US3673974A - Method and mobile marine platform apparatus having floating submerged mat stabilization - Google Patents

Method and mobile marine platform apparatus having floating submerged mat stabilization Download PDF

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US3673974A
US3673974A US20278A US3673974DA US3673974A US 3673974 A US3673974 A US 3673974A US 20278 A US20278 A US 20278A US 3673974D A US3673974D A US 3673974DA US 3673974 A US3673974 A US 3673974A
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platform
ballastable
buoyant
support
mat
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US20278A
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James C Harper
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Dresser Industries Inc
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Dresser Industries Inc
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
    • B63B1/02—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement
    • B63B1/10—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls
    • B63B1/107—Semi-submersibles; Small waterline area multiple hull vessels and the like, e.g. SWATH
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
    • B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
    • B63B35/4413—Floating drilling platforms, e.g. carrying water-oil separating devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B39/00—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude
    • B63B39/06—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude to decrease vessel movements by using foils acting on ambient water
    • B63B2039/067—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude to decrease vessel movements by using foils acting on ambient water effecting motion dampening by means of fixed or movable resistance bodies, e.g. by bilge keels

Definitions

  • ABSTRACT Three levels in a vertical plane, being an elevated work platform, a middle hull and a submersible lower hull are connected together by six telescoping vertical support columns.
  • the lower catamaran hull consists of two pontoon-type tubes connected together by a mat having freeing holes therein to reduce the mats resistance in the vertical plane when submerged.
  • the middle hull is maintained above the water level when the lower hull is at the surface of the water, but settles down into the water to provide buoyant support when the lower hull is submerged.
  • the lower hull being buoyant and ballastable, is raised or lowered in the water by adding or removing water ballast.
  • Action snubbers are provided to work in conjunction with the vertical columns to prevent any quick or fast relative movement between the lower hull and the combined middle hull and upper deck structure.
  • An alternative embodiment utilizes the middle buoyant hull to floatably support a three column structure.
  • Other alternative embodiments include non-telescoping columns, single column platform apparatus and means for varying the amount or number of freeing holes used to affect the mat resistance in the water.
  • FIG. 1 A first figure.
  • This invention relates, generally, to mobile marine platform apparatus, and specifically, to a structure having improved stability, whether in the transit or in the working positions, and which is easily transportable to an offshore location, as well as to a method of maintaining stability of a mobile marine platform apparatus.
  • the offshore petroleum exploration art has long recognized the need for improved stability in mobile marine platforms such as might be used in drilling, workover, salvage operations and the like.
  • the prior art structures have failed to achieve stability in both the transit and the working positions.
  • stability in transit was sacrificed, and vice versa.
  • the optimized stability of such structures failed to provide adequate stabilization in heavy seas.
  • a mobile marine platform apparatus having a buoyant, ballastable structure associated with a telescoping columnar support structure such that the overall height of the apparatus is not severely increased for the transit phase of the operation.
  • a second buoyant structure maintained above water level during the transit mode, provides buoyant support when the lower structure is submerged.
  • a mat structure maintained off the ocean floor, and a new and improved method for using same, provides increased stability for the working phase of the operation. Action snubbing members between the pontoon structure and the upper deck add even further stability to the offshore platform apparatus.
  • a floating, submerged mat structure provides vastly increased stabilization.
  • FIG. 1 is a side elevational view of a complete embodiment of the apparatus according to the invention while in the transient mode of operation;
  • FIG. 2 is a similar view showing the apparatus in the working mode of operation with its pontoon structure lowered;
  • FIG. 3 is a bow elevational view of the apparatus according to FIG. 2;
  • FIG. 4 is a plan view of the mat and pontoon structure according to the invention as illustrated in FIGS. 1-3;
  • FIG. 5 is a side elevational view of an alternative embodiment of the apparatus according to the invention while in the transit mode of operation;
  • FIG. 6 is a side elevational view of an additional alternative embodiment of the apparatus according to the invention in the working mode of operation;
  • FIG. 7 is a plan view of the mat and pontoon structure according to the invention as illustrated in FIG. 6;
  • FIG. 8 is a plan view of an alternative mat and pontoon structure according to the invention as illustrated in FIG. 6;
  • FIG. 9 is an elevational view of the action snubber associated with one or more of the support columns according to the invention.
  • FIG. 10 is a more detailed cross-sectional view of a portion of the action snubber illustrated in FIG. 9;
  • FIG. 11 is a detailed cross-sectional view of a portion of an alternative action snubber
  • FIG. 12 is a side elevational view of an alternative embodiment of the apparatus according to the invention.
  • FIG. 13 is a plan view of the mat structure according to the apparatus of FIG. 12;
  • FIG. 14 is a side elevational view of an alternative embodiment ofthe apparatus according to the invention.
  • FIG. 15 is a plan view of the mat structure according to the apparatus of FIG. 14;
  • FIG. 16 is a side elevational view of an alternative embodiment of the apparatus according to the invention while in the transit mode;
  • FIG. 17 is a similar view of the apparatus of FIG. 16 but having its lower structure further submerged in the water;
  • FIG. 18 is a schematic view, partly in section, of apparatus according to the invention useful in lowering, raising, and maintaining stability of the columns.
  • FIG. 1 there is illustrated a side elevational view of the apparatus 10 illustrated in the transit mode of operation.
  • the apparatus 10 includes an elevated work platform I2 which is positioned above the surface 14 of the ocean at all times in normal use.
  • the platform 12 can be maintained fairly flat, with a low profile, except for the superstructure area 16 associated with the crew s quarters and auxiliary equipment such as the illustrated crane assembly.
  • a drilling derrick, mast, or other rig equipment can also be mounted on the platform 12, for example, as in U. S. Pat. No. 3,078,680 to Wepsala issued on Feb. 26, 1963.
  • the platform 12 is supportedly mounted on six vertical telescoping columns 18 which in turn are connected to two buoyant, ballastable structures 20, three columns to each structure 20 (better seen in FIG. 4).
  • Each of the pontoon structures 20 is equipped with a propeller 22 for causing the apparatus I0 to move through the seas in the transit mode.
  • the propellers 22 can be driven by a conventional power plant and transmission (not shown) from the superstructure area 16.
  • a guidable rudder (not shown) can be suitably disposed on the structure 20 if desired to aid the propellers 22 in guiding the apparatus 10 while underway.
  • the apparatus 10 can also be placed on location by other conventional means, such as with the employment of tugs and/or other assisting equipment if it be desired to aid or even eliminate the internal propulsion system.
  • buoyant structure 24 Attached intermediate the upper and lower ends of the columnar members 18 is a buoyant structure 24, comprising, for example, one or more counter-buoyancy tanks. As shown in FIG. I, the buoyant structure 24 is above the water level 14 during the transit mode of operation. This structure 24 runs both fore and aft, on both sides of the apparatus, and also transverse, as viewed in FIG. 3.
  • FIG. 2 illustrates the apparatus 10 in the working mode of operation, i.e., with the pontoon structure 20 ballasted down beneath the surface 14 of the water.
  • Means for selectively and controllably ballasting and deballasting the structure 20 are well known in the art and need not be mentioned here in detail except to note that the inner tube 26 of column 18 telescopes within the outer tube 28 of column 18, the telescoping action being solely a function of ballasting or deballasting the structure 20, as by adding or pumping out seawater. It should be appreciated, however, that the upper end of column 18 is fix edly secured to the upper platform structure 12, whereas the lower end of column 18 is fixedly secured to the ballastable structure 20.
  • ballast As ballast is added'to the structure 20, it begins to be submerged beneath the surface of the water.
  • the initial partial flooding of the structure 20 causes the apparatus to take a new waterline near the buoyant structure 24 and continued flooding extends the columns 18 further beneath the water.
  • the columns When fully extended, the columns come against heavy stops (not shown) which align the upper and lower units of the apparatus, and prevents further extension.
  • Continued flooding after the column stops have been reached, brings the apparatus 10 to the desired working waterline.
  • ballast pumps bring about the apparatus change in configuration. Removal of the ballast returns the structure to the waters surface since no column lock is necessary in the fully extended position, i.e., the weight of the ballast water maintains the columns fully extended.
  • rachet means or the like, while raising, lowering, or maintaining the lower struc ture submerged.
  • FIG. 3 illustrates a bow elevational view of the apparatus 10 in the working position, i.e., with ballast added to the ballastable structure 20.
  • a mat structure 30, with support frames 32 extends between the pontoons 20.
  • the action snubbers 60 help provide additional stability to the apparatus 10 in heavy seas.
  • a blow elevational view (now shown) of the apparatus 10 in the transit mode would show a catamaran configuration, wherein the mat 30 and buoyant structure 24 are preferably completely out of the water to provide improved towing characteristics.
  • FIG. 4 illustrates in a plan view the mat 30 connecting the two pontoon structures 20.
  • the mat 30 is actually comprised of a pair of mats having a plurality of freeing holes 31 therein to lessen the resistance of the mat to vertical movement in the water.
