Zooming in on higher frequencies

From humble beginnings come great ideas, sometimes. Take expandable casing, for instance. Rumor has it that two Shell scientists were playing with the expandable sleeves that keep wine bottles from clinking together when they had their Eureka moment. And sometimes, a technology that has been developed for one application suddenly finds a much larger audience once someone says, “If it can do that, can it also do this?”

Such was the case with Dr. Jacques Yves Guign?, the co-founder of PanGeo Subsea and the original inventor and developer of what’s called an acoustic corer. Rather than taking an actual core from the near-surface, Guign?’s tool can sit on the seafloor and take multi-aspect acoustic measurements of the seabed subsurface that present geohazards for geotechnical engineering projects.

Guign? found himself at a bar in Stavanger, Norway, with Greg Herrera, a partner with Energy Ventures. Herrera was interested in the corer but had a very different application in mind.

“Greg said, ‘You can see very high resolution 30 m [91 ft] down, so can you focus that deep into the reservoir and see [3,050 m] 10,000 ft with that technology?” said Jim Sledzik, another Energy Ventures partner. “Jacques thought he might be able to do it.”

The result of this conversation is “Acoustic Zoom,” a new seismic methodology that Sledzik said might be able to solve one of the “holy grails” of seismic imaging – higher resolution.

The Acoustic Zoom system captures many wavelengths across a large bandwidth. (Image courtesy of Acoustic Zoom)

Eventually, PanGeo and its investors partnered with Global Geophysical to pursue field trials. They shot a full-scale Acoustic Zoom dataset in the Eagle Ford shale that covers part of one of Global’s larger multi-client datasets.

Sledzik said that the Acoustic Zoom data acquisition resemble microseismic data. Unlike a traditional micro-seismic grid, however, the Acoustic Zoom’s densely packed receiver sensors are laid out in a multispoked star formation but spaced unevenly to capture many wavelengths across a large bandwidth from 200 Hz to well below 50 Hz, and just a few vibrator positions are required. But the nature of the acquisition geometry, in which an antenna probes a 12.5-sq-km (4.8-sq-mile) area at a 45° angle, provides better imaging of the underlying geology, Sledzik said.

Sledzik added that current processing emphasizes the non-specular or diffuse reflections off of subsurface objects like structures and faults that would normally be lost in what is deemed “noise.”

So far, the Acoustic Zoom team, with Global’s participation, has created synthetic datasets and built the beamforming algorithms and software to steer into the data to help direct the imaging process. Phase 2 will deliver an image by applying the Acoustic Zoom beam-former to the real data. Sledzik said the application to the synthetic data was very convincing and proved up the theory.

Meanwhile, Guign?’s team has partnered with Global and PanGeo Subsea to form its own company, Acoustic Zoom Inc., with an aim to commercialize its land applications and also to pursue future offshore reservoir monitoring applications using a modified marine high-frequency vibrator that can record up to 200 Hz. Data results from the Eagle Ford experiment should be available by early 2013; first indications show 140 Hz data at the Eagle Ford formation.

“All of us are very excited to see the results,” Sledzik said.