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Coda waves reveal carbon dioxide storage plume
https://news.psu.edu/story/560867/2019/02/26/research/coda-waves-reveal-carbon-dioxide-storage-plumeCoda waves reveal carbon dioxide storage plume
A'ndrea Elyse Messer
February 26, 2019
UNIVERSITY PARK, Pa. — Pumping carbon dioxide into the ground to remove it from the atmosphere is one way to lower greenhouse gases, but keeping track of where that gas is, has been a difficult chore. Now, a team of researchers from Penn State and Lawrence Berkley National Laboratory are using previously ignored seismic waves to pinpoint and track the gas clouds.
"We usually don't look at coda waves, we usually throw them out," said Tieyuan Zhu, professor of geophysics, Penn State. "If we look at a carbon dioxide plume underground with P waves we don't see any change in shape, but if we use the late-arriving waves, the coda waves, we see a change."
P waves are the fastest seismic body waves that pass through the Earth after an earthquake or explosion. S waves are slower body waves. Coda waves come later and are disorganized, but they can reveal where gases are stored in the ground, because the combination of rock and gas alters the waves.
When carbon dioxide is stored underground, it is pumped over a mile deep into geological spaces and is usually over 150 degrees Fahrenheit and at high pressure. Ideally, researchers would like the gas to stay at that depth forever. Current monitoring methods are difficult, expensive and can only be done periodically. Tracking the plumes with coda waves also has the benefit of better estimation of the total amount of gas in the reservoir, rather than just a local region.
…
http://dx.doi.org/10.1073/pnas.1810903116
Left, schematic illustration of carbon dioxide storage with borehole real-time monitoring system (credit: Patricia L. Craig). Right: seismic P-waves and coda waves before and after carbon dioxide injection. Image: Penn State
A'ndrea Elyse Messer
February 26, 2019
UNIVERSITY PARK, Pa. — Pumping carbon dioxide into the ground to remove it from the atmosphere is one way to lower greenhouse gases, but keeping track of where that gas is, has been a difficult chore. Now, a team of researchers from Penn State and Lawrence Berkley National Laboratory are using previously ignored seismic waves to pinpoint and track the gas clouds.
"We usually don't look at coda waves, we usually throw them out," said Tieyuan Zhu, professor of geophysics, Penn State. "If we look at a carbon dioxide plume underground with P waves we don't see any change in shape, but if we use the late-arriving waves, the coda waves, we see a change."
P waves are the fastest seismic body waves that pass through the Earth after an earthquake or explosion. S waves are slower body waves. Coda waves come later and are disorganized, but they can reveal where gases are stored in the ground, because the combination of rock and gas alters the waves.
When carbon dioxide is stored underground, it is pumped over a mile deep into geological spaces and is usually over 150 degrees Fahrenheit and at high pressure. Ideally, researchers would like the gas to stay at that depth forever. Current monitoring methods are difficult, expensive and can only be done periodically. Tracking the plumes with coda waves also has the benefit of better estimation of the total amount of gas in the reservoir, rather than just a local region.
…