  • the mat 30 could be one continuous (except for the holes 31) member, without the gap 33 as illustrated.
  • the cross frames 32 are used to provide additional strength for the overall structure.
  • the mat 30 can be a solid structure (no holes 31) if desired.
  • FIG. 5 illustrates an alternative embodiment of the apparatus according to the invention, wherein the tip ends of the columns 18 are not necessarily fixedly secured to the platform structure 12.
  • the platform 12 can be supportedly mounted to the buoyant structure 24 solely by the support members 34 if desired.
  • FIG. 6 illustrates an alternative embodiment of the apparatus according to the invention, wherein an apparatus 40, having a working platform 41, is affixed to the top ends of three columnar buoyant support members 42, which may be telescoping if desired.
  • Fixedly secured to the bottom ends of each of the columns 42 is a circular, doughnut-shaped" pontoon structure 43, shown in a plan view in FIG. 7, and partially in cross-section in FIG. 6.
  • the structure 43 can be ballasted and deballasted to control its level within the water.
  • buoyant structure 44 Fixedly secured intermediate the bottom and top ends of the buoyant columns 42 is a buoyant structure 44 providing buoyancy for the apparatus 40 since it is shown in the fully extended, working position.
  • the structure 44 and columns 42 buoyantly support the apparatus 40, the entire vessel with its submerged extension being maintained above the ocean floor 45.
  • water ballast is pumped from the structure 43 to either bring it to the surface or at least closer to the surface of the water. In either event, this action causes the intermediate floatation structure 44 to be raised out of the water to facilitate moving the apparatus 40, either by its own power or otherwise.
  • FIG. 7 illustrates a top plan view of the ballastable structure 43.
  • a mat 50 having a plurality of freeing holes SI, or, alternatively having no freeing holes, relieves some of the resistance to vertical movements in the water.
  • the cross frame members 52 provide additional structural strength to the overall apparatus.
  • FIG. 8 illustrates an alternative embodiment for the pontoon structure useful with the apparatus according to FIG. 6.
  • Individual ballastable pontoon members 53 are provided for each of the columns 42, instead of having a single continuous ballastable structure as illustrated in FIG. 7.
  • a mat 54 having a plurality of freeing holes 55, provides additional stability to the overall apparatus in manner analogous to the other embodiments described herein.
  • the cross beams 56 and circumferential beam 57 provide additional strength to the overall apparatus.
  • FIG. 9 illustrates in an elevational view an action snubber 60 positioned relative to the columnar support member 18.
  • the action snubber 60 is comprised of cylinder 61 attached at its lower end to the pontoon 20.
  • An internal piston 62 has a piston rod 63 attached at its upper ends to the sleeve 28 of the column 18. It should be appreciated, however, that the piston rod 63 could be alternatively attached to the pontoon 20 and the cylinder 61 to the sleeve 28.
  • the fully extended length of the cylinder and piston rod is chosen to be greater than the predetermined distance that the column 18 can be extended to prevent a tension load being applied to the action snubber.
  • the action snubber 60 is filled with a fluid, for example, hydraulic oil, water or another suitable fluid 64.
  • a fluid for example, hydraulic oil, water or another suitable fluid 64.
  • Means are provided, as is exemplary illustrated in FIGS. 10 and 11, to allow the fluid 64 to be displaced from the piston rod end to the blind end, or vice versa, and a tank 65 is provided, with suitable valving, to add fluid to the cylinder or to allow fluid to be displaced from the cylinder 61.
  • the four comer columns 18, in the case of the apparatus described in FIGS. 1 and S are the most important in providing optimized stability. It should be appreciated that the snubbers can be placed inside the columns 18 or mounted external to them in a multiplicity of effective locations.
  • the action snubbers can be attached to the lower hull 20, as well to the upper sleeve 28 of the column 18, by welding, with pins, bolts or any such manner.
  • the snubbers prevent any quick or fast relative movement between the lower pontoon structure 20 and the middle buoyant structure 24.
  • the mat 30 and pontoon structure 20 are below the surface of the water and are not subject to weather reactions such as are caused by wind and wave.
  • the intermediate structure 24 and upper deck 12 attempt to rise or fall with a swell or wave, the submerged mat 30 and pontoon structure tend to remain stable at a depth where the amplitude of the wave action is considerably reduced.
  • the columns I8 would be constantly extending and retracting. In so doing, the upper structures would move about with instability despite the stability of the submerged structure. That is, the stability of the submerged structure would not be transferred to the upper structures. With the action snubbers, the submerged and surface structures react as one structure, improving the vertical steadiness of the entire vessel.
  • the movement of fluid within the snubber is controlled by the size of the component parts thereof.
  • the preferred embodiment contemplates the snubber action requiring about two minutes (120 seconds) end-to-end, as compared to the longest seas, such as in swells having periods of approximately seconds. With such an arrangement, the stability of the mat 30, with its plurality of freeing holes, is transferred to the upper structures 24 and 12. Since the overall apparatus is designed to have an extremely long natural period, as compared to the longest waves, the result is a small vertical movement, if at all, even in long swells and rough seas.
  • the action snubber does not assist in lowering or raising the pontoon structure and mat 30. It does maintain the relationship between the submerged and upper structures after the columns 18 are extended, since the ballast is a pre-tension load. Also, the snubbers control the rate of sinking and of re-floating the pontoons 20.
  • a plurality of cup-shaped compartments 70 are formed in the pontoon structure 20, one for each of the columns 18.
  • the lower end 71 of the upper sleeve 28 is rounded to fit within the compartment 70.
  • the column 18 is also formed to correspond to the shape of the pontoon 20, as is seen in FIG. 3.
  • FIG. 10 there is illustrated a portion, in cross section of an exemplary action snubber 60.
  • This piston 62 mounted on the piston rod 63, has an orifice 80 in the end thereof and a pair of holes 81 and 82 in the sides of the hollow portion -83 of the piston rod 63.
  • the movement of the piston 62 is slowed down an appreciable amount as the fluid passes through the orifice 80 and holes 81 and 82, the direction of fluid flow being dependent upon relative movement between the submerged pontoon structure 20 and the upper structures 24 and 12.
  • FIG. 11 illustrates an alternative piston configuration for an action snubber according to the invention, the piston 85 having an orifice 85 dividing into two passageways 87 and 88 for allowing fluid exchange as the piston is moved in either direction.
  • the piston can be sized to permit fluid to flow around it to either end of the cylinder.
  • an external piping arrangement connecting the two ends of the cylinder produces analogous results.
  • FIG. 12 illustrates a side elevational view of an alternative apparatus 90 illustrated in the working mode of operation.
  • the apparatus 90 includes an elevated work platform 91 which is positioned above the surface 14 of the ocean at all times in normal use.
  • the platform 91 is supportedly mounted on a plurality of buoyant columns 92, for example six columns, which in turn are connected to a lower mat structure 93 (shown in plan view in FIG. 13).
  • the mat 93 can be ballastable and deballastable, as with the pontoon structures 20 in FIG. I, but has a large surface area to maintain stability in a vertical direction.
  • the mat 93 can be a large area plate, with or without freeing holes, supportedly attached to one or more pontoons which are ballastable and deballastable.
  • the columns 92 can be ballasted and deballasted to cause the mat 93 to be moved vertically in the water without the use of a ballastable mat or ballastable pontoons.
  • FIG. 13 illustrates in plan view the mat structure 93 supportedly attached to the columns 92, shown in cross section.
  • the mat is ballastable and deballastable, as by adding or removing air (or water) from the mat.
  • a center hole 94 is located in the center of the mat 93 for access to the ocean bottom, for example, to provide a means for drilling an oil or gas well.
  • the hole 94 can be beneath a similar hole (not illustrated) in the work platform 91 of FIG. 12.
  • the mat 93 could be without the hole 94 and have the drilling or workover operations performed over the sides of the vessel.
  • ballast is added to the mat 93 (or to the supporting pontoons, not shown) or to the columns 92, whereupon the columns 92 begins sinking further into the water. Ballast is added until the mat 93 is an adequate depth beneath the surface of the water, but always maintained floating; that is, off the ocean floor.
  • floating is intended to mean that a structure is maintained off the ocean floor, but not necessarily on the ocean surface. It should also be appreciated hat the mat structures in the different embodiments herein are preferably maintained horizontal, and thus are parallel to the elevated work platforms and to the surface of the water.
  • the mat 93 provides a vastly improved stabilization characteristic because of the huge volume of water between the mat and the ocean surface. For example, if the mat is 100 ft. wide, and 200 ft. long, submerged in 100 ft. of water, there are two million cubic feet of water resting on the mat, all of which has to be displaced to move the vessel in the vertical direction, up or down. Hence. when the apparatus is used in heavy seas, the apparatus remains nonetheless quite stable.
  • FIG. 14 illustrates a side elevational view of an alternative apparatus 95 illustrated in the working mode of operation.
  • the apparatus 95 includes an elevated work platform 96 which is positioned above the surface 14 of the ocean at all times in normal use.
