The bulk of the earthquakes that we have observed tend to be related to the injection of wastewater into these deep wells. The injection stimulates some pressure changes at depth or lubricates the fault in some way that it cause these induced earthquakes to occur —Mark Petersen, National Seismic Hazard Modeling Project
SALT LAKE CITY — The explosive growth in U.S. oil and gas production over the past six years has broken export records that stood for 56 years and has the United States poised to surpass Saudi Arabia as the world's leading oil exporter.
But it's shaking things up — literally — in the Central and Eastern United States. And it provides important information about the potential impacts of injection wells in Utah and across the nation.
A new analysis by the U.S. Geological Survey looking at seismic activity — the most comprehensive to date — shows a 600-fold increase in Oklahoma's earthquake activity compared to what was logged in 2008.
"They are increasing rapidly in these areas, and that causes increased concern over damaging ground-shaking to occur," said Mark Petersen, chief of the USGS's National Seismic Hazard Modeling Project.
Petersen stressed that many of these induced earthquakes are never felt, but the dramatic increases lead to worry that the geologic hazard is becoming more severe because of the potential for earth-shaking events significant enough to cause damage.
"You have to remember that it is the actual shaking of the earth that causes the damage," he said, "not the activity in and of itself."
Petersen led a team that looked at 17 regions spread across eight states that had experienced increased rates of earthquakes, or seismic activity. Zones in Utah were initially included, but then later tossed out because of their relationship to coal mining and "bumps" that can occur as a result of the settling of the earth in deep underground mines.
States experiencing the induced earthquakes analyzed in the study were Oklahoma, Texas, Alabama, Arkansas, Colorado, Kansas, New Mexico and Ohio.
The research was designed to help map the actual geologic hazard of the areas and ultimately help determine if the seismic activity can be predicted with any certainty.
Petersen said questions have been raised over the link between seismic activity and the process of hydraulic fracturing — or fracking — but the research found little evidence of a connection.
Instead, the research pointed to a stronger link between induced earthquakes and the injection of wastewater into deep wells, he said.
"There seems to be a relationship between the earthquakes and the wastewater injection process," he said.
"The bulk of the earthquakes that we have observed tend to be related to the injection of wastewater into these deep wells. The injection stimulates some pressure changes at depth or lubricates the fault in some way that it cause these induced earthquakes to occur."
Petersen said the hazard becomes one that is more manageable, if not predictable, because injection well activity is driven by economics and policy — not natural causes.
Water produced from oil and gas activity — it's estimated that for every barrel of oil produced about 7.6 barrels of water results — is ultimately injected back deep into the ground.
Oklahoma, which saw earthquakes jump from 109 incidents of magnitude 3 or greater in 2013 to five times that amount in 2014, has hundreds of deep wastewater injection wells, of which about 900 are located in what is known as the Arbuckle Formation. The state has ramped up its regulatory oversight on oil and gas activity and put up a website that deals specifically with the increased seismic activity.
Utah has 130 deep injection wells, 122 of which are active, said John Rogers, deputy director of the Utah Division of Oil, Gas and Mining.
None of the wells are located near the 240-mile-long Wasatch Fault, which is primarily located along the western edge of the Wasatch mountains, he said.
About 95 percent of the "produced water" from oil and gas activity is re-injected into the ground where it came from and constitutes a blend of salts, other minerals and hydrocarbon compounds.
Rogers said engineers perform a quarter-mile analysis on proposed injection wells before any receive a permit and none of these have been directly linked to any seismic activity in Utah.
"They go through significant analysis," he said. "And we don't have very many of these like other states have, which is why we don't have some of the problems other states do."
Katherine Whidden, a research seismologist with the University of Utah's seismic center, said the center has not seen any "induced seismicity" in the Uintah Basin, with the exception of Paradox Valley on the border of Utah and Colorado, where there is a project to extract briny water from an aquifer and then reinject it.
The largest known earthquake caused by that activity was magnitude 4.5, she added.
As the incidences of induced earthquakes related to the oil and gas extraction process continues to proliferate, states are grappling with the best safeguards to adopt, as well as conditions to impose for siting injection wells and how to better identify and manage risks.
Rogers is part of a multi-state working group formed last year dealing specifically with induced earthquakes and groundwater protection.
Critics of carbon-based fuels and particularly the fracking process — in which fluid is injected to draw out the oil or gas resource — have been quick to seize on the USGS study and create their own political tremors to urge some type of reform.
Oklahoma last week signaled it is not ready to stem the flow of crude or natural gas production, with state lawmakers voting to prohibit any sort of localized ban on drilling.
To get an idea of seismic activity in Oklahoma, click here to see an interactive map.
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