4D fixED inStAllAtion SEiSmiC 23
'Coil shooting' method improves
imaging of complex geology
Fig. 1.
‘Coil shooting’ is a new Geostreamer is
single-vessel method
the first ever
for acquiring seismic
towed streamer
data over a wide range
to successfully
of azimuths to improve
house both
imaging of complex
geology. Jeremy
pressure and
Cresswell reports.
velocity sensors,
thereby
delivering
“Coil Shooting” enhanced
ist ein neues
resolution and
Einzelschiffverfahren
deeper
zur Erfassung
penetration to
seismischer Daten
provide a higher
über einen breiten
Azimuthbereich, um
quality
die Bildgebung in der
de-ghosted
komplexen Geologie zu
seismic image.
verbessern. Ein Bericht
von Jeremy Cresswell.
El último método
empleado en los
buques monocasco
para obtener datos
sísmicos son los
‘disparos en espiral’
sobre una amplia A
ccording to WesterGeco ‘coil patterns used for some of the work, notably in
shooting’ is a cost-effective the Oseberg field. The objective was to acquire
technique towards better imaging a wide range of azimuths in order to better map
over small to medium sized and characterise the subsurface. But then it fell
gama de azimut, para exploration areas. And the company claims that out of favour, a major reason being the inability of
mejorar las imágenes
‘encouraging results’ may lead to a significant marine acquisition technologies used at that time
de yacimientos
uptake of the technique over the next five or so to accurately position and steer streamer arrays.
geológicos complejos.
years. Basically, coil shooting is a new single- In 2006 WesternGeco revived the idea for 3D
Jeremy Cresswell
informa.
vessel method developed by the company Geco full-azimuth acquisition and the key was its then
for acquiring seismic data over a wide range of groundbreaking Q-marine technology. Steering
azimuths to improve imaging of complex geology. devices, such as Q-Fin could be used to control
By sailing in overlapping circles, a very large the position of the streamers, making it possible
number of shot/receiver positions can be created to maintain constant streamer separation while
and a single source/receiver boat can produce the vessel sailed a circular trajectory. At the
unprecedented offset and azimuth sampling same time, receiver positions could be accurately
which leads to higher quality images with measured.
superior noise suppression. Typically, this might According to WesterGeco, the first field test of
involve an array of 10 seismic and precision- the coil shooting technique was performed during
steering them through a sequence of large 2007 in the Gulf of Mexico. The first commercial
continuously linked circles, 5–7 km in radius. survey using circle shooting was acquired for
The idea is not new as early trials based on Eni in July 2008 on the Tulip project offshore
circular acquisition geometries were tried during Indonesia. The 563 sq.km survey, using with eight
the 1980s for improved imaging of circular streamers, each 6km long, separated by 100m,
shaped salt dome flanks and associated faulting was completed in 49 days. Another milestone
in the Gulf of Mexico and in the North Sea. was a coil shooting trial in the deepwater and
The techniuque was also used when 3D VSP geologically challenging Kozlu sector of the Black
surveys came to the fore, with circular shooting Sea over acreage held by the Turkish National
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