Note: Descriptions are shown in the official language in which they were submitted.
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The present in~ention relates to off-shore type platforms for oil-
~i production units or installations ancl more particularly to platform~ of
the type comprising at least one ool~n articulated on a base anchored to
the sea bed whioh may be so designed as to allow for oil storage owing to
its flui~-tightness.
Its purpose is mainly to permit the storage capaoity of the baae to
be considerably increased and, at the same time, the sea carriage o~ the
whole assembly to its place of submersion and anchoring to the sea bea to
be facilitated.
It consists mainly in designing the base in the form of a tank of
elongated shape capable of floating and of sufficient length to serve as
a support for the column during the carriage to the anchoring location.
In the specific case where the column is artioulated on its base by
~- means of, in particular, a universal or Cardan joint, the articulation is
advantageously provided in proximity to one of the small sides of the base
i~ in the form of a rectangle or the like, so that during the carriage by sea
f-" the column rests on the base lengthwise of the latter. During the ~ubmer-
sion at the anchoring location use is made of ballasting means provided in
~- the base to cause the latter to first assume an inclined position until it
contacts the ground, and then the platform is freed to allow it to assume
: a substantially vertical position under the action of the ~hrust exerted
by appro~riate floats. ~hereafter, there only remains to so balla~t the ba-
se as to cause it to swing about its point of contac~ with the ground, un-
til it entirely rests on the latter. ~-
~ Of course several solutions may be contemplated in designing the base
; to be used as a tank.
According to a first alternatiYe it may be designea in the form of a
t-~ vessel with heave-resisting walls.
Another alternatiYe consists in designing it in the form of a lighter
container with means for allowing the access of sea water therein, during
t'' the carriage, the floatability being obtained by means of floats internal
and/or external to the wall of the said tank base.
In any case, when the submersion and anchoring to the ground axe com-
plated (using any suitable ballasting means to ensure stability), there is
obtained a large-capacity oil-storage tank, in combination, of course,
with any valve system allowing the inflow of water or, on the contrary,
~ its expulsion by the oil to be stored, both i~ andf~m thetQ~k prQ~ d the
j ~ floats if any.
r Apart from the above arran~ements the invention comprises some other
4 arrangements whirh are preferably used at the same time and will be refer-
` red to more explicitely later.
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Also to be pointed out is the fact that the articu-
lated column may not be used with ad~antage unless it is installed
on development si-tes at relatively great depths of the order of
one hundred meters or more. Indeed, such an articulated column
must be provided with floats allowing it to be maintained in sub-
stantially vertical relationship to its base lying on the sea bed.
In smaller depths the sizes of the floats must be increased to ;
ensure a sufficient righting moment on the column. This increased
size of the floats, however, renders the column much more heave-
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sensltlve, so that~/in medium depths of the order of from 40 to
60 m, the articulated column becomes much less advantageous.
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- On the other hand, the known system using mooring buoys
-~ anchored by means of chains suffers from many drawbacks, including
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- rapid wear of the chains and of the flexible oil-loading pipes.
~-~ Another type of column for sea bottom exploitation according to
the present invention is remarkable in that it requires no moor-
- ing chains for its installation, in that the oil-supply pipes
~ connected thereto are subjected to no strain or wear (they may
? be rigid) and in that it requires no righting floats, as an àrt-
-~ 20 iculated column does, since it is rigidly secured to its base.
- Such a platform structure or exploitation column is therefore
~--- an ideal solution on medium-depth exploitation or development ;~
sites.
` Specifically then, the present invention relates to a - ~
reservoir and articulated column assembly comprising elongated ~ ;
hollow base means for assuming a floating condition acting as
a transporting vessel as well as for assuming a su~merged condi-
. - .~ . .
tion resting on a sea bed and serving as a storage reservoir,
said elongated base means having a length which is at least on
the order of the depth of the sea at the location where the base
~. .
,. means is submerged to rest on the sea bed, elongated column
means having a length which is at least almost as great as the
length of said base means, said elongated column means having
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opposed bottom and top ends, and connecting means fixedly car-
ried by said base means at an upper surface thereof and ad~acent
- one end region thereof, said connecting means being connected to
~: said bottom end of said column means for providing an articulated
.. . .
