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Fracking : how far from faults?

Wilson, M. P. and Worrall, F. and Davies, R. J. and Almond, S. (2018) 'Fracking : how far from faults?', Geomechanics and geophysics for geo-energy and geo-resources., 4 (2). pp. 193-199.


Induced earthquakes and shallow groundwater contamination are two environmental concerns associated with the interaction between hydraulic fracturing (fracking) operations and geological faults. To reduce the risks of fault reactivation and faults acting as fluid conduits to groundwater resources, fluid injection needs to be carried out at sufficient distances away from faults. Westwood et al. (Geomechanics and geophysics for geo-energy and geo-resources, pp 1–13, 2017) suggest a maximum horizontal respect distance of 433 m to faults using numerical modelling, but its usefulness is limited by the model parameters. An alternative approach is to use microseismic data to infer the extent of fracture propagation and stress changes. Using published microseismic data from 109 fracking operations and analysis of variance, we find that the empirical risk of detecting microseismicity in shale beyond a horizontal distance of 433 m is 32% and beyond 895 m is 1%. The extent of fracture propagation and stress changes is likely a result of operational parameters, borehole orientation, local geological factors, and the regional stress state. We suggest a horizontal respect distance of 895 m between horizontal boreholes orientated perpendicular to the maximum horizontal stress direction and faults optimally orientated for failure under the regional stress state.

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Publisher statement:© The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Date accepted:16 January 2018
Date deposited:01 March 2018
Date of first online publication:28 February 2018
Date first made open access:No date available

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