US2598329A

US2598329A - Offshore drilling platform and method of constructing same

Info

Publication number: US2598329A
Application number: US34639A
Authority: US
Inventors: Harvey A Wilson
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-06-23
Filing date: 1948-06-23
Publication date: 1952-05-27
Anticipated expiration: 1969-05-27

Description

May 27, 1952 H. A. wlLsoN 2,598,329

OFFSHORE DRILLING PLATFORM AND METHOD OF' CONSTRUCTING SAME Filed June 23, 1948 5 Sheets-Sheet l M M N. mw

y I 1- I I 34- I 2:3 l l :::::l I I 34 May 27, 1952 H. A. wlLsoN 2,598,329

OFFSHORE DRILLING PLATFORM AND METHOD OF' CONSTRUCTING SAME Filed June 23, 1948 3 Sheets-Sheet 2 Har Vey A. VV//son INVENTOR.

ATTORNEY May 27, 1952 H. A. wlLsoN OFFSHORE DRILLING PLATFORM AND METHOD oF coNsTRucTrNG SAME 3 Sheets-Sheet 3 Filed June 23. 1948 @NAi/MA IN V EN TOR.

Harvey A. l/V//son ATTORNEY Patented May 27, 1952 OFFSHORE DRILLING PLATFORM AND METHOD OF CONSTRUCTING SAME Harvey A. Wilson, Brazoria., Tex.

Application June 23, 1948, Serial No. 34,639

12 Claims.

This invention relates to marine foundation structures and particularly to off-shore drilling platforms for oil wells and methods for constructing and erecting same. Y

The drilling of oil wells in oif-shore locations, such as on the continental shelf along the coasts of the United States in water depths ranging from about to 60 feet or more, is increasing greatly in importance and creates many new problems in providing firm and safe support for the heavy drilling rigs employed. Since such locations may be many miles from the shore, open ocean conditions' prevail, including often severe Wind and wave conditions, which make for great expense and diiculty in transporting and erectingr foundations which are adequate to meet the conditions encountered. Submergible barges which have been used with considerable success in relatively shallow land-locked Water areas are generally considered to be impractical when used in the greater depths and under the exposed conditions prevailing in o-shore drilling. Other systems employ elaborate steel structures which involve great expense in fabricating and moving them to the water locations and additionally great expense in removing them when drilling has been completed. In some cases, because of their elaborate and relatively permanent construction, the removal vis impractical and their use involves a very substantial economic loss.

The present invention, therefore, has for its principal object the provision of a much simplied type of drilling platform whichmay be employed for off-shore drilling in any of the water depths commonly encountered and which may be moved to the location with a minimum of difficulty and expense and subsequently removed likewise with a minimum of difliculty and expense.

In accordance with this invention, the platform structure comprises a platform ofv openwork structural form and a pair of structural steelopen-Work supporting piers. The latter are hingedly connected at their upper ends to the sides of the main platform and are adapted thereby to swing relative thereto between laterally extending and-downward vertical positions. When in the latter position, the piers serve to support the main platform section from the water bottom at any desired height above the Water level as determined by the preselected length ofthe pier sections. This entire structure is prefabricated and is moved to the water location by removably mounting the main platform section on the deck of a barge with the pier sections extended laterally about their hinged connections beyond the sides of the barge. The outer ends of the pier sections will normally be supported by suitable iioat members which may-be formed integrally with the ends of the pier sections or releasably attached thereto. As a result, the entire structure may be floated to the desired water location, the float-supported outer ends of the pier sections acting as outriggers which serve to stabilize the floating load during transit. When the structure has been brought to the desired location, the supports for the outer ends of the pier sections are removed, or in the case of permanently connected floats, the latter are filled with water to destroy their buoyancy, and the outer ends of the pier sections are allowed to sink largely of their own weight into the water to the vertical position and brought to rest on the water bottom While the main platform section is still supported on the barge. The pier sections are then firmly locked to the sides of the main platform and the entire structure allowed to settle firmly on to the land bottom by, for example, partially submerging the transporting barge. The load of the main platform will thus be transferred from the barge to the piers which now become the sole supports for the platform. Thereafter the barge is further submerged to whatever extent may be necessary to withdraw it from beneath the main platform and the structure is then ready for operationV thereon of the drilling rig and other equipment which vit is designed to support. When necessary to remove the foundation structure, the barge is sunk to a suliicient depth inthe water to permit its insertion beneath the main platform section and fastened thereto. Then the buoyancy of the barge will be increased suiciently to lift the entire platform structure to free the pier footings from the Water bottom. The pier sections are then swung outwardly about their hinged connections to the' platform until their outer ends are again brought to the Water surface and rendered buoyant in any suitable manner and the yentire structure may then be transported by the barge to any other desired location.l

