Within the past decade, exploration technology advances have really ramped up. One area that has seen vast improvement is the area of marine seismic acquisition, and it was there that Society of Exploration Geophysicists Honorary Lecturer Nick Moldoveanu chose to devote his 2013 lecture.

Titled “Evolution of marine acquisition technology after wide azimuth,” Moldoveanu’s lecture examined some of the amazing acquisition breakthroughs that have taken place since BP shot the first wide-azimuth survey on its Mad Dog field in 2006. But what I found most intriguing was his list of “coming up next” technologies that are not that far in the future.

Moldoveanu noted that the airgun, invented in 1960, has never been the ideal marine source due to issues in reliability; lack of power; and narrow bandwidth, particularly at lower frequencies. To date, only the reliability issue has been addressed.

He said that acoustic energy generated by airguns is quite weak – below 6 Hz to 7 Hz. These frequencies are important for deeper penetration and imaging of steep dips, for better inversion, for improved vertical seismic resolution, and for velocity model-building based on full waveform inversion.

It also would help to have a more environmentally friendly source. The high frequencies that the airguns emit are within the hearing range of marine mammals that communicate at these frequencies, and it has been suggested that these guns could harm hearing or affect feeding and mating cycles. Bolt is currently designing an airgun with a limited high-frequency output.

Another breakthrough would enable simultaneous source shooting in towed-streamer surveys. Simultaneous source shooting is already used on land and is becoming more widely used with ocean-bottom and node technology, but it’s a challenge with marine streamers. It requires more source arrays, meaning more source vessels with a dual source array on each vessel and larger separation between arrays in the crossline direction. It also requires continuous recording, source encoding to minimize the crosstalk between seismic sources, and accurate amplitude processing for time-lapse and reservoir characterization studies.

Another interesting approach is a marine vibrator source. Because of increasing environmental restrictions on airguns, several companies have examined the concept of having a source near the seabed. More recently, a consortium comprising ExxonMobil, Shell, and Total has worked to develop an electric marine vibrator. A paper presented at the 2013 European Association of Geoscientists and Engineers annual meeting announced that the consortium is now splitting this project into two phases: design, build, and test a prototype and then build a full array of marine vibrators. Three companies have been selected to go into the prototype phase, and contracts are being negotiated.

This is just marine, it’s just seismic, and it’s just seismic sources. We could go on to talk about receivers, processing, interpretation, land, geology, petrophysics, well testing … And I’d never stress over a column topic again! Keep up the good work.

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