Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Submerging – raising – or manipulating line of pipe or cable...
Patent
1996-10-04
2000-05-02
Bagnell, David J.
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Submerging, raising, or manipulating line of pipe or cable...
405158, B63B 3503
Patent
active
060564784
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a pipelaying vessel, and more specifically but not exclusively relates to a self-propelled and dynamically-positioned reel pipelaying ship in which a pipe-spooling reel and associated pipe handling equipment are integrated into the structure of the ship. In some embodiments of the pipelaying ship, there is provision for the simultaneous laying of a plurality of pipes, or the simultaneous laying of one or more pipes together with one or more cables.
In prior-art pipelaying vessels as employed in laying offshore subsea pipelines for such uses as the gathering of oil and/or gas from offshore subsea wells, as, for example, in the Gulf of Mexico, it has been conventional to use one of two main methods to lay the pipe. In the first, or "stovepiping", method, a pipeline is fabricated on the deck of a lay barge by welding together individual lengths of pipe as the pipe is paid out from the barge. Each length of pipe is about 40 feet or 80 feet long. Thus, the pay-out operation must be interrupted periodically to permit new lengths of pipe to be welded to the string. The stovepiping method requires that skilled welders and their relatively bulky equipment accompany the pipelaying barge crew during the entire laying operation; all welding must be carried out on site and often under adverse weather conditions. Further, the stovepiping method is relatively slow, with experienced crews being able to lay only one or two miles of pipe a day. This makes the entire operation subject to weather conditions which can cause substantial delays and make working conditions quite harsh. (A modification of the stovepiping technique known as the "J-lay" technique allows the laying of pre-assembled pipestrings up to 240 feet in length, but pipelaying is still discontinuous).
The other principal conventional method is the reel pipelaying technique. In this method, a pipeline is wound on the hub of a reel mounted on the deck of a lay barge. Pipe is generally spooled onto the reel at a shore base. There, short lengths of pipe can be welded under protected and controlled conditions to form a continuous pipeline which is spooled onto the reel. The lay barge is then towed to an offshore pipelaying location and the pipeline spooled off the reel between completion points. This method has a number of advantages over the stovepiping method, among them, speed (up to one mile per hour); lower operating costs (eg smaller welding crews and less welding equipment must be carried on the lay barge); and less weather dependency.
Historically, the technique of laying undersea fluid-carrying pipelines had its rudimentary beginnings in England in the 1940's in a War-time project known as "Operation Pluto". In the summer of 1944, 3-inch nominal bore steel tubes, electrically flash-welded together, were coiled around floating drums. One end of the pipe was fixed to a terminal point; as the floating drums were towed across the English Channel, the pipe was pulled off the drum. In this manner, pipeline connections were made between the fuel supply depots in England and distribution points on the European continent to support the Allied invasion of Europe. (See Blair, J S, "Operation Pluto: The Hamel Steel Pipelines", Transactions of the Institute of Welding, February 1946).
The broad concept of reel pipelaying was also disclosed in British Patent No. 601,103 wherein it was suggested that lengths of pipe can be joined together at the manufacturing plant and coiled onto a drum, mounted on a barge or ship; the loaded barge would then be moved to the desired marine location and the pipe unwound from the drum by fixing one end of the pipe and towing the barge away from the fixed location.
While the concepts described in British Patent No. 601,103 and those actually used in Operation Pluto were adequate for wartime purposes, no known further development work or commercial use of the technique of laying pipe offshore from reels was carried out after World War II. After a hiatus of about fifteen years, research into the reel pipelaying tech
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"The Reel Pipelay Ship--A New Concept," Offshore Technology Conference, Paper No. 2400, May 1975.
Martin Robert George
Thomas Philip Vaughn
Bagnell David J.
Coflexip Stena Offshore Limited
Lagman Frederick
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