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Anti-fracking groups are trumpeting a new study published in Nature Communications as a smoking gun supposedly proving hydraulic fracturing has been causing earthquakes in Texas and Oklahoma. This is just another case of activists being informed on a subject just enough to be dangerous.
The increase in earthquakes in these two states is likely due to disposing of wastewater generated during the hydraulic fracturing process, not the fracturing process itself. The U.S. Geological Survey (USGS) has stated, “Hydraulic fracturing, commonly known as ‘fracking,’ does not appear to be linked to the increased rate of magnitude 3 and larger earthquakes.”
Hydraulic fracturing involves pumping two to four million gallons of water, along with sand and trace amounts of benign chemical additives, into wells drilled into oil- or natural gas-rich rocks at high pressures to create a network of micro-fractures in the rock, allowing the oil and gas to flow up to the surface. About 10 percent to 20 percent of this water returns to the surface as flowback water. This water must be treated and recycled or disposed of in deep underground injection wells, which are regulated as Class II wells by the Environmental Protection Agency.
In Pennsylvania, energy producers recycle 90 percent of the fracking water that flows back up to the surface. The state has not experienced earthquakes from the hydraulic fracturing process. By contrast, Oklahoma and Texas primarily rely on underground injection methods to dispose of fracking wastewater, and this had led to an increase in what geologists call “induced seismicity,” meaning manmade earthquakes.
Oklahoma experienced 585 earthquakes registering a magnitude 3 or higher in 2014, compared to 109 events in 2013, representing a significant increase in earthquake activity. Portions of Texas have had a smaller increase in the frequency of small earthquakes produced by injecting wastewater into the underground injection wells, which led researchers to conclude, “On the basis of modeling results and the absence of historical earthquakes near Azle, [Texas,] brine production combined with wastewater disposal represent the most likely cause of recent seismicity near Azle.”
Although Oklahoma and Texas have experienced increases in earthquakes, North Dakota, which also uses wells to dispose of fracking wastewater, has not experienced any earthquakes as a result of using this method. According to USGS, there are more than 30,000 injection wells for disposing of waste in the United States, but “only a small fraction of these disposal wells have induced earthquakes that are large enough to be of concern to the public.”
Some areas are more prone to induced seismicity because of the local geology. Fortunately, there are precautions state regulators can take to greatly reduce the risk of induced earthquakes. For example, when Ohio experienced a series of earthquakes related to disposing of fracking wastewater, the state implemented rules requiring drillers to monitor pressures within injection wells, preventing drillers from injecting wastewater near known fault lines, and restricting the volume and pumping rates of fracking wastewater injected into wells. These sensible regulations have decreased the risk of earthquakes related to disposing of wastewater in injection wells.
As scientists and regulators continue to investigate the relationship between earthquakes and injection wells, they will gain knowledge that will have great value in preventing earthquakes induced by other technologies, including carbon dioxide sequestration technology and geothermal energy production, which employ similar injection methods.
Anti-fracking activists often point to the earthquakes that occur as a result of wastewater disposal as evidence hydraulic fracturing itself causes earthquakes. That is not an accurate portrayal of the issue, but it’s not necessarily surprising. The spread of misinformation is far more common than human-induced earthquakes.