US3592012A

US3592012A - Laterally reinforced offshore platform

Info

Publication number: US3592012A
Application number: US860285A
Authority: US
Inventors: George E Mott
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1969-09-23
Filing date: 1969-09-23
Publication date: 1971-07-13
Anticipated expiration: 1988-07-13

Abstract

An offshore platform adapted to be fixedly positioned at the floor of a body of water. The deck-supporting structure or jacket includes three or more corner legs which extend to, and are fastened into the substratum by piles connected at the respective leg''s lower ends. The jacket''s upper end is adapted to adjustably or fixedly position a work deck above the water''s surface, which deck accommodates the usual equipment such as derricks, draw works and the like, normally utilized in a well-drilling operation. the deck-supporting jacket is reinforced and stabilized against lateral displacing forces by a series of batter piles held in diagonally positioned pile guides disposed along the respective side faces of said support jacket.

Description

United States Patent {72] Inventor George E. Mott Metairie. La.

[21] Appl. No. 860,285

[22] Filed Sept. 23. 1969 [45] Patented July 13. 1971 [7 3] Assignee Texaco Inc.

New York, N.Y.

[54] LATERALLY REINFORCED OFFSHORE 3.390.531 7/1968 Johnston et al.. 1 6l/46.5 X

3,429,133 2/1969 l-lauber a 61/46.5 3,466,878 9/1969 Esquillan et all 61/46.5 3,512,811 5/1970 Bardgette et al 61/46X Primary Examiner-Jacob Shapiro Att0rneys--l(v E. Kavanagh and Thomas H Whaley ABSTRACT: An offshore platform adapted to be fixedly positioned at the floor of a body of water. The deck-supporting structure or jacket includes three or more comer legs which extend to, and are fastened into the substratum by piles connected at the respective leg's lower ends. The jackets upper end is adapted to adjustably or fixedly position a work deck above the water's surface, which deck accommodates the usual equipment such as derricks, draw works and the like, normally utilized in a well-drilling operation. the deck-supporting jacket is reinforced and stabilized against lateral displacing forces by a series of batter piles held in diagonally positioned pile guides disposed along the respective side faces of said support jacket.

PATENTED JUL 1 3 mm SHEET 1 BF 2 LATERALILY REINFORCED OFFSHORE PLATFORM BACKGROUND OF THE INVENTION One of the primary difficulties encountered in anchoring fixedly positioned marine platforms in an offshore body of water is the need to stabilize and anchor the platform against lateral forces such as above-surface wind forces, subsurface waves, and ocean currents. Predominant among these, are violent storms of hurricane proportion which tend to create oscillating forces that act against the platform and often pose a greater potential danger than a steady upsetting force would.

In the instance of an ocean area characterized by a relatively firm substratum, the anchoring medium, usually piling or the like, as well as the cost factor of the entire marine platform, are substantially minimized. Where, however, the ocean substratum is essentially of an unconsolidated consistency such as in a deltaic environment, the normal upright anchor piling arrangement is frequently found to be inadequate and requires reinforcement if it is to be at all effective.

One expediency found to be successful in supplementing a main anchor pile arrangement for a marine platform, is the use of a series of skirt piles disposed about the platfonn lower end and which are imbedded into the substratum. Such piles are usually driven vertically from a barge or from the platform itself, a predetermined depth into the ocean floor. Thereafter they are fastened to the platform lower end by cementing near the water line. The number of skirt piles, when used in any in stallation, is determinable by several factors including the holding ability of the substratum and the strength capability of the main pile system.

In accordance with presently used procedures for utilizing skirt piles on a marine platform, to be properly positioned the piles are guidably held while being driven by a piledriver or other means. Thereafter the pile end is fastened to the platform usually by grouting or cementing, and then cut off above the fastening joint. As a consequence, proper positioning of the skirt pile arrangement normally embodies the use of false works incorporated into the jacket support structure. The false works consists of members which add to the cost of the unit as a whole as well as to the subsequent cost of moving and handling of the platform. Further, the false work structure generally requires the use of divers to install and remove the parts thereof, an additional factor which gravitates against the use of skirt piling.

