Article,
A survey of the induced seismic responses to fluid injection in geothermal and CO2 reservoirs in Europe
Geothermics, (January 2012)
DOI: 10.1016/j.geothermics.2011.08.002
Abstract
The paper documents 41 European case histories that describe the seismogenic
response of crystalline and sedimentary rocks to fluid injection.
It is part of an on-going study to identify factors that have a bearing
on the seismic hazard associated with fluid injection. The data generally
support the view that injection in sedimentary rocks tends to be
less seismogenic than in crystalline rocks. In both cases, the presence
of faults near the wells that allow pressures to penetrate significant
distances vertically and laterally can be expected to increase the
risk of producing felt events. All cases of injection into crystalline
rocks produce seismic events, albeit usually of non-damaging magnitudes,
and all crystalline rock masses were found to be critically stressed,
regardless of the strength of their seismogenic responses to injection.
Thus, these data suggest that criticality of stress, whilst a necessary
condition for producing earthquakes that would disturb (or be felt
by) the local population, is not a sufficient condition. The data
considered here are not fully consistent with the concept that injection
into deeper crystalline formations tends to produce larger magnitude
events. The data are too few to evaluate the combined effect of depth
and injected fluid volume on the size of the largest events. Injection
at sites with low natural seismicity, defined by the expectation
that the local peak ground acceleration has less than a 10\% chance
of exceeding 0.07 g in 50 years, has not produced felt events. Although
the database is limited, this suggests that low natural seismicity,
corresponding to hazard levels at or below 0.07 g, may be a useful
indicator of a low propensity for fluid injection to produce felt
or damaging events. However, higher values do not necessarily imply
a high propensity. ⺠We document the seismogenic response
of crystalline and sedimentary rocks to fluid injection at 41 European
sites. ⺠The objective is to identify factors that have a
bearing on the magnitude of the largest seismic event. âº
All cases of injection into crystalline rocks produce seismic events,
albeit usually of non-damaging magnitudes. ⺠Injection at
sites with low natural seismicity, defined by the expectation that
the local peak ground acceleration has less than a 10\% chance of
exceeding 0.07 g in 50 years, has not produced felt events. âº
The limited data suggest that low natural seismicity, corresponding
to hazard levels at or below 0.07 g, may be a useful indicator of
a low propensity for fluid injection to produce felt or damaging
events. However, higher values do not necessarily imply a high propensity.