The pier sections will normally be constructed of hollow columns arranged in a suitable geometric pattern and inter-connected by suitable structural cross-bracing to provide structures -which vare generally rectangular in horizontal cross section having very substantial internal rigidity and stability and providing footing area of suitable dimensions. The pier sections, so constructed; may be employed to support the main platform directly from the water bottom. However, to provide even greater stability, piles of suitable form may be forced or driven through the hollow columns into the water bottom and suitably connected to the structural members of the platform to support the load on the piling, as well as on the columns themselves.

The various objects and advantages of this invention and a more detailed idescription of the structure and the method of erection thereof will become apparent from the following detailed description when read in conjunction with the accompanying drawings, which illustrate -useful. embodiments in accordance with this invention.

In the drawings:

Fig. 1 is an end view of a platform structure, in accordance with this invention, in place on a water location;

Fig. 2 is a plan view of the structure taken along line 2-2 of Fig. 1;

Fig. 3 is an end view of the structure showing the piers in laterally extended position relative to the platform section and showing the entire structure mounted on suitable lios-t means for transporting it to a location;

Fig. 4 is a view looking toward one .side of the structure. along line 4-.4-of Fie. 2:

Fig. 5 is an enlarged end view of one of the pier sections oi. the structure; and

Figs 6 and 7 are fragmentary views .of other embodiments. ol footingv arrangements for the pier sections of the structure- .Reeriing to the drawings., the drilling platform structure oompriseea horizontally disposed olatiormsection, indicated generally by the nu.- meral lll, and a pair of Pier Sections. indicated generally by the numerals H. The latter are of a length such thatwhen, io vertice-l position with their lower ends resting on the waterv bottom l2, their upper ends willsupport platform sectionv ill at the desired height above the .mean Water letel., .iadioatedat l3- Platfolm section l0 is of generally rectangular shape, the sides of which are formed by apair of laterally spaced parallel structural steel truss members i4 and l5 connectedacrossthe ends by al pair of similar truss members I6 and Il. The truss members are suitably laced together by in.- ternal longitudinal and transverse bracing trusses, indicated at I8, the whole forming an f openwork platform of sufficient strength and rigidity to support the load to be. carriedtheleby. such as the usual well drilling derrick and other portions of a conventional drilling rig. The upper surface of platform Hl may be covered by. any suitable` type of declging I S. Rlatform -lll will be provided with the usual drillingslot 2D, extending lorisitudinallyv for a portion of the length of platform lll from one end thereof, through which the usual drilling operations may be conducted and which permits the platform to be withdrawn from about the well head when drilling is completed. End truss member l1 may be provided with a re. movable section, indicated. in broken lines at 2l, to permit exit ofv the well head fittings from slot during removal of the platform structure.

Platform section l0 is adapted to be supported in the horizontal position on a structuralcradle 22 rigidly mounted on the deck of aconventional barge 23 which is employed to carry the platform to the water location where, it is to be erected. Platform section l0 isV releasably connected to cradle 22 in any suitable and conventional manner, as by bolts or clamps (not shown), by which platform section lll` is rigidly fastened to the barge deck but which may 'be released when it is necessary to remove the barge during operations to be hereinafter described.

It will be understood that barge 23 may be provided with conventional hull compartments, indicated at 24, fitted with the usual flooding and emptying gear, indicated at 25, which may :be employed to vary the buoyancy characteristics of .the barge so that the height 0f its deck relative to the water level may be increased or decreased as desired.

