Since the fracking boom started, the state of Oklahoma has had numerous earthquakes, in increasing frequency. It has experienced more than 700 earthquakes so far this year, more than all of 2014. In the last seven days, up to Oct. 19, the state has experienced more than 40 earthquakes with a magnitude of 2 or greater within 200 miles, according to Oklahoma’s Stillwaterweather.com website.
Jeremy Boak, director of the Oklahoma Geological Survey, said on Oct. 16 in a quick appearance on MSNBC’s “The Rachel Maddow Show” that the increased frequency of earthquakes in Oklahoma is caused by oil and gas operations. But he said it’s not due to water and chemicals being injected in the ground.
He explained that naturally occurring water already located in the formations for tens of thousands of years is what is really causing earthquakes. “That’s the water that we’re disposing of,” he said. “We’re taking it out of formations, separating the oil and gas, and then we’ve got this stuff that has to be disposed of.”
The disposed water is placed in a deep formation called the Arbuckle Group, he said. Arbuckle is a 7,000-foot sedimentary formation under Oklahoma, which sits on top of the crystalline basement (rocks concealed below the sedimentary formation). The basement helps geologists understand the origin and age of the Earth’s crust.
He characterized the water as “very salty,” even saltier than ocean water or Dead Sea water. This water has been injected into the same rock formation for “many, many years … a long way away from groundwater,” according to Boak, and the stress state deep in the rock is changing and causing some small faults to move. He said these are the ones that are oriented “just right” within the stress field in Oklahoma.
According to Oklahoma’s Office of the Secretary of Energy & Environment, the state experienced 109 magnitude 3+ earthquakes in 2013, five times that number in 2014, and the pace has accelerated even more in 2015. Boak says there have been more than 700 magnitude 3+ earthquakes already this year.
Not only that, but the state maintains the largest oil storage facility in the world in Cushing, Oklahoma. The facility holds 82 million barrels of oil, and it has been designated as a critical national infrastructure by the U.S. government. It’s located in an area covering about 15 percent of the state that’s had this spate of magnitude 4 earthquakes, and Boak is worried that the next one may be bigger.
Other Storage Options
Another name for this old salty water is “produced water” and it contains some of the hydrocarbon chemical properties of the formations it was released from, states the Advanced Water Technology Center. The center, operated by the Colorado School of Mines, was established to advance the science of emerging water treatment processes and hybrid systems.
But according to the center, the old salty water is not all that is being separated from the oil and gas and it’s not always injected back deep into underground rock formations.
Once this trapped water is brought to the surface through hydraulic drilling, it may also “contain water from the reservoir, water injected into the formation, and any chemicals added during the drilling, production, and treatment processes,” the site states.
Produced water is the largest volume byproduct stream associated with oil and gas exploration and production. It generates approximately 21 billion barrels per year in the United States from 900,000 wells. Oil and gas companies construct and operate treatment and disposal facilities and may profit from the byproducts of treated water. The water can be sold for use in agriculture, municipal drinking water, and environmental restoration projects.
When the cost of managing produced water exceeds the value of the hydrocarbon produced from the well, the well is usually shut down.