Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Nat. Hazards Earth Syst. Sci., 15, 2201-2208, 2015
http://www.nat-hazards-earth-syst-sci.net/15/2201/2015/
doi:10.5194/nhess-15-2201-2015
© Author(s) 2015. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
07 Oct 2015
Earthquakes and depleted gas reservoirs: which comes first?
M. Mucciarelli1,2, F. Donda1, and G. Valensise3 1Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Borgo Grotta Gigante 42/c, 34010 Sgonico (Trieste), Italy
2School of Engineering, Basilicata University, Viale dell'Ateneo Lucano 10, 85100 Potenza, Italy
3Istituto Nazionale di Geofisica e Vulcanologia (INGV), Via di Vigna Murata 605, 00143 Rome, Italy
Abstract. While scientists are paying increasing attention to the seismicity potentially induced by hydrocarbon exploitation, so far, little is known about the reverse problem, i.e. the impact of active faulting and earthquakes on hydrocarbon reservoirs. The 20 and 29 May 2012 earthquakes in Emilia, northern Italy (Mw 6.1 and 6.0), raised concerns among the public for being possibly human-induced, but also shed light on the possible use of gas wells as a marker of the seismogenic potential of an active fold and thrust belt. We compared the location, depth and production history of 455 gas wells drilled along the Ferrara-Romagna arc, a large hydrocarbon reserve in the southeastern Po Plain (northern Italy), with the location of the inferred surface projection of the causative faults of the 2012 Emilia earthquakes and of two pre-instrumental damaging earthquakes. We found that these earthquake sources fall within a cluster of sterile wells, surrounded by productive wells at a few kilometres' distance. Since the geology of the productive and sterile areas is quite similar, we suggest that past earthquakes caused the loss of all natural gas from the potential reservoirs lying above their causative faults. To validate our hypothesis we performed two different statistical tests (binomial and Monte Carlo) on the relative distribution of productive and sterile wells, with respect to seismogenic faults. Our findings have important practical implications: (1) they may allow major seismogenic sources to be singled out within large active thrust systems; (2) they suggest that reservoirs hosted in smaller anticlines are more likely to be intact; and (3) they also suggest that in order to minimize the hazard of triggering significant earthquakes, all new gas storage facilities should use exploited reservoirs rather than sterile hydrocarbon traps or aquifers.

Citation: Mucciarelli, M., Donda, F., and Valensise, G.: Earthquakes and depleted gas reservoirs: which comes first?, Nat. Hazards Earth Syst. Sci., 15, 2201-2208, doi:10.5194/nhess-15-2201-2015, 2015.
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Short summary
While the debate is on the possibility that the 2012 Emilia quakes could have been triggered by human activity, we studied the inverse relationship between hydrocarbon and seismicity. Overlapping a data set of gas and oil wells with a database of seismic sources, we found that only 1/19 wells falling on the largest faults is currently productive, while the highest ratio of productive wells is found outside the seismogenic sources. In general, productive gas wells are anti-correlated with faults.
While the debate is on the possibility that the 2012 Emilia quakes could have been triggered by...
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