Abstract:It is important to distinguish between natural earthquakes and those induced by CO2 injection at carbon capture and storage sites. For example, the 2004 Mw 6.8 Chuetsu earthquake occurred close to the Nagaoka CO2 storage site during gas injection, but we could not quantify whether the earthquake was due to CO2 injection or not. Here we simulated changes of pore pressure during CO2 injection at the Nagaoka site and compared them with estimated natural seasonal fluctuations of pore pressure due to rainfall and s… Show more
“…This experiment demonstrates that our monitoring system can reveal temporal variations of pore pressure in the geothermal reservoirs. Because the pore pressure is related to the seismicity 7 , we will be able to use this monitoring system for safe reservoir managements in geothermal power. Figure 8 Monitoring results and geothermal operation data during 3 months.…”
Section: Results and Interpretationmentioning
confidence: 99%
“…To achieve such a large number of CO 2 storage sites, we should manage multi CO 2 storage reservoirs in extensive areas using an innovative monitoring system for the stored CO 2 . Monitoring injected CO 2 in its reservoir is crucial for predicting the risk of CO 2 leakage, increasing efficiency, reducing the cost of CO 2 storage, and reducing the risk of induced seismicity 6 , 7 . Also, the information derived from monitoring is vital to obtain public acceptance for the projects.…”
We have developed a new continuous monitoring system based on small seismic sources and distributed acoustic sensing (DAS). The source system generates continuous waveforms with a wide frequency range. Because the signal timing is accurately controlled, stacking the continuous waveforms enhances the signal-to-noise ratio, allowing the use of a small seismic source to monitor extensive areas (multi-reservoir). Our field experiments demonstrated that the monitoring signal was detected at a distance of ~ 80 km, and temporal variations of the monitoring signal (i.e., seismic velocity) were identified with an error of < 0.01%. Through the monitoring, we identified pore pressure variations due to geothermal operations and rains. When we used seafloor cable for DAS measurements, we identified the monitoring signals at > 10 km far from the source in high-spatial resolution. This study demonstrates that multi-reservoir in an extensive area can be continuously monitored at a relatively low cost by combining our seismic source and DAS.
“…This experiment demonstrates that our monitoring system can reveal temporal variations of pore pressure in the geothermal reservoirs. Because the pore pressure is related to the seismicity 7 , we will be able to use this monitoring system for safe reservoir managements in geothermal power. Figure 8 Monitoring results and geothermal operation data during 3 months.…”
Section: Results and Interpretationmentioning
confidence: 99%
“…To achieve such a large number of CO 2 storage sites, we should manage multi CO 2 storage reservoirs in extensive areas using an innovative monitoring system for the stored CO 2 . Monitoring injected CO 2 in its reservoir is crucial for predicting the risk of CO 2 leakage, increasing efficiency, reducing the cost of CO 2 storage, and reducing the risk of induced seismicity 6 , 7 . Also, the information derived from monitoring is vital to obtain public acceptance for the projects.…”
We have developed a new continuous monitoring system based on small seismic sources and distributed acoustic sensing (DAS). The source system generates continuous waveforms with a wide frequency range. Because the signal timing is accurately controlled, stacking the continuous waveforms enhances the signal-to-noise ratio, allowing the use of a small seismic source to monitor extensive areas (multi-reservoir). Our field experiments demonstrated that the monitoring signal was detected at a distance of ~ 80 km, and temporal variations of the monitoring signal (i.e., seismic velocity) were identified with an error of < 0.01%. Through the monitoring, we identified pore pressure variations due to geothermal operations and rains. When we used seafloor cable for DAS measurements, we identified the monitoring signals at > 10 km far from the source in high-spatial resolution. This study demonstrates that multi-reservoir in an extensive area can be continuously monitored at a relatively low cost by combining our seismic source and DAS.
“…11 Therefore, reducing the cost of CO 2 capture in CCS projects calls for rapid progress in appropriate concepts or technology. Safety is another key factor for CCS projects; CO 2 leakage and injection-induced earthquakes should be carefully evaluated, 12 especially when storage sites are close to residential and industrial areas.…”
Carbon capture and storage has been considered as a realistic approach to reducing atmospheric CO 2 concentrations. However, the cost of capturing high-purity CO 2 typically used for geological storage (e.g., 98%) is high. Direct air capture (DAC), a technology that extracts CO 2 of relatively low-purity from the ambient atmosphere, has been recently proposed as a means to achieve negative CO 2 emissions when the product is sequestered underground. Although the CO 2 produced by DAC is of low-purity, the other gaseous components (mainly nitrogen and oxygen) are not hazardous materials like NO x and SO x that must be typically dealt with by conventional projects in coal-burning plants. Here, we evaluate geological storage of the low-purity CO 2 captured via advanced membrane-based DAC technology. The ubiquity of ambient air is important in reducing transport costs and ensuring social acceptance as the CO 2 product can be both produced and stored at sites in remote areas, such as deserts and offshore platforms. We calculated the density of CO 2 -N 2 -O 2 mixtures via molecular dynamics simulation and evaluated the cost of the low-purity CO 2 storage. Our evaluation suggests that the storage of low-purity CO 2 in geological formations is environmentally acceptable and economically viable.
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