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A newly released publication in the highly respected scientific research journal Science by William Ellsworth of the U.S. Geological Survey provides a much-needed voice of reason in the social debate on oil and gas wastewater disposal, or what is known as “class II injection.”
The article, “Injection-Induced Earthquakes,” does an excellent job of reviewing what we know about earthquakes triggered by injection activities, sheds light on the increase of midcontinent earthquake activity during the past decade, and discusses what can be done to reduce the risk of induced earthquakes.
Residents of Northeast Ohio and the Mahoning Valley have a heightened awareness of injection-induced earthquakes after the string of earthquakes that began March 17, 2011, and led to the magnitude 4.0 earthquake on New Year’s Eve of the same year.
The combination of the D&L Energy’s Northstar No. 1 injection-well design, the coincidence of earthquake timing with injection activity, the proximity of earthquakes to the well location and high-quality seismic monitoring data leaves very little doubt that injection of oil and gas-production wastewater triggered the earthquakes.
Compared to other possible injection-related earthquakes in Arkansas, Oklahoma and Texas during the same year, the Youngstown earthquakes of 2011 are well understood thanks to a joint seismic (earthquake) monitoring effort by the Youngstown State University Department of Geological and Environmental Sciences, Lamont-Doherty Earth Observatory and the Ohio Geological Survey.
In late November 2011, a network of four field-based seismographs were deployed to the region of seismic activity near the Northstar No. 1 injection well. The timing of the deployment was very good as the Dec. 24 and Dec. 31 earthquake recordings provided accurate earthquake data used to locate a previously unidentified fault directly below the injection zone.
Gov. John Kasich ordered the shutdown of the Northstar well, and seismic activity ceased with one last small earthquake Jan. 13, 2012.
What do we know about class II injection and its link to induced earthquakes?
1. The U.S. has approximately 30,000 class II injection wells used for waste- water disposal, and these wells have been in operation for decades with very few incidents of suspected or confirmed induced earthquakes.
2. Class II injection is the U.S. Environmental Protection Agency’s best- management practice for disposal of oil and gas wastewater despite established relationships between injection and earthquakes.
3. Earthquakes can be triggered as injected wastewater effectively reduces friction along previously unidentified or inactive faults near the well.
4. We know from experiments conducted in the Rangely oil field of Colorado between 1969 and 1973 that fluid injection actually can control the occurrence of earthquakes.
There is no doubt that the midcontinent region has seen an increase of magnitude 3.0 or greater earthquakes during the past decade and that some of the locations of increased seismic activity corresponds to oil- and gas-producing areas with active class II wastewater disposal. Some argue the increased activity is a product of improved and more widespread earthquake monitoring, while Ellsworth states that, essentially, none of the earthquakes would have gone unnoticed without enhanced seismic monitoring.
Ohio has a network of more than 190 class II injection wells originally intended for disposal of brine from the 64,000 or so producing wells within the state. Insufficient disposal and treatment facilities within the Marcellus producing areas of Pennsylvania have resulted in dramatic increases in disposal of out-of-state wastewater.
Disposal volumes have increased over the past five years from about seven million barrels per year to about 15 million barrels per year. These numbers are certain to rise as the Utica Shale play is developed.
Class II injection is permitted and regulated by the Ohio Department of Natural Resources Division of Oil and Gas Resources Management.
Before the Youngstown earthquakes, the injection regulations focused solely on protection of groundwater resources.
In response to the earthquake activity, Ohio passed legislation (Senate Bill 315) in 2012 that strengthened class II regulations across the board and gave the ODNR broader authority to minimize future risk of injection-induced earthquakes by prohibiting drilling into the Precambrian basement rocks where most faults originate, by investigating the possible existence of basement rock faults, by requiring continuous pressure-monitoring systems and by equipping injection wells with automatic shut-off systems.
ODNR class II regulatory improvements cannot guarantee earthquakes will not occur in the future; they can only minimize the risk. In light of injection-related seismicity, certain environmental activist groups are calling for a total ban on class II injection in Ohio and elsewhere.
Although a ban on injection has seemingly good intentions, the effort is meaningless without a ready alternative to injection disposal. The geologic formations of Ohio do not have unlimited capacity. Even though more injection wells can and will be constructed, the practice is not sustainable in the long run. The oil and gas industry along with federal and state governments and academic institutions need to work together to develop cost-effective wastewater recycling and purification alternatives to injection disposal.