By Cliff Montgomery – July 29th, 2014
The huge amounts of wastewater pumped into the ground by Oklahoma’s oil and natural gas industries probably have triggered a sudden increase in earthquakes around the region, say researchers.
The scientists say the number of earthquakes in the state increased forty-fold between 2008-13.
Researchers add that the wastewater of four especially active disposal wells may have caused a surge of tremors recorded over 20 miles away from the sites.
The scientists’ findings were recently published in the research journal Science.
The document makes for grim reading. In fact, the scientists found that “twenty percent of the earthquakes in the central United States could be attributed to just four of the wells,” states an editor’s summary of the Science article.
Water is now a fundamental part of oil and natural gas extraction. Though many know it is employed during the process of induced hydraulic fracturing – perhaps better known as fracking – it is also used to grab a few more strains of oil from conventional wells.
During such procedures, a pressurized liquid (often freshwater mixed with chemicals and other agents) is used to break open deep-rock formations which contain oil or natural gas. The injected liquid – along with brine often released during the fracturing process – eventually is separated from the extracted oil or gas. What’s left is a briny wastewater fit only for disposal.
“There is a high ratio of water to oil,” the study’s principal author, Dr. Katie Keranen, told BBC News.
“It differs for each well. The typical nationwide ratio is five to one. [But] We’re seeing much higher ratios, in the hundreds, at the beginning of the well,” added Keranen.
Dr. Keranen works at the Department of Earth & Atmospheric Sciences at Cornell University. Nay-sayers will have a hard time portraying Keranen as an ‘anti-corporate militant’: she previously worked “for ExxonMobil Exploration Company as a geophysicist,” according to her Cornell University biography.
And a growing body of evidence indicates that the disposal of wastewater from the fracking process has, in recent years, been a possible cause of earthquakes in such states as Oklahoma, Texas, Arkansas and Ohio.
In November 2011, a quake which registered a magnitude of at least 5.6 hit the tiny town of Prague, Oklahoma. The high-intensity quake, classified as “severe” by the United States Geological Survey (USGS), injured a handful of people and destroyed 14 houses in the town.
At least one newspaper in the area said that officials had described it as “the largest earthquake ever recorded in the state of Oklahoma.”
A study on the November 2011 quake was conducted by Stephen Horton, who serves as research scientist for the Center for Earthquake Research and Information, University of Memphis. Released about five months after the event, Horton’s report found that injection wells “possibly triggered” the massive earthquake.
A later report on the matter was published in 2013 by the journal Geology. It found a link between wastewater disposal wells and the quake that shook Prague, OK. The researchers wrote “we interpret that a net fluid volume increase after 18 yr of injection lowered effective stress on reservoir-bounding [geologic] faults.”
“Significantly, this case indicates that decades-long lags between the commencement of fluid injection and the onset of induced earthquakes are possible,” added the Geology article.
And the issues of fracking and wastewater may be fraught with other problems in Oklahoma.
“In July 2012 it was reported that Oklahoma officials ignored advice about injecting water into faults, to maintain production of oil and natural gas,” according to The Center for Media and Democracy (CMD), an investigative research and reporting group.
So what is to be done on the matter of wastewater disposal from fracking?
“Induced seismicity is one of the primary challenges for expanded shale gas and unconventional hydrocarbon development,” declared Dr. Keranen to The Cornell Chronicle, which serves as Cornell University’s in-house weekly newspaper.
“Our results provide insight into the process by which the earthquakes are induced,” stated the researcher, who added that “adherence to standard best practices may substantially reduce the risk of inducing seismicity.”
“The best practices include avoiding wastewater disposal near major faults and the use of appropriate monitoring and mitigation strategies,” continued Keranen.
“Earthquake and sub-surface pressure monitoring should be routinely conducted in regions of wastewater disposal, and all data from those should be publicly accessible,” stated Dr. Keranen, who also pointed out that “independent quality assurance checks would increase confidence.”
