By David Pryce
Canadian Association of Petroleum Producers
Questions about the relationship between hydraulic fracturing and seismic activity continue to be asked by the media and the public at large.
This commentary seeks to provide some answers by summarizing the most recent scientific research published on this issue.
Micro and minor seismic events have long been known to be caused by human activity. Scientific literature describes these as induced seismicity.
Human activities that can cause seismic events include mining, geothermal energy extraction, filling the reservoir behind large dams and hydraulic fracturing.
Hydraulic fracturing is a regulated, safe, controlled and essential process for recovering natural gas from deep geological formations such as shale rock. In Western Canada, the petroleum industry has used this process for more than 60 years.
Seismicity typically associated with hydraulic fracturing is best described as microseismic events because of their low magnitude. It is normal to expect microseismicity as a result of hydraulic fracturing: pressurized fluids are injected into a wellbore, lined with steel and cement, to deep underground formations to fracture the rock, thereby freeing trapped natural gas. This process releases energy and causes sub-surface microseismic events. These events are generally contained in the zone where the gas is extracted, are rarely felt on the surface and pose minimal to no risk to structures on the surface. In some cases, hydraulic fracturing has caused minor seismic activity, which is rarely felt on the ground and poses no risk to people, the environment or property.
Comprehensive data and information on seismic activity in Canada is available on Natural Resources Canada’s website.
It says that on average, more than 4,000 earthquakes are recorded in Canada each year, of which “about 50 are generally felt.” In addition, the website says “minor earthquakes have been triggered by human activities.”
Several scientific research papers describing the relationship between hydraulic fracturing and seismic activity have recently been published. This research suggests an emerging scientific consensus that seismic activity from hydraulic fracturing poses minimal risk, as outlined in the following studies.
The B.C. Oil and Gas Commission released a report of its investigation into induced seismicity in the Horn River Basin in August 2012. The report indicates microseismic activity is a routine occurrence associated with hydraulic fracturing. Larger magnitude minor anomalous seismic events (2 ML to 3.8 ML), and smaller micro-seismic events, were recorded between April 2009 and December 2011 by government and industry seismic sensors in the Horn River, a remote area of northeast B.C. Such seismic activity is rarely felt on the surface and usually occurs near where the rock is being fractured (or 2,000 to 3,000 metres below ground). The B.C. OGC report concludes a total of 272 seismic events recorded were “caused by fluid injection during hydraulic fracturing in proximity to pre-existing faults” and notes that “none of the events caused any injury, property damage or posed any risk to public safety or the environment.” More than 8,000 high-volume hydraulic fracturing completions have been performed in B.C. View full report.
In England, the Department of Energy and Climate Change asked a panel of experts to examine a link between a hydraulic fracturing operation near Blackpool and seismic activity. The report, published in April 2012, concluded that hydraulic fracturing did cause “observed seismicity” near the operations area. It also concluded that hydraulic fracturing can proceed if the process is carefully monitored and appropriate precautions are taken. View the full report.
In June 2012, the Royal Society and the Royal Academy of Engineering in Great Britain released a comprehensive government-commissioned review of issues related to hydraulic fracturing, including seismic activity. The report says “microseismic events are a routine feature of hydraulic fracturing and are due to the propagation of engineered fractures.” It concludes there is an emerging consensus that seismicity induced by hydraulic fracturing poses a “negligible” risk of causing surface impacts. The report also points out that “the properties of shale provide natural constraints on the magnitude of seismicity induced by hydraulic fracturing” – because shale is relatively weak, it requires less energy to hydraulically fracture. View the full report.
The U.S. National Research Council reached a similar conclusion. Its June 2012 report, called Induced Seismicity Potential in Energy Technologies, says various forms of human activity, including hydraulic fracturing, can cause slight seismic activity. The report also states that “the process of hydraulic fracturing a well as presently implemented for shale gas recovery does not pose a high risk for inducing felt seismic events.” View the full report.
These reports reflect the results of comprehensive, science-based research conducted by respected and credible organizations, and they are an important contribution to the discussion regarding the development of this important shale gas resource.
Canada’s natural gas producers are developing new industry guidelines that will include monitoring protocols and will establish practices to mitigate induced seismicity. Details will be announced in the coming weeks.
Our objective will continue to be assurance of safe and responsible development of shale gas resources in British Columbia.