US2908141A

US2908141A - Marine platforms

Info

Publication number: US2908141A
Application number: US445303A
Authority: US
Inventors: Jr Richard O Marsh
Original assignee: Raymond International Inc
Current assignee: Raymond International Inc
Priority date: 1954-07-23
Filing date: 1954-07-23
Publication date: 1959-10-13
Anticipated expiration: 1976-10-13

Description

R. O. MARSH, JR

MARINE PLATFORMS a Sheets-Sheet 1 INVENTOR. RICHARD. O. Mes/1 die.

31' wwwamanwum.

A TTO/FNEYS.

Oct. 13, 1959 Filed July 23. 1954 use v R. b. MARSH, JR

MARINE PLATFORMS Filed July 23. 1954 3 Sheets-Sheet 2 I I I I -M T I I I I I m m I I. H WI l I WQ II I .1. IIP LFII I I LIWI IIIIIIIIIIIIII W R/cr/A RD QMA RSH JP.

ATTORNEYS.

0a; 13, 1959 R. o, MARSH, J 2,908,141

MARINE PLATFORMS 5 Sheets-Sheet 3 1 Filed July 23. 1954 INVENTOR- RICHAEDOMQESHJE. v

. v BY A TTORNE'VS'.

2,908,141 r MARINE PLATFORMS.

Richard 0. Marsh, Jr.,-Baltimore, Md., assignor to RaymondiInternational .Inc., New York, N.Y., a corporation .of New Jersey 1 Application July 23,1954, Serial No. 445,303

'2 Claims. (Cl. 61.46.5)

invention relates to mobile -marine platforms of types which can be anchored in any desired off-shore location,-and more particularly it relates to such platforms which are designed for use in ocean depths of considerable magnitude.

Mobile marine platforms of various constructions are well knownbut certain. disadvantages however have been manifested in their actual operation. These types of platforms find utility in many fields .but are mostadvantageous in .oflf-shore oil well drilling operations In order .to meet the requirements of a successful off-shore oil well drillingoperation it is a primary requisite that the plat-- form used be stable regardless of thecondition .of the sea in which it is anchored. In effort to provide this necessary-stability the platforms heretofore known have in many instances employed rigidsupporting studs or columnar structures which extend downwardly from the platform to the anchor means positioned on the sea bot tom. While such constructions, are quite satisfactory for shallow water operations, it obvious that, when the ocean depths at the desired location range intothe hundreds of feet, such rigid members must necessarily be ofsuch magnitude as to be cumbersome, unwieldy and too costly. Since the platform, to be useful, must be self-contained as well as mobile, .the problem of transporting such huge rigid supporting structure becomes a practical impossibility when'substantial ocean depth's are involved. forms in depths beyond 100 feet for example, experience has indicated that cables or similar flexible anchor lines, that .can be conveniently stored on deck when the platform is being. towed, should be used to. interconnect the j Working platform. with its 7 anchorage base. Although yarious platform constructions have been proposed which do employ such flexible anchor'lines they have failed to satisfy the requirements of providing a stable working 7 platform while maintaininga construction which is simple "enough-to avoidcontinual operational difiiculties or breakdowns'ff-It is of course-obvious that the problem of maintaining stability assumes greatly increased proportions when flexible cable or chain means, ratherthan rigid supports and the like, are used to-intercon-nect the Cplatform with its anchorl Any such flexible anchor lines must: be. maintained uniformly under tension the platformis to. resist pitching and tossing under the normal wage action 'andsince the tendency of any floating body is-alternately to rise on the crest and then fall in the troughof; such waves, thereby-alternatelycausing strain .andnsla ck -in cables, the problemof maintaining uniform tension .is;a .difilcult one .Moreoverwhen flexible anchor liuesanetutil-izedzthe problem aoftavoiding tang-ling or snarling. thereof with resultant operational breakdowns is 2. 1 involves the dangerof tangled anchor lines. Moreover in order to provide a suitably broad and stable anchorage base, it would be desirable to have such anchor lines extend downwardly and outwardly at an angle from the platform ,rather than merely vertically. downwardly. With a plurality of individual anchors such an anchorage base is diflicult to maintain since the natural tendency of those anchors will be to shift or creep inWaId1y* tO.a

position beneath the platform; Any such movement of 'cloursenot only destroys "the-broad anchorage base but also, causes the anchor lines to become slack thereby destroying the stability ofthe platform. When it is realized that-sornetinies the ocean depths involved mayrange up to hundreds of feet, the dimensions of such problems take on more serious proportions.

