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. Image Image
Conclusions
• 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.

3. Outline
• Geographic
Context
and
Opera;onal
Challenges
• Oceanographic
Environment
• Strategies
for
Mi;ga;on

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

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
;dal
currents
• River
ouQlow
Intense,
persistent,
and
ver;cally-­‐complex
boundary
current
Sensi;ve
habitats

11. • Tides
and
;dal
currents
• River
ouQlow
Intense,
persistent,
and
ver;cally-­‐complex
boundary
current
Sensi;ve
habitats

12. Operational Challenges
Image
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

13. Oceanographic Environment
Image

14. SeaWiFS
Ocean
Color
Image
Satellite
observa;ons
are
descrip;ve
–
but
not
always
quan;ta;ve.

15. 12
years
of
surface
dri/er
trajectories
(n=450)
Color
=
Current
Speed

16. Image
Why
surface
dri/ers?
• 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

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

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

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

20. 1/3-­‐deg
Gridded
log(NDATA)
Number
of
hourly
velocity
esAmates
from
dri/er
posiAon
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
observa;ons
We
must
know
HOW
the
model
is
wrong,
and
WHEN
it
can
be
trusted

26. 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

27. A regional observation and prediction system
Observa;ons
Model
Forecast

28. A regional observation and prediction system
Image
• 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

29. A regional observation and prediction system
• Seismic
Survey
• Engineering
Design
• Installa;on
• Diving
• ROV
Opera;ons
• Pipelaying
• Incident
Response

30. ObservaAon
System
Status:
18
Sep
2014

31. ObservaAon
System
Status:
18
Sep
2014

32. Observing System Summary
• 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

33. Image Image
Conclusions
• 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

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