  • the platform 96 is supportedly mounted on a single column 97, which may or may not be ballastable, which in turn is connected to a lower mat structure 98 (shown in plan view in FIG. 15).
  • the mat 98 as with the previously discussed mat structures, can be ballastable and deballastable.
  • the ballast feature can come from a pair of pontoons 99, or perhaps a single circumferential pontoon as illustrated in FIG. 7.
  • the ballast feature can come from ballasting and deballasting the single column 97.
  • the large surface area of the mat 98, with or without the freeing holes 100, causes the apparatus 95 to have vastly improved stabilization, especially in view of a single column being exposed to the action of the waves.
  • a hole 101 can be provided in the mat 98 to coincide with a similar hole 103 in the work platform 96.
  • the mat 98 is illustrated as having a number of freeing holes 100, but having some of the holes closed, as with a metal plate 102.
  • the plate could be welded, hinged and locked, or any other such means as to close the hole.
  • the holes also could be selectively closed with a shutter mechanism. In any event, depending upon the wave action and time period, it may be desirable to selectively open or close a given number or geometry pattern of the freeing holes to provide optimum stabilization, even to the point of closing all the holes and effectively having a solid mat.
  • the column 97 can be telescoping if desired, in the manner of the telescoping columns in FIG. 1.
  • an intermediate floatation structure could be added to the columns 97 if desired, in the manner of structure 24 in FIG. I.
  • ballast is added until the column 97 and mat structure 98 is an adequate depth beneath the surface of the water but always maintained floating.
  • the ballast is removed, causing the mat to be raised vertically in the water to some desired level.
  • the apparatus could be towed with the mat submerged to the working depth.
  • FIG. 16 illustrates a side elevational view of an alternative apparatus 110 in the transit mode of operation.
  • the apparatus 110 includes an elevated work platform 111 which is positioned above the surface 14 ofthe ocean at all times in normal use.
  • the profile of the apparatus 110 is seen to change as the columns 112 extend through the platform 111. Except during the times the columns 112 are moving with respect to the platform 111, the columns are locked into the platform 111, for example, with lock pins (not shown).
  • An intermediate buoyant member 113 is fixedly attached to the platform 111 by means of the support structures 114.
  • a mat structure 115 Attached to the lower end of the columns 112 is a mat structure 115, the mat 115 being ballastable and deballastable to cause the mat to sink further into the water.
  • the mat 115 can be a non-ballastable plate supportedly attached to a ballastable and deballastable pontoon structure (not shown).
  • the columns 112 can be ballastable and deballastable to cause the mat 115 to rise or sink further into the water.
  • FIG. 17 illustrates a side elevation view of the apparatus 110 in the working mode of operation.
  • ballast is added until the intermediate member 113 settles down into the water. After the lock pins are removed, additional ballast causes the mat 115 to continue sinking in the water. At the desired depth, the operations of the vessel, for example drilling, may be commenced. As with the other mat structures described herein, the submerged, floating mat provides vastly improved stabilization in heavy seas.
  • ballast is removed and the column 112 begins to move up through the platform 111. At a given point, the lock pins are reinserted. Additional loss of ballast then causes the intermediate structure 113 to be lifted out of the water to facilitate towing in the transit mode of operation.
  • FIG. 18 illustrates schematically a means for aiding the raising, lowering and maintaining of the mat structures variously described herein.
  • the column 120 has a series of rachet teeth 121 on one side of the column and a second series of rachet teeth 122 on the other side of the column.
  • the column 120 is shown as being movable with respect to an elevated work platform 123, such as would be the case in an apparatus as is illustrated in FIGS. 16 and 17.
  • the double racheting means as being readily adaptable to the telescoping columnar configuration of FIG. 2, wherein one portion of the telescoping column can be controlled with respect to the other portion.
  • the column 120 is seen to pass through a hole 124 in the platform 123.
  • Fixedly attached to the platform 123 is a pair of air cylinders 125 and 126.
  • the DOWN RACI-IET" cylinder 125 has a piston rod 127, to which a rachet dog 128 is pivotally attached by pin 129.
  • a spring 130 is attached to both the piston rod 127 and the rachet dog 128. In operation, the dog 128 can pivot down against the spring 130, but is blocked from pivoting up against the piston rod 127.
  • the UP RACHET" cylinder 126 has a piston rod 135, to which a rachet dog 136 is pivotally attached by pin 137.
  • a sPring 138 is attached to both the piston rod 135 and the rachet dog 136. In operation, the dog 136 can pivot up against the spring 138, but is blocked from pivoting down against the piston rod 135.
  • the air cylinders 125 and 126 are each connected by compressed airlines 140 and 141 to a rachet control panel 142.
  • the column can only go down.
  • the air cylinder 126 is the only one activated, thus allowing the column to move up only. Should the mat be in the desired position, such as fully extended down, both cylinders can be activated to prevent movement in either direction.
  • both cylinders can be activated to prevent movement in either direction.
  • the double racheting mechanism can be used, if desired, in conjunction with the action snubber systems elsewhere described herein.
  • a mobile marine platfonn apparatus comprising:
  • a platform structure adapted to support supplies and equipment
  • buoyant, ballastable structure fixedly secured to the lower end of each of said columnar members, including means to ballast and deballast said ballastable structure to submerged and floating positions, respectively;
  • a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance.
  • a mobile marine platform apparatus comprising:
  • a platform structure adapted to support supplies and equipment
  • a buoyant, ballastable structure fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structure to submerged and floating positions, respectively, and
  • a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance.
  • a mobile marine platform apparatus comprising:
  • a platform structure adapted to support supplies and equipment
  • each of said ballastable structures being fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structures to submerged and floating positions, respectively;
  • a flotation structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structures are submerged a predetermined distance.
  • a mobile marine platform apparatus comprising:
  • a platform structure adapted to support supplies and equipment
  • a buoyant, ballastable structure fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structure to submerged and floating positions, respectively;
  • a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance, said platform structure being fixedly attached to said second buoyant structure.
  • a mobile marine platform apparatus comprising:
  • a platform structure adapted to support supplies and equipment
  • buoyant, ballastable structure comprising a plurality of pontoons, and including in addition thereto, a perforated mat connected between said pontoons, fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structure between varying depths of submersion;
  • a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance, said platform structure being fixedly attached to said second buoyant structure.
  • a mobile marine platform apparatus comprising:
  • a platform structure adapted to support supplies and equipment
  • a buoyant, ballastable structure comprising a pontoon having a center portion comprised of a perforated mat, fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structure between varying depths of submersion;
  • a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance, said platform structure being fixedly attached to said second buoyant structure.
  • a mobile marine platform apparatus comprising:
  • a platform structure adapted to support supplies and equipment
  • submersible means fixedly secured to the lower ends of said support members for extending said support members beneath the sea while maintaining said platform structure at or above the surface of the sea.
  • the platform apparatus including in addition thereto at least one action snubber member connected between said platform structure and said submersible means.
  • said action snubber comprises a liquid filled piston and cylinder having means for said fluid to move from one end of said cylinder to the other end of said cylinder as said platform apparatus moves vertically with respect to said submersible eans.
  • said submersible means includes a cup-shaped chamber for each of said plurality of columnar support members and each of said support members has a member rounded at one end for fitting into said chamber, whereby said telescoping action is slowed down as said rounded member enters said chamber.
  • a mobile marine platform apparatus comprising:
  • a mat assembly fixedly secured to said columnar members and parallel to said platform structure, said mat assembly being adapted to be lowered to a given depth beneath the surface of water while always floating above the water floor, wherein said mat assembly comprises at least one metal plate having a plurality of freeing holes therein.
  • a mobile marine platform apparatus comprising:
  • a mobile marine platform apparatus comprising;
  • At least one buoyant structure fixedly secured to the underside of said platform structure, being maintained a given distance from said platform structure;
  • said mat assembly comprises at least one metal plate having a plurality of freeing holes therein.

Abstract

Three levels in a vertical plane, being an elevated work platform, a middle hull and a submersible lower hull are connected together by six telescoping vertical support columns. The lower catamaran hull consists of two pontoon-type tubes connected together by a mat having freeing holes therein to reduce the mat''s resistance in the vertical plane when submerged. The middle hull is maintained above the water level when the lower hull is at the surface of the water, but settles down into the water to provide buoyant support when the lower hull is submerged. The lower hull, being buoyant and ballastable, is raised or lowered in the water by adding or removing water ballast. Action snubbers are provided to work in conjunction with the vertical columns to prevent any quick or fast relative movement between the lower hull and the combined middle hull and upper deck structure. An alternative embodiment utilizes the middle buoyant hull to floatably support a three column structure. Other alternative embodiments include non-telescoping columns, single column platform apparatus and means for varying the amount or number of freeing holes used to affect the mat resistance in the water.

Description

United States atent Harper [54] METHOD AND MOBILE MARINE PLATFORM APPARATUS HAVING FLOATING SUBMERGED MAT STABILIZATION [72] Inventor: James C. Harper, Houston, Tex.
