Recently, attention has been drawn to the earthquake hazard associated with the production of oil and gas from previously unproductive formations due to the unprecedented increase in earthquake activity in the central U.S and its possible association with oilfield operations.  Earthquakes can be induced as part of the process to stimulate the permeability of tight shale formations, or by disposal of wastewater associated with stimulation and production.  A pre-stressed fault can be brought to failure causing an earthquake by increasing the pore fluid pressure which reduces the frictional strength of the fault.  By design, hydraulic fracturing induces numerous microearthquakes as part of the process to create a connected fracture network to enhance formation permeability. These microearthquakes are nearly always too small to be felt at the surface. None have, thus far, been large enough to cause structural damage.  In contrast, high-volume and long-term injection of fluids into deep wells for a variety of fluid disposal purposes have induced earthquakes with magnitudes as large as 5.7 and several have caused structural damage and injuries.  The increased hazard posed by these industrial earthquakes has proven difficult to integrate into standard earthquake hazard models.  Better knowledge of the stress and pressure conditions at depth, the hydro-geologic framework, and the location and orientation of faults near injection sites will be needed to develop a more quantitative assessment of the earthquake hazard posed by fluid injection.

Hydraulic fracturing, fluid injection, and induced earthquakes

248th National Meeting (2014)

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