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the industry bar in on-platform radio
communications, by specifying 100 per
cent RF coverage of all platform operations
and maintenance areas.
Up to 2001, Petrobras had used a
‘passive repeater’ system to distribute
the 450 MHz production and maintenance
communications band about the platforms.
This involved a network of antennas
located across each of its platforms to
distribute and re-distribute the signal. “It
was a success in some areas, but not in
others,” Cumin explains. “So we
approached Radio Frequency Systems for a
system guaranteed to achieve 100 per cent
coverage.”
group in its Sao Paulo centre, Amauri Soares,
concurs with Dorst’s view, and cites the
dense-packed nature of RF reflection and
attenuation objects on each platform as a
further challenge. “The platforms are all
unique—they are all different,” he says.
“Each deck area can measure as much as 120
metres by 100 metres in area, with the deck
crammed with metal machinery and rooms.
There are many people moving about on the
platform as well—often up to 110 personnel.
The combination of the RF reflections caused
by the metal objects, coupled with the
prospect of RF ‘fades’ (caused by personnel
as they move about the decks) makes for a
challenging design environment!”
Unique structures
The project entailed innumerable
challenges, not the least being the wide
variety of platform structures that RFS
had to address. In addition to Petrobras’s
more conventional fixed platforms, it also
requested RFS address RF communications
on its two deepwater structural innovations:
the ‘floating production storage and offloading’
(FPSO) and the ‘semi-submersible’
platforms. The FPSO is essentially a ship fitted
out for drilling and product storage, and
long-term at-sea location at the well site. The
‘semi-submersible’, on the other hand, is a
floating drilling unit fitted with pontoons and
columns that, when flooded with
seawater, cause the structure to submerge to
a predetermined depth. Both the FPSO and
the semi-submersible are moored to the
seabed at the drilling location, and
connected to the well by flexible risers.
“What was interesting here, is that these
structures really demanded a hybrid
approach to the RF design,” explains RFS’s
Vice President of Americas Wireless
Distributed Communications Systems (WDCS),
Ron Dorst. “The buildings on the multideck
platforms are essentially similar to
high-rise building structures. The columns
and pontoons of the semi-submersibles, on
the other hand, have much more in common
with the many rail and road tunnels and
metros that RFS has worked on throughout
the world. So what we’ve had to do is
combine our know-how from the road and
rail sector with that of in-building, to come
up with the optimal oil platform solution.”
Chief designer with the RFS WDCS design
From prototype to project
The solution proposed by Soares and his
team was based on realizing ‘contoured’
RF coverage, tailored to achieve 100
per cent coverage of the operations and
maintenance points on each of the
Petrobras platforms. RFS’s Stationmaster II
omnidirectional antennas were proposed to
achieve RF coverage in the open outdoor
deck areas, while a network of RFS
point-source omnidirectional indoor
antennas were suggested for the platform’s
closed deck areas. In these areas, the RF
signal would be distributed via power
dividers and directional couplers to ensure
balanced coverage to all points.
Feeder connections to each RF device
would be achieved via RFS’s CELLFLEX
foam-dielectric coaxial feeder cable. For
the more tunnel-like areas of the
platforms, such as the semi-submersible’s
columns, pontoons and submarine deck,
RFS proposed using its world-renowned
RADIAFLEX RCF series broadband radiating
cable to provide homogeneous RF
distribution.
On the basis of this proposal, Petrobras
commissioned RFS in 2002 to develop a
prototype system for the first of these
platforms, an exploration drilling rig known
at P23. “This was the first to use RFS’s
distributed RF approach,” explains
Petrobras’s Cumin. “The P23 prototype
proved a success. The main gains [on
this platform] related to the speed of
communications and the assurance that
every part of the platform was covered.
For example, if you have to close a valve for
Petrobras’s platform P25 is a semisubmersible
platform located in the
deep waters surrounding the
Campos Basin’s Albacora oil field.
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