AAPG Explorer - American Association of Petroleum Geologists

AAPG
EXPLORER
Play Fairway study available for free
400-KM Integrated Dataset Used in Study
By SUSAN R. EATON, EXPLORER Correspondent
Aeromagnetic, gravity and reflection
seismic data were integrated with
refraction seismic data – on both
conjugate margins of the North Atlantic –
to unravel the Scotian Margin’s history of
rifting and drifting.
In 2009, deploying
100 multi-component
ocean bottom
seismometers, the
group acquired a
400-kilometer-long
refraction seismic
line across the
Scotian Basin and
the northeastern end
WILSON
of the East Coast Magnetic Anomaly
(ECMA), a pronounced feature previously
thought to delineate the northern limit of
the basin’s rift footprint.
The refraction line, shot in a dip
orientation, imaged the Moho at an
estimated depth of 40 kilometers.
Investigators noted the existence of
seaward dipping seismic reflectors along
the entire Scotian Margin and across the
Atlantic Ocean, in Morocco, suggesting
the margin’s volcanic origin – and they
interpreted a high velocity feature on
the 2009 refraction line, pointing to the
existence of a continuous, “under-plated
body.”
In other words, the ECMA doesn’t
terminate because of reduced volcanic
activity – rather, its magnetic signature is
masked by an increased thickness of the
overlying sedimentary package.
But what does this tectonic analysis
mean for oil and gas exploration?
Geologists say it confirms that a
volcanic margin runs along the entire
length of the Scotian Basin to the
southern Grand Banks, setting up a
broad tectonic and depositional fairway
for the development of an extensive
Lower Jurassic source rock.
12 JULY 2011 WWW.AAPG.ORG
Courtesy of OETR, Offshore Energy Technical Research Association, Halifax, Nova Scotia
An excellent 3-D image of the Autochthonous salt basin of the Scotian Basin.
‘Bonanza’ Potential
Integrating all of these diverse data sets
was a monumental task undertaken by
Paris-based Beicip-Franlab – the data were
fed into a 3-D petroleum systems modeling
package, leading to a predictive basin
model for petroleum reservoir facies, source
rocks and seals.
The model calculated both qualitative
and quantitative hydrocarbon volumes and
associated risk factors for each of the six
geographical zones, tripling the yet-to-find
resource estimates (121 Tcf of natural gas
and eight billion barrels of oil) for offshore
Nova Scotia in the process.
The study’s final compilation, a Play
Fairway Atlas consisting of 300-plus plates,
is available for free to industry (www.
novascotiaoffshore.com).
“An oil company can take the Atlas and
start prospecting in the basin with the 10
horizons that are internally consistent and
rigorously checked,” said AAPG member
Hamish Wilson, program director of the PFA
study and principal advisor with RPS Energy
Ltd., Henley-on-Thames, England.
“We set out to find reasons why the
oil industry should come back to Nova
Scotia,” Wilson continued, pointing to global
competition in “hot” exploration areas on the
West African conjugate margin. “We thought
we might have to try to make a silk purse out
of a sow’s ear.”
But based on the study’s results, Wilson,
like others, is bullish about the area’s
potential.
“I believe that our optimism is warranted,”
he said. “There’s a rigorous science
underpinning this Play Fairway Analysis.
“There’s clearly a play risk here,” he
continued, “but the seismically mapped
structures are big enough, and there’s
source rock.
“If it works, it’s a bonanza for Nova
Scotia.” EXPLORER