Friday, December 14, 2012

Fracking and Earthquakes - Update

Scientists from the American Geophysical Union meeting in San Francisco last week discussed the latest evidence of a connection between increased seismic activity in shale gas production regions and the disposal of fracking wastewater in injection wells located in those areas. 

Several scientists presented data that indicated a 5.7 Oklahoma quake in 2011, the largest ever in the state's history, likely was caused by fluid injection. In addition, scientists from the U.S. Geological Survey presented data from a series of earthquakes since 2001 in Colorado and New Mexico’s Raton Basin that they said supported their conclusion that these quakes also were related to wastewater injections.

The data appear to conclusively show an increase in seismic activity in some shale exploration areas. Oklahoma, for example, has had over 250 earthquakes since 2010 compared to an annual average of two or three in the years prior. Scientists are uncertain, however, what the exact relationship is between the rising quake trend and fracking wastewater injection since injection wells were commonly used by mining companies and petroleum producers in these regions long before fracking became common. 

Nor are they sure why quakes appear to be caused by injection wells in some areas and not in others. In a study of earthquakes in the Dallas-Forth Worth area in the Barnett Shale of Texas, the data showed all earthquakes were within two miles of high-volume injection wells. However, there were no quakes at all near other wells.

In North Dakota, a state geologist concluded that an earthquake in Williams County on September 28 was characteristic of past seismic activity in the area and was not related to hydraulic fracturing. The earthquake had a magnitude of 3.3 and occurred at a depth of approximately 2,000 feet, much shallower than the depths at which most fracking in the Williston Basin is done, according to the geologist, who stated that it is generally believed that fracking does not contribute to earthquakes.

Elsewhere, Ohio officials recently lifted a moratorium on injection well permits after implementing new requirements for injection well construction. The new rules are in response to a series of eleven quakes near Youngstown, Ohio that scientists concluded were directly related to an injection well in the area. Similarly, the British government announced this week that it has lifted its ban on fracking after putting new rules in place for oil producers in the shale areas of northwestern England. 

In the U.S., the Environmental Protection Agency is conducting a review of fracking wastewater disposal practices, but is looking primarily at wastewater pollutant discharges. There has been no suggestion to date that the agency will expand its possible regulatory framework to include potential seismic implications. The EPA plans to propose new wastewater disposal standards for public comment in 2014.  

No comments: