Energy Technologies: How They Work and Their Induced Seismicity Potential - Induced Seismicity Potential in Energy Technologies - page 81

smaller than those being proposed for large power plant and industrial plant operations, 17
these projects provide data for assessment of the potential for induced seismic activity asso-
ciated with large-scale CCS.
Induced Seismicity Risks
The risk of induced seismicity from CCS is currently difficult to assess accurately.
The NETL reported that no harmful induced seismicity had been associated with any of
the global CCS storage demonstration projects as of February 2011. 18 However, the volumes
of CO 2 injected at these sites so far are small in comparison to the volumes being considered
for future proposed large CCS projects. Unlike most water disposal wells, CCS involves
continuous CO 2 injection at high rates under high pressures for very long periods of time.
The potential therefore exists to increase pore pressures throughout a volume with the stor-
age reservoir that is much larger than those affected by other energy technologies. Given
that the potential magnitude of an induced seismic event correlates strongly with the fault
rupture area, which in turn relates to the magnitude of pore pressure increase and the volume
in which it exists, it would appear that CCS may have the potential for significant seismic
risk. The combination of hydro-chemical-mechanical effects such as mineral dissolution
may also exacerbate the problem (Espinoza et al., 2011). Some factors could also serve to
mitigate risk such as low viscosity and lower injection pressure and limits of permanent
pressure change in the reservoir depending upon variables such as reservoir thickness.
DISCUSSION
Geothermal, enhanced geothermal, oil and gas, unconventional oil and gas, and CCS
technologies all involve fluid withdrawal and/or injection, thereby providing the poten-
tial to induce seismic events. The rates, volumes, pressure, and duration of the injection
vary with the technology as do the potential sizes of the earthquakes, the mechanisms to
which the earthquakes are attributed (Table 3.4), and the possible risk and hazards of the
induced events.
Induced seismicity is commonly characterized by large numbers of small earthquakes
that persist during, and in some cases significantly after, fluid injection or removal. At
several sites of seismicity caused by or likely related to energy technologies, calculations
based on the measured injection pressure and the measured or the inferred state of stress in
17 Approximately 3,000 million metric tonnes (~3,300 million tons) of CO 2 are reported to have been emitted by the
United States in 2009 from the combined activities of electricity and heat production, manufacturing and construction, and
other industrial processes including petroleum refining, hydrocarbon extraction, coal mining, and other energy-producing
industries. Data available at www.iea.org/co2highlights/co2highlights.pdf.
18 See www.netl.doe.gov/technologies/carbon_seq/FAQs/permanence4.html.