[73] Assignee: Dresser Industries, Inc., Dallas, Tex.
[22] Filed: March 17, 1970 211 App]. No.: 20,278
Related US. Application Data [63] Continuation-in-part of Ser. No. 872,314, Oct. 29,
1969, abandoned [52] US. Cl. ..114/0.5 D, 114/435 [51] Int. Cl. ..B63b 35/00, B63b 35/44 [58] Field of Search ..114/0.5 D,43.5,77, 125,124, 114/665 R, 0.5 R; 61/465 [56] References Cited UNITED STATES PATENTS 3,442,239 5/1969 Wilson ..l l4/0.5 D 3,207,110 9/1965 Laborde et al.. ..1 l4/0.5 D 3,515,084 6/1970 Holmes ..1l4/0.5 D
Primary Examiner-Trygve M. Blix Attorney-Robert W. Mayer, Thomas P. Hubbard, Jr., Daniel Rubin, Raymond T. Majesko, Roy L. Van Winkle, William E. Johnson, Jr. and Eddie E. Scott [57] ABSTRACT Three levels in a vertical plane, being an elevated work platform, a middle hull and a submersible lower hull are connected together by six telescoping vertical support columns. The lower catamaran hull consists of two pontoon-type tubes connected together by a mat having freeing holes therein to reduce the mats resistance in the vertical plane when submerged. The middle hull is maintained above the water level when the lower hull is at the surface of the water, but settles down into the water to provide buoyant support when the lower hull is submerged. The lower hull, being buoyant and ballastable, is raised or lowered in the water by adding or removing water ballast. Action snubbers are provided to work in conjunction with the vertical columns to prevent any quick or fast relative movement between the lower hull and the combined middle hull and upper deck structure. An alternative embodiment utilizes the middle buoyant hull to floatably support a three column structure. Other alternative embodiments include non-telescoping columns, single column platform apparatus and means for varying the amount or number of freeing holes used to affect the mat resistance in the water.
20 Claims, 18 Drawing Figures P'A'TENTEDJUL] I972 SHEET 1 [F9 "Him;
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ATTORNEY PA'TENTEDJuL'mn 3,673,974
' sum ans 9 RACHET I42 CONTROL UP DOWN RACHE-T RACHET l25 I Flaws INVENTOR JAMES C. HARPER ATTORNEY METHOD AND MOBILE MARINE PLATFORM APPARATUS HAVING FLOATING SUBMERGED MAT STABILIZATION RELATED APPLICATION This application is a continuation, at least in part, of my US. application Ser. No. 872,314, filed Oct. 29, 1969 and now abandoned.
BACKGROUND OF THE INVENTION This invention relates, generally, to mobile marine platform apparatus, and specifically, to a structure having improved stability, whether in the transit or in the working positions, and which is easily transportable to an offshore location, as well as to a method of maintaining stability of a mobile marine platform apparatus.
The offshore petroleum exploration art has long recognized the need for improved stability in mobile marine platforms such as might be used in drilling, workover, salvage operations and the like. Despite many attempts by those in the art to fill this need, the prior art structures have failed to achieve stability in both the transit and the working positions. Thus, in achieving stability for working, stability in transit was sacrificed, and vice versa. Further, even the optimized stability of such structures failed to provide adequate stabilization in heavy seas.
It is therefore the primary object of the present invention to provide a new mobile marine platform apparatus having improved stability, both in the transit and in the working positrons.
It is another object of the invention to provide an offshore platform apparatus having new and improved apparatus for converting from the transit to the working position and vice versa.
It is yet another object of the invention to provide a new apparatus providing stability for marine platforms, such apparatus being maintained off the ocean floor in the working position of the platform.
It is still another object of the invention to provide a mobile marine platform apparatus having flexible submerged means which in combination with other unique apparatus described herein have time constants longer than that of the longest ocean waves to provide increased stability of the platform apparatus.
It is another object of the invention to provide a new and improved method for improving the stability of floating, mobile marine platform apparatus.
The objects of the invention are accomplished, briefly, by a mobile marine platform apparatus having a buoyant, ballastable structure associated with a telescoping columnar support structure such that the overall height of the apparatus is not severely increased for the transit phase of the operation. A second buoyant structure, maintained above water level during the transit mode, provides buoyant support when the lower structure is submerged. A mat structure maintained off the ocean floor, and a new and improved method for using same, provides increased stability for the working phase of the operation. Action snubbing members between the pontoon structure and the upper deck add even further stability to the offshore platform apparatus. Throughout the various embodiments, a floating, submerged mat structure provides vastly increased stabilization.
These and further objects, features and advantages of the present invention will be apparent from a reading of the following detailed description and accompanying drawing, in which:
FIG. 1 is a side elevational view of a complete embodiment of the apparatus according to the invention while in the transient mode of operation;
FIG. 2 is a similar view showing the apparatus in the working mode of operation with its pontoon structure lowered;
FIG. 3 is a bow elevational view of the apparatus according to FIG. 2;
FIG. 4 is a plan view of the mat and pontoon structure according to the invention as illustrated in FIGS. 1-3;
FIG. 5 is a side elevational view of an alternative embodiment of the apparatus according to the invention while in the transit mode of operation;
FIG. 6 is a side elevational view of an additional alternative embodiment of the apparatus according to the invention in the working mode of operation;
FIG. 7 is a plan view of the mat and pontoon structure according to the invention as illustrated in FIG. 6;
FIG. 8 is a plan view of an alternative mat and pontoon structure according to the invention as illustrated in FIG. 6;
FIG. 9 is an elevational view of the action snubber associated with one or more of the support columns according to the invention;
FIG. 10 is a more detailed cross-sectional view of a portion of the action snubber illustrated in FIG. 9;
FIG. 11 is a detailed cross-sectional view of a portion of an alternative action snubber;
FIG. 12 is a side elevational view of an alternative embodiment of the apparatus according to the invention;
FIG. 13 is a plan view of the mat structure according to the apparatus of FIG. 12;
FIG. 14 is a side elevational view of an alternative embodiment ofthe apparatus according to the invention;
FIG. 15 is a plan view of the mat structure according to the apparatus of FIG. 14;
FIG. 16 is a side elevational view of an alternative embodiment of the apparatus according to the invention while in the transit mode;
FIG. 17 is a similar view of the apparatus of FIG. 16 but having its lower structure further submerged in the water; and
FIG. 18 is a schematic view, partly in section, of apparatus according to the invention useful in lowering, raising, and maintaining stability of the columns.
Referring now to the drawing in more detail, especially to FIG. 1, there is illustrated a side elevational view of the apparatus 10 illustrated in the transit mode of operation. The apparatus 10 includes an elevated work platform I2 which is positioned above the surface 14 of the ocean at all times in normal use. As will be explained hereinafter, the platform 12 can be maintained fairly flat, with a low profile, except for the superstructure area 16 associated with the crew s quarters and auxiliary equipment such as the illustrated crane assembly. Although not illustrated, a drilling derrick, mast, or other rig equipment can also be mounted on the platform 12, for example, as in U. S. Pat. No. 3,078,680 to Wepsala issued on Feb. 26, 1963.
The platform 12 is supportedly mounted on six vertical telescoping columns 18 which in turn are connected to two buoyant, ballastable structures 20, three columns to each structure 20 (better seen in FIG. 4). Each of the pontoon structures 20 is equipped with a propeller 22 for causing the apparatus I0 to move through the seas in the transit mode. The propellers 22 can be driven by a conventional power plant and transmission (not shown) from the superstructure area 16. It should be appreciated that a guidable rudder (not shown) can be suitably disposed on the structure 20 if desired to aid the propellers 22 in guiding the apparatus 10 while underway. It should further be appreciated that the apparatus 10 can also be placed on location by other conventional means, such as with the employment of tugs and/or other assisting equipment if it be desired to aid or even eliminate the internal propulsion system.
Attached intermediate the upper and lower ends of the columnar members 18 is a buoyant structure 24, comprising, for example, one or more counter-buoyancy tanks. As shown in FIG. I, the buoyant structure 24 is above the water level 14 during the transit mode of operation. This structure 24 runs both fore and aft, on both sides of the apparatus, and also transverse, as viewed in FIG. 3.
FIG. 2 illustrates the apparatus 10 in the working mode of operation, i.e., with the pontoon structure 20 ballasted down beneath the surface 14 of the water. Means for selectively and controllably ballasting and deballasting the structure 20 are well known in the art and need not be mentioned here in detail except to note that the inner tube 26 of column 18 telescopes within the outer tube 28 of column 18, the telescoping action being solely a function of ballasting or deballasting the structure 20, as by adding or pumping out seawater. It should be appreciated, however, that the upper end of column 18 is fix edly secured to the upper platform structure 12, whereas the lower end of column 18 is fixedly secured to the ballastable structure 20. As ballast is added'to the structure 20, it begins to be submerged beneath the surface of the water. The initial partial flooding of the structure 20 causes the apparatus to take a new waterline near the buoyant structure 24 and continued flooding extends the columns 18 further beneath the water. When fully extended, the columns come against heavy stops (not shown) which align the upper and lower units of the apparatus, and prevents further extension. Continued flooding, after the column stops have been reached, brings the apparatus 10 to the desired working waterline.
