Method for installing an undersea catenary riser

A method of attaching a first pipe section to a pre-reeled pipe, the method comprising

• unreeling said pre-reeled pipe so as to launch it in the sea from a vessel;
• supporting said unreeled pipe near a top end thereof in a first support located on said vessel;
• attaching said first pine section to the end of said supported unreeled pipe using attaching means on said vessel;
• supporting said first pipe section near a top end thereof in a second support;
• releasing said first support;
• lowering said first pipe section with the unreeled pipe attached thereto;
• supporting in said first support said first pipe section near said top end thereof.

A method of attaching a pre-reeled pipe to a non-pre-reeled pipe section, the method comprising:

• supporting in a first support located on a vessel said non-pre-reeled pipe section near a top end of said non-pre-reeled pipe section;
• unreeling part of said pre-reeled pipe on said vessel;
• straightening said unreeled part of said pre-reeled pipe and thereby imparting a characteristic stress profile which is formed in the coiling/straightening process;
• attaching one end of said unreeled part of said pre-reeled pipe to the end of said supported pipe section using attaching means on said vessel;
• wherein said pipe section does not have said characteristic stress profile.

A method of installing an undersea pipe system, comprising:

• unreeling a first pre-reeled pipe so as to launch it in the sea from a vessel;
• supporting said first unreeled pipe near a top end thereof in a first support located on said vessel;
• attaching a first non-pre-reeled pipe section to the end of said supported pipe using attaching means on said vessel;
• supporting said first non-pre-reeled pipe section near a top end thereof;
• and
• attaching at least one additional non-pre-reeled pipe section to the end of said first non-pre-reeled pipe section using said attaching means on said vessel.

A vessel for launching two types of piping which together constitute an underwater pipe system, said vessel comprising:

• a reel for holding at least one length of coiled piping;
• guiding/retaining apparatus comprising:
• a pipe straightener for straightening the coiled piping as it is unreeled;
• a puller for urging the pipe in a substantially downward direction;
• and
• a support for holding the pipe and supporting the pipe's weight;
• said vessel further comprising a launching ramp for presenting discrete straight non-pre-reeled pipe sections to said guiding/retaining apparatus;
• and
• a working station having a connecting apparatus adapted to connect a non-pre-reeled pipe section to a supported end of an unreeled pipe and adapted to connect an unreeled pipe to a supported end of a non-pre-reeled pipe section, wherein said working station is positioned downstream of the straightener, between said straightener and said support.

An undersea pipe system installed using a vessel comprising:

• a reel for holding at least one length of coiled piping;
• guiding/retaining apparatus comprising:
• a pipe straightener for straightening the coiled piping as it is unreeled;
• a puller for urging the pipe in a substantially downward direction;
• and
• a first support for holding the unreeled pipe and supporting the pipe's weight;
• said vessel further comprising a launching ramp for presenting discrete straight non-pre-reeled pipe sections to said guiding/retaining apparatus;
• and
• a working station having a connecting apparatus adapted to connect separate non-pre-reeled and unreeled pipe sections together, wherein said working station is positioned downstream of the straightener, between said straightener and said support, said undersea pipe system being installed using the following method:
• unreeling a said coiled pipe so as to launch it in the sea from a vessel;
• straightening said un-reeled pipe and thereby imparting a characteristic stress profile which is formed in the coiling/straightening process;
• supporting a top end of said unreeled pipe in said first support;
• and
• attaching a first non-pre-reeled pipe section to the top end of said supported unreeled pipe using said connecting apparatus;
• wherein said first pipe section does not have said characteristic stress profile.

An undersea pipe system comprising:

• a section of pipe on the sea bed having a characteristic stress profile which has been formed from a coiling/straightening process;
• a first series of pipe sections connected to said sea bed section, said first series of pipe sections not having the characteristic stress profile typical of coiled and straightened pipe sections;
• a further section of coiled and straightened piping connected to said first series of pipe sections;
• a second series of pipe sections connected to said further section of coiled and straightened piping, said second series of pipe sections not having said characteristic stress profile;
• wherein said second series of pipe sections is connected to a floating unit.