Underground gas storage (UGS) is a practice that is becoming widely implemented to cope with seasonal peaks of gas consumption. When the target reservoir is located in a faulted basin, a major safety issue concerns the re-activation of pre-existing faults, possibly inducing (micro-) seismicity. Faults are reactivated when the shear component of traction exceeds the acceptable limiting strength. It has been observed that this occurrence can happen "unexpectedly" during the life of a UGS reservoir, i.e., when the actual stress regime is not supposed to reach the failure condition. A numerical investigation has been carried out to shed light in this respect, by analyzing the mechanisms and the critical factors that can be responsible for a fault activation during different UGS stages. The model is applied in a physical context representative of the typical UGS reservoirs located in The Netherlands, in terms of reservoir properties, fault geometry and pressure history. The numerical results show that "unexpected" fault re-activations are likely to occur during UGS when micro-seismicity had been already experienced in the primary reservoir exploitation, even if the pore pressure does not exceed the initial undisturbed conditions.

Numerical investigation of fault activation in underground gas storage reservoirs

M. Ferronato
;
A. Franceschini;M. Frigo;P. Teatini;C. Zoccarato
2019

Abstract

Underground gas storage (UGS) is a practice that is becoming widely implemented to cope with seasonal peaks of gas consumption. When the target reservoir is located in a faulted basin, a major safety issue concerns the re-activation of pre-existing faults, possibly inducing (micro-) seismicity. Faults are reactivated when the shear component of traction exceeds the acceptable limiting strength. It has been observed that this occurrence can happen "unexpectedly" during the life of a UGS reservoir, i.e., when the actual stress regime is not supposed to reach the failure condition. A numerical investigation has been carried out to shed light in this respect, by analyzing the mechanisms and the critical factors that can be responsible for a fault activation during different UGS stages. The model is applied in a physical context representative of the typical UGS reservoirs located in The Netherlands, in terms of reservoir properties, fault geometry and pressure history. The numerical results show that "unexpected" fault re-activations are likely to occur during UGS when micro-seismicity had been already experienced in the primary reservoir exploitation, even if the pore pressure does not exceed the initial undisturbed conditions.
2019
Geomechanics and Applications for Sustainable Development
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/3352395
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