partially
submerged hull may be arrayed 3ide-by-side in parallel
adjacent manner.
A protect barrier may be constructed
alongside at least one wide of the partially submerged
hull by dredging solid material from the water buddy
floor and heaping it alongside the partially submerged
lo hull which I arranged in V-pattern with another
partially submerged hull. The protective barrier
- aye -
! g
conY~ructed alongside at least one lye of the partially
~ubmarg~d hull may be formed by dredging solid and
liquid material from the water body floor and phrasing
the dreaded material, before duping the frozen
material on the waler body floor alongside ha partially
submersed hull.
A protective barrier may be ¢onstructad along-
side at least one side of thy partially submerged hull
by dredging solid and liquid material from the water
lo body floor, duping the dredged material on the our-
face of ice surrounding the partially submerged hull
thereby sinking thy ice and the dredged material onto
the water body floor. The dredged material is allowed
to freeze prior to submerging,
tarrier protection for the partially submerged
hull may Allah be created by partially submerging it
Lotte one ship hull 80 thee it projects radially from
the main partially submerged hull. A plurality of ship
hull on a radially deposed pattern may be placed
around the c1rcumfer~nce of the main partially ~ubmergad
hull. This is useful when the main hull us left in
place a production or Tories platform.
The invention it directed to a movable oil well
drilling and production structure capable of forming in
a relatively Lowe body ox water which may be
contested with ice and other objects a temporary or
permanan~ water bDtto~ founder oil well drilling,
production or storage facility comprising: a vessel
capable of being at least partially aubmercJed to ret on
the bottom ox the body of water or on a peal constructed
- 6
on the bottom of the water body and of ~ufficiant mast
and ~trenyth to provide stability for oil well drilling,
production so storage operation and movement r~sl~tance
again waves ice and other object; an oil wall
drilling rip, production or Turks facility carried by
the vowel and D protaçtor-retainer located under the
drilling fig or production facility and extending
downwardly from byway the bate of ha drilling rig or
~roductlon solute to the bottom of ho vessel Jo that
when thy visual it founded on the bottom of the body of
worry or on the pad, the protector-retainer prO~eCtB
drill to and oil well production cawing from
interference by ice, wave or other ox jacket, and
restrains any fluid produced during the drilling or
operation of the oil well from entering the surrounding
body of waxer.
I
- 6 ( a
The vessel may include means for ejecting
ballast from the interior of the hull to thereby refloat
the partially submerged visual. The vessel may be self-
propelling The vessel may have an oil well drilling
rig mounted on the deck of eye hull. The vessel may
also have a monopoly (an oil retaining cavity) built
into part of the interior of` the hull below the drilling
rig The hull of the vessel may be mounted on top of a
second whip hull to provide a double Decker hull. The
vessel may have two oil well drilling rigs moLInted on
the deck of the hull and two monopoly built into the
interior of the hull, one below each drilling rig.
Normally, the second monopoly would be at a reasonable
distance prom the first monopoly
In zones where the water body floor is mainly
clay-like in character, refloating may become a problem
due to suction created at the bottom of the vessel. In
order to overcome this suction action, it might be
desirable to install a number of pipes in the bottom of
the hull or lnje~ting air or water at suitable pressure
thereby relieving the suction force. In certain Sue-
Sheehan, to withstand extreme lateral forces ho increasing
the overall specific gravity of the submerged vessel, it
may be necessary to use iron ore pellets as ballast
instead of sand or the like
no withstand ice pressures, and the like, the
hull can be strengthened by using heavy steel cross-
struts, inter-rib reinforcing. Alternatively or in
accompaniment t the spaces between the frame members of
the hull can be filled with concrete and steel rein-
for cement. The rudder and propeller of the vessel can
be protected within a housing formed in the vessel body
so that the propeller and rudder can be used repeatedly
as the vessel is submerged for a time, refloated and
moved to a new site and then submerged again prior to
drilling a the new site.
To prevent freezing of ballast waxer, such
freezing bring capable of damaging the hull body, by
expansionary ice force, insulation Jo reduce heat loss
from the interior of the hull can be installed, or the
ballast water can be heated by sore suitable economical
means. The vessel can be equipped with its own dredge
in, sand and water pumping equipment so that it is
self-reliant.
