16 controllEd sourcE ElEctromagnEtic rEsonancE
places. Another issue encountered by the team related to
the use of the sparker array.
In the outer Mackenzie Delta the presence of plumes
of fresh river water had the potential to render the
sparker inoperable because of reduced conductivity.
However, luckily, only one recording interruption occurred
that was attributed to this phenomenon.
Tony Atkinson of the GSC confirmed that about
seven continuous days of surveying were carried out
successfully using the Applied Acoustics system. “Initially
power was held to 1500 Joules,” he said “because we
were unsure what the rate of wear would be for the
120 tip Squid. Although we were shooting on distance,
the fire rate was about three seconds. The array was
recovered once a day for inspection and it became clear
near the end of the job that tip wear was minimal, so
with nothing to lose, the sparker was fired at the full
Fig. 3. The 120-tip Squid Sparker array under tow in Halifax Harbour,
2400 Joules for the last day of the project. “
Nova Scotia, during trials in 2007.
“Initial processing of the Multi Channel Data is
Photograph: Geological Survey of Canada (GSC).
complete,” said Pat Campbell, CSR’s Beaufort Project
➠
interface from the ship’s Hypack navigation system. Manager, “we are currently interpreting and integrating
The CSP-D seismic power supply is one of a range the 2008 seismic data with previously collected data from
from Applied Acoustics which have a distinguished the area.”
record of performance, double layers of safety circuitry The subsea permafrost knowledge gained from this
and a valuable ‘soft start’ to gradually increase the study is important to those wishing to develop the area
power output easing the load on the generator. It also in future years. A second survey of Multi Channel seismic
has a unique dual voltage output providing exceptional and high resolution analogue data collection is planned
versatility with boomers as well as sparkers. for the summer.
“We have worked with the CSP seismic energy sources Having confirmed the signal to noise and resolution
from Applied Acoustics before for some inshore work,“ was a major improvement with this system compared
said Ray Burke, CSR’s Research & Development Manager, with earlier investigations, the goal in the follow-up
“so we were confident the unit would provide minimum survey will be for CSR to maintain the high power into
reverberation, consistent pulse shape clarity and good the Squid 2000 in anticipation of obtaining better
results,” he added. penetration.
The Beaufort Sea is generally shallow and sub-
bottom permafrost is known to occur out to a depth of
Subsea navigation
80metres. The study proved this area was no exception Applied Acoustic Engineering is a leading company in
with permafrost occurring as shallow as just 25metres in the design and manufacture of a wide range of subsea
navigation and positioning products, and marine seismic
survey equipment.
The extensive product range includes the innovative
USBL tracking system, Easytrak, a variety of positioning
and release beacons and seismic devices for offshore
geotechnical and seabed analysis known as sub-bottom
profiling.
All products use acoustics, underwater sound waves,
in location, positioning, navigation and data acquisition
applications.
Applied Acoustic Engineering will be exhibiting
Underwater Intervention, Location: New Orleans, USA,
between 17th–19th February 2010 and at Oceanology
International at the London Excel between 9th-11th
March 2010. l
Enter 16 or ✔ at www.engineerlive.com/ihss
Fig. 4. The Squid 2000 sound source on deck prior to deployment from
its catamaran, showing the clusters of sparker tips. Neil MacDonald is Technical Manager with Applied Acoustics,
Photograph: Geological Survey of Canada (GSC). Great Yarmouth, Norfolk, UK. www.appliedacoustics.com
www.engineerlive.com
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44