Each of the pier sections Il is constructed of a `plurality of parallel rows of hollow columns 26, suitably spaced apart and inter-connected by angle braces 21 and girts 28 so as to form a rigid structure of generally rectangular form having a length substantially equal to that of the sides of platform section IB and a width suitable to provide a supporting area of the desired dimensions required to form stable supports for the platform .eeotioo4 and the anticipated load to be carried thereby. The pier sections may be made up from a plurality of end-aligned segments, columns 26 being provided with suitable connection means, ,such as bolting flanges 29, for connecting the segments together to provide pier sections of any desired length. |ihe lupper ends of columns 2,6 of each of the pier sections are rigidly tied into and enclosed within a structural frame, composed of inner and outei` side trusses 3l) and 3|, respeo tively, and end trusses 32. 32. The upper ends of columns ,26 preferably terminate a short distence below the upper edges of the framing trusses leaving a space 32a therebetween which may be employed in a manner to be hereinafter described. Side trusses 30 are designed to lie flat against side tlllSS members I4 and l5 of main platform section l0 when the pier sections are in their vertical positions and releasable locking or Clamping means of any suitable form, such as bolts 33, extend, between contiguous members of the platform and pier sections to tie these sections tightly together when the platform Structure is erected. A plllllity of strong hinge devioesd'arc arranged at intervals along the upper edge Qf the sides of platform section mand are connected to the upper edges oi trusses 30 to therebyrorm hinge connections between the sides of the platform section and the upper ends of the pier sections. By means ofthese hinged connections, pier sections ll may be swung laterally relative to platform section l0, between laterally extended and vertically downwardA positions. Booms 35 extend upwardly from the outer sides of pier sections Il and their upper ends are con.

nected through conventional block-.and-tackle riggingV 3.6. to the upper deck of platform section l0 and thence to Winches 31. By means of this rigging the pier sections may be swung upwardly and outwardly relative to the platform section. Due-to their weight, the pier sections Will nor. mally tend to swing to their vertical positions alongside the platform section but block-andtackle rigging 38 is provided between the lower face `of the platform section and intermediate portions ofl the pier sections to assist this Inovement and particularly to draw the pier sections snugly against the sides of the platform section to enable these sections to be readily clamped together.

In one embodiment in accordance with this invention, the outer ends of columns 26 extend through hollow pontoons 39 which are rigidly fastened thereto and have flat bottoms adapted to form footings for the pier sections when resting upon the water bottom. Pipes 40 communicate with the interior of the pontoons and are connected by flexible valved pipes 4| and 42 which lead to a liquid pump 43 and an air compressor 44, respectively suita-bly mounted on the platform section, which are adapted to supply water for ilooding the pontoons and air to eject the water as may be required. Discharge pipes 45 communicate with the interior of the pontoons and extend upwardly through the pier sections to above the normal water level to provide means for discharging fluids from the pontoons.

The above-described structure may be transported to an off-shore location and erected in the following manner:

The pre-fabricated structure will be installed on barge 23 with platform ysection l0 securely bolted to cradle 22. Pier sections Il will have their upper ends connected to the platform section by means of hinges 34 and will have their outer ends swung outwardly on opposite sides of the barge toward the water. Pontoons 39 will be made sufficiently buoyant to form oating supports for the outer ends of the pier sections. Temporary braces 45a may be installed between the outswung pier sections and sides of the platform section to impart additional rigidity to the structure during transit to the off-shore location on which the structure is to be erected. The barge bearing the structure, arranged as illustrated in Fig. 3, will then be towed to the drilling location. During transit over the water, the

widespread pier sections, having their outer ends supported on buoyant pontoons 39, will serve as outriggers which will effectively balance and stabilize the barge and the platform structure and render the transit to the location relatively safe and easy. Furthermore, it will be evident that by this arrangement the entire platform structure may be pre-fabricated in its entirety in safe harbor areas and brought to the location as a single unit, thereby eliminating the need for transporting massive erecting equipment to the location, and for operating such bulky equipment often far out at sea where often the prevailing wind and wave conditions make it impracticable and often impossible to employ such erecting equipment.

