CONTROLLED SOURCE ELECTROMAGNETIC RESONANCE
Efficiency drives in a recovering market
After a period of major belt tightening in 2009 we find ourselves at mid-2010 with the marine seismic exploration market showing global activity increasing month-on-month. Neil Grosse reports.
W
hat a difference a year makes. Rising like a phoenix from the ashes of last year, we expect the
exploration industry of 2010 to strive for ever increasing efficiencies to cope with the still volatile market conditions. A number of key technology areas merit
attention for their potential contribution to improved efficiency of acquisition and enhancements to the quality of acquired geophysical datasets. Firstly, new streamer technologies have
already demonstrated their capabilities and will continue to do so. Dual sensor streamer technology pioneered by PGS with GeoStreamer provides an elegant solution to the limitations imposed by the free-surface ghost effect.
Fig. 1. PGS vessel Ramform Valiant deploying source array and streamers. Photograph: Petroleum Geo-Services
In this effect, energy reflected back with reverse polarity from the sea surface results in attenuation in the frequency spectrum which is dependent on the streamer depth.
Improved frequency content Shallow towed conventional streamers favour higher frequencies at the expense of low, whereas deep tows favour lower frequencies while notching at frequencies within the seismic bandwidth. However, collocating particle velocity sensors with the conventional pressure sensors in dual sensor streamers allows the two signals to be combined during processing and as there is no polarity reversal from the sea surface reflection for the velocity measurement, this combination
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