in height between the dock and the barge
deck. Small compared to the height of the
structure (95m), but any mismatch could
cause it to topple and collapse when being
pulled onto the barge. The whole mission
would have been compromised if the tides
floated the barge higher or lower than the
dock by more than 25mm. With the help of
electronic sensors and a senior controller
with over six years experience to adjust
the water flow and the subsequent weight
of the barge, the megastructure was
successfully loaded aboard and set off to
the South China Sea.
SHALLOWWATER danger
In August 2012, the lower supporting part
of the central platform was placed in the
sea. The difficulties in locating a 190m tall
and 32,000 ton megastructure at a specific
spot in the water appeared tough, but
compared to the ensuing challenges, this
operation was a mere warm-up.
Once the topside megastructure arrived, a
new challenge presented itself – how would
engineers load it onto the lower part of
the central platform? The upper structure
was equivalent to the combined weight of
five Eiffel Towers and there was no single
floating crane in the world able to lift such
a heavy object.
One alternative would have been to break
the structure into smaller components
and to then assemble it piece by piece.
While this sounded feasible, it would have
required a much longer time to finish the
construction of the central platform and
meant risking a delay to the project. The
whole project cost over HKD3 billion.
Delaying it would have resulted in an
astronomical rise in costs, ranging from
several hundred thousand dollars to
several million dollars a day in extra
expenses.
Under pressure
While engineers were struggling with
problems on the surface of the ocean, the
conditions deep under the sea presented
Husky Energy with huge challenges.
The company was responsible for the
underwater operations, but with the
immense pressures and temperatures
close to freezing, the sea was a hazardous
place to work. At 1,500m deep, equivalent
to 30 Olympic-size swimming pools (50m)
laid end to end, an area equivalent to a
standard credit card experienced six tons
of force. This was no place for man to
thrive – or even survive.
“Principally, our golden rule is safety
first,” says Mr Malcolm Paisley, Manager
of Deepwater Production, Husky Energy
China. To live by this principal, Husky
Energy deployed robotic devices called
remote operative vehicles (ROVs) to
work in the depths of the sea. They had
to install all the machinery on the seabed,
and were operated by Husky Energy
engineers working at a control panel
1,500m above. “In a marine environment,
the ROV is often the eyes, the hands
and even the ears of the people that are
designed to do the work,” says Mr Tracy
Mosness, Vice President of Production
and Development, Husky Energy China.
Monitoring well-top conditions is vital.
Husky Energy built devices right on top of
the drilling wells to monitor and control
the production of the wells. These devices,
each weighing 60,000 tons, were attached
to the wells on the seabed by the ROVs.
These devices ensured that the gas
continued to flow and could begin its
journey from wellhead to the central
platform. That journey of 79km takes
the natural gas a day, owing to the low
temperature and extremely high water
pressure. At that depth, temperature and
pressure, chemicals can materialise that
physically block the pipes. Husky Energy
uses not only engineering expertise, but
also chemical engineering to ensure that
doesn’t happen.
Innovation ...
Back on the surface, engineers were
grappling with the challenge of installing
the central platform that would connect
the deep-sea world to the surface.
The engineers decided to make use
of a natural force – tides. They used a
technique known as ‘float-over deck
installation’. This was precision work
with no room for error.
This complex process required the upper
part of the structure on the barge to be
placed on top of the lower part of the
structure when the tide rose. When the
tide fell, the lower water level allowed the
upper part of the structure to attach to
The depth of the sea and the
extreme weather presented
Husky Energy engineers with
challenges never before faced
in the South China Sea.
Sphere
#35
2014
24
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Think Big: Liwan Gas Fields
