Extended Pipeline Bundle Length for Field Development

Abstract

Abstract Towed Pipeline production systems (Pipeline Bundles) are currently fabricated and installed in the North Sea and Norweigian Sea regions from the fabrication facility of a major subsea contractor in Wick, Scotland. The site is located approximately 6 miles north of Wick and extends from the shoreline at Sinclairs Bay landward for approximately 7.8km in an east-west orientation. The current limit for the fabrication of a single Pipeline Bundle is 7.7km. The company has undertaken a Research and Development study on Pipeline Bundle Extended Lengths (Pipeline Bundle lengths up to 15km) to investigate a means to connect several Pipeline Bundle sections together in order to be able to satisfy the requirements of fields where long tie-backs may be required. Pipeline Bundle length extension can be achieved by onshore tie-in through mechanical connection, Golden welds or fabricated at a different site with a suitable length capacity. The key benefit of the extended Pipeline Bundle length is to reduce the overall cost of field development by eliminating the requirement for: Interconnecting towheads (Pipeline Bundle end structures),Tie-In spools,Extended hire of tow vessels,Additional Diver/ROV support vessel time for the tie-in of interconnecting towheads. As a consequence of this length increase, this paper asseses the feasibility of Extended Pipeline Bundle length in the following areas; Pipeline Bundle Tie-in,Pipeline Bundle Pre-commissioning,Required weather window launch - to DNV-OS-H01 Ref.[3],Launch force requirement,Control Depth Tow Method (CDTM) Tow Fatigue,Pipeline Bundle manoeuvring during tow,Application for HT fields – Design Temperature of up to 160°C,Pipeline Bundle Installation - Venting and Flooding The paper will also demonstrate the commercial advantage of towing longer Pipeline Bundles as against multiple Pipeline Bundle tows.