When the drilling location has been reached, temporary braces 45a will be removed and pontoons 39 filled with water through pipes 40. This allows the ends of the pier sections to sink of their own weight in the water and swing in toward the platform section about hinges 34. Ordinarily the ballasting of barge 23 will have been arranged to maintain the platform section at a sufficient height so that, as the pier sections swing to the vertical position along-side the platform section, the bottoms of the pontoons will clear the water bottom and allow the pier sections to freely assume the desired vertical position. If found necessary, block-and-tackle gear 38 may be employed to draw the pier sections snugly against the sides of the platform section. Bolts 33 will then be inserted between these sections to rigidly lock the pier sections to the platform sections. The buoyancy of barge 23 will then be reduced by admitting water ballast into its hull compartments and the whole structure will thus be allowed to settle vertically until pontoons 38 rest rmly on the water bottom. The load of the platform section will thusbe transferred to the pier sections. Cradle 22 may now be disconnected from the platform section, thereby freeingl the barge, whichl will now be additionally ballasted to'lower it in the water by whatever amount may be necessary to permit the barge and cradle to be withdrawn from beneath platformsection I0. The structure will now be in place with platform section I0 entirely supported on pier sections Il. With the structure thus erected, it will-be seen that the upper .ends of the pier sections will be flush with the upper deck of ,the platform section and thereby provide subfstantial extensions thereof, to increase the available working area of the platform. The upper surfaces of the piers may also be covered with suitable decking, such as `decking 29, on the main platform section.

The platform structure, as thus erected, may now be employed for conducting drilling operations therefrom in the usual manner. It will be understood, that the usual drilling equipment, including the derrick, may be installed on platform section I0 before transit to the locationor allor part of this .equipment may be installed after the structure has been erected on location.

Since columns 26 are hollow and open at lboth ends, it will be obvious that they may be employed for transmitting high velocity water jets from the surface to the water bottom towash out any irregularities in the bottom beneath the pontoons in order to level the structure, if such levelling is found necessary.

When drilling operations are completed, -the structure may be removed by reinserting barge 23 beneath platform section I0 and increasing the buoyancy of the barge sufficient to bodily lift the structure until the pier ends are clear of the Water bottom. Bo1ts 33 will be withdrawn freeing the pier sections for swinging about hinges 34. Pontoons 39 will now be emptied through discharge pipes 45 by admitting air from compressor 44 through pipes 42 and 44. As the water ballast in the pontoons is reduced and their buoyancy increased proportionally, they will rise to the surface swinging the outer ends of the pier sections outwardly and upwardly'until they attain their original position on the surface, as illustrated in Fig. 3. This movement may be assisted and controlled if necessary or desirable by suitable manipulation of block-and-tackle

rig# ging

36 and 38 and their associated Winches. Temporary braces 45a may now be re-installed and the entire structure will be ready for transit to another location.

While the hollow column pier sections, resting on the pontoon footings as above described, will often provide a sufficient degree of Supporting strength and rigidity for the structure, in accordance with another embodiment of this invention; additional means are provided, when deemed necessary, whereby to increase the strength'of the supporting piers and prevent any possibility of shifting of the structure, dueto wave, wind or current action, or to vibration generally present during drilling operations.

In accordance with this embodiment, when the structure has been erected on locations as previf ously described, cylindrical piles 46, of any-suitabler and conventional construction adapted to pass through-columns V26, are inserted into the upper ends of the latter and forced or driven therethrough, by conventional means, into the water bottom to thus additionally stiffen the pier sections and anchor them rmly into the water bottom. Piles 46 will be selected 4of such a length` that when they have been driven' into the.water..bottom for thedesired distance, their upper ends will extend `into space 32a'above the upper .ends of. columns 2.6.. (See Figs. 1 and .15, particularly)- The upper ends of the piles will be-.cutaoif and suitablyleyelled. and beams. will be installed .across Vthe tops of` .the piles and beneath the :upper members ofthe vtrusses framing thenupper ends of the. pier sections. The platformload may :th-us be transferred .directly to .the 'piles with the `hollow columns serving as a reinforcing Itemplate for the piles. When. it becomes necessary Vto remove .the structure, it wilizibe lifted .slightly .on :barge .23, after the latter has. been reinserted under platform section. fli, as. previously described, to relieve the pressure on beams 4l. The latter will then be removed, after which piles.. 4 will Vbe withdrawn by genemily eonuentionalimeans; Thereupon the oper.- ations previously. described .will be .conducted to raise the pier sections and prepare :the .structure for removal toV another location.

