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25 July 2008 -
Fugro Provide Solutions for Devon Energy do Brasil
The decision to combine the teamwork of two leading Fugro companies
from Brazil and the USA will give Devon Energy do Brasil Ltda optimum
services in oceanographic current measurement in deepwater, on
their offshore Block BM-BAR-03, approximately 120 miles off the
northern Brazilian coast.
“The dynamics of the oceanography in this region can be challenging,”
explains Rosemary Smith, Senior Oceanographer. “The North Brazil Current
(NBC) and its subsurface component, the North Brazil Undercurrent (NBUC),
transport oceanic waters north westwards along the northern coast of Brazil
. Once north of the equator these currents feed a system of zonal counter
currents which flow eastwards. Large, anti cyclonic eddies (NBC rings) can
form from the North Brazil Current and propagate northwards. They are
thought to transport up to half of all the surface waters north westwards.
The NBC rings are of concern to drilling operations, as they are known to
cause strong currents that can lead to down time during drilling operations.
Devon identified a need to monitor these currents over a period of
12 months and the data provided by the two companies, Fugro Brasil
Ltda (Rio de Janeiro and Macae, Brazil) and Fugro GEOS Inc (Houston, USA
will primarily support operational planning for an exploration drilling
program.
Current measurement configurations will also provide data to support
the derivation of design criteria should the oil and gas prospect
develop further. Knowledge and understanding of currents, the underlying
water masses, and the interaction of wind and wave are all vital for
the design and safe operation of production systems and key offshore
oil and gas development components.
“To monitor these occurrences, a deep water mooring with multi oceanographic
instrumentation has been deployed in 2,525 meters of water. To date, the
mooring is one of our longest with service visits occurring once every four
months,” adds Paul Williams, Operations Manager. “Our Brazilian and Houston-based
companies, Fugro Brasil Ltda and Fugro GEOS Inc, provided the best possible
vessel service options to Devon. While vessel requirements for oceanographic
mooring deployment, servicing and recovery are of relatively short
duration, vessel availability has been in short supply. Thanks to the
efforts of Fugro Brasil Ltda a major issue of transportation was
effectively eliminated.”
With the approval of Devon, Fugro GEOS Inc ran the ultra long mooring requirements
through design software using a current profile based on existing data near the
north of the BM-BAR-3 location. The analysis identified potential problems
with mooring ‘knockdown’ due to the impact of the currents on the mooring string.
Moorings typically consist of instruments suspended on a taut wire, anchored to
the seabed by a clump weight. Knockdown can affect the quality and integrity
of the measured data if it is not minimized. In environments like the north of
Brazil, it is impossible to design a mooring that will suffer no knockdown, but
it is possible to minimize the effect.
To mitigate the chances of knockdown, the use of plasma rope was selected to support
the mooring, rather than the more commonly used wire rope. Plasma rope is buoyant
unlike wire rope and requires far less inline floatation thereby reducing the
knockdown effect. It is also stronger and does not suffer corrosion.
An additional component to the study program requested by Devon Energy do Brasil
was a vessel mounted ADCP (VMADCP) currents survey and CTD profiles over the
study area. This survey, conducted following the mooring deployment, involved
running a number of survey lines using an ADCP to map the current features in
real-time. These data provide spatial detail of the current features in the
upper layer of the water column. A deepwater rated CTD is used to collect
full water column conductivity (salinity) and temperature profiles at key
locations. These data provide valuable information on the water column
structure and the various water masses that are causing the observed circulation
patterns.
The rapid accomplishment of the first phase of the project has been significant.
After the seamless mooring deployment the survey report was compiled within just
five days. The graph below shows some of the observations.
“Fugro Brasil Ltda and Fugro GEOS Inc, understand the processes and circulation
features involved at the location,” explains Paul Williams. “Jointly we continue
to advise Devon scientifically of what to expect. Knowledge of observed situations
from the ocean environment is vital to operations but so is teamwork between the
two Fugro companies, to ensure total client satisfaction. We look forward to
more successful collaboration with Devon Energy do Brasil in the future.”
Further information on Fugro Brasil Ltda is available www.fugro-br.com and on Fugro GEOS Inc from www.geos.com
For further information, please contact:
Rob Smith
VP Sales & Marketing – Fugro GEOS Inc
Paulo Martins
Sales & Marketing Director - Fugro Brasil Ltda
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