Abstract

Bayu-Undan is an existing gas field located North West of Darwin comprising of two main platforms, a satellite platform and an export pipeline to the Darwin LNG facility operated by ConocoPhillips. Phase 3 of the Bayu-Undan development included the lay of two flexible pipelines and one umbilical. The umbilical was installed by a leading seabed-to-surface EPIC contractor utilising a multirole construction and diving support vessel in September 2014, which presented a number of specific challenges:

  • The umbilical system was unusual for the following reasons:

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      Free-hanging catenary of umbilical to avoid in-place rigid spools (*)

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      Shallow water depth of J-tube bellmouth

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      Umbilical ancillaries that were designed before installation challenges were fully understood

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      The proximity of J-tube and lay corridor to the flare bridge

  • Detailed engineering on the following topics was completed to address the installation challenges:

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      Installation Analysis of different methods for comparison, using a leading finite element based hydrodynamics simulation software

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      Design of bespoke stern-mounted horizontal lay spread

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      Rigging design for product limit conformance

  • The following factors influenced a successful offshore campaign:

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      Good weather

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      Smooth deck handling of umbilical

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      Good interface between vessel and platform team

This paper presents a case study of the engineering and installation activities and provides lessons learnt for the entire operation.

(*) the "dynamic" umbilical will be further refered as "free-hanging" umbilical as, being fixed both ends, it didn't experience any real dynamic behaviour.

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