Scientists Find ‘Direct Link’ Between Earthquakes And Process Used For Oil And Gas Drilling
by Emily Atkin, Think Progress
September 16, 2014 at 2:59 pm
A team of scientists with the U.S. Geological Survey have found evidence “directly linking” the uptick in Colorado and New Mexico earthquakes since 2001 to wastewater injection, a process widely used in the controversial technique of hydraulic fracturing, or fracking, and conventional drilling.
In a study (.PDF) to be published in the Bulletin of the Seismological Society of America on Tuesday, the scientists presented “several lines of evidence (that) suggest the earthquakes in the area are directly related to the disposal of wastewater” deep underground, according to a BSSA press release. Fracking and conventional natural gas companies routinely dispose of large amounts of wastewater underground after drilling. During fracking, the water is mixed with chemicals and sand, to “fracture” underground shale rock formations and make gas easier to extract.
The USGS research is just the latest in a string of studies that have suggested the disposed water is migrating along dormant fault lines, changing their state of stress, and causing them to fail.
For their research, the four California-based USGS scientists monitored the 2,200 square mile Raton Basin, which goes from southern Colorado into New Mexico. They pointed out that the Basin had been “seismically quiet” until 1999, when companies began “major fluid injection” deep into the ground. Earthquakes began in 2001 when Colorado wastewater injection rates were under 600,000 barrels per month, and and since then there have been 16 earthquakes that could be considered large (above a magnitude of 3.8, including two over a 5.0 magnitude), compared with only one – a 4.0 magnitude quake – in the 30 years prior.
“These earthquakes are limited to the area of fluid injection, they occur shortly after major fluid injection activities began, and the earthquake rates track the fluid injection rates in the Raton Basin,” the paper said, noting the scientists’ comparisons of the timing and location of earthquakes with the timing and location of injected wastewater. By the mid-2000s, Colorado’s wastewater injection rates were up to 1.9 million barrels per month.
Taking that and the unexpected frequency of the earthquakes into consideration, the paper noted that it was “highly unlikely” that the quakes could have been due to any random fluctuations underground.
“Detailed investigations of two seismic sequences places them in proximity to high-volume, high-injection-rate wells, and both sequences occurred after a nearby increase in the rate of injection,” the study’s accompanying press release said. “A comparison between seismicity and wastewater injection in Colorado and New Mexico reveals similar patterns, suggesting seismicity is initiated shortly after an increase in injection rates.”
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