These and other disadvantages of the constructions I heretofore known are overcome by the present invention whichprovide's'a mobile marine platform relatively simple 'in construction and in its principles of operation, and designed moreover to provide a working deckspace which is stable under all the, usual conditions of the surrounding sea, and furthermore capable-of operation in ocean depths of the orderof 100 to 600 feet; The platform ,of the invention comprises a unitary floatmember carrying an elevated deck structureand a unitary anchor member connected to saidv float member by. flexible anchor cables or chains. -Both members are buoyant and have hollow chambers which are provided. with suitable conduit connections designedto permit the entry and removal of Water as desired in order that their buoyancy can be adjustably controlledJ The horizontal dimensions of the anchor body areconsiderablygreater than those ofthe float body so as to providev a broad based anchorage meansand said anchor body is-preferably provided with an open central portion of a size'sufficient to encompass the float fbody; Thus in the mobile condition of the platform both members may float on the-surface of-the water with'the float member positioned within the central open- In order to successfully operate such plat-- ing of the anchor member. Furthermore .it is preferable according -.to the invention that the float and anchor members be so proportioned relative to. one another that the net. buoyancy of the float memberbe great-enough to support the weight of the anchor body when the'latter is completely flooded :with water.

Preferably the anchor memberis in the formof a large hollow sheet metal ring-which maybe ofcircu-lar cross-section; However, thew-ring may be rectang-ular, square or polygonalcross-section. Also, the float memf ber may preferably be in the form of a hollow, sheet sponding .to-the shape of the anchor member. I

In operation, the platform is towed to the desired.- olffrneta'lring either circular or 'othershape preferably correshore location and the anchor member is then flooded with water thereby causing the same to submerge until it finally comes to a position of rest o-nithe sea bottom.

During this descent ofthe anchor body, the anchor cables, which run from winches provided on the elevated deck through suitable guide means on thefloat member to the anchor member, are' of courseslacked off. Withthe anchor member in this position,thefloat member and its elevated-deck are in effect tied to the ocean floor; but, since such float member is still free to rise and falliin' the I trough of surfacewaves, stability is lacking. To provide ofjcoursel ofdistinct, importance. 'Heretofore proposed j as a consequence of any severe strain being applied, to the caus or cables running to that particular anchor. This thisflessential stability the floatrnember'is partially flooded with water so. as to decrease its buoyancy toanamount which is insufficient to support theweight of the anchor member. "Tension is then applied to the cables by taking upon therwinches, and the float member is thereby pulled downuntil it is totally'submerged below thewa'ter surface a'ta leyel which is'below the trough 'of the largest 1 contemplated waves. ,Due, to the continuous,., upward buoyant force upon the float member" in this position,

' Fig. 1 isan elevatl iform of the invention anchored in operating position.

- anchormembers, and Fig. 7 is a view similar to Fig. 6 but showing an alter- ;native embodiment. V

I Referring now in further detail to the drawings and j member.

and therefore the working deck space will be maintained stable. And if this working deck space is origlnally constructed at. a suflicient height above the float vmember,

itjcan'be maintained at a level which is above the crest :Ofthe, highest contemplated waves even when the float jrnember is ,thus submerged. When it is desired to move I the platform to a new sea location the water is pumped font of theinterior of the float member thereby increasing .the buoyant force exerted by said member to its original amount which by initial design is greater than the weight .of the anchor body. Once this has been accomplished the float member will lift the anchor member from the sea bottom and will itself return to the water surface.

Then by. taking up on the winches, the anchor body can beraisedfurther, and when it nears the surface of the water by pumping out its hollow interior, it can be floated the remaining distance to the surface. The platform is then in position for movement to the next off-shore drilling location.

. Other and more specific objects, features and advan-- tages of the invention will appear from the detailed description given below, taken in connection with the accompanying drawings which form a part of this specification and illustrate by way of example the present preferred embodiment of the invention.

In thedrawings:

onal view showing the mobile plat- Fig. 2 is a schematic elevational view showing the platform in mobile condition with both float and anchor members at the Water surface. Fig. 3 is a somewhat schematic elevational view, showingthe platform with the parts thereof in the positions 'assum ed after the anchormember has been submerged.

' the anchor cables will be continuously held under tension the like linkages as well as wire or other forms of rope or cables. This working deck is supported from the float member 21 by rigid tubular or fabricated supporting columns 27 which rise from said float member and maintain the deck 26 at a fixed elevation thereabove. In constructing the platform the dimensions of these supports 27 and the consequent elevation of the deck 26 are calculated, having in mind the size ofthe waves which are to be encountered by the platform at its off-shore drilling location. As will be more fully described'hereinafter it is necessary'that the deck 26 be constructed at a sufficient elevation above float member 21 so that when said member is submerged to a level beneath the trough of the largest wave, the deck is at the same time positioned at a level above the crest of the highest wave.

An oil well derrick 28 of common construction is mounted on deck 26 and is of course designed to sink the customary type oil' well casing 29 down throughthe open central portion of the float and the anchor members into the sea bottom 30. Similarly mounted on the working deck 26 are conventional pumps 31 which are designed to be connected via suitable hose means 38, 39 and'42, .43

(Fig. 7) and fluid port means 40, 41 and 44, 45, with the interiors of the anchor and float members respectively when it is desired to'introduce or remove water from either of these members. i I

Referring now to Fig. 6 one means of rigging the anchor cables 23 is there shown. Each cable 23 is secured at its lower end to an eye 32 provided on the outer surface of the anchor member. The other end of the cableis led through a hollow conduit 33 which is welded in position in the interior of the float member 21 extending from the bottom to the top thereof with said float member being suitably bored at 34 and 35 in alignment with said conduit so as to permit passage of the cable. Tubular supports 27 are welded or otherwise secured to the exterior of the float member in alignment with conduits 33. These tubular supports are similarly hollow and the cables 23 pass .therethrough and are led to the deck winches 25. In the alternate embodiment shown in Fig. 7 each cable 23 is secured to an eye 36 provided on V the exterior of the anchor member and extends therefrom particularly to Fig.1 there is shown a mobile marine 1 platform 20 which comprises a ring-shaped, water tight 'floatfme'mber 21 and a similarly ring-shaped water tight anchor'rnember 22. Both of these members are preferably fabricated from steel or other suitable sturdy structural material such as is capable of withstanding the enormous stresses to which a device of this type must be subjected. It should be understood that while these members are preferably ring-shaped as shown, they may also f assume various other shapes such as a rectangular frame-.

'like'strubtur. It is preferred however that the anchor member be substantially largerrthan the float member and be provided with an open central portion 22' which is large enough to receive said float member. When ring- 'shaped,the anchor member preferably has a diameter approximately twice that of the diameter of the float Thus when this type of platform is to be used in oceandepths ranging from 100 to 600 feet the float member can for-example have adiameter of approximately 200 feet and theanchor member a diameter of approximately 400 feet. Interconnecting these two members are a plurality of an'chor cables or chains 23 which i are secured at one end to the anchor member and extend therefrom to or through suitable guide means 24 provided on the float .member and thence upward to winch and pulley means 25 positioned on a working deck 26.

The cables are preferably, although not necessarily, arranged in crisscrossed relation as shown. The. word eablesflasaused herein, isintended to include chains or to a pulley guide 37 mounted on the external surface of the. float'member 21, and through the pulley guide to the deck winches. a r

Referring now to Figs. 2 to 5 the operation of the vdevice will be described:

Fig. 2 portrays the platform 20in the mobile condition ready to 'be towed to the desired off-shore drilling location. As shown both the anchor and

float members

21, 22 arefloating at the surface of thewater with the floatmember 21 positioned within the open central portion 22' of the anchor member. Whenthe platformhas been towed to the desired drilling location, water is introduced into the interior of the anchor member so as to flood the same and thereby cause it to submergeto the position shown in Fig. 3, resting on the bottom of the i seal Various means for flooding this anchor member may be used, but for purposes of illustration a Water hose 38 and an air hose 39 may be connected as shown in Fig. 7 and water pumped into the interior of the anchor member 22 through hose 38 by the pump 31 while air is permitted to evacuate through hose 39. Suitable means may if desired be provided for permitting disconnection of these 'hoses prior to the complete submerging and downward descent of the anchor member. As the anchor member descends to its position of'rest on the sea bottom 30 as shownxin Fig. *3, the winches 25 are released so as to slack off anchor cables 23 thereby permitting the float member 21 to remain on the surface. In this position the float member. and its elevated, deck structure will i of coursebe in eifect tied to the desired off-shore drilling location. However due to the flexibility of cables 23 he 1 st .1 udi t k Ev fqqur e r e an ta Fwithmny surfacewavesmhich may :be present in the pariticular area.

