American Oil and Gas Reporter - July 2022 - 44

Acquisition Technologies
Expand Capabilities, Quality
Of 3-D Seismic Surveys
By Kari Johnson
Special Correspondent
Major changes are afoot for geophysics.
High oil and natural gas prices and geopolitical
risks have caused many around
the world to rethink the present energy
situation as well as the continuing crucial
role for oil and gas in the future.
Outside of the United States, geophysical
surveys are imaging conventional oil
reserves from Latin America to Asia and
the Middle East. In America, the industry's
transition to unconventional resource plays
has had major impacts on the role of geophysics
in field development. This generally
has involved a shift from the conventional
realm of using large-scale 3-D surveys to
guide drilling decisions to more targeted
applications that aim largely at optimizing
horizontal well spacing and completion
designs in resource plays.
With operators in major shale basins
increasingly concentrating on infill development,
experts say geophysics' application
in well placement and completion
engineering workflows will continue to
expand. However, that is not to suggest
conventional development is off the table.
Strong commodity prices are making all
types of conventional geology more economically
attractive. In the heartland, for
instance, small independents are finding
sufficient payback on shooting focused
3-D surveys in the search for carbonate
oil traps. At the same time, geophysical
companies report they are advancing technology
to be more versatile across industries,
including future carbon capture
and sequestration projects.
" The growth of U.S. oil and gas markets
over recent years was driven by shale
and fracturing, with blanket drilling programs
targeting formations considered
homogeneous enough to forego seismic, "
says Robin Ellis, Sercel's vice president
of sales and marketing. " As these areas
mature, seismic can help target remaining
sweet spots that are economic with higher
oil prices. "
Innovation in seismic acquisition
technology has continued, with the move
toward wireless nodal systems and lowfrequency
recording. Nodal systems
offer more flexibility than cable-based
systems and are well suited for many
geographic settings and terrain conditions,
says Ellis.
Low-Frequency Data
Growing interest in full-spectrum
broadband capture has led to the development
of vibrator trucks that can create
frequencies down to 1.0-1.5 Hz. This, in
turn, has prompted a need for better
sensors for low-frequency signal detection,
says Ellis. Having multiple octaves increases
final resolution, creating a much
sharper image with reduced noise and
maximum signal strength.
To record low frequencies, Sercel has
developed a new digital sensor that replaces
moving coil geophones. This thirdgeneration
QuietSeis®
band digital sensor measures frequencies
as low as 1 Hz and up to 400 Hz, he reports.
The sensors are integral to the
Sercel WiNGNT
Nodal system.
" Sensor sensitivity is related to the
After completing a seismic survey for the world's largest carbon capture storage project
earlier this year in North Dakota, Paragon Geophysical Services is preparing to launch
new 3-D acquisition programs in Oklahoma, Wyoming and Montana, and resume ongoing
surveys in southern Nebraska and Kansas.
44 THE AMERICAN OIL & GAS REPORTER
alloy spring and copper coil windings, "
explains Ellis. " When geophones were
deployed in strings, variation introduced
in manufacturing would be cancelled out.
Now with single geophones, variations
in manufacturing impact recorded phase
and amplitude with even the best manufacturing
process. "
The biggest variations occur at low
frequencies. Sercel tested a line of 5-Hz
cabled geophones side-by-side with WiNG
nodes with micro electromechanical systems
(MEMS) sensors. " The variation
was quite appreciable, " Ellis states. " Traditional
geophones introduced fuzziness
or what we call data jitter that was clearly
visible on processed time slices. "
A MEMS sensor is not susceptible
to data jitter because it is built like a
semiconductor from small silicon wafers.
An etching process replaces manual
winding and springs, Ellis describes.
" QuietSeis takes accuracy to a whole
different level. Devices are identical for
all intents and purposes. We believe in
it enough that all new products have
MEMS sensors, " he relates.
ultrasensitive broad
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