, connection of said column means at sald bottom end thereof to sald
base means according to which saicl column means is movable in all
directions at said articulated connection with respect to said
base means, so that said column means while connected by said con-
~ necting means to said base means is capable of extending horizontal-
:~i 10 ly along the upper surface of said base means with the top end of
~: said column means situated adjacent an end region of said base ~:~
. means which is opposed to said one end region thereof while said ; -
base means assumes said floating condition acting as a vessel -`
for travelling to the location where said base means is to be
. submerged while transporting said column means to the latter loc- :
ation, float means carried by said column means for causing the
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latter automatically to assume an upright condition when the base
~- means is submerged to engage the sea bed with said column means
when in said upright condition having its top end situated above -~ .
20 the surface of the sea, so that upon submerging of the base means ~
.-~- to the sea bed at said location said column means will assume ~:
. . . : ~ .
~ its upright condition with its top end situated above the sur-
;
face of the sea without changing the length of said column means,
and ballast means carried by and operatively connected to said ;
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base means for controlling the submerging thereof.
. The present invention also specifically relates to a
method for installing at an off-shore location an~assembly which
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~: includes an elongated base means the length of which is on the
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order of the depth of the sea at the latter location and an elon-
Y~ 30 gated column means articulated to the base means at one end region ~.
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.~` thereof, comprising the steps of initially placing said base
means in a floating condition and transporting the column means
,.` connected to the base means to said off-shore location while said ~;
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base means is in said floating condition, and travels, while float-
ing on the sea, to said off-shore location, said column means
carrying float means for causing the column means to assume an ;~ :
upright conditlon upon submerging of the base means, and submerg- -~
ing said base means onto the sea bed at said off-shore location :~ :
while said float means provides for said column means an upright
~. . ,:
1 attitude extend.ing upwardly from said one end region of said base
,` means when the latter has been submerged, said oolumn means hav-
ing a length sufficiently great for a top end thereof to be sit-
uated above the surface of the sea when said base means is sub-
merged.
,- The invention will be better understood and other pur-
~: poses, details and advantages of the latter will appear more .
clearly from the following explanatory description of several
exploitation platforms forming mooring and loading columns ac- ~.
`~ cording to the principles of the invention, given solely by way
of example and made with reference to the appended non-limitat- ~ ~
. ive drawings wherein: --
;
. Figures 1 and 2 are diagrammatic elevational and side
, :.
views, respectively, of the whole articulated column and its base, - :`
designed to be installed on sea beds at relatively great depths
~ during sea transportation to the mooring location,
-- Figures 3 and 4 are elevational views illustrating the `
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; various operations involved in the installation of the column
assembly on the sea bed,
.
Figures 5 and 6 illustrate such an assembly in the
!~ ~ transport position, according to a modification of the invention; -~
and
- Figure 7 illustrates another modification of a gravity ;
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tank according to the invention.
According to a presently preferred form of embodiment
' of the invention, an off-shore platform of the type comprising ~:
-. columns articulated on a base by means of a universal or Cardan
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joint, notably for oil-fields about 100 to 150 m deep, i5 designed
and installed as follows or in a similar manner.
The base of such a platEorm is constituted by a tank
capable of being used for oil storage on the sea bed, the said
1 tank being elongated in shape and its length being of the same ~ -
,~ order of magnitude as the length of the articulated column, thus
allowing the said tank to be used, during sea-borne transporta-
,:~
tion, to support the column articulated thereto and resting on
the said tank lengthwise thereof.
Sot according to the form of embodiment diagrammatically
- illustrated in Figures 1 and 2, the said tank intended to serve
'5~, as a base for the column is constituted by a parallelepipedic
~, fluid-tight container 1 the selected length L of which is a little
greater than the height H of submersion at the anchoring loca-
. - :
tion on the underwater ground.
The length L is therefore sufficient to allow the col-
umn 2 to lie on the upper surface of the tank so as to be supported
` at its base end by a support 3 arranged in proximity to one of
the smaller sides of the parallelepided, with the unversal or
Cardan joint 4 possibly mounted from the outset, whereas it
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rests, at its other hand, on another temporary support such as
5. The platform is assumed to be equipped with tanks such as 6
and 7 serving as floats and possibly as ballasting means.
Moreover, it will be noted that the support 3 is ~n ; ;~
the form of a pedestal carried by the top surface of the base-
v; reservoir 1 and extending upwardly to an elevation higher than ;
..... .
' the highest elevation of the top surface of the base-reservoir 1,
with the universal joint 4 being situated at the top end of the
:...
pedestal 3, so that in this way this universal joint 4 is sit- -`
uated at an elevation higher than the highest elevation of
the top surface of the base-reservoir 1. In this way it is
possible without diminishing the volume in the interior of the
base-reservoir 1 and without complicating the structure thereof
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to accommodate the column 2 in the marlner shown in Figure 1 ex-
;~ tending along the upper portion of the base-reservoir 1.
r;/ The said tank is provided at its ends with ballasting
devices 8 and 9 intended to be used during the submersion as
will be described later.
The tank, which must scrve as a means of sea-borne
transportation between the shore building-yard and the drilling
site or the storage location may be designed in various manners.
According to a first alternative, as assumed in Fig-
10 ures 1 and 2, the tank (the length of which is therefore of the
order of from 100 to 150 m or more) may be designed as a vessel
whose upper portion is made fluid-tight. This solution may be
perfectly contemplated, but it necessarily involves a heavy
structure since the walls of the vessel must be capable of with- -
' standing the heaving motion. -
v ~ Another solution consists in ensuring the floatability
of the tank not by itself but by means of appropriate float means
provided either in the tank, as shown at 10 in Figures 5 and 6, ?
or above, as shown at 11 in Figure 6. These various methods may
20 be used jointly.
The latter solution is more advantageous, since the - -
walls of the tank are not notably subjected to heave, of care
is taken up to allow sea level to obtain within the tank through
-- - inlets combined of course with valves, in which case the floats,
" - constituted for example by cylinders 10 and/or 11, must be so
;~ designed as to support the apparent weight of the whole assembly.
In this case, the structure of the tank may be much lighter. -~
- The cylinders 10, 11 as well as the ballasting devices
.. ~ . ~.
8 and 9 are combined with valve and pump systems to allow them
to be emptied or filled with water at will.
A third solution is illustrated in Figure 7 where it is
assumed that the structure of the tank consists of an assembly,
e.g., welded, of longitudinal pipes 13 in combination with trans-
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verse couples 14. Also in this case, the sea level can be al-
lowed to obtain within the enclosed spaces thus formed (by means
of suitable valves as in the previous case), so as to neutralize
the heave effect, the floatability being obtained by means of
pipes 13 either emptied or filled as described.
- Other forms of embodiment are of course possible.
:. .
In any case, whatever the form of embodiment adopted,
the transportation and submission are effected as follows:
Figures 1 and 2 show the assembly constituted by the
10 tank and the column lying the length o* the upper wall of the
said tank. The assembly floating in that position with a shallow
draught is moved from the building workshop to the submersion site
~- either by means of an individual engine or by towage.
The ballasts 8 and 9 are empty or partially empty. So
are the float cylinders where such floats are used. In this case,
(Figures 5 to 7) sea water is allowed to enter the tank through
suitably controlled valves or inlets.
The submersion is performed as follows. In a first
stage, a preliminary lowering of the assembly is effe~ted by par-
20 tially filling some of the ballast means 8, 9, while at the same ;~
tlme, of course, ensuring the transverse stability of the assembly
owing to the said ballast means.
Thereafter, in a second stage, the filling is performed,
more specially, of the ballast 8 which are nearest to the uni-
versal joint 4, thus causing the tank to sink together with the
~- platform.
,.` A result of that operation, the tank lower end adjacent
,f~
~` to the bottom of the column sinks until it contacts the sea bed
l 15 (Figure 3), whereas its other end continues to float. During
s~ 30 - this movement, transverse stability is ensured by the unfilled
~ upper ballasts 9 or the unfilled cylindrical floats (Figures 5
,- to 7) and also by the column main float 6 when submerged.
~-` In a third stage, the temporary attachment or fastening
between the upper portion of the column and the tank 5 is released,
r . 7
52~
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thus allowing the column to assume a substantially upright posi-
tion under the action of its floats 7, while remaining connected - ;
to the tank through only the universal joint at its bottom end
and so being allowed to oscillate freely tFigure 4).