To eliminate thisundesirable motion and to render the .platform substantially stable, ;the interiorof the float I :member 21 is partiallyflooded with water, as shown e :the floatrmember toaposition where the same is held at :a 1etve'lwhich1is .belowthe .troughof the largest waves -.-.contemplated in thevparticular area, it is possible to .cre- -ate arelationship of the-parts .of the platform structure whereinthe cables .23 areecontinuously held under ten- .sionidueeto thecontinuous upwardthrust caused bythe .ibuoyant .force'acting .on thefloat-member 21. In this :positionzthe float member will .remain substantially stationaryrandthe elevated deck structure 26 willof course present a most stable working area; As mentioned above .the initial design of this deck 26 it is of course im- :portant to build the same at suflicient elevation .above the "floatlmernber 21 .so that, when the latter is held in his submerged position, the deck itself will still .be maintained .at a level which .is sufficiently raised above the crest of thelargestcontemplated waves.

. It .will be observed that .sincethe anchor member has .a..diameter which is substantially larger than the diameter of the float member, the anchor cables descend downwardly and outwardly from the float member thereby providing a broad, and stable anchorage base.

In a yp cal case, for example, where the anchor ring has a diameter of 400 feet and a cross-sectional diameter =95, IZQJ e L i t ismadaef l inch-st el p a s we tw uc i fn i hh heod .Qf.. ons which if d r mi tb iuaeassslsay 2000 to 25 tons y addi .ean tete tatt a e qrthereqt- In uch a e e flo ring member 2 may have adiameter, of about 200 feet and a cross-sectional diameter of 20 'feet giving a norbuoyancy. when. empty .of. approximately 6000 tons.

The weight of such a float ring plus the weight of the deck, deck supports and drilling equipment would amount to about 800 tons and the necessary cables another 80 tons thereby leaving a net buoyancy of about 5120 tons. When the anchor member has been submerged, this net buoyancy of the float member can be reduced to 1000 tons by partially flooding the same with 4120 tons of water or other ballast. Then by taking up on the winches the float member can be submerged, and when submerged the buoyant force acting thereon will create a total tension in the cables of about 1000 tons, ample to retain the platform structure in substantially stable condition in the presence of quite heavy seas but insuflicient to raise or dislodge the anchor ring which has a weight of 1500 tons. A platform of this description is particularly suitable for off-shore oil drilling.

Similar but smaller arrangements may be used for other purposes, such as soil test boring rigs, etc. and then the overall diameter of the anchor ring may, for example, be 50 feet with a cross-sectional diameter of feet. Such an anchor member if made, for example, of %1 inch steel plate would weight about 75 tons, which could be increased to 100 tons by adding concrete or the like. In this case the float ring 21 might have an overall diameter of 25 feet and a cross-sectional diameter of 10 feet to provide a buoyancy of about 180 tons. Assumin that this float ring were constructed of /8 inch steel plate, it would weigh approximately 18 tons, which together with about 10 tons of deck structure, 2 tons of cables and .other while the cables assume angular positions.

'7 'tons of boring equipment would' bring the total weight to about 37 tons leaving a net buoyancy'of 143 tons for the float member. By partially'flooding the same with 93 tons of water ballast, this buoyancy canbe reduced to 50 tons, thereby permitting the float unit to be submerged and create a 50 ton-tension in the anchor cables, which would be adequate to hold the platform stable but would be insufficient to lift the 75 'ton anchor'ring.

In view of the above factors the advantages of th'e present invention may now be better appreciated as compared to prior proposals involving pluralities o'f anchoring cables each connected to individual anchors. "If such individual anchors are placed directly below the platform, then, depending upon wind and wave conditions, the platform will tend'to move to one side Or an- But any such sideways movements of the platform "will of course necessitate suspension of the drilling operation. On'the other hand, if, to prevent such sideways move- .ment of the platform, the individual anchors are dropped in positions laterally outward of the platform so that the cables therefrom are inclined inwardly'in var-ious directions and upwardly to the platform, the following difiicultywill occur. If the water conditions are such *astend to cause the platform to travel in one direction, thenthe holding tension will be largely confined to the cables which extend down to the anchors positioned in-the opposite direction, andthe remaining cables will become slack or have very little tension. Thus the'holding action will be confined to a few individual anchors-and those'will tend to be dragged along the ocean bottom inwardl'yof the assembly, thereby allowing the platform to shift its position and eventually perhaps allowing all the cables to become loosened and entangled and allowing the submerged float means to rise up toward the surface of the sea.

With the present invention however using a unitary heavy, single anchorage, particularly if in the form of "a ring larger than the float member, there will be no possibility of one part of the anchorage creeping along the ocean surface with respect to-other parts and accordingly all of the cables will retain their uniform tension and thus hold the platform submerged to the desired degree and at the desired location. i I

"location the winches '25 will be freed so'as to release the tension on cables 23 thereby permitting the float member 21 to rise to the surface of the water under the action of the buoyant force thereupon. When this member reaches the surface, as shown in Fig. 5, water hose 42 and air hose 43 are connected and the water pumped out of the interior of the float member by means of pumps 31. This action of course restores to that float member its original buoyancy which by design, is in excess of the weight of the anchor member 22. Therefore by then taking up on the winches 25 and thus applying tension to the cables 23, the anchor member may be raised from the bottom of the sea to an intermediate position such as is shown in dotted lines in Fig. 5 or at a position nearer the water surface. When this position of the anchor member is reached water hose 38 and air hose 39 are then connected to that member and the water pumped out from the interior thereof, thereby restoring its buoyancy and permitting the anchor member to rise to the surface of the water and return to its initial position as shown in Fig. 2.

Various means may be provided by which these

hoses

38 and 39 are attached to the anchor member when the, latter is in an intermediate position preferably near the water surface. This can be accomplished bydivers or other expedients if necessary. Depending upon the depths of the water in which the platform is to be anchored the precise mechanism for elevating the anchor member may of course vary. Thus as described above in con- A7 :nection with, Fig. 6, a simple rig has been shown which may be used'with success in relatively shallow depths. However when the depths involved range towards the '500:foot mark, 'the'rig shown in Fig. 7 may be preferred, since the pulley guide 37 on the exterior of the float member provides a better angle of lift which permits the 'anchor'member to be pulled up a greater distance from the sea bottom thereby decreasing thedepth to which e diver or other means'must descend in order to attach -water hose 38 and air hose 39.

The'invention, in addition 'to being useful for offshort oil drilling purposes, may be used for providing either mobile or permanent bridge piers, docks and airplane runways over deep waters. I

"Although certain particular embodiments of the invention are herein disclosed for purposes of explanation, 'various further modifications thereof, after study of this ,specificatiomwill be apparent to those skilled in the art to which the invention pertains. 'Reference should accordingly be had to the appended claims in determining.

;the scope of the invention. What is claimed and desired to be secured by Letters Patent,'is:

1. A mobile marine platform comprising a buoyant, generally ring-shaped float member carrying a working deck structure supported at a level thereabove, a univtary, generally ring-shaped, normally buoyant anchor member having an open central portion of a size sufli cient to encompass the float member, said float and anchor members resting on the water surface with the float member nesting within the open central portion of the anchor member when the platform is in the mobile condition, a plurality of anchor cables interconnecting extend downwardly and outwardly from the float member to the anchor member, said float member having an original buoyancy greater than the weight of said anchor member when the latter is flooded, means for controlling the buoyancy of the float member by flooding or deflooding samewhereby its buoyancy may be decreased by partially flooding the same until the net buoytheanchor member, andmeans for taking iup on said cables'whereby said float member can be pulled down to a level beneath the trough ofthe waves with the deck remaining above the wave crests the cables thereby held under uniform tension sufficient 'to maintain the deck substantiallylstable. 2. A mobile platform comprisinga buoyant float member having an elevated deck supported thereabove,'"a unitary anchor member that is normally buoyant and has a periphery greater than that of said float member and anopen central portion of a'size sufiicient to receive the float member, said float and anchor members floating on the water surface with the float member positioned within the open central portion of the anchor member when the platform is in the mobile condition, said anchor member being adapted to be flooded with water and to sink to the sea bottom when the platform is in the operative position, a plurality of anchor cables extending from said float member downwardly and out- -wardly to said anchor member, meansprovided'on the deck and connected with said cables for taking up or slacking oif 'on the cables, and means for flooding and deflooding the float member operable to decrease its buoyant force to a value less than the weight of the flooded anchor member whereby said float member can be the elevated deck substantially stable, said float member havinga maximum effective buoyancy when deflooded great enough to support the weight of the flooded anchor 'member whereby the latter may be raised from the sea bottom by means of the cables so that the platform may be moved to a new location.

'R eferences Cited the file of this patent T 3 UNITED STATES PATENTS Great .Britain j Oct. 29;

"1,291,034 I Lindquist Jan. 14, 1919 2,399,611 Armstrong May 7, 1946 2,476,309 Lang July 19, 1949 2,534,480 Shannon Dec. 19, 1950 1 FOREIGN PATENTS V Y