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Seismic Monitoring to Advance Carbon Sequestration Technology

Researchers led by the University of Tokyo and Kyushu University can help to further enhance carbon sequestration efforts using their Portable Active Seismic Source device, which will allow for extended kilometer-scale subsurface monitoring to detect CO2 leaks.

To counter the increasing threat of climate change, underground carbon sequestration has emerged as a promising contender. However, there are still major issues that need to be resolved before such technology may be scaled up. Fortunately, in an effort spearheaded by researchers at the University of Tokyo and Kyushu University, one of the challenges to scaling up may be addressed by finding ways to monitor carbon reservoirs cheaply and conveniently such that prompt attention may be given to leaks or other operational issues.

Such underground carbon storage facilities may be tracked with seismic waves, which are created by earthquakes or man-made sources. Unfortunately, currently used technologies require costly and bulky equipment and are not suited to monitor kilometres of underground carbon storage facilities.

Thankfully, the work from a research group from the Graduate School of Engineering, The University of Tokyo and the International Institute for Carbon-Neutral Energy Research, Kyushu University has resulted in a highly portable, centimetre-scale seismic source, named the Portable Active Seismic Source (PASS), which allows for cheaper and more convenient monitoring of carbon reservoirs. Though their device was originally designed for space research, like collecting data on the surface of the Moon and Mars, the team has also found potential uses for their device closer to home.

As lead author Professor Takeshi Tsuji explained, “Because of the device’s small size, the vibrations it produces are relatively weak, but when these vibrations are produced continuously, the resulting signals can be stacked together, allowing transmission over long distances. With a four-centimetre motor, the signal could be transmitted one kilometre – the scale needed for monitoring strata used to store carbon dioxide.”

The compact device makes the setup and utilisation process much easier, compared to that of a regular seismic source that spans multiple metres. Being powered by a 12-volt car battery, it is comparatively much more portable than a regular source, and it may also be transported by a drone to hard-to-reach locations.

The team trialed the usage of PASS at two sites—at a riverbank and at the embankment of tailing in a mining area. Professor Tsuji mentioned that from the trials, the PASS system seemed to be suitable for use in more varied applications across the fields of science and engineering, such as natural disaster monitoring, as well as the imaging of ongoing construction projects of tunnels, dams, and embankments.

The cheap and convenient monitoring allowed by the newly developed PASS device will be especially useful for alerting maintenance staff of sudden changes in the structures of the reservoirs that cause CO2 leakage. This also serves to improve the safety of such large-scale geoengineering projects, which may warrant greater public approval of such projects. [APBN]

Source: Tsuji et al. (2022). 4 cm Portable Active Seismic Source (PASS) for Meter-to Kilometer-Scale Imaging and Monitoring of Subsurface Structures. Seismological Research Letters.