It is therefore one of the objects of the invention to provide an offshore marine platform adapted to be firmly fixed into a relatively soft substratum. A further object is to provide a fixed offshore platform which utilizes pile anchoring to establish a firm position in the ocean floor whereby to successfully counteract displacing forces both above and below the water's surface. A still further object is to provide a marine platform of the type contemplated in which the holding ability of main pile members extending through the platform legs is supplemented by batter piles carried in appropriate pile guides extending substantially diagonally from the leg upper end to the ocean floor. Still another object is to provide an offshore platform which utilizes a pile anchoring arrangement adapted to provide a rigid foundation for the platform jacket without adding appreciably to that part of the platform structure which ordinarily encounters wind and wave forces. Still another object is to provide an offshore platform in which a main pile anchoring arrangement, together with a supplemental batter pile arrangement, are so carried by the platfonn as to afford an internal distribution of stresses normally imposed on the platform as a result of inclement water and weather conditions. And a still further object is to provide a platform support jacket in which inclined skirt piles function to transmit at least a part of the lateral upsetting forces imposed on the structure, axially into the anchoring substratum.

SUMMARY OF THE INVENTION In overcoming the above-mentioned problems and operating difi'rculties peculiar to a marine platform located in tidal waters, there is presently provided such a unit which is normally positioned at the floor of a body of water and which supports a working deck above the water's surface. The deck is adapted to hold materials essential to a well-drilling and/or producing operation. The platform further comprises essentially a support structure or jacket in the form of a plurality of peripherally arranged main legs incorporated into a structure which extends from an elevation above the water's surface to the ocean floor. The respective main legs are normally disposed in a substantially vertical disposition but are advantageously battered outwardly from a vertical posture whereby to afford a wider more stable anchoring base.

Each side or vertical face of the support structure defined by adjacently positioned legs is provided with lateral interlocking elements. Each side or face of the structure is further provided with at least one pile guide member which extends in a diagonally downward direction from a leg upper end to a point intermediate adjacent legs lower ends. Said pile guide member encloses a batter pile which is driven through and grouted to the pile guide, and which is imbedded at its lower end into the substratum in substantial axial alignment with said guide.

The batter pile guide is rigidly positioned to both upper and lower ends of the support jacket whereby to absorb at least a part of the stress and strain imposed on the platform structural components due to the lateral displacing forces. Further, the peripherally spaced batter pile guides, being firmly locked into the support jacket structure, tend to distribute said lateral external force throughout the structure thereby avoiding damage to the latter and overcoming any tendency to either displace or upset the platform.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical elevation illustrating a marine platform of the type contemplated being anchored into the substratum of a body of water.

FIG. 2 is a plan view taken along the 2-2 in FIG. 1.

FIG. 3 is a segmentary view on an enlarged scale and in cross section of a portion of the platform jacket shown in FIG. 1.

FIG. 4 is a segmentary view on an enlarged scale and in cross section of the lower end of a jacket leg as shown in FIG. 1.

DESCRIPTION OF THE INVENTION Referring to the drawings, in one embodiment of the apparatus shown in FIG. 1 the illustrated platform 10 consists of a working deck 11 supported 50 or 60 feet above the waters surface by a superstructure or jacket 12. The jacket, in its normal upright submerged position, extends from a point above the waters surface to the ocean floor. Deck 11 carries an upstanding derrick 15 together with a crown block at its upper end for suspending drill pipe strings, tools and other equipment which are lowered through an opening in the deck and into the ocean substratum.

The

respective comer legs

13 and 14 are horizontally braced by a plurality of vertically spaced intermediate members such as

cross bracing members

16, 17 and 18 which terminally connect to the adjacent legs. The upper side of support jacket 12 is adapted to receive deck 11 after said structure or jacket has been floated to and submerged at a drill site. Each comer leg for example may position a vertically aligned socket of sufficient diameter to tightly register and align corresponding downwardly extending deck columns such as 19 and 21.

