A weekend temblor allegedly linked to oil drilling operations in central Oklahoma was the largest quake ever recorded in the state, the U.S. Geological Survey (USGS) announced Wednesday.
Saturday’s earthquake in the Arbuckle rock formation region has been updated to a magnitude of 5.8, USGS reported, and it was reportedly felt in five other states.
Because the area’s oil operations have been previously linked to seismic activity by the Oklahoma Corporation Commission, Gov. Mary Fallin last Saturday declared a 30-day state of emergency in the area around the city of Pawnee. The Governor’s Office also reported that six buildings were uninhabitable on the Pawnee Nation reservation as a result of quake-related damage.
The state also ordered the shutdown of 37 oil industry wastewater wells in the area around the quake’s epicenter. Some of the wells in the Arbuckle region have been ordered closed by Saturday, while others slightly more distant must be shut down by Sept. 13, Corporation Commission Director Tim Baker said in a letter over the weekend.
The relationship between hydraulic fracturing, or fracking, and the increase in seismic activities in the western and central United States has been disputed and debated in recent years. But a USGS report issued earlier this year concluded that millions of people in states such as Oklahoma, Colorado and Kansas face increased quake risks as a result of oil and gas drilling activities.
A report published last year on the website of the American Petroleum Institute (API), however, downplayed the seismic dangers of wastewater disposal resulting from fracking operations.
“While millions of hydraulic fracturing treatments have been performed over the last 60 years, there have been just a few isolated events of induced seismicity that have resulted in ground shaking, none of which resulted in damage of any significant consequence at the surface,” the institute’s report said.
Fracking involves the injection of pressurized water
— mixed with sand and some chemicals
— into dense rock formations under the earth to extract oil and gas. Wastewater from this process, which is six times saltier than seawater, is pumped thousands of feet below groundwater sources as a method of disposal.
API did not respond to specific questions from AMI Newswire about the situation in Oklahoma. In an email, API spokesman Mike Tadeo said only, “Safety is our core value. This remains under investigation.”
Chad Warmington, president of the Oklahoma Oil and Gas Association, told AMI that his members were comfortable with the state’s actions to close down the 37 wells because state officials made the decision based on reliable data and good science. The Corporation Commission’s job is to balance safety and industrial activities in order to serve the best interests of the state’s residents, Warmington said.
“Oklahoma went from having no earthquakes to having quite a few in a small area,” he said.
The shutdown will also have negative impacts on oil companies operating in the region and on industry-generated income going to the state, Warmington said.
He stressed that there is currently no other economically or environmentally responsible way to deal with the brackish wastewater from drilling operations other than injecting it deep into the ground.
Scientists still don’t fully understand the exact mechanism that causes wastewater injection in certain regions to increase seismic activity, Warmington said. Though there is a correlation between injection and seismic activity in the 11-county area around the Arbuckle region, many other regions of the state produce oil without such negative effects, he said.
“The geology is such that we have a lot of faults and traps in terms of rock structures that confine oil and natural gas,” Warmington said. Without such formations, the state would not have the energy resources it does, he said.
Thousands of other disposal wells operate in the state without such seismic effects, Warmington said.
In addition, most of the wastewater in the Arbuckle formation comes not from fracking activities but from production wells, according to the Corporation Commission.
In a statement released after the quake, the USGS said that it could not immediately conclude that the 5.8-magnitude quake was the result of industrial activities in the region.
“However, we do know that many earthquakes in Oklahoma have been triggered by wastewater fluid injection,” a USGS news release said. “The USGS will continue to process seismic data in the following days and weeks that will help answer this question.”
The Governor’s Office reported that state officials are working closely with the federal Environmental Protection Agency, which oversees disposal wells in nearby Osage County.
An USGS report released in March concluded that seven million residents in the central and eastern United States now live with the potential for damage-causing agitation due to earthquakes triggered by human activities. In some of these areas, the damage risks are similar to the risk posed by natural earthquakes in parts of California.