It should be appreciated that the ballast pumps (not shown) bring about the apparatus change in configuration. Removal of the ballast returns the structure to the waters surface since no column lock is necessary in the fully extended position, i.e., the weight of the ballast water maintains the columns fully extended. However, as explained hereinafter with respect to FIG. 18, it is sometimes helpful to use rachet means, or the like, while raising, lowering, or maintaining the lower struc ture submerged.
FIG. 3 illustrates a bow elevational view of the apparatus 10 in the working position, i.e., with ballast added to the ballastable structure 20. As will be better seen in FIG. 4, a mat structure 30, with support frames 32, extends between the pontoons 20. As will be explained hereinafter with respect to FIGS 9, I0, and 11, the action snubbers 60 help provide additional stability to the apparatus 10 in heavy seas. It should be appreciated that a blow elevational view (now shown) of the apparatus 10 in the transit mode would show a catamaran configuration, wherein the mat 30 and buoyant structure 24 are preferably completely out of the water to provide improved towing characteristics.
FIG. 4 illustrates in a plan view the mat 30 connecting the two pontoon structures 20. The mat 30 is actually comprised of a pair of mats having a plurality of freeing holes 31 therein to lessen the resistance of the mat to vertical movement in the water. However, if desired the mat 30 could be one continuous (except for the holes 31) member, without the gap 33 as illustrated. The cross frames 32 are used to provide additional strength for the overall structure. Furthermore, as illustrated and described hereinafter, the mat 30 can be a solid structure (no holes 31) if desired.
FIG. 5 illustrates an alternative embodiment of the apparatus according to the invention, wherein the tip ends of the columns 18 are not necessarily fixedly secured to the platform structure 12. Thus, it should be appreciated that the platform 12 can be supportedly mounted to the buoyant structure 24 solely by the support members 34 if desired.
FIG. 6 illustrates an alternative embodiment of the apparatus according to the invention, wherein an apparatus 40, having a working platform 41, is affixed to the top ends of three columnar buoyant support members 42, which may be telescoping if desired. Fixedly secured to the bottom ends of each of the columns 42 is a circular, doughnut-shaped" pontoon structure 43, shown in a plan view in FIG. 7, and partially in cross-section in FIG. 6. As with the other ballastable structures described herein, the structure 43 can be ballasted and deballasted to control its level within the water.
Fixedly secured intermediate the bottom and top ends of the buoyant columns 42 is a buoyant structure 44 providing buoyancy for the apparatus 40 since it is shown in the fully extended, working position. Thus, with the buoyant structure 43 in the fully extended position, the structure 44 and columns 42 buoyantly support the apparatus 40, the entire vessel with its submerged extension being maintained above the ocean floor 45.
To move the apparatus 40 to the transit mode of operation, water ballast is pumped from the structure 43 to either bring it to the surface or at least closer to the surface of the water. In either event, this action causes the intermediate floatation structure 44 to be raised out of the water to facilitate moving the apparatus 40, either by its own power or otherwise.
FIG. 7 illustrates a top plan view of the ballastable structure 43. A mat 50, having a plurality of freeing holes SI, or, alternatively having no freeing holes, relieves some of the resistance to vertical movements in the water. The cross frame members 52 provide additional structural strength to the overall apparatus.
FIG. 8 illustrates an alternative embodiment for the pontoon structure useful with the apparatus according to FIG. 6. Individual ballastable pontoon members 53 are provided for each of the columns 42, instead of having a single continuous ballastable structure as illustrated in FIG. 7. A mat 54, having a plurality of freeing holes 55, provides additional stability to the overall apparatus in manner analogous to the other embodiments described herein. The cross beams 56 and circumferential beam 57 provide additional strength to the overall apparatus.
FIG. 9 illustrates in an elevational view an action snubber 60 positioned relative to the columnar support member 18. In general, the action snubber 60 is comprised of cylinder 61 attached at its lower end to the pontoon 20. An internal piston 62 has a piston rod 63 attached at its upper ends to the sleeve 28 of the column 18. It should be appreciated, however, that the piston rod 63 could be alternatively attached to the pontoon 20 and the cylinder 61 to the sleeve 28. The fully extended length of the cylinder and piston rod is chosen to be greater than the predetermined distance that the column 18 can be extended to prevent a tension load being applied to the action snubber.
The action snubber 60 is filled with a fluid, for example, hydraulic oil, water or another suitable fluid 64. Means are provided, as is exemplary illustrated in FIGS. 10 and 11, to allow the fluid 64 to be displaced from the piston rod end to the blind end, or vice versa, and a tank 65 is provided, with suitable valving, to add fluid to the cylinder or to allow fluid to be displaced from the cylinder 61.
While the preferred embodiment of the invention contemplates the use of one or more such action snubbers with each of the columns 18, a fewer number can be used ifdesired. The four comer columns 18, in the case of the apparatus described in FIGS. 1 and S are the most important in providing optimized stability. It should be appreciated that the snubbers can be placed inside the columns 18 or mounted external to them in a multiplicity of effective locations. The action snubbers can be attached to the lower hull 20, as well to the upper sleeve 28 of the column 18, by welding, with pins, bolts or any such manner.
In the operation of the snubbers, it should be appreciated that they prevent any quick or fast relative movement between the lower pontoon structure 20 and the middle buoyant structure 24. In the working mode of operation, the mat 30 and pontoon structure 20 are below the surface of the water and are not subject to weather reactions such as are caused by wind and wave. As the intermediate structure 24 and upper deck 12 attempt to rise or fall with a swell or wave, the submerged mat 30 and pontoon structure tend to remain stable at a depth where the amplitude of the wave action is considerably reduced.
However, without the action snubber or some analogous means, the columns I8 would be constantly extending and retracting. In so doing, the upper structures would move about with instability despite the stability of the submerged structure. That is, the stability of the submerged structure would not be transferred to the upper structures. With the action snubbers, the submerged and surface structures react as one structure, improving the vertical steadiness of the entire vessel.
The movement of fluid within the snubber is controlled by the size of the component parts thereof. The preferred embodiment contemplates the snubber action requiring about two minutes (120 seconds) end-to-end, as compared to the longest seas, such as in swells having periods of approximately seconds. With such an arrangement, the stability of the mat 30, with its plurality of freeing holes, is transferred to the upper structures 24 and 12. Since the overall apparatus is designed to have an extremely long natural period, as compared to the longest waves, the result is a small vertical movement, if at all, even in long swells and rough seas.
It should be appreciated, however, that the action snubber does not assist in lowering or raising the pontoon structure and mat 30. It does maintain the relationship between the submerged and upper structures after the columns 18 are extended, since the ballast is a pre-tension load. Also, the snubbers control the rate of sinking and of re-floating the pontoons 20.
Referring again to FIG. 2, a plurality of cup-shaped compartments 70 are formed in the pontoon structure 20, one for each of the columns 18. The lower end 71 of the upper sleeve 28 is rounded to fit within the compartment 70. The column 18 is also formed to correspond to the shape of the pontoon 20, as is seen in FIG. 3.
The effect of the columns 18 extending during ballasting is the same as if upper structures 12 and 24 were relieved of the weight of pontoon 20, and the upper structures may become quite active during the ballasting operation due to surface wind and waves. The rise and fall of the upper structures may extend and retract the columns 18 at this point in the cycle. Should this happen, the cushion chamber 70 prevents the two parts from slamming together with any real damaging force. As the shaped end portion 71 enters the cushion chamber 70, it must clear out the water trapped therein. The clearance between the two parts is sized to permit the column ends 71 to enter the compartment 70 relatively slowly and thus prevent damage.
Referring now to FIG. 10, there is illustrated a portion, in cross section of an exemplary action snubber 60. This piston 62, mounted on the piston rod 63, has an orifice 80 in the end thereof and a pair of holes 81 and 82 in the sides of the hollow portion -83 of the piston rod 63. Thus, as explained with respect to FIG. 9, the movement of the piston 62 is slowed down an appreciable amount as the fluid passes through the orifice 80 and holes 81 and 82, the direction of fluid flow being dependent upon relative movement between the submerged pontoon structure 20 and the upper structures 24 and 12.
FIG. 11 illustrates an alternative piston configuration for an action snubber according to the invention, the piston 85 having an orifice 85 dividing into two passageways 87 and 88 for allowing fluid exchange as the piston is moved in either direction.
Although not illustrated, other action snubbers for use with apparatus according to the invention will become apparent from the embodiments illustrated. For example, instead of flowing through the piston, the piston can be sized to permit fluid to flow around it to either end of the cylinder. Also, an external piping arrangement connecting the two ends of the cylinder produces analogous results.
