After pulling massive amounts of fossil fuels out of the Earth’s crust so we can burn it up into our atmosphere, we have a good sense of where the stuff goes. Our oceans. A global greenhouse. Our lungs. But what happens to the ground formerly occupied by those fossil fuels?
It’s becoming increasingly clear that oil and gas extraction processes are actually weakening the structural integrity of the Earth’s crust just enough to cause more frequent earthquakes, in places not used to them.
Oklahoma, for instance, is not known for earthquakes. Yet the central U.S. has seen an elevenfold jump in recent years, including the Sooner State’s largest earthquake on record. This 5.7-magnitude quake occurred on November 6, 2011 near Prague, Oklahoma. And research published yesterday in Geology from the University of Oklahoma, Columbia University, and the U.S. Geological Survey has made a direct connection to the disposal of wastewater from conventional oil production:
A new study in the journal Geology is the latest to tie a string of unusual earthquakes, in this case, in central Oklahoma, to the injection of wastewater deep underground. Researchers now say that the magnitude 5.7 earthquake near Prague, Okla., on Nov. 6, 2011, may also be the largest ever linked to wastewater injection. Felt as far away as Milwaukee, more than 800 miles away, the quake — the biggest ever recorded in Oklahoma — destroyed 14 homes, buckled a federal highway and left two people injured. Small earthquakes continue to be recorded in the area.
The recent boom in U.S. energy production has produced massive amounts of wastewater. The water is used both in hydrofracking, which cracks open rocks to release natural gas, and in coaxing petroleum out of conventional oil wells. In both cases, the brine and chemical-laced water has to be disposed of, often by injecting it back underground elsewhere, where it has the potential to trigger earthquakes. The water linked to the Prague quakes was a byproduct of oil extraction at one set of oil wells, and was pumped into another set of depleted oil wells targeted for waste storage.
As Climate Progress has written before, this practice of disposing chemical-laced water generated during the extraction of oil and gas has far-reaching effects. Drillers have been doing this for more than a decade, and the researchers note that the Oklahoma quake did not actually require very much wastewater. In fact, because we have been doing this for so long, the built-up pressure in the Earth’s crust changes the criteria of how quakes happen. The study’s abstract notes:
Significantly, this case indicates that decades-long lags between the commencement of fluid injection and the onset of induced earthquakes are possible, and modifies our common criteria for fluid-induced events.
So we could be paying for more than a decade of wastewater injection and fracking for quite some time with earthquakes. There’s not much more room 9,000 feet down. Wellhead records indicate that pressure in these areas underground increased by a factor of ten from 2001 to 2006.