Geomechanical modeling of fault responses and the potential for notable seismic events during underground CO2 injection
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Date
2013
Publication Type
Conference Paper
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no
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Abstract
We summarize a number of recent modeling studies related to the potential for fault reactivations and induced seismicity during underground CO2 injection. The model simulations were conducted using coupled multiphase fluid flow and geomechanics, including fault-frictional weakening enabling analysis of sudden (seismic) fault rupture, with some of the numerical analyses extended to dynamic modeling of seismic source, wave propagation, and ground motion. These model simulations show that the critical factors in determining the likelihood and magnitude of such an event are the local in situ stress field, fault orientation and size, fault strength, and injection pressure. We analyzed the case of activation of a 1 km long minor fault that might have gone undetected during the site investigation and show that the maximum seismic magnitudes would likely be less than about 3.6, even if the entire 1 km fault would to be activated. We then include seismic wave propagation generated by the rupture and show how the acceleration and deceleration of the rupture generate waves and result in a peak ground acceleration of about 0.1 g, except for a localized –0.6 g of horizontal peak acceleration at the faults intersection with the ground surface. The modeling shows that these are high frequency events that would not cause any substantial damage but could certainly be felt by the local population. We may also considered that fault reactivation, even associated with relatively small seismic or aseismic events, could potentially increase CO2 seepage out of the intended storage complex and therefore reduce the effectiveness of a CO2 storage operation. Under these circumstances, we recommend a staged, learn-as-you-go approach, involving a gradual increase of injection rates combined with continuous monitoring of geomechanical changes, as well as siting beneath a multiple layered overburden for multiple flow barrier protection, should an unexpected deep fault activation occur.
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published
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Book title
GHGT-11 Proceedings of the 11th International Conference on Greenhouse Gas Control Technologies
Journal / series
Volume
37
Pages / Article No.
4774 - 4784
Publisher
Elsevier
Event
11th International Conference on Greenhouse Gas Control Technologies (GHGT-11)
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
Organisational unit
02818 - Schweiz. Erdbebendienst (SED) / Swiss Seismological Service (SED)