FIG. 12 illustrates a side elevational view of an alternative apparatus 90 illustrated in the working mode of operation. The apparatus 90 includes an elevated work platform 91 which is positioned above the surface 14 of the ocean at all times in normal use. The platform 91 is supportedly mounted on a plurality of buoyant columns 92, for example six columns, which in turn are connected to a lower mat structure 93 (shown in plan view in FIG. 13). The mat 93 can be ballastable and deballastable, as with the pontoon structures 20 in FIG. I, but has a large surface area to maintain stability in a vertical direction. Alternatively, the mat 93 can be a large area plate, with or without freeing holes, supportedly attached to one or more pontoons which are ballastable and deballastable. Alternatively, the columns 92 can be ballasted and deballasted to cause the mat 93 to be moved vertically in the water without the use of a ballastable mat or ballastable pontoons.
FIG. 13 illustrates in plan view the mat structure 93 supportedly attached to the columns 92, shown in cross section. In the preferred embodiment of the mat 93, the mat is ballastable and deballastable, as by adding or removing air (or water) from the mat. A center hole 94 is located in the center of the mat 93 for access to the ocean bottom, for example, to provide a means for drilling an oil or gas well. Quite obviously, the hole 94 can be beneath a similar hole (not illustrated) in the work platform 91 of FIG. 12. Alternatively, the mat 93 could be without the hole 94 and have the drilling or workover operations performed over the sides of the vessel.
In the operation of the apparatus of FIGS. [2 and I3, ballast is added to the mat 93 (or to the supporting pontoons, not shown) or to the columns 92, whereupon the columns 92 begins sinking further into the water. Ballast is added until the mat 93 is an adequate depth beneath the surface of the water, but always maintained floating; that is, off the ocean floor. For purposes of this specification, floating" is intended to mean that a structure is maintained off the ocean floor, but not necessarily on the ocean surface. It should also be appreciated hat the mat structures in the different embodiments herein are preferably maintained horizontal, and thus are parallel to the elevated work platforms and to the surface of the water.
It should be appreciated that the mat 93 provides a vastly improved stabilization characteristic because of the huge volume of water between the mat and the ocean surface. For example, if the mat is 100 ft. wide, and 200 ft. long, submerged in 100 ft. of water, there are two million cubic feet of water resting on the mat, all of which has to be displaced to move the vessel in the vertical direction, up or down. Hence. when the apparatus is used in heavy seas, the apparatus remains nonetheless quite stable.
It should likewise be appreciated that the absence or presence of the freeing holes in the mat is a factor in the stability characteristics of the apparatus, since the surface area of the mat is directly affected by such holes, and also by the access hole 94 shown in FIG. 13.
FIG. 14 illustrates a side elevational view of an alternative apparatus 95 illustrated in the working mode of operation. The apparatus 95 includes an elevated work platform 96 which is positioned above the surface 14 of the ocean at all times in normal use. The platform 96 is supportedly mounted on a single column 97, which may or may not be ballastable, which in turn is connected to a lower mat structure 98 (shown in plan view in FIG. 15). The mat 98, as with the previously discussed mat structures, can be ballastable and deballastable. Alternatively, the ballast feature can come from a pair of pontoons 99, or perhaps a single circumferential pontoon as illustrated in FIG. 7. Alternatively, the ballast feature can come from ballasting and deballasting the single column 97. In any event, the large surface area of the mat 98, with or without the freeing holes 100, causes the apparatus 95 to have vastly improved stabilization, especially in view of a single column being exposed to the action of the waves. For drilling access, a hole 101 can be provided in the mat 98 to coincide with a similar hole 103 in the work platform 96.
In FIG. 15, the mat 98 is illustrated as having a number of freeing holes 100, but having some of the holes closed, as with a metal plate 102. The plate could be welded, hinged and locked, or any other such means as to close the hole. Alternatively (not illustrated), the holes also could be selectively closed with a shutter mechanism. In any event, depending upon the wave action and time period, it may be desirable to selectively open or close a given number or geometry pattern of the freeing holes to provide optimum stabilization, even to the point of closing all the holes and effectively having a solid mat. It should be appreciated that the column 97 can be telescoping if desired, in the manner of the telescoping columns in FIG. 1. Likewise, an intermediate floatation structure could be added to the columns 97 if desired, in the manner of structure 24 in FIG. I.
In the operation of the apparatus of FIGS. 14 and 15, ballast is added until the column 97 and mat structure 98 is an adequate depth beneath the surface of the water but always maintained floating. To return to the transit mode of operation, the ballast is removed, causing the mat to be raised vertically in the water to some desired level. Alternatively, the apparatus could be towed with the mat submerged to the working depth.
FIG. 16 illustrates a side elevational view of an alternative apparatus 110 in the transit mode of operation. The apparatus 110 includes an elevated work platform 111 which is positioned above the surface 14 ofthe ocean at all times in normal use. As compared with the apparatus of FIG. 1, in which the platform profile remains fairly constant, the profile of the apparatus 110 is seen to change as the columns 112 extend through the platform 111. Except during the times the columns 112 are moving with respect to the platform 111, the columns are locked into the platform 111, for example, with lock pins (not shown). An intermediate buoyant member 113 is fixedly attached to the platform 111 by means of the support structures 114. Attached to the lower end of the columns 112 is a mat structure 115, the mat 115 being ballastable and deballastable to cause the mat to sink further into the water. Alternatively, the mat 115 can be a non-ballastable plate supportedly attached to a ballastable and deballastable pontoon structure (not shown). Alternatively, the columns 112 can be ballastable and deballastable to cause the mat 115 to rise or sink further into the water.
FIG. 17 illustrates a side elevation view of the apparatus 110 in the working mode of operation.
In the operation of the apparatus 110, ballast is added until the intermediate member 113 settles down into the water. After the lock pins are removed, additional ballast causes the mat 115 to continue sinking in the water. At the desired depth, the operations of the vessel, for example drilling, may be commenced. As with the other mat structures described herein, the submerged, floating mat provides vastly improved stabilization in heavy seas. When it is desired to reverse the operation, ballast is removed and the column 112 begins to move up through the platform 111. At a given point, the lock pins are reinserted. Additional loss of ballast then causes the intermediate structure 113 to be lifted out of the water to facilitate towing in the transit mode of operation.
FIG. 18 illustrates schematically a means for aiding the raising, lowering and maintaining of the mat structures variously described herein. The column 120 has a series of rachet teeth 121 on one side of the column and a second series of rachet teeth 122 on the other side of the column. For ease of illustration, the column 120 is shown as being movable with respect to an elevated work platform 123, such as would be the case in an apparatus as is illustrated in FIGS. 16 and 17. However, those skilled in the art will appreciate the double racheting means as being readily adaptable to the telescoping columnar configuration of FIG. 2, wherein one portion of the telescoping column can be controlled with respect to the other portion.
Referring again to FIG. 18, the column 120 is seen to pass through a hole 124 in the platform 123. Fixedly attached to the platform 123 is a pair of air cylinders 125 and 126. The DOWN RACI-IET" cylinder 125 has a piston rod 127, to which a rachet dog 128 is pivotally attached by pin 129. A spring 130 is attached to both the piston rod 127 and the rachet dog 128. In operation, the dog 128 can pivot down against the spring 130, but is blocked from pivoting up against the piston rod 127.
In a similar manner, the UP RACHET" cylinder 126 has a piston rod 135, to which a rachet dog 136 is pivotally attached by pin 137. A sPring 138 is attached to both the piston rod 135 and the rachet dog 136. In operation, the dog 136 can pivot up against the spring 138, but is blocked from pivoting down against the piston rod 135.
The air cylinders 125 and 126 are each connected by compressed airlines 140 and 141 to a rachet control panel 142.
In the operation of the racheting apparatus of FIG. 18, if the air cylinders and 126 are both activated, the pistons 127 and are extended, the dogs 128 and 136 are engaged, respectively, with the rachet teeth 121 and 122, and the column 120 will not move with respect to the platform 123. If it is desired, to move the column 120 down, the air cylinder 126 is deactivated, thus disengaging the rachet dog 136. The ballast being added to the lower section of the column, the mat for example (not shown in FIG. 18), thus causes the column 120 to move down with respect to the platform 123. However, since the column cannot move up because of the engaged rachet assembly, the system will not respond up and down to the heavy seas. The column can only go down. In an analogous manner, in raising the column, the air cylinder 126 is the only one activated, thus allowing the column to move up only. Should the mat be in the desired position, such as fully extended down, both cylinders can be activated to prevent movement in either direction. It should be appreciated that the double racheting mechanism can be used, if desired, in conjunction with the action snubber systems elsewhere described herein.
Thus there has been illustrated and described herein various semi-submersible offshore vessels having vastly improved stability characteristics during the working mode of operation, some of which have the catamarans stability and speed on the surface during the transit mode. By having a submerged mat structure maintained off the ocean floor, the entire apparatus is observed to be only slightly affected by the most severe weather. Again, by using action snubbers in cooperation with the telescoping columns designed to have time constants longer than the longest seas, an even higher degree of stability is achieved.
