US3524322A - Splay footed platform anchor - Google Patents

Description

Aug. 18, 1970 l. POGONOWSKI SPLAY FOO'I'ED PLATFORM ANCHOR 2 Sheets-Sheet 1 Filed June 27. 1968 Q a; i .EM l n; 0 i i 2 L x Z i x E 7 Kw W M i M v t g- 13, 1970 l. c. POGONOWSKI 3,524,322

SPLAY FOOTED PLATFORM ANCHOR Filed June 2'7. 1968 2 Sheets-Sheet 2 1 .E. T /fl United States Patent 3,524,322 SPLAY FOOTED PLATFORM ANCHOR Ivo C. Pogonowski, Houston, Tex., assiguor to Texaco Inc., New York, N.Y., a corporation of Delaware Filed June 27, 1968, Ser. No. 740,585 Int. Cl. B63c 23/16; E02b 17/00 US. Cl. 6146.5 9 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a marine drilling, and/or producing platform for an offshore oil site. It relates in particular to such a platform which, in normal operating position rests on the floor of a body of water and is there anchored by piling. The anchoring means takes the shape of a splayed or spread pile arrangement to provide a more firm anchor, and stabilizing resistance against lateral storm forces.

Offshore drilling and production platforms should be designed today for maximum versatility. This feature would include not only the ability to be readily moved between drilling sites but also the ability to function properly under adverse weather conditions and in varying ocean floor conditions. For example, the factor of weather by itself is pertinent since stormy seas create not only surface turbulence but also large lateral forces. The latter is further aggravated by the activity of periodic tides and water currents peculiar to an area.

As the desirability for more exploratory and production work at deep water sites increases, the complexity of drilling platforms increases correspondingly. Primarily, for deeper water the platform must possess a greater ability to withstand the above noted under water forces, but of a greater magnitude. One inescapable factor is the widely diverse character of the anchoring media suggested by variations in composition and consistency of the ocean floor at different locations. It is an accepted assumption that varying soil and mud compositions require varying forms of pile arrangements to assure maximum platform holding efficiency. Underconsolidated deltaic clay soils for example offer most difiicult anchoring conditions and ideally could support the structure against lateral forces by axially loaded heavily inclined pile to avoid excessive bending.

For example the frictional retaining ability of a pile in a particular anchoring media will depend to a large extent on the pile length, or on the area of contact be tween the pile surface and the anchoring media. Further, in the usual platform structure built by floating equipment it is customary to drive the anchoring piles into the ocean substratum at a substantially vertical disposition. Often some slight digression from a vertical holding arrangement is achieved by enclosing the piles within hollow platform legs which are in turn directioned outwardly. In either instance however the platform is fixed by a series of relatively upright imbedded piles.

With such an arrangement, an inherent weakness persists, notably lateral wave and wind forces tend to rock or tilt the platform along one side of the base while tending to raise the opposite side from the ocean floor. This upward force exerts an axial pull on all of the anchor,- ing piles in the base except those at the pivoting side. Were the anchoring piles imbedded at an angle, particularly to form a flared arrangement about the platform or any one leg rather than a vertical arrangement, overall holding ability would be greatly enhanced in soft soils. For example, the novel flared piling arrangement provides a stable holding means, and further in many underconsolidated floor consistencies the use of splayed or angularly imbedded piles suggests the only alternative to limited ability to penetrate the anchoring media.

To achieve a dispersed pile pattern in any offshore platform is virtually impossible by use of presently known equipment. Normally, pile drivers whether barge or platform mounted, direct an imbedding force against the pile in a generally vertical direction. To offset the hammer mechanism from a vertical position for other than a vertical setting, tends to decrease the downward thrust because of frictional and other losses.

Toward overcoming the above stated problems there is presently disclosed a unique and novel marine plat form for use at an offshore oil drilling or production site. The platform is adapted for firm anchoring or positioning in a substream in such manner as to avoid displacement and tipping of the unit under severe weather conditions. The novel anchoring feature is achieved by provisions of one or more support members which afford lateral thrust reaction to the unit, said support members also function to guide one or more piles from the lower end thereof into the ocean floor.