During installation, the shore-fabricated jacket 12 is barged, floated or otherwise conveyed to the offshore location and controllably submerged. Anchor piling having been previously positioned In the acket legs. then driven through said legs and into the substratum Deck 11 is then floated or carried to the jacket and lowered onto the latter whereby

deck columns

19 and 21 engage, and are received by the acket upper end Jacket I2 and deck 11 are then unified by a series of welded joints which connect the deck columns to the jacket Base element 22 at the jacket foot, comprises a series of cylindrical members connected to the respective legs lower ends. Bearing plates 34 attached to bottom members 22 assist in supporting the jacket as it is floated and guidably lowered into position.

In accordance with the invention,jacket 12 is provided with a first or main anchoring system comprising a plurality of peripheral, embedded main piles. A second or supplementary anchoring system includes a plurality of skirt piles depending downwardly from the jacket and being likewise embedded in the substrate.

Main anchoring means comprises as shown in FIG. 1, at least one pile 23 driven through each comer leg as at 13. Pile 23 is formed normally of a heavy walled, elongated tubular member assembled of shorter sections which are sequentially added to the pile upper end as the latter is driven further into the substrate. Following normal practice, pile 23 and leg 13 are unitized by welding or similar means. It is appreciated that each corner leg of the jacket can be provided with a plurality of elongated piles rather than with a single pile which piles, although not presently shown, are disposed in parallel relationship and mutually fastened into place within the leg interi-' Further in accordance with the invention, jacket 12 is provided with the secondary piling system including a plurality of skirt piles which, when similarly embedded into the substrate, serve to supplement the holding function of main piles 23. Referring again to FIG. 1, the sides ofjacket 12 are defined by a plurality of substantially vertical planar surfaces bounded laterally by adjacent corner legs such as 13 and 14. A skirt pile guide 26 is disposed across each of said planar faces, lying substantially within the plane in a generally diagonal direction extending between the upper end of one leg 13 to a point intermediate the respective adjacent legs lower ends.

In one embodiment, skirt pile guide 26 comprises an elongated open ended cylindrical tube. Said tube is fastened externally preferably by welding, to the respective vertically spaced jacket across members l6, l7 and 18. Skirt pile guide 26 is preferably positioned as shown in FIG. 1, to form an intersecting junction with the upper end of leg 13 whereby a mutual upward facing pile inlet opening 36 is formed. Thus, a pile may be lowered downwardly through leg l3, or in the alternative driven through the pile guide 26.

Referring to FIG. 4, skirt pile guide 26 is of a sufficient inner diameter to slidably receive atleast one skirt pile 27. The latter, similar to main pile 23, comprises an elongated heavy walled tubular member adapted to be driven at the upper end for embedment into the substrate. Skirt pile guide 26, and, if desired pile 23 also, can be provided with an inner collar 28 having a center opening large enough to slidably register pile 27 as the latter passes through the pile guide and enters the substrate. A flow inlet 29 communicated with annular space 31, includes a grout conduit 33 extending to the waters surface and communicated with a source of grouting material. Said conduit 33 is adapted to carrying a fluid flow of grout from the source thereof and which is introduced to fill the annular space 31 whereby to form an elongated solidified collar 32 to position pile 27 in place within guide 26.

As shown in FIG. 1, although the lower end of skirt pile 27 lies substantially within the planar face defined by

legs

13 and 14, said pile 27 pierces the substratum at an entry angle intermediate the angles of embedment of the respective leg piles. The additional piling strength afforded to th: jacket by the skirt pile system is not therefore limited in function to resisting vertical forces. The skirt pile and guide also exert a downward reaction force in opposition to the overturning moment induced into the jacket as a result of laterally directed wind and wave forces.

