Fracking and labquakes

Abstract

Local fracture events (or labquakes) during compression of shale rocks have been studied by acoustic emission. They are assumed to simulate quakes induced by hydraulic fracturing (fracking) or other water injection activities. Results are compared with those obtained during compression of porous Vycor glass, which are known to display statistical features very similar to those characterising natural earthquakes. Our acoustic emission results show that labquake energies are power law distributed, which is consistent with recent statistical analysis of fracking-/water injection-induced quakes. The data confirm a Gutenberg–Richter behaviour with exponents larger than the exponents characterising the energy distribution of natural earthquakes. In contrast to natural earthquakes, labquakes in shales do not show time correlations, which indicates that the probability of aftershocks is smaller than in the natural scenario (e.g. during Californian earthquakes).

Keywords:

• Fracking
• labquakes
• acoustic emission
• shale rocks
• Vycor glass

Acknowledgments

We are grateful to Ian Bradford (Schlumberger) for providing the shale samples.