The respective support members are disposed in an oblique relationship to the upright and therefore direct the piles into the anchoring media in a generally splayed or dispersed arrangement. Said support members are normally under water and include an opening in the top side, adapted to receive a mobile pile driving mechanism controlled or lowered from the water. surface, whereby the piles may be driven or imbedded by remote control.

It is among the objects of the invention then to provide a novel marine platform adapted to be firmly anchored in the floor of a body of water. A further object is to pro vide a leg supported marine platform, the legs of which include anchoring footings which extend at varying angles into the ocean floor. A still further object is to provide an anchoring arrangement of piles for an offshore platform wherein at least a portion of said piles are disposed in a splayed or spread arrangement to achieve a firm grip on the substratum. FIG. 1 is a vertical elevation of a marine, oil drilling platform showing the novel pile footing arrangement. FIG. 2. is a sectional view of the platform shown in FIG. 1, taken along line 22. FIG. 3 is a segmentary view on an enlarged scale and in partial cross section, of a portion of the platform anchoring means shown in FIG. 1, and FIG. 4 is a cross section on an enlarged scale taken along lines 4-4 in FIG. 3.

An offshore platform 10 embodying a pile anchoring arrangement of the type contemplated is shown in FIG. 1. This particular form of marine platform is exemplary of, although not exclusive to the many types presently known and employed wherein the novel anchoring means might be utilized. For the purpose of the following description, the marine platform shown is of the monopod type consisting of a single upright column 11 which, when in a submerged position, extends substantially from the ocean floor to a point above the surface. A drilling or production deck 12 is fixed to the upper end of column 11 and is maintained by under braces 13 and 14. Such deck or decks 12 are fitted to accommodate the normal drilling component of men, equipment and storage facilities, including derrick 15 extending upward from the deck surface.

Deck 12 is normally elevated a predetermined height above the water surface to permit an efficient operation and be beyond the reach of waves. To provide the platform with a degree of versatility the respective deck or decks are desirably removable from the platform whereby A base 16 comprising footing elements 16, 21, 22 and 23 respectively depends from the lower end of column 11 to provide an adequately wide seating surface which rests on the ocean floor. The horizontal span of base 16 is contingent to some extent on the height of column 11, but also on the consistency of the supporting substratum. Column 11 is preferably positioned concentrically with the base by lower piers 51, 52 and 53 to equally distribute loading stresses on the latter.

A plurality of elongated, peripherally spaced support legs 17 and 18 rigidize the column against external forces exerted against the column sides both above and below the water. Such support legs enclose, and are normally fastened to piles 19 and 20- which extend from the leg lower end and are imbedded in the ocean substratum. The upper ends of the respective legs are spaced longitudinally along the column such that piles 19 and 20 enter the substratum at a slightly acute angle from an upright position.

As a matter of practicality, platform 10 in its entirety is constructed to be controllably buoyant and thus adaptable to be floated to a drilling position and submerged by controlled flooding. One embodiment of column 11 comprises essentially a uniform diameter cylindrical member formed of end welded cylindrical steel rings. It is contemplated that a marine platform of the central column type is feasibly operable in water depths of between 150 and 1,000 feet. The column is therefore of an adequate cross sectional diameter with respect to its length, to assure maximum rigidity at depths wherein the forces acting against the column are greatly accentuated. While not presently shown, the column, following known practice, may include a plurality of conductor pipes which reach from the deck level to the ocean floor and accommodate the usual pipe strings for drilling and production purposes.

Column 11 may advantageously be constructed to embodying a plurality of strategically placed fluid tight tanks. The latter are interconnected to a control system of necessary pumps, valves, and manifolding to either store oil pumped from the substratum, or to regulate the buoyancy and attitude of the platform in the water. This latter feature is of course well known and widely practiced in the art. However, in view of the diverse and specious equipment enclosed in column 11, passage through the column interior is virtually impossible.

