Were the May 2012 Emilia‐Romagna earthquakes induced? A coupled flow‐geomechanics modeling assessment

Abstract

Seismicity induced by fluid injection and withdrawal has emerged as a central element of the scientific discussion around subsurface technologies that tap into water and energy resources. Here we present the application of coupled flow‐geomechanics simulation technology to the post mortem analysis of a sequence of damaging earthquakes (Mw = 6.0 and 5.8) in May 2012 near the Cavone oil field, in northern Italy. This sequence raised the question of whether these earthquakes might have been triggered by activities due to oil and gas production. Our analysis strongly suggests that the combined effects of fluid production and injection from the Cavone field were not a driver for the observed seismicity. More generally, our study illustrates that computational modeling of coupled flow and geomechanics permits the integration of geologic, seismotectonic, well log, fluid pressure and flow rate, and geodetic data and provides a promising approach for assessing and managing hazards associated with induced seismicity.

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

“…Lastly, our structural model could be used as reference to perform a geologically realistic 3D geomechanical modeling of the stress changes resulting from the combined effects of wastewater injection and hydrocarbon withdrawal from the reservoir. Such a modeling would enable to model the observed induced seismicity and to quantitatively assess the likelihood to trigger earthquakes on optimally oriented faults evidenced in our study34. At a more general scale, our results reinforce the need of a multidisciplinary approach combining advanced seismological analysis with reliable structural models of hydrocarbon reservoirs for a thorough understanding of induced seismicity.…”

On the physics‐based processes behind production‐induced seismicity in natural gas fields

“…In all scenarios, the pressure drop in the producing reservoir compartment was significantly stronger than the pressure drop in the fault zone (i.e., at the rupture point). Hence, we conclude that the assumption of similar pressure drops in the fault and adjacent reservoirs, as suggested in previous studies [e.g., Mulders , ; Orlic et al ., ; van den Bogert , ; Wassing et al ., ; Orlic , ; Juanes et al ., ], is a poor approximation of several physical processes. The deviation of the magnitudes in the different scenarios can be explained by different shear stress accumulation during production, different pore pressure distribution in the fault (i.e., fault strength), and different caprock rheology.…”

Current challenges in monitoring, discrimination, and management of induced seismicity related to underground industrial activities: A European perspective

“…The two strongest events of the sequence caused structural and nonstructural damage to residential, industrial, and public buildings as well as 27 fatalities [ Masi et al , ]. The 20 May earthquake occurred on the western segment of the Middle Ferrara fault, while the 29 May earthquake nucleated about 10 km to the southwest of the 20 May event epicenter and occurred on the Mirandola fault, which bounds the Cavone oil field from the north [ Juanes et al , ] (see Figure ). The proximity of the sequence to this industrial site encouraged speculation on the possibility that earthquakes have been affected by anthropogenic factors.…”

“…These results have raised political discussions and strong debates in Italy and worldwide [ Cartlidge , ]. On April 2014 the company managing the exploitation of the Cavone field funded a research activity to be carried out by another group of experts, which demonstrated that there was no physical reason to suspect that pressure changes associated to the exploitation of the Cavone oil field triggered the earthquakes that occurred in the Emilia Romagna region in 2012 [ Astiz et al , ; Juanes et al , ]. Furthermore, a quantitative probabilistic approach proposed by Dahm et al [] to discriminate induced, triggered, and natural earthquakes was applied to this seismic sequence.…”

“…In this case, a few months after the occurrence of the earthquake sequence that culminated with a magnitude 5.9 ( M l ) event on 20 May 2012 and a magnitude 5.8 ( M l ) event 9 days later, there was an intense public discussion concerning the possible relationship between these earthquakes and the hydrocarbon production operations in the epicentral area. The public concerns prompted the Italian government to charge an international expert panel to investigate the relationship between hydrocarbon extraction operations in Emilia and the 2012 earthquake sequence [ Juanes et al , ]. In numerous other cases, the possible relationship between reported earthquakes and human operations remained debated for years, even at scientific level.…”