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Publication numberUS3824943 A
Publication typeGrant
Publication dateJul 23, 1974
Filing dateMar 13, 1972
Priority dateMar 16, 1971
Publication numberUS 3824943 A, US 3824943A, US-A-3824943, US3824943 A, US3824943A
InventorsMo O
Original AssigneeMo Och Domsjoe Ab
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Drilling platform
US 3824943 A
Abstract
A floating platform for drilling after natural deposits beneath the floor of the sea. The platform has a reduced cross section at the sea surface, a service deck above the sea surface, and a substructure extending downwardly below the sea surface. The platform is monolithic and comprises a plurality of vertical cells of concrete. A bottom deck closes the bottom of the vertical cells and is adapted to be positioned deep below the sea surface and above the floor of the sea. The vertical cells are arranged such that at least one but not all of the cells extend from the bottom deck to the top deck and the center of gravity of the platform is below its center of buoyancy.
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Description  (OCR text may contain errors)

United States'Patent 11 1 1111" 3,824,943

M0 g 1451 July 23,1974

1 1 DRILLING PLATFORM 3,572,043 3 1971 Clara ..61 46 3,681,923 8/1972 Hyde [76] Inventor- Gmnsundvelen 3,708,987 1 1973 Roulet (it al. 61 46 Nesbru, Norway [22] Filed: Mar. 13, 1972 OTHER PUBLICATIONS The 011 and Gas Journal of Sept. 14, 1970, pages 60,

[21] Appl. No.: 233,879 1 [30] Foreign Application Priority Data Primary Examiner-Jacob Shapiro Mar. 16, 1971 Norway 1008/71 Attorney Agent Taylor and Hinds [52] US. Cl. 114/.5 D, 114/.5 T, 61/465, ABSTRACT 175/7 A floating platform for drilling after natural deposits beneath the floor of the ea The platform has a re- Field of Search 61/465, T, duced cross section at the sea surface, a service deck 114/5 D; 9/8; 175/7 above the sea surface, and a substructure extending downwardly below the sea surface. The platform is [56] References Cited monolithic and comprises a plurality of vertical cells UNITED STATES PATENTS of concrete. A bottom deck closes the bottom of the 2,940,266 6 1960 Smith 61/465 vertical cells and is adapted to be Positioned p 55 4 below the sea surface and above the floor of the sea. 61/465 X The vertical cells are arranged such that at least one 6 /465 but not all of the cells extend from the bottom deck to 2,972,973 2 1961 Thearle 3,154,039 10/1964 Knapp 3,273,526 9 1966 016m rh d g 11415 T the top deck and the center of gravity of the platform anning H4 .5 T v is below its center of buo anc 3,510,892 5/1970 Monnereau et al 9/8 7 y y 3,535,884 10/1970 Chaney 61/465 7 Claims, 2 Drawing Figures ,II'III' rIIII'II DRILLING PLATFORM The invention relates to a floating drilling platform for drilling after and production of natural deposits under the sea.

The new and characteristic which form the basis for the present invention, is the thought that a platform of that type which has a reduced cross-section at the floating line, e.g. semi-submersible state, can be made monolithic of concrete as one or more vertical cells, preferably tube shaped, with a bottom. This very simple construction will, as showed below, offer many advantages compared with the conventional floating platforms.

For a better understanding of the invention it will be described further by means of an example.

FIG. 1 shows a vertical section B B through the platform and FIG. 2 shows a horizontal section A A.

1 is a cell which is terminated under the water surface, 2 is a cell which is terminated above the water surface and 3 is a cell without a bottom which the drill 4 passes through. 5 is the workingor service deck of the platform and 6 is the drilling tower.

The tubes may have varying wall thickness and diameter. It is, however, an advantage if the variations are small, since the platform in that case can be made by means of slip forms.

It will immediately appear from the figure that it is easy to achieve the center of gravity to be below the center of buoyancy and there are thus no problems at tached to the stability.

The cells may during the drilling be filled withair,

sand or water. There must always be some air present for buoyancy, while sand is an excellent ballast material. Other solid ballast material, of course, can be used. Water will be the natural medium for trimming.

The cells may also be used for tanks, e.g. for oil storage or as a dumping place for polluted materials.

A series of advantages are achieved in that the drilling takes place through a tube. The work will not be hindered by waves or ice. Such a solution means a big advantage, especially for the divers, since their work often becomes restricted due to the difficulties in getting up and down through the wave area. The tube will also beable to collect spill of oil, and prevent the oil from spreading in the sea.

As it appears from the figure, the platform will extend downwards much deeper than other floating platforms. The figure shows a platform which has a sub structure nearly double the height of the drilling tower,

e.g. a sub structure of 70 80 metres. This is 3 4 times the normal depth of a sub structure of a semisubmersible platform. At these depths the sea is practically calm irrespective of the waves on the surfaceThe large weight of the concrete, the reduced cross-section of the platform at the floating line and possibly ballast of sand all adds to the stability, and the result is a platform whichv lies far more steady in the sea than other floating platforms. In contrast to the existing platforms, a platform according to the invention will thus not need to interrupt the work due to bad weather. This is of large importance in so called wild-cat"-drilling, and absolutely of vital improtance for production. None of the existing floating platforms may be used for production, namely because production must go on continously irrespective of the weather. The weight and stability of the platform is also necessary, if it is to be provided with industrial plants, fishplate arrangements etc. The service deck can thus be provided with industrial equipment, quay installations, and the like.

The large sub structure of the platform is also advantageous for conventional anchoring, since the anchors may be fastened far down and thus obtain a greater effect since the chain or the wire remains lying more horizontally. Dynamic anchoring may be employed.

The cell formed concrete structure is in itself particularly favourable. The construction can take up very large pressure-forces, since buckling problems practically do not exist. This is of importance with regard to the large water pressures in question, and with more occasional local stresses, e.g. from ice.

A platform according to the invention offers no production difficulties, since the production can be performed exclusively by means of simple method and modest aids. A natural way is to cast the bottom and a bit of the walls in a dry-dock, tow this out to a deep sea area and thereafter erect the walls by means of slip forms, while the platform gradually sinks down in the water. Alternatively, the platform may be provided with its own propulsion equipment.

Compared with a conventional semi-submersible platform, the platform according to the invention has the following advantages:

a. a simpler manufacture, b. a more robust construction,

c. substantially better stability,

d. no corrosion, i.e., little maintenance,

e. protection for the drilling work,

f. possibilities for collecting spill of oil,

g. cheap storage or oil etc.,

h. probably more favourable with regard to price and building time, i. conventional anchoring becomes more efficient. 'The platform is more difficult to move than other floating platforms. This plays less importance if it operates within a limited geographical area, and is completely without inportance for a production platform.

It will immediately be understood that the design of the invention which is shown on the drawing and described above, is only meant to illustrate the inventive thought, and that this may be varied in a series of ways within the idea of the invention.

1 claim:

1. In a floating platform for drilling after natural deposits beneath the floor of the sea having a reduced cross section at the sea surface, a service deck above the sea surface and a sub structure extending downwardly below the sea surface, the improvement wherein said platform is monolithic and mobile, and comprises a plurality of contiguous vertical cells of concrete at least one of the cells lengthened to above sea level to form a support for a service deck, a service deck permanently fixed to said platform, the nonlengthened cells located a substantial distance below the deck section so that the top of said non-lengthened cell or cells is at a substantial depth below the surface of the sea, a drilling structure on said service deck, a bottom deck closing the bottom of said vertical cells and adapted to be positioned deep below the sea sur- 7 face and above the floor of the sea, the whole structure being constructed and arranged such that the center of gravity of said platform is below the center of buoyancy thereof.

2. An improved platform according to claim 1 further including a drill extending from said service deck down through one of said verticle cells to the sea floor.

3. An improved platform according to claim 1 wherein said sub structure extends at least 70 meters below the surface of the sea.

4. An improved platform according to claim 1 wherein said platform includes a first group of adjacent vertical concrete cells extending from said service deck to said bottom deck and a second group of vertical concrete cells in surrounding adjacency with said first group and extending from said bottom deck upwards to ballast material.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2940266 *Jul 30, 1956Jun 14, 1960Shamrock Drilling CoMethod of constructing an offshore well drilling island
US2972973 *May 6, 1958Feb 28, 1961Ernest L ThearleOffshore platform
US3154039 *Jul 25, 1962Oct 27, 1964Jersey Prod Res CoStable floating foundation
US3273526 *Nov 15, 1963Sep 20, 1966Lawrence R GlostenStable ocean platform
US3360810 *May 21, 1965Jan 2, 1968Shell Oil CoFloating reservoir vessel of the displacement type
US3434442 *Apr 19, 1967Mar 25, 1969Mobil Oil CorpOffloading moored production storage unit
US3510892 *Nov 29, 1967May 12, 1970Automatisme Cie GleFloating platform
US3535884 *Jun 30, 1967Oct 27, 1970Sun Oil CoOffshore drilling and production structure
US3572043 *Feb 24, 1969Mar 23, 1971Ernest A ClaraUnderwater structure
US3681923 *Apr 28, 1969Aug 8, 1972Hyde Winfield HMethod and apparatus for controlling subnatant oil seepage
US3708987 *Jul 23, 1971Jan 9, 1973Cimadevilla AConcrete reservoir for underwater use
Non-Patent Citations
Reference
1 *The Oil and Gas Journal of Sept. 14, 1970, pages 60, 61.
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3863457 *Jun 13, 1973Feb 4, 1975Selmer As Ing FSubmarine foundation and offshore working platform
US4004531 *Oct 3, 1975Jan 25, 1977Texaco Inc.Drilling system for deep water offshore locations
US4112864 *Oct 8, 1976Sep 12, 1978Seatek CorporationHeave stabilization of semi-submersible platforms
US4241685 *Nov 6, 1978Dec 30, 1980Iti Ltd.Self-stabilizing floating tower
US4498412 *Jun 2, 1983Feb 12, 1985Gotaverken Arendal AbOffshore platform
US4702648 *Apr 26, 1985Oct 27, 1987Jan StageboeTension leg platform
US4703709 *Apr 23, 1984Nov 3, 1987Institut Francais Du PetroleFloating modular system
US4766836 *Aug 28, 1986Aug 30, 1988Institut Francais Du PetroleModular system for the offshore production, storage and loading of hydrocarbons
US5983822 *Sep 3, 1998Nov 16, 1999Texaco Inc.Polygon floating offshore structure
US6015245 *Sep 8, 1997Jan 18, 2000Frimm; Fernando C.Semisubmersible offshore vessel
US6230645Oct 13, 1999May 15, 2001Texaco Inc.Floating offshore structure containing apertures
US6244347Jul 29, 1999Jun 12, 2001Dril-Quip, Inc.Subsea well drilling and/or completion apparatus
US8499581Oct 5, 2007Aug 6, 2013Ihi E&C International CorporationGas conditioning method and apparatus for the recovery of LPG/NGL(C2+) from LNG
US8540460Oct 21, 2010Sep 24, 2013Vetco Gray Inc.System for supplemental tensioning for enhanced platform design and related methods
Classifications
U.S. Classification114/264, 405/210, 175/7
International ClassificationE21B15/02, E21B15/00, E21B43/01, E21B43/00
Cooperative ClassificationE21B15/02, E21B43/01
European ClassificationE21B15/02, E21B43/01