Base 16, fixed at the column 11 lower end, includes a plurality of members so constructed and fastened one to the other to assure the platform a degree of stability when in a submerged position. Base 16 may assume a variety of geometric configuration such as a triangular (FIG. 2), square, or other, in achieving its intended purpose. In FIG. 2, base 16 is seen to include at least 3 tubular conduits 21-23 inclusive, joined at the respective ends and welded to provide at least a part of the structure with water tight integrity. The tubular conduits are subdivided into fluid tight compartments which, as in the instance of the column 11, are connected to a fluid control system such as pumps, manifolds and the like for regulating the fluid content of the respective tanks.

The primary purposes of the in-built tanks is two-fold. First, they function as buoyant members in controllably regulating the attitude of the platform both at the water surface and during submerging of the same to a predetermined position. A second feature of the tanks embodies the storage of oil as it is removed from the substratum or alternatively holding of water as ballast. However, the structural function of the base is to assure the column being maintained vertically under all operating conditions.

As above mentioned, normally the submerged column structure is subjected to forces exerted by under water currents and also by conditions at the surface. The latter is accounted for by storms and generally turbulent waters which act against the column upper end and deck 12. Beneath the water surface, currents and tides peculiar to the platforms environment, apply in effect, a discontinuous bending moment to the column which varies at different points of elevation in accordance with the water de th.

Io stabilize the upright column with respect to the base, and to minimize bending stress, legs 17 and 18 serve as terminal structural elements, in both tension and compression, extending between the base and the column upper end. A series of rigid intermediary members, otherwise defined as pile guides, comprise essentially elongated tubular elements fixed at the lower end to the base, and at the upper end to column 11 outer wall.

These shorter intermediary members 42 and 43 for example extend between base 16 and column 11. Said members are fixed at a lower elevation along the column than the legs 17 and 18. Similarly, additional intermediary members such as 51, 52 and 53 may extend from the column to the base at difierent column elevations.

The purpose of these intermediate structural legs or pile guides is to both rigidize the column against vertical bearing forces and also against bending forces due to environmental conditions. Referring specifically to FIG. 3 each intermediary member or pile guide 42 is fixed at its lower end to a base member, and at the upper extremity to the outer edge of column 11. The normal function of pile guide 42 is to retain a pile longitudinally therein until such time as the platform has been submerged into place. Thereafter the pile is urged, while being guided, into the substratum a predetermined depth to securely position the platform.

The splayed or spread disposition of the respective platform anchoring points is achieved by so placing the intermediary pile guides, as well as the main legs 17 and 18 as to assume an angle from the vertical. With the respective pile guides fastened at different column heights, the pattern formed by the lower ends of the piles imbedded in the substratum will be relatively flared or wide spread and consequently constitute an eflicient, versatile anchoring means.

Referring to FIG. 3, the lower end of pile guide 42 overhangs the base 16 at the juncture of members 22 and 23. The guide pile lower ends may be further provided with a cylindrical, detachably fastened sleeve 26.

Removable sleeve 26 is provided with a flange 27 at the inboard end, which flange engages a similar flange 28 at guide 42 lower end. Sleeve 26 is rigidly engaged to guide 42 by a removable clamp 29, or by bolting directly through mating flanges 28 and 29. Sleeve 26 in essence defines a disposable rigidizing member between the centrally disposed pile 54, and guide tube 42. An annular space 56 formed between contiguous surfaces of pile 54 and sleeve 26 houses a seal or collar 31. The latter comprises spaced seal rings 32 and 33 disposed at opposite ends of the sleeve to form tight annular seals. In the usual manner a fluidized material such as cement or the like, which will harden to a rigid mass is forced into annular space 56 between rings 32 and 33, thereby establishing upon setting rigid connecting collar '31. Sleeve 26 is provided with an inlet 36 connecting with line 37, the latter extends upward to a source of fluidized cement or grouting at the water surface. A'second outlet 36 provided in sleeve 26 upper end is also communicated with annular space 56 for overflowing excessive grouting material after the collar space has been filled.