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A mobile marine platfonn apparatus, comprising:
a platform structure adapted to support supplies and equipment;
a plurality of telescoping columnar members, each being fixedly secured at its upper end to said platform structure;
a buoyant, ballastable structure fixedly secured to the lower end of each of said columnar members, including means to ballast and deballast said ballastable structure to submerged and floating positions, respectively; and
a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance.
2. A mobile marine platform apparatus, comprising:
a platform structure adapted to support supplies and equipment;
a plurality of telescoping columnar members, each being fixedly secured at its upper end to said platform structure;
a buoyant, ballastable structure fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structure to submerged and floating positions, respectively, and
a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance.
3. A mobile marine platform apparatus, comprising:
a platform structure adapted to support supplies and equipment;
a plurality of telescoping columnar members, each being fixedly secured at its upper end to said platform structure;
a plurality of buoyant, ballastable structures, each of said ballastable structures being fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structures to submerged and floating positions, respectively; and
a flotation structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structures are submerged a predetermined distance.
4. The apparatus according to claim 3 wherein said plurality of ballastable structures comprises a pair of parallel pontoons.
5. The apparatus according to claim 4, including in addition thereto, a perforated mat connected between said parallel pontoons.
6.A mobile marine platform apparatus, comprising:
a platform structure adapted to support supplies and equipment;
a plurality of telescoping columnar members;
a buoyant, ballastable structure fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structure to submerged and floating positions, respectively; and
a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance, said platform structure being fixedly attached to said second buoyant structure.
7. A mobile marine platform apparatus, comprising:
a platform structure adapted to support supplies and equipment;
a plurality of columnar members;
a buoyant, ballastable structure comprising a plurality of pontoons, and including in addition thereto, a perforated mat connected between said pontoons, fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structure between varying depths of submersion;
a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance, said platform structure being fixedly attached to said second buoyant structure.
8. A mobile marine platform apparatus, comprising:
a platform structure adapted to support supplies and equipment;
a plurality of columnar members;
a buoyant, ballastable structure comprising a pontoon having a center portion comprised of a perforated mat, fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structure between varying depths of submersion;
a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance, said platform structure being fixedly attached to said second buoyant structure.
9. A mobile marine platform apparatus, comprising:
a platform structure adapted to support supplies and equipment;
a plurality of telescoping columnar support members, each being fixedly secured at its upper end to said platform structure, whereby the profile of the platform remains substantially constant regardless of the telescoping positions of said support members; and
submersible means fixedly secured to the lower ends of said support members for extending said support members beneath the sea while maintaining said platform structure at or above the surface of the sea.
10. The platform apparatus according to claim 9, including in addition thereto at least one action snubber member connected between said platform structure and said submersible means.
11. The platform apparatus according to claim 10 wherein said action snubber comprises a liquid filled piston and cylinder having means for said fluid to move from one end of said cylinder to the other end of said cylinder as said platform apparatus moves vertically with respect to said submersible eans.
12. The platform apparatus according to claim 11 wherein said piston requires a period of time to move from one end of the cylinder to the other end of the cylinder longer than the time of the longest seas to be encountered by said apparatus.
13. The platfonn apparatus according to claim 12 wherein said period of time is at least 15 seconds.
14. The platform structure according to claim 9 wherein said submersible means includes a cup-shaped chamber for each of said plurality of columnar support members and each of said support members has a member rounded at one end for fitting into said chamber, whereby said telescoping action is slowed down as said rounded member enters said chamber.
15. A mobile marine platform apparatus, comprising:
an elevated platform structure adapted to support supplies and equipment;
a plurality of columnar members fixedly secured to said platform structure, whereby said platform structure is maintained above the surface of the water;
a mat assembly fixedly secured to said columnar members and parallel to said platform structure, said mat assembly being adapted to be lowered to a given depth beneath the surface of water while always floating above the water floor, wherein said mat assembly comprises at least one metal plate having a plurality of freeing holes therein.
16. The apparatus according to claim 15 wherein some of said holes have been selectively closed to achieve optimum stability in a given sea condition.
17. A mobile marine platform apparatus, comprising:
an elevated platform structure adapted to support supplies and equipment;
a single vertical columnar member fixedly secured at its upper end to said platform structure whereby said elevated platform structure is maintained above the surface of the water;
a metal plate fixedly secured to the lower end of said columnar member and parallel to said platform structure, said metal plate having a plurality of freeing holes therein; and
means to cause said mat assembly to be lowered further in the water short of the ocean floor.
18. The apparatus according to claim 17 wherein some of said holes have been selectively closed to achieve optimum stability in a given sea condition.
19. A mobile marine platform apparatus, comprising;
an elevated platform structure adapted to support supplies and equipment;
at least one buoyant structure fixedly secured to the underside of said platform structure, being maintained a given distance from said platform structure;
a plurality of columnar members adapted to move with respect to said platform structure;
a mat assembly fixedly secured to said columnar members and parallel to said platform structure;
means to lower said mat assembly in the water;
means to secure said platform structure to said columnar members; and
means to release said means to secure said platform structure to said columnar members, whereby said mat may be lowered further in the water short of the water floor after said at least one buoyant structure has settled into the water without a further lowering of said platform structure, wherein said mat assembly comprises at least one metal plate having a plurality of freeing holes therein.
20. The apparatus according to claim 19 wherein some of said holes have been selectively closed to achieve optimum stability in a given sea condition.

Claims (20)

1. A mobile marine platform apparatus, comprising: a platform structure adapted to support supplies and equipment; a plurality of telescoping columnar members, each being fixedly secured at its upper end to said platform structure; a buoyant, ballastable structure fixedly secured to the lower end of each of said columnar members, including means to ballast and deballast said ballastable structure to submerged and floating positions, respectively; and a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance.
2. A mobile marine platform apparatus, comprising: a platform structure adapted to support supplies and equipment; a plurality of telescoping columnar members, each being fixedly secured at its upper end to said platform structure; a buoyant, ballastable structure fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structure to submerged and floating positions, respectively; and a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance.
3. A mobile marine platform apparatus, comprising: a platform structure adapted to support supplies and equipment; a plurality of telescoping columnar members, each being fixedly secured at its upper end to said platform structure; a plurality of buoyant, ballastable structures, each of said ballastable structures being fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structures to submerged and floating positions, respectively; and a flotation structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structures are submerged a predetermined distance.
4. The apparatus according to claim 3 wherein said plurality of ballastable structures comprises a pair of parallel pontoons.
5. The apparatus according to claim 4, including in addition thereto, a perforated mat connected between said parallel pontoons.
6. A mobile marine platform apparatus, comprising: a platform structure adapted to support supplies and equipment; a plurality of telescoping columnar members; a buoyant, ballastable structure fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structure to submerged and floating positions, respectively; and a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance, said platform structure being fixedly attached to said second buoyant structure.
7. A mobile marine platform apparatus, comPrising: a platform structure adapted to support supplies and equipment; a plurality of columnar members; a buoyant, ballastable structure comprising a plurality of pontoons, and including in addition thereto, a perforated mat connected between said pontoons, fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structure between varying depths of submersion; a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance, said platform structure being fixedly attached to said second buoyant structure.
8. A mobile marine platform apparatus, comprising: a platform structure adapted to support supplies and equipment; a plurality of columnar members; a buoyant, ballastable structure comprising a pontoon having a center portion comprised of a perforated mat, fixedly secured to the lower end of at least one of said columnar members, including means to ballast and deballast said ballastable structure between varying depths of submersion; a second buoyant structure fixed intermediate the ends of at least one of said columnar members to floatably support said platform apparatus when said ballastable structure is submerged a predetermined distance, said platform structure being fixedly attached to said second buoyant structure.
9. A mobile marine platform apparatus, comprising: a platform structure adapted to support supplies and equipment; a plurality of telescoping columnar support members, each being fixedly secured at its upper end to said platform structure, whereby the profile of the platform remains substantially constant regardless of the telescoping positions of said support members; and submersible means fixedly secured to the lower ends of said support members for extending said support members beneath the sea while maintaining said platform structure at or above the surface of the sea.
10. The platform apparatus according to claim 9, including in addition thereto at least one action snubber member connected between said platform structure and said submersible means.
11. The platform apparatus according to claim 10 wherein said action snubber comprises a liquid filled piston and cylinder having means for said fluid to move from one end of said cylinder to the other end of said cylinder as said platform apparatus moves vertically with respect to said submersible means.
12. The platform apparatus according to claim 11 wherein said piston requires a period of time to move from one end of the cylinder to the other end of the cylinder longer than the time of the longest seas to be encountered by said apparatus.
13. The platform apparatus according to claim 12 wherein said period of time is at least 15 seconds.
14. The platform structure according to claim 9 wherein said submersible means includes a cup-shaped chamber for each of said plurality of columnar support members and each of said support members has a member rounded at one end for fitting into said chamber, whereby said telescoping action is slowed down as said rounded member enters said chamber.
