Fracture propagation during shale gas hydraulic fracturing

Kim and Moridis, International Journal of Rock Mechanics and Mining Sciences. March 2015. Link to abstract.

A recently published study on numerical simulations of fracture propagation during hydraulic fracturing operations in shale gas systems supports previous studies on fracture growth to be in the range of about a few hundred meters. Researchers examined the likelihood of hydraulic fracture propagation (the spread of fractures) travelling long distances to connect with drinking water aquifers. 

The simulations indicate that typical hydraulic fracturing operations do not appear to generate an unstable growth of a fracture in the shale gas reservoir to the drinking water aquifer unless unrealistic high pressure and high injection rates are directly applied to an extremely weak and homogenous geological formation that extends up to the near surface. Instead, the models showed that hydraulic fracturing produced stable fracture propagations, supporting the argument from the real data in the previous studies, for example, no greater than 460 m of vertical fracture propagation inferred from microseismic signals (see SHIP News, "Safe distance between hydraulic fractures and groundwater", 10 July 2012).

Modelling of fault activation and seismicity by injection directly into a fault zone associated with hydraulic fracturing of shale gas reservoirs

Rutqvist et al., Journal of Petroleum Science and Engineering. March 2015. Link to abstract.

Researchers expanded upon a previous study by injecting directly into a 3D representation of a hypothetical fault zone located in the geologic units between the shale gas reservoir and the drinking water aquifer. As before, modelling results suggest it is unlikely that activation of a fault by shale gas hydraulic fracturing at great depth could create a flow path that could reach shallow groundwater. Furthermore, these results suggest that it is unlikely that induced seismicity would be felt at land surface.

Text modified from United States Environmental Protection Agency EPA.