on the oceanography of brazil’s equatorial margin: hazardous offshore currents and strategies for...

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

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•  Brazil’s Equatorial Margin has both extraordinary development opportuni;es and significant opera;onal challenges.

•  Strong and variable ocean currents are a primary concern.

•  Exchange between blue-‐water and coastal regimes is poorly understood.

•  A regional ocean observing and predic;on system can provide improved situa;onal awareness to mi;gate the impact of strong currents on offshore opera;ons, enhance safety, and protect the environment.

Conclusions

Outline

•  Geographic Context and Opera;onal Challenges •  Oceanographic Environment

•  Strategies for Mi;ga;on

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Geographic Context

BEM poten;al may be similar to West Africa Zaedyus find in French Guiana is encouraging Coastline is extensive, sensi;ve

Total Quieroz Galvao BP BHP Billiton

Quieroz Galvao

BG BP OGP BHP Billiton

ExxonMobil Chevron BP OGP BHP Billiton

OGP Ecopetrol ExxonMobil Petrobras

•  Tides and ;dal currents •  River ouQlow

Intense, persistent, and ver;cally-‐complex boundary current

Sensi;ve habitats

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Operational Challenges ENSCO 8503 Tullow French Guiana

•  Remote loca;on

•  Extensive coastline with sensi;ve ecosystems

•  Strong and variable ocean currents

•  Poorly understood connec;ons between offshore and coastal regimes

Holding sta;on with 90% thrust

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Oceanographic Environment

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SeaWiFS Ocean Color

Satellite observa;ons are descrip;ve – but not always quan;ta;ve.

12 years of surface dri/er trajectories (n=450)

Color = Current Speed

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•  Direct measure of surface velocity, exchange processes

•  Analog for anything dri]ing at the ocean surface

•  Excellent for model valida;on

•  Easy to deploy from a variety of plaQorms

•  Inexpensive à robust sta;s;cs

Why surface dri/ers?

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Histogram of all dri]er-‐derived current measurements in each BEM region

Average measured current speed as a func;on of WATER DEPTH Gray dots are all measurements

Average measured current speed as a func;on of WATER DEPTH Gray dots are all measurements 1000 m

1/3-‐deg Gridded log(NDATA)

Number of hourly velocity esAmates from dri/er posiAon record

1/3-‐deg Gridded Current Velocity

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Numerical Ocean Model VELOCITY (kts)

Models are ALWAYS wrong

Models are ALWAYS wrong Models can be useful if constrained and validated by observa;ons We must know HOW the model is wrong, and WHEN it can be trusted

Strategies for Mitigation

To mi;gate the impact of strong ocean currents and operate successfully in the equatorial margin we require enhanced situaAonal awareness, specifically: •  Accurate measurement of currents TODAY

•  Accurate forecast of currents TOMORROW

Observa;ons Forecast Model

A regional observation and prediction system

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•  In-‐situ measurements of ocean currents •  Inexpensive •  Sustainable •  Spa;ally diverse

•  Family of appropriate numerical models •  Global and regional blue-‐water ocean models •  Coastal models with accurate ;dal and river forcing •  Local oil spill models for incident response


•  Seismic Survey •  Engineering Design •  Installa;on •  Diving •  ROV Opera;ons •  Pipelaying •  Incident Response


ObservaAon System Status: 18 Sep 2014

•  Surface dri]ers have been deployed in the BEM about every two weeks since July 2014

•  Surveys u;lizing expendables (CTD, SV, CP) expected to begin in early 2015

•  Regional 1/32o model run daily – working on dri]er data assimila;on

•  Interpre;ve reports generated weekly

Observing System Summary

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•  Brazil’s Equatorial Margin has both extraordinary development opportuni;es and significant opera;onal challenges.

•  Strong and variable ocean currents are a primary concern.

•  Exchange between blue-‐water and coastal regimes is poorly understood.

•  A regional ocean observing and predic;on system can provide improved situa;onal awareness to mi;gate the impact of strong currents on offshore opera;ons, enhance safety, and protect the environment.

•  A prototype observing and predicAon system is operaAonal TODAY

Conclusions

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Thank you

Dr. David M. Fratantoni Horizon Marine, Inc. Massachusejs, USA [email protected]

Mr. Andre Gellers Horizon Marine do Brasil Rio de Janeiro, Brasil [email protected]