As the earthquake debate continues, the U.S. Geological Survey and Oklahoma Geological Survey said Monday that oil and natural gas activity is a “likely contributing factor” to the swarm of earthquakes throughout the state over the past few years, and the risk of a big earthquake is growing.
The rate of earthquakes in the state has jumped about 50 percent since October, “significantly increasing the chance for a damaging 5.5 or greater quake in central Oklahoma,” the report stated.
However, the Oklahoma Independent Petroleum Association noted there still is no definitive link between energy activity and the state’s recent earthquakes.
“Disposal wells have been used in Oklahoma for more than half a century and have met and even exceeded current disposal volumes during that time. Because crude oil and natural gas is produced in 70 of Oklahoma’s 77 counties, any seismic activity within the state is likely to occur near oil and natural gas activity,” the Oklahoma Independent Petroleum Association said in a statement.
“Despite that, no Oklahoma-based researchers, the men and women with the greatest understanding of Oklahoma’s geological structures, have definitively linked seismic activity in central Oklahoma to oil and natural gas activity. The OIPA and the oil and gas industry as a whole support the continued study of Oklahoma’s increased seismic activity, but a rush to judgment provides no clear understanding of the causes.”
The average oil well in Oklahoma produces about 10 times more saltwater than oil. Oil and natural gas companies dispose of the produced water by injecting it deep underground through disposal wells. More than 10,000 injection wells are scattered throughout the state.
The state has experienced 145 earthquakes of magnitude 3.0 or greater so far this year, already surpassing the record of 109 set last year.
Bill Leith, senior science advisory for earthquakes and geological hazards at the U.S. Geological Survey, said the advisory was aimed at boosting preparedness.
“Building owners and government officials should have a special concern for older, unreinforced brick structures, which are vulnerable to serious damage during sufficient shaking,” Leith said.
While earthquake swarms have occurred in other parts of the country, Oklahoma Geological Survey seismologist Austin Holland said what Oklahoma is experiencing is different.
“A rate change like this is unprecedented, both if you look at potential natural and induced causes,” he said. “Never before have we seen anything like this. We’re probably seeing a combination of causes coming together to create a perfect storm.”
To help determine the cause and risk of the quakes, scientists have installed a network of seismic monitor stations throughout Oklahoma. Up from only five working monitors a few years ago, the state now has 15 permanent stations and 17 temporary stations. Another eight permanent stations are scheduled to become operational by the end of the year.
The Oklahoma Geological Survey also has received a grant of about $1.8 million from the National Energy Technology Laboratory to study the tremors.
“There will be a lot of modeling and seismology to understand which wells may be causing earthquakes and how that process may be happening in the subsurfaces that are much deeper than injection intervals,” Holland said.