By Dave Fratantoni, Andre Gellers, and Neha Sharma

1. On the Oceanography of
Brazil’s Equatorial Margin:
Hazardous Offshore Currents
and Strategies for Mitigation
Dave Fratantoni, Andre Gellers, and Neha Sharma
Horizon Marine, Inc.
Massachusetts, USA

2. Conclusions
• Brazil’s Equatorial Margin has both extraordinary development
opportunities and significant operational challenges.
• Strong and variable ocean currents are a primary concern.
• Exchange between blue-water and coastal regimes is poorly
Image Image
understood.
• A regional ocean observing and prediction system can provide
improved situational awareness to mitigate the impact of strong
currents on offshore operations, enhance safety, and protect the
environment.

3. Outline
• Geographic Context and Operational Challenges
• Oceanographic Environment
• Strategies for Mitigation

4. Image
Geographic Context
BEM potential may be
similar to West Africa
Zaedyus find in
French Guiana is
encouraging
Coastline is extensive,
sensitive

6. Total
Quieroz Galvao
BP
BHP Billiton
Quieroz Galvao
BG
BP
OGP
BHP Billiton
ExxonMobil
Chevron
BP
OGP
BHP Billiton
OGP
Ecopetrol
ExxonMobil
Petrobras

10. • Tides and tidal currents
• River outflow
Intense, persistent, and
vertically-complex
boundary current
Sensitive habitats

11. • Tides and tidal currents
• River outflow
Intense, persistent, and
vertically-complex
boundary current
Sensitive habitats

12. Operational Challenges
Image
ENSCO 8503
Tullow
French Guiana
• Remote location
• Extensive coastline with
sensitive ecosystems
• Strong and variable ocean
currents
• Poorly understood
connections between
offshore and coastal
regimes
Holding station
with 90% thrust

13. Oceanographic Environment
Image

14. SeaWiFS Ocean Color
Image
Satellite observations are descriptive – but not always quantitative.

15. 12 years of surface drifter trajectories (n=450)
Color = Current Speed

16. Image
Why surface drifters?
• Direct measure of surface
velocity, exchange processes
• Analog for anything drifting at
the ocean surface
• Excellent for model validation
• Easy to deploy from a variety of
platforms
• Inexpensive  robust statistics

17. Image
Histogram of all drifter-derived current
measurements in each BEM region

18. Average measured
current speed as a
function of WATER
DEPTH
Gray dots are all
measurements

19. Average measured
current speed as a
function of WATER
DEPTH
Gray dots are all
1000 m measurements

20. 1/3-deg Gridded log(NDATA)
Number of hourly velocity
estimates from drifter
position record

21. 1/3-deg Gridded Current Velocity

22. Image
Numerical Ocean Model
VELOCITY (kts)

23. Models are ALWAYS wrong

24. Models are ALWAYS wrong

25. Models are ALWAYS wrong
Models can be useful if constrained
and validated by observations
We must know HOW the model is
wrong, and WHEN it can be trusted

26. Strategies for Mitigation
To mitigate the impact of strong ocean currents and
operate successfully in the equatorial margin we
require enhanced situational awareness, specifically:
• Accurate measurement of currents TODAY
• Accurate forecast of currents TOMORROW

27. A regional observation and prediction system
Observations Model Forecast

28. A regional observation and prediction system
Image
• In-situ measurements of ocean currents
• Inexpensive
• Sustainable
• Spatially diverse
• Family of appropriate numerical models
• Global and regional blue-water ocean models
• Coastal models with accurate tidal and river forcing
• Local oil spill models for incident response

29. A regional observation and prediction system
• Seismic Survey
• Engineering Design
• Installation
• Diving
• ROV Operations
• Pipelaying
• Incident Response

30. Observation System Status: 18 Sep 2014

31. Observation System Status: 18 Sep 2014

32. Observing System Summary
• Surface drifters have been deployed
in the BEM about every two weeks
since July 2014
• Surveys utilizing expendables (CTD,
SV, CP) expected to begin in early
2015
• Regional 1/32o model run daily –
working on drifter data assimilation
• Interpretive reports generated weekly

33. Conclusions
• Brazil’s Equatorial Margin has both extraordinary development
opportunities and significant operational challenges.
• Strong and variable ocean currents are a primary concern.
• Exchange between blue-water and coastal regimes is poorly
Image Image
understood.
• A regional ocean observing and prediction system can provide
improved situational awareness to mitigate the impact of strong
currents on offshore operations, enhance safety, and protect the
environment.
• A prototype observing and prediction system is operational TODAY

34. Image
Thank you
Dr. David M. Fratantoni
Horizon Marine, Inc.
Massachusetts, USA
dave@horizonmarine.com
Mr. Andre Gellers
Horizon Marine do Brasil
Rio de Janeiro, Brasil
andre@horizonmarine.com