Energy Technologies: How They Work and Their Induced Seismicity Potential - Induced Seismicity Potential in Energy Technologies - page 65

Figure Schematic diagram of a horizontal well following a 10-stage hydraulic fracture treatment. Upper right
inset shows a magnified view of the induced fractures (yellow) created during the hydraulic fracture treatment.
The relative depths of local water wells is shown near the surface for scale, labeled “domestic well.” The forma-
tion depth and horizontal well length vary from area to area; the depth and well length numbers shown are
approximate averages for North America. The well is fractured in stages from the end of the well (stage 1) to
the start of the well (stage 10). Each hydraulic fracture stage is isolated within the wellbore as discussed in the
text. Depths and distances of 2,000-10,000 feet correspond to about 600-3,000 m. SOURCE: Adapted after
Southwestern Energy, used with permission.
addition approximately 50 weaker events were detected after additional seismic stations were deployed (De Pater
and Baisch, 2011). Cuadrilla Resources initiated an extensive study of the incident, including installing portable
seismic stations and a detailed seismic analysis as well as geomechanical studies and core studies, which were
released to the public on their website. The research demonstrates that the hydraulic fracturing induced the seismic
events. A report by Geosphere Ltd. (Harper, 2011) suggests the propagation of the fracturing fluid and pressure
went farther than expected along the bedding planes. A nearby, apparently unstable fault was reactivated by
the increase in fluid pressure, which caused the seismic events (Harper, 2011).
SOURCES: De Pater and Baisch (2011).