CASE FOR THE BOTTOM-TOW METHOD FOR LAYING OFFSHORE PIPELINES

The greater expense of using conventional pipe laying techniques in deeper and rougher northern North Sea waters in terms of hardware, men and time delays has promoted interest in bottom towing. The basic components in the bottom-tow system are a shore make-up area and a towing vessel. The make-up area can vary, but might be between 1,000 and 5,000 ft. Sleepers are installed for making up pipes and for storage of pipe-strings. A launchway is prepared with roller or track dolly units, and there is also space for material and cable storage, pontoon and rigging areas, and so on. The towing was done by an 8,000 hp supply and anchor-handling tug. Inspection of a 2,000 ft pipeline towed over a 240 mile route out and back over the Norwegian trench showed the effectiveness of the approach. A commercial installation has been completed involving the connection of three 2,600 ft sections of 32 in. diameter pipeline to the booster platform providing recompression of gas from Frigg field en route to Peterhead, Scotland. The strings, which form part of a twin pipeline system, were placed in 310 ft of water. The costs of installation by towing are said to be 30% to 70% less than those for a traditional lay-barge, depending on commitment times for lay-barges and other specific factors. On top of this saving there is a saving through ploughing in, because a trenching barge is not needed, and an additional saving due to the elimination of damage repair facility down-time costs.

• Corporate Authors:

  Institute of Petroleum

  61 New Cavendish Street
  London W1M 8AR,   England 
• Publication Date: 1976-11

Media Info

• Pagination: 3 p.
• Serial:
  • Petroleum Review
  • Volume: 30
  • Issue Number: 359

Subject/Index Terms

• TRT Terms: Construction; Economic analysis; Offshore structures; Petroleum pipelines; Pipe laying; Pipelines; Towing devices; Tugboats; Underwater pipelines
• Candidate Terms: Pipe laying ships
• Old TRIS Terms: Economic analysis (Pipelines)
• Subject Areas: Bridges and other structures; Construction; Economics; Marine Transportation; Pipelines; Terminals and Facilities;

Filing Info

• Accession Number: 00157626
• Record Type: Publication
• Source Agency: Engineering Index
• Files: TRIS
• Created Date: Aug 4 1977 12:00AM