United States Patent (19) Oksuzler

Transcription

1 United State Patent (19) Okuzler 54 75) 73) ) (52) 58 56) METHOD AND APPARATUS FOR POSITONING AN OFFSHORE PLATFORM JACKET Inventor: Yalcin Okuzler, Plano, Tex. Aignee: Mobil Oil Corporation, New York, N.Y. Appl. No.: 814,958 Filed: Dec. 31, 1985 Int. Cl.'... EO2D 25/00 U.S. Cl /209; 405/205; 405/203 Field of Search /203, 205, 209, 204, 405/207, 208 Reference Cited U.S. PATENT DOCUMENTS 3,633,369 1/1972 Lawrence /209 3,823,564 7/1974 Crout et al /209 4,112,697 9/1978 Chow. 4,135,842 io/1979 Blight et al /209 11) Patent Number: 4,690, Date of Patent: Sep. 1, ,161,376 7/1979 Armtrong /204 4,260,291 4/1981 Young et al /203 4,293,240 10/1981 Ogimoto et al /203 4,556,342 12/1985 Tannahill /2O3 4,629,365 12/1986 Kuriiwa M. 405/228 FOREIGN PATENT DOCUMENTS l/1965 United Kingdom. Primary Examiner-Corneliu J. Huar Aitant Examiner-Kritina I. Hall Attorney, Agent, or Firm-Alexander J. McKillop; Michael G. Gilman; Charle J. Speciale (57) ABSTRACT A method for poitioning an offhore platform jacket i ued wherein the jacket i loaded on a barge in a con ventional manner and towed out to ea to a predeter mined offhore location. The barge i ubmerged, and the buoyant jacket i detacted. The jacket i towed away, and the barge i reurfaced for additional ue. 2 Claim, 13 Drawing Figure T=1OOO TONS

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10 1. METHOD AND APPARATUS FOR POSITONING AN OFFSHORE PLATFORM JACKET 4,690,586 BACKGROUND OF THE INVENTION An offhore platform ued in the production of hy drocarbon i contructed in everal phae. Portion of the offhore platform are manufactured onhore and aembled either in cloe proximity to the place of man ufacture or at the location where the offhore platform i to be poitioned for production. One portion of an offhore platform that i manufactured onhore and towed to the location where the offhore platform i to be poitioned i the jacket. An offhore platform jacket i normally fabricated in a yard adjacent to a lipway. After fabrication, it i kidded onto launch beam, firt over the kid beam 14 on dock, then over the kid beam 16 on a launch barge. The barge i then towed out to ea by a tugboat 20. Subequent to the ocean tow, it i launched into the ea over tilting (rocker) beam 22, located at the end of the kid bean (ee FIGS. 1-4). A great majority of hallow water jacket (thoe that cannot be lifted off becaue of weight limitation) and all of deep-water jacket follow thi routine before they are finally upended, piled and their deck intalled. During the launching operation, both jacket and barge uually undergo one of the highet tre level. Approximately ten (10%) percent by weight of addi tional teel i required in many jacket in order to reit the one-time evere launching tree. Thi additional teel, which i not needed except for launching, be come part of the permanent tructure and attract addi tional wave and current load throughout the life of the Structure. Generally, the trength of the launch barge i alo teted during launching. The barge are heavily rein forced around the tilting beam upport. One jacket may deliver up to twenty thouand (20,000) ton of load onto each pin of the rocker beam. SUMMARY OF THE INVENTION invention provide a method for poitioning an off hore platform jacket which avoid the concentration of tre to a few point and minimize the mechanical 45 tre to which the barge ued to tow the platform jacket to it offhore location i ubjected. The method of the preent invention eliminate the expenive, ome time dangerou, highly treed condition of jacket and barge. By uing the preent invention, a launch barge will tow the jacket to it offhore location. The barge i then ubmerged, and the jacket i detached. The barge i completely ubmerged, and the jacket i towed away. The barge i reurfaced for additional ue. By avoiding unloading tree, the ize and weight of the jacket may be reduced to a ize and weight neceary for platform ue. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A illutrate a plan view of loading a jacket onto a launch barge. FIG. 1B i an elevational view of FIG. 1. FIG. 2 illutrate a launch barge with a jacket thereon. FIG. 3 illutrate a prior art method for unloading a 6 jacket from a launch barge. FIG. 4 illutrate a launch barge with a jacket thereon anchored to the ocean floor. 2 FIG. 4A i a rear view of FIG. 4. FIG. 5 illutrate the barge of FIG. 4 with the an chor in tenion. FIG. 5A i a rear view of FIG. 5. FIG. 6 illutrate the barge of FIG. 5 partially ub merged. FIG. 6A i a rear view of FIG. 6. FIG. 7 illutrate the barge of FIG. 6 completely ubmerged. FIG. 8 illutrate the barge of FIG. 7 with the jacket detached. FIG. 9 illutrate the barge of FIG.8 with the jacket towed away. DESCRIPTION OF THE PREFERRED EMBODIMENT The preent invention dicloe a method for unload ing a jacket ued in an offhore platform without the high tre load currently aociated with launching a O jacket from a launch barge. Referring now to FIG. 4, jacket 12 may be loaded onto a barge 24 in any conventional manner, uch a that decribed in conjunction with FIGS. 1 and 2. Cargo barge 24 illutrated in FIG. 4 i called a Tenion Leg Barge (TLB), and it i equipped with cable and anchor to facilitate controlled ubmergence of a loaded barge. Tenion Leg Barge 24 i illutrated a connected to anchor 26 and 28 through cable 30 and 32, repec tively. Although Tenion Leg Barge 24 i anchored to the ocean floor 34 through anchor 26 and 28, it i to be undertood that additional method of anchoring barge 24 are alo poible in the cope of the preent invention. For example, anchor pile may be driven into the ocean floor ahead of time, or anchor, intead of being low ered from the Tenion Leg Barge, can be dropped to the ocean floor, alo ahead of time. In addition, the Tenion Leg Barge may be grounded on a ubmerged iland, if o deired. FIG. 5 illutrate the arrangement of FIG. 4 with cable 30 and 32 drawn taut to partially ubmerge barge 24. Cable may be drawn taut by winche or the like located at point 36 and 38 on barge 24. At thi point, the tenion on cable 30 and 32 i approximately five tons. Referring now to FIG. 6, the tenion i increaed on cable 30 and 32 to approximately 900 ton while barge 24 i being partially flooded to continue with a con trolled ubmergence. Contained on barge 24 are buoy ancy tank 40 which are ued to keep the barge lightly buoyant. A illutrated in FIG. 7, the controlled flooding and cable tenioning continue until the upper leg of jacket 12 are ubtantially ubmerged. At thi point, barge 24 i fully flooded except for the high-preure buoyancy tank 40, which keep the barge lightly buoyant. Jacket 12 i completely weightle or buoyant. FIG. 8 illu trate jacket 12 a being releaed from barge 24 a quick releae hook 42 are diconnected. Jacket 12 may then be towed away by tug 20 while barge 24 i ubmerged. Barge 24 may be pulled further away from jacket 12 by increaing the tenion on cable 30 and 32 to approxi mately 1,000 ton. FIG. 9 illutrate barge 24 after jacket 12 ha been towed away. Anchor 26 and 28 may be loaded on barge 24 by being pulled up from ocean floor 34 by derrick 44. At thi point, all the water ha been pumped out of barge 24, and it i again floating on the urface.

11 3 Uing the method of the preent invention, jacket 12 may be deigned o that it i lighter and le expenive. Furthermore, jacket 12 will not be ubjected to the high level of tre due to the conventional launching of jacket 12 from a launch barge 18, uch a depicted in FIG. 3. Furthermore, Tenion Leg Barge 24 alo will not be ubjected to the high launching tree that launch barge 18 wa ubjected. A a reult, barge 24 hall not need to undergo thorough ubtantial rein forcement every time a jacket i to be launched. Fur thermore, barge 24 can be ued to facilitate the deintal lation of exiting platform when time come for their abandonment. While the preent invention ha been decribed by way of preferred embodiment, it i to be undertood a not being limited thereto, but only by the cope of the following claim. I claim: 1. A method of poitioning an offhore platform jacket compriing the tep of: loading and ecuring the platform jacket onto a ten ion leg barge; 4,690,586 5 O towing aid tenion leg barge to a predetermined offhore location; laying anchor on the floor of the ocean at aid prede termined offhore location; attaching line between aid anchor and aid tenion leg barge to poition and maintain aid barge above aid predetermined offhore location; partially ubmerging aid tenion leg barge by hort ening aid line between aid anchor and aid ten ion leg barge; completing the ubmerging of aid tenion leg barge by flooding aid barge with eawater; and releaing aid platform jacket from aid tenion leg barge and towing aid jacket off aid barge while aid barge i ubmerged. 2. The method of claim 1 including: pumping aid eawater from aid tenion leg barge once aid platfrom jacket ha been towed there from to reurface aid barge; and removing aid line between aid anchor and aid tenion leg barge. k k k k