American Oil and Gas Reporter - May 2015 - 79

SpecialReport: Study In Geophysics
Data Harvesting
A key seismic surveying goal is to
deliver data to processing as quickly and
reliably as possible. But with the move
away from cabled surface systems in
North America, achieving this goal has
been a challenge, says Ellis, because
nodal systems typically allow access to
the seismic data only when the field
recording units are retrieved physically.
However, fast data retrieval is possible.
"One of our clients collected the data,
uplinked to a satellite, downlinked to its
Houston processing center, did some
initial processing, and then bounced it
back to the field within a couple minutes,"
describes Ellis.
This approach enables the people controlling the frac to make decisions in
very close to real time, even in a cablefree environment. "At the very least, the
data could influence the next stage and
conceivably even the current stage," reflects Ellis.
Look, too, for more companies to
equip all their acquisition-related vehicles

with wireless data harvesting, he ventures.
"High-speed data harvesters can be placed
in any vehicle, right down to the vehicle
that drives the crew to the field," Ellis
advises.
He says the driver turns it on before
leaving camp, and the system automatically harvests data throughout the day.
Harvesters have a range of up to one
kilometer, and typically are downloaded
at the end of the day.
"Nodal-based surveys are faster to
completion than cabled surveys, but the
time savings has been lost to organizing
the data at the end of acquisition," says
Ellis. "Opportunistic harvesting kickstarts processing and quality control,
shortening the time to deliver the final
dataset to the interpreters."
Geophysical Forensics
Reprocessing older seismic data can
provide significant new insight into regional trends, says Mark Gresko, director
of geology and geophysics at ION Geophysical. Modern processing techniques
often add greater detail and more accurate

placement of subsurface features.
Gresko, who has a Ph.D. in geophysics
from the Virginia Polytechnic Institute
and State University, says these techniques
do a better job of removing multiples
and attenuating noise. Key algorithms
for prestack time and depth migrations
improve image quality and resolution. A
wide band process brings back frequencies
that previously were suppressed, he says.
Together, he suggests, these new techniques bring more detail and reliability
to the data.
One challenge in properly reprocessing
older data is understanding the conditions
and real positioning of the original survey,
which Gresko refers to as geophysical
forensics. Survey design and acquisition
have a strong effect on the data collected,
he notes.
Another obstacle in reprocessing older
datasets is obtaining the data themselves.
"Often, these surveys were stored on tape
media," points out Gresko. "Media degrades, can be problematic to access, and
sometimes simply are lost."
On top of that, he says the original

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American Oil and Gas Reporter - May 2015

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