Skip to content

Is Shale Gas Production or People’s Perceptions Seismically Active?

March 11, 2012

It is important to put seismic activity in natural gas development into proper context.  Minor and imperceptible seismic activity is extremely common around the world.  Before and during operations, natural gas production companies study the seismicity of the areas where they are operating and design operational plans for each well based on an understanding of the specific geology.

“Oklahoma Geological Survey seismologist Austin Holland said seismic events around development activity are “really quite inconsequential. In separate comments on a potential earthquake risk from hydraulic fracturing, Stanford University geophysicist Professor Mark Zoback stated that the typical energy released in these instances “is the equivalent to a gallon of milk falling off the kitchen counter.” (1)

Furthermore, seismic activity can also occur in mining operations, driving piles for bridge, building construction, and drilling geothermal wells, in seismically active areas. Under the right conditions, every time pressure is applied or reduced from an underground rock formation there is at least a small risk of a seismic activity. There are about 1.3 million 2-2.9 magnitude quakes every year around the world.

Examples:

The Bulletin of the Seismological Society of America,  published “We’ve studied how fairly shallow underground coal mining causes earthquakes that, depending on their size, might pose a ground-shaking hazard to nearby surface structures……” (2)

Each quarter, South Africa’s Council for Geoscience “published “Most of the events (seismic) are associated with deep-level gold mining of the reefs on the periphery of the Witwatersrand basin. The largest mining related seismic event ever to occur in South Africa took place on the 9 March 2005 and registered 5.3 on the local Richter magnitude scale.” (3)

An article “Coal Mining Causing Earth”  reported “ The magnitude-5.6 quake that struck Newcastle in New South Wales on December 28, 1989, killed 13 people, injured 160, and caused 3.5 billion U.S. dollars’ worth of damage. That quake was triggered by changes in tectonic forces caused by 200 years of underground coal mining……” (4)

Today, shale gas production is in the headlines for causing small, repeated earthquakes. These micro quakes have been linked to various aspects of the hydraulic fracturing operation such as the injection of fracking wastewater into containment wells deep below ground. Most of the quakes are minuscule, Magnitude 2 or 3 or less, and pose no public health or safety risks.

“What is believed to happen, is when the old fracking flowback water is injected into the deeper disposal wells, it reduces the friction in the fault. This doesn’t cause a quake; it just speeds up the process. The quake will happen somewhere down the line anyway, but this process may be making them happen sooner.”

Only a fool would want to sweep shale induced seismic activity under the rug, no matter how insignificant. The industry has taken steps to reduce risk of seismic activity from the injection at wastewater wells.

The Center for Strategic and International Studies reports, “Regulators and operators can take, and are already taking, a number of actions to reduce the future likelihood of seismic activity from wastewater injection, including assessing seismic risk when identifying or permitting injection sites, requiring seismic monitoring at active well sites, and limiting well pressure thresholds by decreasing the amount of water pumped into wells as well as the pressure at which it is pumped. Discussions are also under way about whether and how to handle the issue of large-volume injection at or near fault zones.” (5)

“Wastewater from natural gas extraction cannot be discharged directly into waterways without undergoing treatment. The EPA is developing natural gas wastewater standards for water that is taken to wastewater treatment facilities as some plants are not properly equipped to handle the wastewater. Another important option is to recycle and re-use wastewater, thereby reducing the volumes that ultimately must be disposed of in injection wells. Technological advancements are increasingly making this cost-competitive option. In addition, firms are now developing and employing “green” frack components, finding better ways to treat and recycle liquids flow, and exploring ways to reduce the amount of water used in fracking operations through advanced minimization technologies—all of which could result in the generation of less wastewater.” (5)

In closing, there is increased emphasis, not only in the mechanical aspects of completing these wells, but also on the geophysics and geologic aspects of where to drill and how to be more precise in designing shale gas production.  Seismologists have been able to demonstrate that seismic data can be processed and analyzed such that sweet spots in shale sections can be identified prior to drilling.

Photo: Shale gas is a natural gas locked in the matrix of low porosity shale rocks. Compliments of British Geological Survey

References: (1) “Seismic Activity and Natural Gas Development,” America’s Natural Gas Alliance; http://anga.us/critical-issues/seismic-activity (2) Physorg.com, Seismologists Study Mining-Induced Earthquakes, http://www.physorg.com/news3360.html (3) A summary of recent research in seismology in South Africa, L.M. Linzera, CSIR NRE: Mining; http://www.iugg.org/members/nationalreports/southafrica07-iaspei.pdf (4) “Coal Mining Causes Earth Quake Study Says,” National Geographic News, January 3, 2007, Richard A. Lovett; http://www.freerepublic.com/focus/f-bloggers/2691845/posts (5) Center for Strategic and International Studies, “Fracking and Seismic Activity,” by By Frank A. Verrastro, Lisa Hyland, and Molly Walton, Jan 12, 2012;  http://csis.org/publication/fracking-and-seismic-activity

Advertisements
No comments yet

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: