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2.
Relative to the large number of waterflood projects for secondary recovery, the small
number of documented instances of felt induced seismicity suggests such projects
pose relatively small risk for events that would be of concern to the public.
3.
The committee has not identified any documented, felt induced seismic events
associated with EOR (tertiary recovery). The potential for induced seismicity is
low in EOR operations as pore pressure is not significantly increased beyond the
original levels in the reservoir because injected fluid volumes tend to be balanced
by fluid withdrawals.
Unconventional Oil and Gas: Hydraulic Fracturing for Shale Gas Development
F
indings
1.
The process of hydraulic fracturing a well as presently implemented for shale gas
recovery does not pose a high risk for inducing felt seismic events. Thirty-five
thousand wells have been hydraulically fractured for shale gas development to
date in the United States. To date, hydraulic fracturing for shale gas production
was cited as the possible cause of one case of felt seismic events in Oklahoma
in 2011, the largest of which was
M
2.8. The quality of the event locations was
not adequate to fully establish a direct causal link to the hydraulic fracture treat-
ment. Hydraulic fracturing for shale gas development has been confirmed as the
cause of induced seismic events in one case worldwide—in Blackpool, England
(maximum
M
2.3).
2.
One case of induced seismicity (maximum
M
1.9) was documented in Oklahoma in
the late 1970s as being caused by hydraulic fracturing for oil and gas development
for conventional oil and gas extraction.
p
roposed
a
ction
When a seismic event occurs that appears to be associated with hydraulic fracturing and
is considered to be a concern to the health, safety, and welfare of the public, an assessment
is needed to understand the causes of the seismicity (see protocol that follows).
Injection Wells for the Disposal of Water Associated with Energy Extraction
F
indings
1.
The United States currently has approximately 30,000 Class II wastewater disposal
wells; very few felt induced seismic events have been reported as either caused by
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