COWI , Denmark

An ingenious land streamer has been devised by Dr. Carsten Ploug at COWI in Lyngby, Denmark. Dr. Ploug worked with Pro-Seismic to develop his streamer which consists of self-orienting gimbaled phones.  The 200 m long streamer is equipped with 95 geophones, separated 1.25 to 2.5 m along the cable. The differentiated geophone spacing with short spacing close to the vibrator facilitates improved data quality in the shallowest part of the subsurface while achieving the ability to acquire data from more than 1 km in depth due to the 200 m maximum offset.

The land streamer is primarily developed for deployment on paved roads. The gimbaled geophones are, however, towed off the main streamer on drop leads, facilitating data collection on dirt roads as well, because it allows each geophone to rest on more stable ground before each record is taken. In addition to the cost-effective advantage of the land streamer system, acquisition on public roads does not require special permitting to cross private or restricted areas.

Wood blocks level streamer on pavement and reduce wear

Dr. Ploug utilizes an IVI MiniVibe II for both towing the streamer and as the energy source. Geometrics Geodes are used for recording the data and for correlating in real time. High-speed hardware correlators are included is each box and any number of channels can be correlated in less than 1 second. The smaller correlated data sets speed data transmission back to the host PC (in this case a laptop computer), so many more shots can be taken each day. An unstack feature allows noisy shot to be rejected and repeated without significant loss of survey efficiency.

It is hard to argue with the quality of  Dr. Ploug's data. Shown here is a stacked CDP section with frequencies in excess of 100 hz and penetration to over 1.0 second. Data were taken in Denmark in southern Jutland as part of a study to map deeply buried groundwater aquifers.

More than 150 km seismic acquisition in 2002 is a testament to the reliability of the COWI system. Dr. Ploug and his system are available world-wide for consulting and data collection. The total seismic system includes the MiniVibe II and land streamer concept as well as a distributed system with Geometrics Geodes and traditional seismic cables and geophones. The entire system is packed in a 40 feet container which may be shipped world-wide. Contact: Dr. Carsten Ploug, cpl@cowi.dk, +45 4597 1469.

Processed section from data collected with the COWI streamer yields high frequencies

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