DRAWINGS
In the drawings.
FIGURE 1 represents a perspective view of a
tanker converted for use as an artificial island and
drilling platform
FIGURE 2 represents a perspective view of two
hulls, one above the other, converted for use as an
artificial island and drilling platform;
FIGURE 3 represents a side elevation view of
the double Decker hull with a drilling rig erected in
place over a monopoly in the hull;
FIGURE 4 rcprcscnts an end elevation view of
the double Decker hull;
FIGURE 5 represents a side elevation view of
the double Decker hull supporting two drilling rigs, one
-- 8 --
rig for drilling the primary oil well and a second rig
for drilling a second oil will or a relief well;
FIGURE 6 represent a side elevation view of
the two rig double Decker hull combination depicted in
FIGURE 5 above, illustrating the manner in which a
relief hole it drilled to intersect with the main
drilling hole,
FIGURE 7 represents a plan view of a converted
hull equipped with two Minneapolis for dual fly drilling
capability
FIGURE 8 represents an end elevation view of
the hull depicted in FIGURE 7 above resting on the sea
floor;
FIGURE 9 represents a plan vie of two
converted hulls placed in parallel aligned position;
FIGURE 10 represent an end elevation view of
the twin hull depicted in FIGURE 9 above;
FIGURE 11 represent a plan view of a hull
converted according to the invention, together with a
dual-direction conveyor belt arrangement which can be
utilized for manufacturing protective ice-earth debris
and dumping it alongside the hull to provide a submerged
protective barrier for the hull;
FIGURE 12 reappearance a front elevation view of
the ship hull depicted in FIGURE 11 above, illustrating
the manner in which debris it placed on either side of
the hull to provide a projection barrier for the hull;
FIGURE 13 represents an end elevation view of
a pair of converted double Decker hulls placed in
parallel adjacent alignment with one another;
IRE 14 represent a plan elevation view of
a hull equipped with bottom debris pumping and spraying
equipment for use in spraying sand and soil onto the ice
perimeter surrounding the hull;
FIGURE 15 represents a plan elevation view of
a converted hull which may be detached in thy mid-region
to provide an artificial drilling island comprising the
two detached portions of the hull arranged in parallel
adjacerlt positions
FIGURE 16 represents a plan elevation view of
two adjacent aligned converted hulls, surrounded by
reinforcing barrier debris and a plurality of radially
disposed tanker Howe around the perimeter of the
barrier;
FIGURE 17 represents a plan elevation view of
two converted hulls arranged to provide a wedge arrange-
mint for withstanding ice and wave forces;
FIGURE 18 represents an end elevation Al view
ox the two Howe described in FIGLlRE 17 above;
2Q FIGURE 19 reprint a plan view of the manner
in which four converted hull can be utilized to provide
a protective whip harbor;
FIGURE 20 represents a plan view of the manner
in which two converted hulls can be arranged in end to
end relationship to provide an aircraft landing strip
FIGURE 21 represents a side elevation view of
a twin hull design pitted with a new bow section
FIGURE 22 represents a plan elevation view of
a twin hull design fitted with a new boy section;
- 10
FIGURE 23 reprint a side elevation view of
a twin hull design fitted with a new bow section and a
gunwales height extension;
FIGURE 24 represents a plan elevation view of
a twin hull design fitted with a new bow section and a
gunwales height extension;
FIGURE 25 represents a side elevation view of
a double Decker twin hull combination design, with the
lower twin hulls fitted with a new bow section;
FIGURE 26 represents a plan elevation view of
a double Decker twin hull combination design, with the
lower twin hulls fitted with a new bow section.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIGURE 1, a ship hull I accord-
15 in to one aspect of the invention, is equipped with and carries a drill rig 4. The hull is shown located in a
large body of ice 6. While not shown, the bottom of the
I
- AYE -
Sue
hull 2 rests on the bottom of the body of water support-
in the ice 6. The drill rig 4 is positioner towards
the stern of the hull 2 ahead of the wheel house 8. The
bow of the hull carries a heliport 12 which serves as a
landing pad for a helicopter 10. The helicopter 10
serves to provide 8uppl it for operation of the hull-
drill rig assembly. The hull 2 is suitable for opera-
lion in water of about 20 meres depth. This leaves
about 5 Quoter of freeboard.
FIGURE illustrates the manner in which,
according to another aspect of the invention, one
hull 14 is positioned above and secured to a second
hull 16 in double Decker manner. This double Decker
hull combination enables the hull-rig combination to
operate in deeper waters than the single hull version,
for example, waters of about 45 metros depth.
The double Decker hull arrangement as shown in
FIGURE 2 can be manufactured in a number of ways. One
possible way it to clean away the normal cock e~luil~ment
on a hull, sink the hull with suitable ballast, move
second floating hull into position over the submerged
hull, and then secure the two hulls together by suitable
bracing such as steel beams, welding and the like.
Wedges must be inserted in the tapered spaces that
normally exit between the deck of the underlying hull
and the bottom of the superimpose hull to offset the
lateral camber ousto~arily built Unto the fleck of the
underlying hull.
Normally, in Arctic waters. such as the
Beau fort Sea, either the single hull or douhle-decker
-- 11 --
hull design, when founded upon the floor of the water-
body, should be oriented with its bow facing to the
northwest into the direction of prevailing winds, waves
and ice migration prevalent in those areas. Even so, in
some locations, a wave deflector may be required along
one side to increase freeboard and limit the volume of
water token on deck from maximum broadside waves.
FIGURE 3 represents a side elevation view of
the double Decker hull design depicted in FIGURE I The
upper hull 14 is secured Jo the lower hull by welding
cables, steel reinforcement, and the like. As can be
teen in FIGURE 3, the drill rig 4 is positioned above a
monopoly 18 which extends vertically prom the fleck of
the upper hull 14 through the two hulls, to the bottom
of the lower hull 160 The monopoly 18 is an enclosed
cavity open to the atmosphere with overflow drains into
the hull or hull compartments. As can be seen in
FIGURE 3, the drill rig 4, by being positioned above the
monopoly 18, can raise and lower drill stem 20 through
the monopoly 18 into the scabbed below the bottom of
hull 16 for drilling in the manner of a conventional oil
well.
A very significant advantage of the moon-
pool 18 design is that if there it a blow-out of the
well being drilled, the crude oil that is blown out can
be initially contained within the confines of the moon-
pool 18 and then directed into the hull or compartments
thereby completely preventing pollution in the delicate
environment of the Arctic. If the blow-out is extensive
and long lasting, the escaping crude can be directed
automatically or pumped into the sizable compartment in
the upper hull 14 and the lower hull 16. The capacity
of these two hulls, even if partially taken up with
ballast, it significant and can in most cases contain
four to six months "wild" production from the well.
FIGURE 4 shows an end elevation view of the
double Decker hull design including the upper hull 14,
the lower hull 16 and the monopoly 180 FIGURE 4 also
illustrates the wedges 22 which are welded or secured in
place between the upper and lower hulls in order to off-
set the camber of the deck of the lower hull 16 and
provide a stable secure fit between the upper hull 1
and the lower hull 16.
As FIGURE 5 demonstrates, the double Decker
lo hull design can be fitted with two drilling rigs 4 and
I In such a case, the ship is also fitted With two
Minneapolis 18 and 26 respectively. The second rig 24 can
be used for drilling a relief hole to intersect with the
main hole being drilled by rig 4 if for sore reason,
such as a blow-out or a collapsillg formation, it icky
necessary to interconnect with the first hole. The
auxiliary rig 24, rather than acting as a relief mews-
urea can be used to drill a second hole at the same time
that the first hole is being drilled The direction of
the two hole can be diverged by means of directional
drill bit. This tandem arrangement can be important in
areas where the drilling season is short.
FIGURE 6 illustrates in side elevation view
the manner in which a relief hole 28 can intersect with
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Jo
main hole 30 utilizing the dual rig arrangement, fig 4
and rig 24, discussed above.
FIGURE 7 illustrates in plan elevation view a
typical single hull 32 with two Minneapolis 34 and 36.
FIGURE 8 illustrates in end elevation Al view the manner
in which a berm 38 may be built up on one side of
hull 32. Alternatively, the berm 3Q allows reduced
ballasted weight on relatively weak soils err the
depth of such toils make it impracticable to remove
them.
FIGURE 9 depicts in plan elevation view a
twin-hull alignment that can be utilized where the sea
bed soil is weak or where the predicted ice or wave
forces may be greater than can reasonably be endured by
a single hull. the parallel arrangement of the win
ship 40 and 42 immediately doubles the lateral
no instance for the same effective ballasted weight,
Alternatively, this win hull arrangement can allow a
reduced ballasted weight on relatively weak soil of low
stability where the extensive depth of such soils makes
it impractical to remove them. FIGURE 10 demonstrates
in end elevation view the twin hull concept 40 and 42,
and thy manner in which the two hulls are founded on the
sea-bed.
FIGURE 11 illustrator a system which can be
u~2d for manufacturing solid debris for distributing
along the yea floor to build-up a protective barrier
along the sides ox the vessel 46. The vessel shown has
two Minneapolis 48 and 50. The system consists of a
suction line 52 which has one end resting on the sea
floor. The line 52, by means of suction exerted by Bud
and sand pump 54, or the like, draws up clay, sand, sea
water, and other solid material from the sea bottom and
deposits it on a tony moving conveyor 56 which extends
substantially the length of the vessel 46. The
solid water mixture deposited on the conveyor 56, when
ambient temperatures are well below freezing such as in
the Arctic during the winter, freezes into a solid mass
as it is conveyed along the conveyor 56. At the end of
10 the conveyor 56, away from pump 54, the solid material
is deposited onto an adjacent conveyor 58 which runs in
a direction parallel with and opposite to conveyor 56~
Conveyor 56 is normally located at the edge of the hull
of the vessel 46. By means of a mechanical arm or
manual power, or the like, the frozen solid debris
traveling along conveyor 58 can be broken into lumps
which are then pushed over the side of the vessel so as
to wink to the bottom of the water body. In this way, a
barrier of idea material, which should remain in frozen
condition for a significant length of time, can be built
up alongside the submerged hull of the vessel 46. Thus
provides valuable protection for the hull 46 against
lateral pressures exerted by waves and ice. The system
described can be utilized for depositing a similar
barrier along the opposite side of the hull 46. To slow
down thawing of the frozen debris once it has been
deposited in the sea waxer, cedar bark or other cheap,
available coarse material with insulating qualities can
be incorporated in the debris while it is hying frozen.
30 Such material can be carried into the vessel's hold
-- 15 --
initially or be brought to the site in a supply ship or
the like.
FIGURE 12 depicts in an end elevation view the
method whereby debris 60 and 62 can be built up along
each ire of the vessel 46.
FIGURE 13 represents in end elevation view a
combination of vessel hulls which can be achieved by
combining the twin-hull concept of FIGURE 9 with the
double Decker hull concept of FIGURE 12~ This
combination can be utilized in areas where the water
depth is in the range 20 to 45 metros and excessive ice
and wave action pressures are encountered, thereby
requiring extra stability.
FIGURE 14 in plan elevation view illustrates a
lo system whereby suction pumps in combination with suction
lines which draw solid and liquid material from the sea-
bed can be utilized for pumping and spraying sand, silt
and other bottom material onto the ice surface surround-
in the vessel 68. The Betty material is allowed to
Roy to by contlguou~ with the ice. Eventually, with
build-up, the heavy weight of the solid material pumped
onto the ice around the perimeter of the vessel 68 Jill
submerge the ice whereupon everything will sink to the
yea bottom In this way, with repeated build-up of ice,
25 and depositing of sand and debris onto the surface of
such fillip ice, an effective ice-solid barrier wall
can be built up around the perimeter of the vessel 63.