Pile guide 42, in the instance When but a single pile is to be accommodated thereby, is provided as shown in FIG. 4, with positioning means such as a plurality of longitudinal bearing tracks 38, 39 and 41 extending longitudinally of guide tube 42 and peripherally spaced to support and locate the pile 54. The latter is maintained substantially concentric with guide tube 42 to insure proper alignment and rigidity during insertion by the pile driving mechanism.

Guide tube 42 is structurally rigid and connected at one end to column 11 to provide the column with necessary lateral support. As shown in FIG. 3 the upper end of guide 42 fastens to column 11 outer wall, being fixed to the surface of the latter by welding or bolting as is most feasible. In an alternate arrangement, guide tube 42 may be connected by a column encircling collar or the like to engage the side of the column 11 in providing the required lateral support.

In either structure, guide 42 is adapted at the upper end to receive a mobile pile driving mechanism 46 shown in FIG. 3. The latter is supported from a cable 47 and lowered from the water surface either from a barge adjacent to deck 12, or directly from deck 12. Toward facilitating operation of pile drive mechanism 46,: a guide system might be provided such as vertical tracks or taut cables extending from the water surface to inlet 48 of the guide 42. Guide 42 is opened at the top, defining inlet or aperture 48 of suflicient dimension to admit the pile driving mechanism 46. The latter upon entering the guide tube engages bearing tracks 38, 39 and 41 thereby entering the leg immediately behind and in alignment with the upper end of pile 54.

Pile driving mechanism 46 comprises in essence standard drive apparatus adapted to facilitate mobility of the unit. The unit includes a main body, formed to re ceive a reciprocably moveable hammer or anvil 61. The latter includes a forward aligning and clamping head 62 which locks onto the upper end of a pile to be driven. Remote activation of the hammer, where the latter is in place, thereafter causes the pile to be controllably imbedded by the hammer impact a predetermined depth.

Pile mechanism 46 will of necessity be retracted periodically from pile guide 42 for the purpose of adding additional lengths of pile in accordance with the consistency of the substratum into which the pile is being driven, and with the pile guide length. The pile is thus retained within the guide tube by a locking or clamping mechanism during transportation of the platform and prior to being driven as desired.

At the drilling site, the platform is controllably submerged, or at least partially submerged, by adjusting the buoyancy to bring base 16 into position whereby the base resets upon the ocean floor oris in a horizontal attitude. To initially fix or anchor the platform, piles within upright legs 17 and 18 are driven into the ocean substratum by a conventional pile driving mechanism either carried on deck 12 or on a derrick bai'ge positioned adjacent to the platform. Each of said legs 17 and 18 may of course hold a plurality of piles as is customary, which then are disposed in a substantially upright position and driven into the substratum a predetermined length in accordance with the soil consistency and the expected operating conditions to which the platform will be subjected. When so postured, the unit is lowered to contact the ocean floor. Simultaneous with the setting of the main piles, the supplementary or splayed footings comprising piles 54, 56, and 57 may be inserted. This is achieved by guiding mobile pile driving mechanism 46 from the water surface to a submerged position, there to enter opening 48 in the guide 42 top side, whereby the lowered end is guided into contact with a pile upper end. The pile end, and drive unit 46 are then locked into a unit by remotely actuating the locking clamps 62. Thereafter, actuation of the driving mechanism causes the pile to be progressed into the substratum.

In the instance of a relatively long pile length which exceeds the length of the guide member 42, the pile as mentioned is elongated by removal of driving mechanism 46 to permit the addition of pile lengths to the pile upper end. The latter is achieved by welding the added length to the original length. The additional pile length may be inserted at the rear of guide 42 or through other convenient opening as in the guides upper side. In a similar manner, the added length may be guided to the original pile by access members formed in the guide upper surface. Driving mechanism 46 is again inserted and the pile further driven into the substratum. After reaching a prescribed anchoring depth, grouting material is directed to the sleeve 26 which long way of line 37, and inlet 36, rigid connecting collar 34 between the pile and the guide tube.

