Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Moldoveanu, N. Articles by Abriel, W. Search for Related Content GeoRef GeoRef Citation

Over/under towed-streamer acquisition

A method to extend seismic bandwidth to both higher and lower frequencies

Schlumberger WesternGeco, Houston, USA

Gary Hampson, Larry Sydora and William Abriel

Chevron, San Ramon, USA

Corresponding author: moldoveanu1{at}houston.westerngeco.slb.com

Seismic resolution of towed marine-streamer data is affected by free-surface reflections. They strongly modulate the spectrum reducing energy at the so-called notch frequencies, f_n = iv/2z {i = 0,1,...,}, in which v is the water velocity and z is the source or receiver depth. As a result there is a very strong loss of useful low-frequency energy and usually a similar loss at higher frequencies. The ghost effect occurs both at the source and at the receiver. At the source, the upgoing part of the source wavefield is reflected off the free surface with inverted polarity before its delayed journey into the Earth. At the receiver, the upgoing part of the receiver wavefield is reflected off the free surface with inverted polarity before it travels down to the receiver again. The over/under acquisition method allows separation of the up- and downgoing wavefields at the source (or receiver) using a vertical pair of sources (or receivers) to determine wave direction. In this article, we present the results of two experiments conducted in the Gulf of Mexico in 2004 and 2006 to investigate the use of over/under sources and receivers.