Wells filled with waste injection fluids at oil and gas fields across the United States are at risk of small earthquakes triggered by larger temblors across the globe, according to a new study published Thursday.
Waste injection wells are on the rise as domestic energy production soars and companies increasingly use water and chemicals to unlock natural gas from shale or force oil from wells, a process known as hydraulic fracturing, or fracking.
As oil and gas industries pump waste into sub-surface wells, the pressure can weaken nearby faults and leave them vulnerable to seismic waves passing by from other earthquakes – even ones on the other side of the Earth, according to a new study published in the journal Science.
Squeezed Like a Sponge
Waves from major shakers travel enormous distances through Earth's crust. As they do so, said lead author Nicholas van der Elst, a researcher at Columbia University's Lamont-Doherty Earth Observatory, they “squeeze rock formations like a sponge.” This opens up new passageways for fluids to get into faults and weaken them, he said.
Van der Elst and colleagues found that a large earthquake in February 2010 in Chile set off a mid-size earthquake and a series of tremors in the oil fields around Prague, Okla. – 5,000 miles distant. A year and a half later, in Nov. 2011, a magnitude 5.7 earthquake rattled the region that researchers say was also linked to the Chile quake. They also linked earthquakes in Japan in 2011 and Sumatra in 2012 to mid-size tremors near waste injection well fields in western Texas and southern Colorado.
Wastewater well injection has been going on at the Oklahoma, Texas and Colorado sites for decades. The tremors and earthquakes at those sites came anywhere from six to 20 months after the distant earthquakes, with the delay probably due to the seismic waves' opening up of new passageways for underground fluids to infiltrate faults – weakening them over time, van der Elst said.