- When at a subsequent date, it becomes necessary to move the platform to a different site, the latter is disengaged from its anchoring piles in the usual manner. This consists of severing the pile by an explosive charge or other means at a'point, near the ocean floor, whereby the platform is freed. The latter is then free to be raisedto a floating position by controlled manipulation of the respective buoyancy tanks within column 11 and base 16. In the surfacedfcondition, sleeve 26, is removed from the respective guide tubes lower end thereby clearing the tube for the application of a new replaceable sleeve and the insertion of a new pile length. The platform is then ready to be floated to a new position and again anchored.

Other modifications and variations of the invention, as hereinbefore set'forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In a marine platform for an offshore oil producing facility, said platform being adapted for partial submergence in a body of water and to be fixedly anchored in the water substratum and derrick means adapted to carry a mobile pile imbedding device;

(a) at least one support column disposed in a substantially upright position and extending from said ocean floor toward the water surface;

(b) elongated guide tube means having one end engaging said support column and having an open lower end disposed in a direction toward the ocean floor;

(c) said guide tube means further including a guide passage adapted to receive and position at least one anchoring pile, and to fixedly engage said at least one pile after the latter has been imbedded into the ocean substratum from said guide tube open end; and

(d) means forming an aperture in said guide tube at a point spaced from said open end, said means forming said aperture being sufiiciently large to accommodate passage of pile imbedding device when the latter is supportably lowered form the water surface by said derrick means, whereby said imbedding device impacts said pile at the upper end for imbedding the same into said substratum.

2. In a marine platform as defined in claim 1, wherein: said elongated guide tube means is disposed at an angle offset from an upright disposition.

3. In a marine platform as defined in claim 1, wherein; said elongated guide tube means is disposed at an angle displaced downwardly from a horizontal plane.

4. In a marine platform as defined in claim 1, including: a base lying at a generally horizontal disposition and radiating outwardly from the lower end of said at least one support column, said elongated guide tube means including at least one rigid guide tube having an upper end thereof connected to said base thereby to laterally support said column.

'5. In a marine column as defined in claim 4, wherein: said elongated guide tube means includes a plurality of guide tubes, each having the uppermost end thereof engaging said support column at spaced apart elevations along the latter.

6. In a marine column as defined in claim 1, wherein said guide tube means includes:

(a) at least one elongated guide tube,

(b) means in said guide tubefor retaining said pile therein during embodiment of the latter into said substratum, and for fixing said pile in said guide tube subsequent to the latter be imbedded in said substra-um.

7. In a marine platform for an offshore oil drilling and production site being adapted for anchoring in the ocean floor and including;

(a) an elongated column disposed in a generally upright position and extending from the ocean floor to a position above the waters surface supportably carrying a deck above said surface;

(b) a base at the column lower end being normally resting in contact with the ocean floor and having base elements spaced outwardly of said column;

(c) a plurality of rigid legs extending upwardly from said base elements, the respective leg upper end being supportably connected to said column;

(d) pile guide means including a plurality of pile guide tubes, having the lower end connected to said base, and an upper end connected to said column at a point spaced downwardly from said elongated column upper end, and

(e) said plurality of pile guide including; at least one pile having an inboard portion rigidly connected thereto, said pile having an outboard portion imbedded in the ocean floor.

' 8. 'In a marine platform as defined in claim 7, including; a collar removably connected to the lower end of said pile guide means and being adapted to be firmly locked to a portion of a pile extending therethrough for positioning said pile with respect to said platform.

9. In a marine platform as defined in claim 7, including; a collar removable positioned at the lower end of said pile guide means, said collar including a rigid joint between said collar and said pile whereby said pile is firmly locked to said guide means.

References Cited- UNITED STATES PATENTS 2,775,095 12/1956 Harris 6146 3,429,133 2/1969 Hauber 6l46.5

FOREIGN PATENTS- 1,020,555

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