DEEP7 2017 - Subsea 7 - page 19

is also scalable. The Andrew installation
consisted of four interconnected Bundle
systems, and we have since developed
multi-bore Bundle Connector Systems
that will enable multiple Bundle
structures in excess of 33km.
We have successfully introduced
product modularisation into Pipeline
Bundle assembly with our recent
integration of boost pumps within
the towhead. We have designed
a module component to house a
70-tonne multiphase boost pump
which is efficiently installed using a
standard module handling frame. This
system allows for economic future
installation (delivering cost savings
around 80% over a conventional
retrofit assembly) and makes pump
module enhancements possible.
Lifted or towed installation?
Conventional construction vessels have
crane capacities of around 400-600 tonnes,
and, although flagship vessels like the
The controlled depth tow can be
performed in higher sea states than
offshore lifting and significantly
minimises field access requirements.
Existing carrier technology allows for
Bundle installation in water depths to
700 metres, and potential installation
depths to around 1500 metres are
possible by using low-cost external
buoyancy pipes.
Pipeline Bundles installed to date have
not exceeded 7.6km in length, this
restriction reflects the current capacity
of our specialist fabrication yard in
Scotland. Analysis has confirmed that
considerably longer Pipeline Bundles
can be towed by CTDM.
Recent studies also confirm that
fatigue induced in Pipeline Bundles
on longer transit journeys to more
remote locations can be addressed and
mitigated. As we demonstrated with
a 27.1km Pipeline Bundle tie-back for
BP’s Andrew Field in 2011, the concept
Seven Arctic can lift up to 900 tonnes,
deployment operations of this type can
still restrict the workable weather window.
Through our delivery of prefabricated
Pipeline Bundles since 1980, Subsea 7
has developed world-leading capabilities
in the design, engineering, procurement,
onshore construction, launch, tow-out and
installation of these prefabricated systems.
Pipeline Bundles have included more
sophisticated manifolds and SSIVs, cooling/
warming spools, HIPPSs and boosting
pumps and other integrated functionality.
The next stage is to extend the scope of this
cost-effective and reliable technology by
building up prefabricated towed structures
into complete subsea production facilities, or,
for larger fields, by combining a number of
systems, such as subsea processing and wax
control within a single structure. Our world-
leading expertise in the design of modular
subsea structures is based on our wider field
development capabilities, which enable us
to select from alternative flow concepts to
optimise field architectures and economics.
Onshore assembly and testing of the plant.
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