Fracking the Cause of Low-Level Seismic Activity - B.C. Oil and Gas Commission Report
A report by the B.C. Oil and Gas Commission says hydraulic fracturing is responsible for low-level earthquakes in British Columbia.
"Anomalous" seismic activity detected in remote parts of the Horn River Basin was investigated in the province's northeastern corner.
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1. The seismicity observed and reported by NRCan in the Horn River Basin between April 2009 and December 2011 was induced by fault movement resulting from injection of fluids during hydraulic fracturing.
2. No injuries or property damage were reported as a result of the induced seismicity. Only one event was reported by NRCan to have been felt at the ground surface.
3. The fractures developed during the hydraulic fracturing operations studied within the investigation were effectively confined to the target Horn River shales by the overlying Ft. Simpson shales. No effects on shallow aquifers or the environment were identified.
4. The magnitude and frequency of the induced seismicity investigated by the Commission may be influenced by numerous factors including pump rate, breakdown pressure and proximity to pre-existing faults.
5. No casing deformation was reported in the vertical portion of wellbores and no reservoir containment issues were identified. Minor casing deformation within the horizontal well portion of target shale formations occurred in 2 instances. The cause of the casing deformation could not be conclusively linked to the seismicity.
6. Fault mapping provided by operators shows abundant sub parallel north-south trending faulting through the Etsho and Tattoo areas. These faults are generally deep seated and do not show displacement above the Ft. Simpson shale. The Ft. Simpson shale is considered to be a ductile fracture barrier. Fault reactivation in this structural setting is not considered a threat to shallow overlying aquifers.
7. Seismograph station additions are needed to the CNSN to improve monitoring for induced seismicity in northeast British Columbia.