15. A mobile marine platform apparatus, comprising: an elevated platform structure adapted to support supplies and equipment; a plurality of columnar members fixedly secured to said platform structure, whereby said platform structure is maintained above the surface of the water; a mat assembly fixedly secured to said columnar members and parallel to said platform structure, said mat assembly being adapted to be lowered to a given depth beneath the surface of water while always floating above the water floor, wherein said mat assembly comprises at least one metal plate having a plurality of freeing holes therein.
16. The apparatus according to claim 15 wherein some of said holes have been selectively closeD to achieve optimum stability in a given sea condition.
17. A mobile marine platform apparatus, comprising: an elevated platform structure adapted to support supplies and equipment; a single vertical columnar member fixedly secured at its upper end to said platform structure whereby said elevated platform structure is maintained above the surface of the water; a metal plate fixedly secured to the lower end of said columnar member and parallel to said platform structure, said metal plate having a plurality of freeing holes therein; and means to cause said mat assembly to be lowered further in the water short of the ocean floor.
18. The apparatus according to claim 17 wherein some of said holes have been selectively closed to achieve optimum stability in a given sea condition.
19. A mobile marine platform apparatus, comprising; an elevated platform structure adapted to support supplies and equipment; at least one buoyant structure fixedly secured to the underside of said platform structure, being maintained a given distance from said platform structure; a plurality of columnar members adapted to move with respect to said platform structure; a mat assembly fixedly secured to said columnar members and parallel to said platform structure; means to lower said mat assembly in the water; means to secure said platform structure to said columnar members; and means to release said means to secure said platform structure to said columnar members, whereby said mat may be lowered further in the water short of the water floor after said at least one buoyant structure has settled into the water without a further lowering of said platform structure, wherein said mat assembly comprises at least one metal plate having a plurality of freeing holes therein.
20. The apparatus according to claim 19 wherein some of said holes have been selectively closed to achieve optimum stability in a given sea condition.
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Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3739737A (en) * 1971-09-17 1973-06-19 R Baier Marine platforms
US3786525A (en) * 1972-06-01 1974-01-22 Us Army Transportable mooring buoy assembly
US3986471A (en) * 1975-07-28 1976-10-19 Haselton Frederick R Semi-submersible vessels
US4165702A (en) * 1974-07-08 1979-08-28 Santa Fe International Corporation Method of constructing a twin hulled, column stabilized, semi-submersible derrick barge
US4753185A (en) * 1983-04-05 1988-06-28 Marvin Steve Worley Floating vessels
US4886398A (en) * 1983-08-26 1989-12-12 Alsthom Atlantique Institut Francais du Petrole Sea platforms for improving their dynamic balance
US5140924A (en) * 1990-10-05 1992-08-25 Dixon John D Elevating stern platform for swath vessels
US5279240A (en) * 1990-08-14 1994-01-18 Worley Marvin S Floating oil/gas production terminal
US6102625A (en) * 1995-12-06 2000-08-15 Fred. Olsen Wave dampener for floating structures
US20040067109A1 (en) * 2000-11-13 2004-04-08 Jack Pollack Vessel comprising transverse skirts
US20040265069A1 (en) * 2003-06-24 2004-12-30 Purvis John C. Mat supported offshore structure
US20070278796A1 (en) * 2006-06-06 2007-12-06 Power Daniel E System for generating electricity from fluid currents
US20110101697A1 (en) * 2008-07-01 2011-05-05 Oceana Energy Company Systems and methods for supporting underwater energy conversion devices
US20120034034A1 (en) * 2010-08-03 2012-02-09 Technip France Truss heave plate system for offshore platform
JP2013531578A (en) * 2010-06-08 2013-08-08 ウェル−ヘッド レスキュー アーベー Life-saving vehicle
US20140000502A1 (en) * 2012-06-27 2014-01-02 Technip France Floating offshore platform and centralized open keel plate
US20140305359A1 (en) * 2013-04-10 2014-10-16 Technip France Floating offshore platform with pontoon-coupled extension plates for reduced heave motion
US9359991B2 (en) 2009-10-29 2016-06-07 Oceana Energy Company Energy conversion systems and methods
US9446825B1 (en) 2013-12-10 2016-09-20 Hugh Francis Gallagher Self-propelled, catamaran-type, dual-application, semisubmersible ship with hydrodynamic hulls and columns
CN106985983A (en) * 2017-02-21 2017-07-28 中交第二航务工程局有限公司 Increase the heave plate of engineering ship stability
US10302068B2 (en) * 2016-10-31 2019-05-28 Zentech, Inc. Conversion of movable offshore drilling structure to wind turbine application
US11084553B2 (en) * 2016-11-09 2021-08-10 Horton Do Brasil Technologia Offshore, Ltda. Floating offshore structures with round pontoons

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3739737A (en) * 1971-09-17 1973-06-19 R Baier Marine platforms
US3786525A (en) * 1972-06-01 1974-01-22 Us Army Transportable mooring buoy assembly
US4165702A (en) * 1974-07-08 1979-08-28 Santa Fe International Corporation Method of constructing a twin hulled, column stabilized, semi-submersible derrick barge
US3986471A (en) * 1975-07-28 1976-10-19 Haselton Frederick R Semi-submersible vessels
US4753185A (en) * 1983-04-05 1988-06-28 Marvin Steve Worley Floating vessels
US4886398A (en) * 1983-08-26 1989-12-12 Alsthom Atlantique Institut Francais du Petrole Sea platforms for improving their dynamic balance
US5279240A (en) * 1990-08-14 1994-01-18 Worley Marvin S Floating oil/gas production terminal
US5140924A (en) * 1990-10-05 1992-08-25 Dixon John D Elevating stern platform for swath vessels
US6102625A (en) * 1995-12-06 2000-08-15 Fred. Olsen Wave dampener for floating structures
US20040067109A1 (en) * 2000-11-13 2004-04-08 Jack Pollack Vessel comprising transverse skirts
US8579547B2 (en) * 2000-11-13 2013-11-12 Single Buoy Moorings Inc. Vessel comprising transverse skirts
US20040265069A1 (en) * 2003-06-24 2004-12-30 Purvis John C. Mat supported offshore structure
US7001108B2 (en) * 2003-06-24 2006-02-21 Purvis John C Mat supported offshore structure
US20070278796A1 (en) * 2006-06-06 2007-12-06 Power Daniel E System for generating electricity from fluid currents
US7453166B2 (en) 2006-06-06 2008-11-18 Oceana Energy Company System for generating electricity from fluid currents
US20090096216A1 (en) * 2006-06-06 2009-04-16 Oceana Energy Company System for generating electricity from fluid currents
US7604454B2 (en) 2006-06-06 2009-10-20 Oceana Energy Company System for generating electricity from fluid currents
US20110101697A1 (en) * 2008-07-01 2011-05-05 Oceana Energy Company Systems and methods for supporting underwater energy conversion devices
US10060473B2 (en) 2009-10-29 2018-08-28 Oceana Energy Company Energy conversion systems and methods
US9359991B2 (en) 2009-10-29 2016-06-07 Oceana Energy Company Energy conversion systems and methods
JP2013531578A (en) * 2010-06-08 2013-08-08 ウェル−ヘッド レスキュー アーベー Life-saving vehicle
US20120034034A1 (en) * 2010-08-03 2012-02-09 Technip France Truss heave plate system for offshore platform
US8444347B2 (en) * 2010-08-03 2013-05-21 Technip France Truss heave plate system for offshore platform
AU2013281122B2 (en) * 2012-06-27 2017-01-12 Technip France Floating offshore platform and centralized open keel plate
US20140000502A1 (en) * 2012-06-27 2014-01-02 Technip France Floating offshore platform and centralized open keel plate
US8967068B2 (en) * 2012-06-27 2015-03-03 Technip France Floating offshore platform and centralized open keel plate
CN104411577A (en) * 2012-06-27 2015-03-11 泰克尼普法国公司 Floating offshore platform and centralized open keel plate
CN104411577B (en) * 2012-06-27 2017-05-31 泰克尼普法国公司 Floating offshore platform and middle opening keel plate
US20140305359A1 (en) * 2013-04-10 2014-10-16 Technip France Floating offshore platform with pontoon-coupled extension plates for reduced heave motion
US9302747B2 (en) * 2013-04-10 2016-04-05 Technip France Floating offshore platform with pontoon-coupled extension plates for reduced heave motion
US9446825B1 (en) 2013-12-10 2016-09-20 Hugh Francis Gallagher Self-propelled, catamaran-type, dual-application, semisubmersible ship with hydrodynamic hulls and columns
US10302068B2 (en) * 2016-10-31 2019-05-28 Zentech, Inc. Conversion of movable offshore drilling structure to wind turbine application
US11084553B2 (en) * 2016-11-09 2021-08-10 Horton Do Brasil Technologia Offshore, Ltda. Floating offshore structures with round pontoons
CN106985983A (en) * 2017-02-21 2017-07-28 中交第二航务工程局有限公司 Increase the heave plate of engineering ship stability

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