SUBSEA SYSTEMS Jessica Tippee • Houston
Subsea variable speed drive
passes shallow-water test
The first full-scale prototype of a subsea variable speed drive (VSD)
has been successfully tested in a sheltered harbor in Vaasa, Finland.
The test is the latest in a five-year joint industry project (JIP), which
started in 2013, between Statoil, Total, Chevron, and ABB. The JIP
aims to develop transmission, distribution, and power conversion
systems for subsea pumps and gas compressors operating in water
depths up to 3,000 m ( 9,842 ft), transmission distances up to 600 km
(373 mi), and power levels up to 100 MW.
Over three weeks last November, the subsea VSD, designed for
subsea gas compression, was operated in a back-to-back configuration
directly with the grid, without motor loads. This so-called “power-in-the
loop” test, means that only a few hundred kilowatts of losses need to
be supplied from the grid.
“The water test was carried out successfully and achieved all the
set targets,” said Bazmi Husain, ABB’s chief technology officer. “We
have demonstrated the successful and reliable operation in a number
of high stress conditions. This achievement underlines our ability to
push technology to its limits.”
The subsea VSD features a pressure compensated design, whereby
all its power components are cooled by being submerged in oil. The
water test proved that the electronic and power components can meet
the thermal performance demanded. Prior to the water test, the main
drive sub-assemblies and components were pressure tested at 300 bar
( 4,351 psi) in Statoil’s R&D facility in Trondheim, Norway.
Taking power distribution from onshore to the seabed frees up the
limited space on topsides installations. Costs are reduced by having
one cable that is distributed to many subsea loads. Operational costs
are reduced, energy and CO2 emissions are lowered, while marine
pollution is cut and decommissioning simplified, according to ABB.
The JIP is now preparing for a 3,000-hour shallow-water test of a
subsea power system with two variable speed drives in a parallel,
combined with subsea switchgear and controls. This test is targeted
to start later this year. The first installation of the new subsea power
systems in offshore production sites are expected to begin in 2020.
Statoil extends subsea
Statoil has awarded new subsea maintenance framework agreements
to Aker Solutions, TechnipFMC, and OneSubsea with a combined value
of more than NOK8 billion ($969 million). These extend current ar-
rangements until 2023, with further extension options totaling 20 years.
If these are exercised and all aspects of the assumed work scope are
performed, the total value could reach NOK40 billion ($4.84 billion).
The agreements concern the supply of equipment to Statoil-operated
subsea wells on the Nor wegian continental shelf, and maintenance of
equipment on more than 500 wells and onshore. This includes wells
planned in developments of the Johan Castberg and Snorre Expansion
projects in the Barents Sea and North Sea.
Most of the onshore maintenance work will be at the Ågotnes Base
outside Bergen, and at the Polar Base in Hammerfest.
Aker Solutions’ services agreements, related to both bases, cover
subsea lifecycle services, including offshore installation and retrieval
of equipment, maintenance, engineering, and operations support.
Newton Labs, Ashtead collaborate
on subsea laser scanning project
Ashtead Technology has completed a subsea laser scanning project
for Subsea 7 on Chevron’s Captain field in the UK central North Sea.
It used Newton Labs’ M210UW and M3200U W subsea laser scanning
systems. Ashtead designed and engineered deployment tools that
allowed the scanning systems to capture accurate images at water
depths of 110 m (361 ft) using divers.
The program included an internal casing inspection and a horizontal
mapping survey to capture more than 100 short- and long-range scans.
This allowed Ashtead to generate a 3D model of the structure with
what the company claims was sub-millimeter accuracy.
This was Newton Labs’ first subsea project using its recently
launched M3200UW laser scanner, designed to operate with either
a scanning or a fixed laser line to measure underwater objects to
0.02 mm accuracy.
It is ROV or diver-operable, and fitted with a high-resolution camera,
allowing data to be streamed live, in real time. The scanner is also
said to provide detailed under water inspection and measurements by
means of optical triangulation. The projected laser line sweeps the
target surface and the high-resolution camera captures and records
the visual data to create a point cloud 3D model.
MacGregor to provide moorings
for Bangladesh FSRU
Summit LNG Terminal Co. has contracted MacGregor, part of
Cargotec, for the fabrication, engineering, and project management
of a complete subsea mooring and riser system. The MacGregor
system, which includes Flintstone mooring connectors, will serve
Summit’s floating storage and regasification unit (FSRU) in Bangladesh. Delivery is expected in 4Q 2018.
This order is part of a project to support Summit LNG Terminal’s
development of Bangladesh’s power-supply infrastructure. The FSRU
is expected to be ready for operation on the site during 1Q 2019. •
The shallow-water test in proved that the electronic
and power components can meet the thermal
performance demanded. (Image courtesy ABB)