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Slip Tendency Analysis, Fault Reactivation Potential and Induced Seismicity in the Val d'Agri Oilfield (Italy)
Author(s) -
Vadacca Luigi,
Rossi Daniele,
Scotti Anna,
Buttinelli Mauro
Publication year - 2021
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2019jb019185
Subject(s) - induced seismicity , geology , seismology , slip (aerodynamics) , stress field , seismic hazard , fault (geology) , pore water pressure , tectonics , active fault , fluid pressure , fluid dynamics , petrology , oil field , geotechnical engineering , petroleum engineering , mechanics , thermodynamics , physics , finite element method
The Val d'Agri basin hosts an oil‐field, the largest in onshore Europe, and it is one of the areas of highest seismic hazard in Italy. In an unproductive marginal portion of the reservoir, wastewater is re‐injected by a high‐rate well. Since the beginning of re‐injection in June 2006, a spatio‐temporal correlation between microseismicity ( M L ≤ 2.0) and wastewater injection has been observed (suggesting induced seismicity). In this study, we perform a slip‐tendency analysis on the fault system involved in the induced seismicity through a coupled fluid‐flow and geomechanical numerical model simulating the stress partitioning due to the tectonic forces and to the fluid injection. The model results show that the fluid diffusion is strongly dependent on the active stress field and the geological structure in which fluids are injected, which conditioned the occurrence of seismicity that aligned on a small portion of a NE‐dipping fault. However, another fault located closer to the injection well and where no seismicity was detected, is the better well‐oriented fault with the active stress field and, also, the one more susceptible to the pore pressure increase. These results suggest different types of fault deformation acting in the Val d'Agri oilfield as response to the fluid injection (i.e., a mixed‐mode fault slip behavior). Understanding the stress partitioning in tectonically active regions where underground activities such as fluid injection are ongoing is fundamental to give strong constraints for the discrimination between natural and induced seismicity, and finally for a more reliable and robust definition of seismic hazard.