FIGURE lo shows in plan elevation manner a
split hull design which can be detached at its mid-
region and the two separate hulls placed alongside one
- 16 -
another in parallel manner to provide a twin hull con-
figuration as illustrated above in FIGURE 9.
FIGURE 16 illustrates in plan elevation view a
system that can be used for reinforcing an artificial
island created by a twin hull combination, and a harrier
reef built up around the periphery of the twin hulls, to
withstand for a long period of time extremely severe ice
and wave forces emanating from any direction. A number
of hull, ten are shown, ballasted so that they sink to
and rest on the sea floor, are arranged in radial
pattern around the circumference of the twin hull-
surrounding barrier island combination. The ballasted
hulls that are arranged radially should have their noses
the ends of the hull remote from the twin hull-barrier
combination) cut down, sloped downwardly, or submerged
below the ice level on the water/ so that any ice what
may contact the nose of those hulls will tend to ride
up on the hull, and translate the forces downwardly.
This is preferable Jo having the ice Inset the noses
I head-on and thereby impart the forces through the hulls
directly onto the peripheral barrier protecting the twin
hulls. Preferably, the radially disposed partially sub-
merged hulls are initially ballasted with large objects
such as rocks and the like and transported partially
I submerged to the site. Rocks are preferred so that if
any holes are punched in the Howe by ice, the ballast
will not wow out through the hole onto the sea floor,
thereby losing e~fec~ivenea3 as ballast. ennui no longer
of use, the holes can be sealed, the hull refloated and
transported.
-- 17 --
FIGURE 17 illustrates a variation of the twin
hull concept illustrated in FIGURE 9 whereby two
hulls 70 and 72 are arranged in a Y pattern (inverted in
FIGURE 17~. The point of the V faces the direction of
prevailing wind, ice and waves The space between the
arts of the V are filled with sand, solid debris and the
like in order to prevent the two Veranda hulls from
being forced to move under the pressure from ice and
waves. FIGURE 18 illustrates in end elevation view the
manner in which the V-arranged hulls are founded on the
sea floor.
FIGURE 19 illustrates in plan elevation view
an arrangement of three hulls, together with a shorter
ship hull, to provide a protected harbor area for a
supply ship or a production transportation ship for a
well which has been drilled in hostile waters such as
the Arctic Ocean, Three of the vessels 74, I and 78,
are arranged so that their respective boys or sterns
intersect to provide a generally "U-shapedi' configure-
lion. The pen end of the "U" is partially closed by
means of a vessel of shorter length 80. The supply
ship 82 can enter and leave the protected area formed by
the linked vessel arrangement through the opening exist-
in between vessels 78 and 80.
FIGURE 20 illustrates the manner in which two
vessels 84 and a may be arranged in end to end align-
mint BY as to form a long surface which can be converted
into a runway for aircraft. Normally, two vessels
arranged in this manner should be of sufficient length
18 -
to provide a landing and takeoff area for transport
aircraft such as Hercules or Caribou aircraft.
FIGURES 21 and 22 illustrate an embodiment of
the invention wherein two hulls 90 and 92 ore arranged
side-by~side, in parallel alignment, in twin-hull
pattern, the combination being it'd with a new bow
section 94. A rig 96 is mounted at the fore of hull 92
and optionally a relief rig 98 can be positioned at the
aft section of hull 900
FIGURES 23 and 24 illustrate a further
embodiment of the invention wherein two hulls 100 and
102 are arranged in twin-hull pattern, the combination
bring fitted with a gunwale height extension 104 and a
new bow suction 1060 A rig 108 is mounted at the fore
of hull 102 and optionally a relies rig 110 can be
positioned at the aft section of hull 100~
Flyers 25 and 26 illustrate a further
embodiment of the invention wherein two hulls (one hull
I identified a 112 while thy skin cannot by Zen in
either FIGURES 25 and 26) are arranged in twin-hull
pattern while a second pair of hulls 114 and 116 are
superimposed in double Decker twin-hull pattern upon the
underlying twin hulls 112 and the unseen hull. A new
bow section 118 it fitted at the front ox the lower twin
hulls. A new tern section 120 is fitted at the rear ox
the upper twin hull 114 and 116. Drilling rig 1~2 and
optional relief rig 124 are mounted on the upper twin
decks. This configuration provides double height and
double lateral stability.
