Fluid injection induced seismicity reveals a NE dipping fault in the southeastern sector of the High Agri Valley (southern Italy)

Abstract

On 2 June 2006 the wastewater produced during the oil and gas field exploitation in High Agri Valley (southern Italy) started to be managed by disposal through pumping the fluids back into the subsurface at the Costa Molina 2 (CM2) injection well, located in the southeastern sector of the valley. The onset of microearthquakes (Ml ≤ 2) after 4 days at about 1.3 km SW of CM2 well suggests fluid injection induced seismicity by the diffusion of pore pressure. Moreover, the space-time evolution of 196 high-resolution relocated events reveals a previously unmapped NE dipping fault. We investigate the physical processes related to the fluid injection induced seismicity and delineate the previously unmapped fault by jointly analyzing seismicity data, geological observations, fluid injection data, the stratigraphic log of the CM2 well, and the electrical resistivity tomography survey carried out in the study area.

Inversion of inherited thrusts by wastewater injection induced seismicity at the Val d’Agri oilfield (Italy)

“…This result contrasts with previous interpretations that ascribed to an unknown normal-fault of the basin bounding system the observed microseismicity11. Such focal mechanisms are also coherent with the current NE-trending extensional local stress field inferred by borehole breakouts (Figs 1A and 2B) and S-wave anisotropy122627.…”

“…1) by a high-rate injection well (Costa Molina 2, CM2). A spatio-temporal relationship between micro-seismicity (M L  ≤ 2.2) and wastewater injection has been observed1112, with hypocenters that align along a NE-dipping structure located a few kilometers to the SW of the well. The aim of this work is to understand the potential of earthquakes in the area by investigating the presence of faults near the injection well, their extent, geometry and relation with the major Quaternary faults that bound the extensional basin.…”

Finite element modelling of stress field perturbations and interseismic crustal deformation in the Val d'Agri region, southern Apennines, Italy

“…The finite element model (A) effectively reconciles a series of observed features from the Alta Val d'Agri area, including: (i) the lack of clearly recognized coseismic surface fault ruptures associated with the 1857 earthquake; (ii) the evidence for the activity of NE-dipping normal fault segments (Burrato and Valensise, 2008;Ferranti et al, 2008Ferranti et al, , 2014Improta et al, 2010;Maschio et al, 2005;Pantosti and Valensise, 1988;Stabile et al, 2014) in an area dominated at surface by SW-dipping, Quaternary fault scarps (Benedetti et al, 1998); and (iii) the lack of evidence for major extensional offsets of the Top Apulian reflector from seismic profiles tied with deep well logs (Shiner et al, 2004). According to our finite element modelling (Fig.…”

Aseismic Motions Drive a Sparse Seismicity During Fluid Injections Into a Fractured Zone in a Carbonate Reservoir

“…This might be the case for injections in Soultz‐sous‐Forêts or in Fenton Hill, where the seismicity occurred clustered in time, but followed a diffusion law over the long term range (Shapiro et al, ). A similar pattern is observed on the wastewater disposal of the oil and field production of High Agri Valley in the South of Italy (Stabile et al, ). Moreover, the microseismic events are generally used to follow the fluid diffusion in the reservoir monitoring.…”