Publication Date:
2016-10-05
Description:
For induced microseismicity associated with hydraulic fracturing, the frequency-magnitude distribution is typically characterized by a falloff with increasing magnitude that is significantly faster than for seismicity along active fault systems. This characteristic may arise from a break in scale invariance, possibly due to mechanical layering that typifies fine-grained sedimentary rocks in many shale gas and tight oil reservoirs. The latter would imply the presence of spatio-temporal magnitude correlations. Using three microseismic catalogs for well stimulations in widely separated locations with varying hydraulic-fracturing methods, we show that events with similar magnitudes indeed tend to cluster in space and time. In addition, we show that the inter-event time distribution can be described by a universal functional form characterized by two power-laws. One exponent can be related to the presence of inter-event triggering as in aftershock sequences and is a consequence of the Omori-Utsu law. The other one is a reflection of the intrinsic spatial variation in the microseismic response rates. Taken together, these features are indicative of non-trivial spatio-temporal clustering of induced microseismicity and, hence, of direct relevance for time-dependent seismic hazard assessment.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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