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
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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
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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
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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.
