Multicomponent seismic has its challenges, in processing and interpretation as well as added cost. But it could take on an important role in plays like the Bakken oil shale.

Speaking at the first annual Developing Unconventional Oil conference in Denver, Chris Friedemann, senior vice president-corporate marketing for ION Geophysical Corp., explained the uses of seismic technology in shale-oil plays. ION has more than 150 shale-related projects, most of them in North America and most of them involving gas rather than oil, because oil shales are harder to image.

But this does not deter ION and other geophysical companies from moving into the oil-prone shale arena, he noted, because seismic technology is a critical factor in shale development.

Friedemann outlined several applications for seismic, including reservoir delineation, mapping, characterization, determining lithology, assessing rock brittleness, and fracture monitoring. Additionally, emerging technologies such as wide-azimuth acquisition, high channel counts, cableless systems, in-wellbore seismic, high-fidelity three-component seismic, and new processing and interpretation techniques are adding new tools.

High channel counts, for instance, are providing better sampling density. Friedemann said that only a few years ago, a seismic survey might have consisted of 2,000 to 3,000 channels; surveys today are 10,000 to 20,000 channels. Increased channel count plus longer offsets increases the fold, and in this case, more is definitely better.

Cableless acquisition systems are also making large seismic surveys more operationally friendly. With shale plays typically occurring outside of the traditional oil patch and often characterized by considerably more infrastructure, he said, contractors need a system that’s acceptable to landowners.

Also increasing in use in shales is multicomponent seismic. Simply put, adding the shear component to the compressional component when measuring acoustic waves gives a different set of information, which helps to better constrain the model. Unfortunately, the shear response in unconventional gas reservoirs is easier to measure than it is in unconventional oil plays.

Shear waves tend to travel in the direction of the fracture orientation, so fast-moving shear waves indicate fracture direction. But when shear waves hit a zone of fractures, they split into fast and slow waves.

The delay between fast and slow waves is proportional to the fracture volume.

This velocity contrast is not nearly as pronounced in oil shales, he said. Still, operators need shear-wave information to fully characterize their reservoirs. In one case, an operator who did the shear experiment was able to locate a “sweet spot” and drilled a well that produced 100 barrels per day without the need for hydraulic fracturing, a five-time improvement in production simply based on efficient well placement.

Finally, microseismic monitoring provides the ability to “see” for the first time the extent and orientation of hydraulic fractures.

“Tremendous progress has been made in just the past three years,” Friedemann said.

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