Eg...6"illustrates another modification of supporting arrangements for the structure. In this modification. .the integral pontoons 39 are dispensed: with, itbeing understood that they will be replaced. by releasable Vfloats (not shown) which will beemployed to support the endsof the pier sections .during transit. this modificationpiles 46 willfbe driven through columns 2.6: while the structure is sti-ll supported on the transporting barge with theV lower ends of the pier sect-ions suspended slightly above -the'water bottom; With Athe -piles driven into the water bottom, the load of the Istructure will be placed on the upper ends of the piles in the wmanner previously described, and the "pier sections Will serve primarily as a bracing template for the pilesha-ving' some freedom of longitudinal movemen-t relative to the piles.

Fig. I illustrates stillv another footingmodifcation in which pontoons 3!! arereplaced by a .solid steel plate 48 to serye .as .a footing for the pier sections when the platform load has been transferred thereto. .this modification, it will be understood that releasable floats will be attached t the ends of the pier sections .'to-supportthem in transit. This `footing arrangement-may be employed. with piles 4.6, as illustrated, .or Without thefpiles, as in the .casco-f the principal embodiment rst `described above.

It, will be understoodthatnumerous changes and alterations may be made in the structural details of the several embodiments of the structure and in the steps of the erection methods herein described within :the scope of the ap- Dended claims but without departing from the spirit .of this invention.

What Irelaim and .desire to secure by 'Letters Patent is: v

1The method of. constructing. an off-shore drilling platform, comprising, pre-fabricating a platformstructure including a main platform section and a pair of elongated pier sections having hinged lconnection at their upper ends to opposite sides of said main platform section for swingingmovement relative thereto between laterally extended andverticaldownward positions, bodily transporting said structure with said pier sections .in laterally extended positions to a water location on removable-float means, sinking the outer ends of saidpier sections to the vwater bottom while said main platform section remains supported by v said float means, reducing the buoyancy of said float means to thereby'transfer the load of .said mainplatform section from said float'` means VVto saidpier sections. and there- 8 after removing said float means from-beneath said main platform section.

2. The method of constructing an .off-shore drilling platform, comprising, .prefabricating -a platform structure including a main platform section and a pair of elongated piersections hav.- ing hinged .connection at their upper ends to opposite .sides of said main platform ysection for swinging movement relative thereto betwcenlat.- erally .extended and vertical downward positions, bodily transporting said structure with said 'pier sections inlaterally extended .positions to a water location on removable float means, sinking the outer .ends of said pier section-s. .to the water bottom while said main platform section remains supported by .said float means, locking said pier sections to the sides of said main platform .section at one or more .points spaced below said hinged connections, reducing the buoyancy Qfsaid float means .to thereby transfer the load of said platform section to said pier sections, and thereafter removing said float means from 'beneath said main lplatform section.

13;The method of constructing an .off-shore drilling platform, comprising, prefabricating a platform structure including a main platform section .and a pair .of elongated pier sections having hinged connection at their upper ends to opposite sides of said main platform section for swinging movement relative thereto .between laterally extended and vertical downward positions, bodily. transporting said structure to a water location with said pier sections in laterally extended positions, said main platform section being supported during transportation on a removable buoyant float means and the outer .ends of said pierA sections being independently supported on other oat means, removing the floating supports for the outer ends of saidV pier sections whereby to permit same to sink to the water bottom and assume vertical positions along side .said .main platform section while the latter remains supported by said removable float means, locking said pier sections tothe sides of said main platform section at one or more .points spaced below saidhinged connections, reducing the buoyancy of said removable float means to lower said structure sufficiently to set said piers firmly on the water bottom and thereby transfer the load of said platform section to` said pier sections, and thereafter withdrawing said removable` float means from beneath said main platform section.