In a four stage, the tank ballast chamber or chambers 9
opposite to the column bottom are filled. The tank then pivots
about its lower edge 16 (Figures 3 and 4) which is in contact
with the sea bed. The edge 16 thus bearing upon the sea bed along
the full width of the tank ensures the transverse stability of
the assembly during that time and prevents it from inclining lat- ~;
erally. The movement may thus continue until the tank lies en~
tirely on the sea bed. The articulated production column thus ;i-
assumes its normal position (Figure 4).
It should be noted that, according to an advantageous ;
form of embodiment represented by phantom lines 161 in Figure 3,
the lower end of the base tank may receive a rounded shape which,
as is known both from experience and through calculations, allows
the stability during the pivoting movement to be increased.
The tank being thus laid on the sea bed, it is to be
noted that at that moment the said tank and its floats are filled
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with water. It is furthermore desirable in order to ensure suf- - -
~. . .
i ficient anchoring, to fill at least one of the compartment of the
,-~ tank or of the ballast chambers with sand, concrete or baryta
; ballast, whereas all the other compartments, floats or internal
~ spaces presently filled with water will be available later to
,`- receive storage oil.
To perform the storage use is made, as is known, of a
~' system of pumps and valves allowing the oil to enter by driving
`~ the water before it.
In particular, these means will be connected to a pro-
duction platform located at a distance and connected thereto by
an oil pipeline. The platform 2 itself may be designed in the
form of a loading platform allowing for ship mooring, according
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. to the arrangements provided Eor, notably, in U.S. Patent No. . 3,980,037 in the name of the applicant company.
As su~ficiently appears from the foregoing description
~ of design and operation, the unit or installation according to
3 the invention offers over the already existing similar units a
. great number of advantages:
- the possibility of maximum simplification o the opera-
~` tions required to install the platform and its base, :~.
. - the possibility, owing to the considerable dimensions
10 of the base, the length of which is of the same order of magni-
~ tude as the depth of the working site, of obtaining a large-size ~:~
s storage tank, ..
~. - and yet, the possibility of sea-borne transportation .
; with absolute safety owing to the relatively light floating as-
sembly obtained, especially in those cases where water is allowed ; .
. to enter the floating tank during transportation, the floatability ,.being ensured by floats. ;~-.
Thus, the elongated base means 1 which is capable of
serving as a storage reservoir as well as a floating transport-
20 ing vessel, has the illustrated elongated configuration providing :
I this base means 1 with a length which is at least on the order of,
. although actually somewhat longer than, the depth of the sea at .
-. the location where the base means is to be anchored to the sea
bed, this base means 1 fixedly carrying at its upper surface
. :.
adjacent one end region thereof the connecting means 3, 4 which
~:: serves to connect to the base means 1 the elongated column 2 in
.--. a manner articulating the column 2 to the base means 1 for free
movement in all directions with respect thereto with the column
,....... .
- means 2 being capable of extending along the upper surface of `~
;` 30 the base means 1 throughout the full length which the column
. ..... means 2 has in its finally installed condition where the column ``
- means 2 will have an upper end region situated above the surface ~ :
.- of the sea. The column means 2 is releasably connected with the
. ;.,,. . . . ... , ,,j ... . .. .
base means 1 at an end region of the latter distant from the
end region where the connecting means 3, 4 is located by way of
a releasable conecting means 5 so that when, due to operation of ~. :
the ballast means 8, which is carried by the base means 1, the
structure has the condition indicated in solid lines in Figure 3, :
the releasable connecting means 5 can be opexated to release the
column means 2 from the base means 1, so that the float means 6,
7 operatively connected to and carried by the column means 2 will
then be operative to cause the column means 2 to assume its upright
condition indicated in dot-dash lines in Figure 3. Thereafter,
the ballast means 9 which is situated at an opposite end region .
of the base means 1 from the ballast means 8 can be operated to
cause the base means to assume the position indicated in Figure 4, ~.
,.~: .,
so that the base means 1 first turns downwardly in one direction ~;
to assume the position shown in solid lines in Figure 3, and ~:
~;; then turns downwardly in an opposite direction to assume the posi
y~ tion shown in solid lines in Figure 4. --
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