Energy Technologies: How They Work and Their Induced Seismicity Potential - Induced Seismicity Potential in Energy Technologies - page 37

Energy Technologies:
How They Work and Their
Induced Seismicity Potential
Much of the energy used in the United States comes from fluids pumped out of the
ground. Oil and gas have been major energy sources in the country for over 100 years, and
new developments in the production of natural gas indicate that it may provide a significant
source of energy for the nation during the twenty-first century. Geothermal power has been
used to supply energy in the United States for almost as long as oil, although major elec-
tricity generation from geothermal energy sources began only in the 1960s at The Geysers in
Northern California. A 2006 report on the potential of geothermal energy (MIT, 2006) sug-
gested it could be a major contributor to the nation's energy supply in the coming decades.
Efforts to reduce concentrations of carbon dioxide (CO 2 ) in the atmosphere have spurred
development of technologies to capture and store (sequester) CO 2 . Projects to accomplish
carbon capture and storage (CCS) from industrial facilities are currently being piloted in
the United States and elsewhere in the world. Underground injection of CO 2 has also been
commonly used to enhance oil and gas recovery.
This chapter reviews the potential for induced seismicity related to geothermal energy
production, conventional oil and gas development (including enhanced oil recovery [EOR]),
shale gas development, injection wells related to disposal of wastewater associated with
energy extraction, and CCS.
GEOTHERMAL ENERGY
Geothermal energy exists because of the substantial heat in the Earth and the tem-
perature increase with depths below the Earth's surface. Depending upon the regional
geology—including the composition of the rocks in the subsurface and any of the fluids
contained in the rocks—the temperature increase with depth (the thermal gradient) may
be fairly steep and represent the source of sufficient geothermal energy to allow com-
mercial development for electricity generation. The largest actively producing geothermal
field in the United States at The Geysers in Northern California generates approximately
725 megawatts of electricity per year (“megawatts electrical” or MWe). This is enough
to power 725,000 homes or a city the size of San Francisco. Currently this geothermal
field supplies nearly 60 percent of the average electricity demand of the northern coastal
region of California.