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The predominant force is from ice and the
maximum lateral force on the vessel founded within the
land fast ice, including wind and current forces, may
amount to as much as 118,000 tones. The effective
submerged weight to resist lateral movement will depend
upon sea-bed conditions buy it likely to average about
236,000 Tony for the single ship hull concept.
While a bottom sea depth of about 20 metros is
feasible for the jingle converted hull configuration, if
drilling it to be conducted in waters deeper than about
20 metros, then in place of the double-deck~r hull
design, if required, a sand-base or rock-base island can
be built up to within a depth of 20 metros below the
high waxer mark end the jingle hull design founded on
what island.
The single or double Decker hull concept pro-
vises a relatively inexpensive movable drilling island
which, in the short time available in Arctic regions,
can be advantageously moved by towing or self-propulsion
to a prospective drilling site, sunk so that it rests on
the sea floor by use of permanent and temporary ballast,
and then Atari a well is drilled (typically 90-180
days), be refloated and moved to a new drilling site.
In this way, the jingle or double Decker hull concept
provides the possibility of drilling two oil well holes
per year in different locations, one typically in the
winter, the second typically in the summer. In an
average year, with some ice breaker assistance, it
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should be possible to refloat and transfer the rig-
vessel to a now location in June or July of each year.
During period when the seas are generally calm, the
sinking of the hull to the sea bed will be a relatively
easy operation. When water are rough and lateral
forces from ice pressure prevail, sinking the hull to
revs on thy sea bottom will require more bottom
preparation and care.
The depth to which a vessel may be sunk as a
grounded drilling island will depend on the freeboard
required in relation to the extreme peak wave heights on
the bow and sides of the hull. Considerable water and
spray may be accepted over the deck surface and drained
way through suppers during extreme wave action.
Alternatively, wave and spray deflectors can be built
along the sides of the hull to increase the effect of
freeboard. Ideally, temporary ballast used to submerge
the hull should be in the form of sea water so that it
can be easily pumped out prior to moving at a new site.
However, send and other heavier material will sometimes
be used for temporary ballast in order to provide
increased stability to the hull when founded on the sea
bottom. To refloat the hull, the sea water used as
ballast may by pumped out. If sand ballast is used, it
may he necessary to remove the sand by solve suitable
jeans before sufficient buoyancy of the hull can be
achieved to refloat the visual A complicating factor
in areas where the sea bottom it mostly clay is the
possibility of strong suction forces being exerted on
the bottom of the hull. To overcome this, it may be
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desirable to install a number of small pipes to the
bottom of the hull (preferably outside the hull) for
injecting air or water at suitable pressure into the
interface between the clay Betty and the keel ox the
hull. Alternatively, a sand bed can be put down prior
to founding the hull on the bottom to prevent suction
problems.
To withstand the substantial external ice and
wave force, the hull must typically be strengthened.
One method may involve adding additional vertical steel
members between the main frames to withstand the ice
forces over the range of height in which they would act.
A second alternative may be to fill between the main
frames with concrete and additional steel reinforcement
a required.
To protect the propeller and rudder of the
vessel from ice damage, and She like, the propeller area
of the vessel should be protected. This may include
housing the propeller in a suitable housing that is
sufficiently strong to wlth~tand the substantial ice
pressures that might be exerted.
To prevent damage to the interior of the hull
that might occur due to freezing of ballast water and
the like within the hull at portions of the hull that
remain above the water level, insulation to reduce heat
105g or ballast heating water means may be used.
Waves acting on the ship will cause scour
erosion to the water body floor supporting the vessel
and suitable scour protection should be used. However,
in Arctic waters, this scour time will usually be fairly
I
short, that is, from the time of founding of the vessel
upon the sea bottom to freeze up. Thus, if the vessel
is founded on cohesive material or if limited scour can
be tolerated, scour protection may not be required.
S Sand berms or submerged frozen blocks can be provided
alongside thy hull to provide passive resistance or to
increase the path of foundation failure.
