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The frequency of induced earthquakes in Oklahoma spiked in 2014 when record
high oil prices of more than $100 per barrel led many producers to increase petroleum recovery from the older, conventional oil fields that are common in this state
through the use of enhanced oil recovery (EOR) techniques. The most common type
of EOR treatment is known as a waterflood. As the name implies, large amounts of
water are injected into wells around the perimeter of the oil field, literally flushing
the oil out of the rocks and rafting it toward central recovery wells. Substantial volumes of contaminated saltwater are flushed through the formation and recovered
along with the oil. The disposal of these massive quantities of EOR wastewater
down UIC wells was responsible for the 2014 spike in Oklahoma induced seismicity, not fracking. Once oil prices subsided in 2015, so did the earthquakes.
Nearly anything that changes the stress state on faults can induce earthquakes.
For example, the weight of water filling up deep reservoirs after the construction of
large dams has been known for some time to cause earthquakes (McCully 1996).
Called reservoir-induced seismicity (RIS), it was first observed in 1932 at the Quedd
Fodda Dam in Algeria, although the first systematic investigations of the possible
links between seismic activity and the depth of water in an impoundment were not
carried out until the 1940s by the USGS at Hoover Dam on the Colorado River.
Other triggers for induced seismicity include tunneling and mining operations, oil
and gas extraction, and geothermal power generation (Davies et al. 2013).
Most faults are under some degree of stress, which can gradually increase over
time due to gravity, erosion, or tectonic forces. As long as this stress does not exceed
Fig. 7.6 Earthquakes above Magnitude 3 recorded in the central U.S. between 1973 and 2016,
showing a dramatic increase in frequency when oilfield wastewater injection ramped up in
Oklahoma after 2009. (Source: U.S. Geological Survey webpages)
7 Effects on Landscapes
The frequency of induced earthquakes in Oklahoma spiked in 2014 when record
high oil prices of more than $100 per barrel led many producers to increase petroleum recovery from the older, conventional oil fields that are common in this state
through the use of enhanced oil recovery (EOR) techniques. The most common type
of EOR treatment is known as a waterflood. As the name implies, large amounts of
water are injected into wells around the perimeter of the oil field, literally flushing
the oil out of the rocks and rafting it toward central recovery wells. Substantial volumes of contaminated saltwater are flushed through the formation and recovered
along with the oil. The disposal of these massive quantities of EOR wastewater
down UIC wells was responsible for the 2014 spike in Oklahoma induced seismicity, not fracking. Once oil prices subsided in 2015, so did the earthquakes.
Nearly anything that changes the stress state on faults can induce earthquakes.
For example, the weight of water filling up deep reservoirs after the construction of
large dams has been known for some time to cause earthquakes (McCully 1996).
Called reservoir-induced seismicity (RIS), it was first observed in 1932 at the Quedd
Fodda Dam in Algeria, although the first systematic investigations of the possible
links between seismic activity and the depth of water in an impoundment were not
carried out until the 1940s by the USGS at Hoover Dam on the Colorado River.
Other triggers for induced seismicity include tunneling and mining operations, oil
and gas extraction, and geothermal power generation (Davies et al. 2013).
Most faults are under some degree of stress, which can gradually increase over
time due to gravity, erosion, or tectonic forces. As long as this stress does not exceed
Fig. 7.6 Earthquakes above Magnitude 3 recorded in the central U.S. between 1973 and 2016,
showing a dramatic increase in frequency when oilfield wastewater injection ramped up in
Oklahoma after 2009. (Source: U.S. Geological Survey webpages)
7 Effects on Landscapes