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Geologic CO2 Sequestration

Geologic Carbon Sequestration

With increased awareness of global climate change due to the increase in atmospheric CO2 concentrations, it has been proposed that CO2 be captured and put underground (geologic CO2 sequestration). To make a significant impact on CO2 accumulation, billions of tons of CO2 per year need to be injected and sequestered in the subsurface. One of the concerns associated with geologic CO2 sequestration (GCS) at the proposed volumes is inducing seismicity. To date, there are few large scale injections of CO2 for sequestration. CO2, however, has been injected safely underground for years in many oil and gas reservoirs to extract more oil and or gas, with little seismic impact. However, these formations are relatively shallow, had low regional seismicity to begin with, and pressures were balanced to extract fluids as wells inject CO2. Some initial pilot projects meant to sequester CO2 in oil and gas environments are, however, currently under way Examples are the Weyburn project in Canada , the Sleipner project in the North Sea, and the In Salah Project in Algeria. To date, all have had low seismicity and are not in populated areas.

In addition to depleted oil and gas reservoirs, it is being proposed that deep saline water formations, coal gas, and shale and other formations be used to sequester CO2. Many of the issues surrounding EGS-induced seismicity will also carry over to GCS, both from a technical and community impact point of view. No large-scale injections have been carried out in any of these areas. Small injections (few hundred to several thousand tons) have yielded very low if any seismicity. The USDOE is currently sponsoring seven U.S. regional partnerships to investigate many technical as well as regulatory issues associated with GCS. As these multiyear projects proceed, induced seismicity will be addressed and factored into the overall risk-benefit calculations.

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