The exact requirements for foundation treat-
mint and scour protection will Append on the local
sea-bed conditions and depth of urea specific to each
site. Geotechnlcal investigations of the proposed site
should be carried out in advance in order to prepare a
proper design for foundation treatment and make plans
or all necessary materials and equipment.
The V arrangement of two ships us illustrate
in FIGURES 17 and 18 has two possible advantages:
(a) It allows a wedge of sand to be placed in
a protected area between the two vessels for increased
lateral ruttiness; and
(b) It allow the possibility of having the
main and emergency drilling wells placed on separate
vessels Father than having two Minneapolis on one vessel)
and thereby provide an alternative safety procedure in
the event of blow-out or fire
Temperature, Precipitation and Visibility
Typical weather summaries c3enerated from
station in the euphoria Sea area provide the following
general data:
(1) Extreme low temperatures occur from
December to March inclusive and range from -42~C to
- 22 -
-50C. Mean daily temperatures during the same months
range from -25C to -30DC~
( 2 ) Mean wind speeds do not vary greatly
throughout the year but tend to be least in February and
greatest in September and October.
(3) Fog is worst during June to August with
visibility less than 10 km. occurring nearly 20~ of the
lime. Blowing snow occurs about 12~ of the time from
October to April.
Ice Conditions in the effort Sea
Ice in the Beau fort Sea consists of two main
features the polar pack which is in constant rotational
counterclockwise motion due to the rotation of the
earth, and the land fast ice which forms in the autumn
and breaks up in the early summer.
During a typical summer, the permanent polar
pack resides between 2~0 and 400 km. offshore. In the
fall, driven by offshore winds, the polar pack advances
to about the edge so the 100 mete Squibb contour
existing to the north of aniline Canada. ~irnulta-
nuzzle, in early October, a band of new lank fast ice
begins to form along the shore. The final width of this
lank fast ice zone is very much dependent on the
sequence of events at freeze-up. The ultimate extent of
the land fat ice is related Jo water depth, with the 20
moire sea-bed contour normally defining the off-shore
fast ice limits, which are reached in a series of growth
stages by February or March.
Because the land fast ice is stationary while
the permanent polar pack is in continuous motion, a
winter transition zone exists between the two lee zones.
During the fall, the pressure of the polar pack against
the thin first year land fast ice causes considerable
deformation and the southern boundary of the transition
zone consequently becomes marked by an area of heavy
ridge activity The most active area is generally a
band between 5 and 10 km. wide known as the shear zone
To the north, the transition zone continues out to about
the 100 moire water depth, but this is extremely
variable, and there is no distinct boundary between this
zone and the polar pack. Generally, there is a gradual
increase in multi-year ice concentration moving north,
but this is usually difficult to detect in mid-winter
overflight.
As early as March, the polar pack can start to
recede, creating a lead between it and the land fast
ice. Depending on surface weather, the width of the
lead and ice concentrations can vary on a daily basis.
Initially the land fast ice remains intact, but as
break-up progresses , floes pull away from the outer
edge while the Mackenzie River outflow and other rivers
erode the inner side. In this manner, the land fast ice
is generally breached by late June or early July on the
west side of the MacKenzie River Delta and at the Horton
I Rover in Franklin Bay. The remaining fast ice breaks
out shortly thereafter.
Summer ice concentrations between the 20 and
100 moire water depths can be extremely variable. In
good years, virtually open water can exist throughout
from early July to late October. In adverse summers,
- 24 -
there is no significant clearing until late August, and
freeze up begins in early October.
As can be appreciated, these ice conditions
can generate varied and tremendous hazards and pressures
for oil exploration actlvl~y in the Beau fort Sea. The
various aspects of the invention disclosed above should
enable mankind to deal with these adverse conditions
more effusively and lest expensively.
As will be apparent to those skilled in the
art in the light of the foregoing disclosure, many
alteration and modifications are possible in the
practice of this invention without departing from the
spirit or scope thereof. Accordingly, the scope of the
invention is to be construed in accordance with the
substance defined by the following claims.
I
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