4. The method of constructing an off-shore drilling. platform, comprising, prefabricating a platform structure including a main platform sectionand a pair of :elongated pier sections having hinged connection at their upper endsto oppositesides of said main platform sectionfor swinging movement relative thereto between latorally extendedand vertical downward positions, each of said pier sections being constructed of a plurality of hollow-columns spaced apart and rigidly inter-connected by suitable bracingand framing members to formv a rigidv open-work structure having substantial .cross-sectional area, bodily transporting said structure to a water location with said pier sections, in laterally ex tended positions, said main platform sectionfbeing supported during transportation on a removable buoyant float means and the outer. ends of said pier sections being independently supported on other float means, removing the floating supports for the outer ends of said pier sections whereby to permit same to sink to the water bottom and. assume vertical positions along side said main platform section while the latter remains supported on said removable float means, locking said pier sections to the sides of said main platform section at one or more points spaced below said hinged connections, reducing the buoyancy of said removable float means to lower said structure sufficiently to set said pier sections firmly on the water bottom and thereby transfer the load of said platform section to said pier sections, driving piles longitudinally through said columns into said water bottom, and thereafter withdrawing said removable float means from beneath said main platform section.

5. An ofi-shore drilling platform, comprising, a prefabricated articulated structure including a main platform section and elongated end sections normally extending laterally outwardly from opposite sides of said platform section and hingedly connected thereto to constrain said end sections to fold inwardly to a vertical position alongside said platform section, said end sections being of sufficient length to extend from said platform section to the bottom underlying a water body of limited depth.

6. An off-shore drilling platform, comprising, a prefabricated articulated structure including a main platform section and elongated end sections normally extending laterally outwardly from opposite sides of said platform section and hingedly connected thereto to constrain said end sections to fold inwardly to a vertical position alongside said platform section, said end sections being of sufficient length to extend from said platform section to the bottom underlying a water body of limited depth, and clamping means for locking said end sections when in vertical position to the sides of said platform section.

'7. An off-shore drilling platform, comprising, a prefabricated articulated structure including a main platform section and elongated end sections normally extending laterally outwardly from opposite sides of said platform section and hingedly connected thereto to constrain said end sections to fold inwardly to a vertical position alongside said platform section, said end sections being of sufficient length to extend from said platform section to the bottom underlying a water body of limited depth, clamping means for locking said end sections when in vertical position to the sides of said platform section, and hollow footings of controllable buoyancy carried by the outer ends of said end sections.

8. An off-shore drilling platform, comprising, a prefabricated articulated structure including a main platform section and elongated end-sections normally extending laterally outwardly from opposite sides of said platform section and hingedly connected thereto to constrain said end sections to fold inwardly to a vertical position alongside said platform section, said end-sections being of sucient length to extend from said platform section to the bottom underlying a water body of limited depth, and piles extending through said end-sections into said bottom and having supporting connections to said platform section.

9. An off-shore drilling platform, comprising, a prefabricated articulated structure including a main platform section of generally rectangular box-like shape having vertical sides, and elongated end sections having generally rectangular head frame portions at their upper ends and normally extending laterally outwardly from opposite sides of said platform section, the upper ends of said head frame portions being hingedly connected at their inner edges to the adjacent upper edges of said platform section, whereby saidiend sections may fold inwardly to a vertical position alongside said platform section, said end sections being of sufcient length to extend from said platform section to the bottom underlying a water body of limited depth.

10. In an off-shore drilling platform according to claim 9, clamping means for locking the sides of said head frame portions when said end sections are in vertical position to the adjacent sides of said platform section.

11. In an off-shore drilling platform according to claim 9, hollow footings of controllable buoyancy carried by the outer ends of said end sections.

12. An off-shore drilling platform according to claim 9, wherein each of said end sections is composed of a plurality of end-aligned separable segments for varying the length thereof.

HARVEY A. WILSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,358,951 Helmick Nov. 16, 1920 1,681,533 Giliasso Aug. 21, 1928 2,210,408 Henry Aug. 6, 1940 2,327,118 McKnight Aug. 17, 1943 2,398,351 Baker Apr. 16, 1946 2,429,952 Willey Oct. 28, 1947