In one embtfdiment of the invention, using two skirt piles for tiguous with the lower end of the elongated leg 14. In such an instance. the lower end of the skirt pile guide 26 can be directed slightly outward from the planar face of the above mentioned legs in order that the skirt pile 27 passing therethrough will not interfere with the main pile passing downward through a main leg In an alternate embodiment of a skirt pile arrangement, skirt pile guide 26 is so disposed with the upper end thereof at the upper end of leg 13. The pile guide lower opening however is disposed substantially between the lower extremities of the respective legs 13 and M. In such an instance the skirt pile enters the substratum at a point approximately between the piles of the respective legs of 13 and 14.

For inserting a skirt pile of the type described, the latter can be driven through the skirt pile guide 26 by means of a follower removably carried at the upper end of the pile. The pile is thereby driven in the usual manner utilizing the follower as an intermediate, until the pile has reached a predetermined depth. Thereafter the follower is removed and the skirt pile fastened into place to the skirt pile guide as here noted.

Obviously, many modifications and variations of the invention as hereinabove 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:

I. A marine platform for fixed positioning at an offshore body of water, said platform including an elongated support jacket disposed in a substantially upright position in said body of water,- having a base at one extremity thereof anchored to the substratum, and having an upper end at the waters surface, a work deck supportably connected to said jacket upper end and being normally elevated beyond the waters surface,

said jacket including a plurality of main legs disposed in a substantially upright attitude extending from said base to said jacket upper end,

first pile means including at least one elongated anchor pile received in each one of a pair of adjacently positioned main legs, said at least one elongated anchor pile having a portion thereof depending from a main leg lower end and being imbedded in the substratum,

supplementary pile guide means connected to said jacket including;

a pile guide member having an elongated guide piece disposed in a plane common to the plane of the respective adjacently positioned main legs, and being fixed at opposed ends thereof to said jacket,

said pile guide member having an inlet opening positioned at the upper end of one of said adjacently disposed main legs and having an outlet opening at the jacket base intermediate the lower ends of said respective adjacently positioned main legs, and

' a secondary piling means retained in said supplementary pile guide means, said secondary piling means including at least one anchor pile fixedly positioned in said guide member and having one end extending from the guide member lower outlet opening and being embodied in the substratum.

2. In a marine platform as defined in claim 1 wherein; said pile guide member terminates at said jacket base at a point contiguous with the lower end of the other of said adjacently positioned legs.

3. In a marine platform as defined in claim 1 wherein; said guide member terminates at said base at a point approximately midway between the lower ends of the respective adjacently positioned leg ends.

4. In a marine platform as defined in claim 1 wherein; said jacket includes; a plurality of a vertically spaced horizontal cross braces lying in the plane of said adjacently positioned main legs, being terminally fixed to the latter, and said guide member being connected to the respective plurality of cross braces.

5. In a marine platform as defined in claim 1 wherein; said guide member includes; a single anchor pile received therein, having a portion thereof disposed substantially the length of the guide member.

Claims

1. A marine platform for fixed positioning at an offshore body of water, said platform including an elongated support jacket disposed in a substantially upright position in said body of water, having a base at one extremity thereof anchored to the substratum, and having an upper end at the water''s surface, a work deck supportably connected to said jacket upper end and being normally elevated beyond the water''s surface, said jacket including a plurality of main legs disposed in a substantially upright attitude extending from said base to said jacket upper end, first pile means including at least one elongated anchor pile received in each one of a pair of adjacently positioned main legs, said at least one elongated anchor pile having a portion thereof depending from a main leg lower end and being imbedded in the substratum, supplementary pile guide means connected to said jacket including; a pile guide member having an elongated guide piece disposed in a plane common to the plane of the respective adjacently positioned main legs, and being fixed at opposed ends thereof to said jacket, said pile guide member having an inlet opening positioned at the upper end of one of said adjacently disposed main legs and having an outlet opening at the jacket base intermediate the lower ends of said respective adjacently positioned main legs, and a secondary piling means retained in said supplementary pile guide means, said secondary piling means including at least one anchor pile fixedly positioned in said guide member and having one end extending from the guide member lower outlet opening and being embodied in the substratum.