UT: Oil and gas water disposal linked to more earthquakes
A new study by the University of Texas strengthens the links between earthquakes and the disposal of wastewater from oil and gas operations deep underground.
The study found that the depth of wells drilled for wastewater disposal, the volume of water, and the rate at which the water is pumped into the well are factors that contribute to the increase in earthquakes in regions where oil and gas is produced.
The problems come when disposal wells, drilled thousands of feet deep, reach so-called basement rock formations, which are older, more brittle and have larger faults.
The additional pressure from wastewater can cause the faults to slip, leading to earthquakes, according to the study. That helps explain why earthquakes have been more prevalent in Oklahoma, where basement formations can be reached in as little as 4,000 feet, less than half the depth in the Permian Basin in West Texas.
“The issue is injecting water and creating this pressure,” said Bridget Scanlon, the lead author of the study.
Extracting oil and gas produces millions of gallons of wastewater, from the brine left from ancient seas that flows out with oil to the chemical-laced water used in hydraulic fracturing.
In the days of conventional drilling, when wells were sunk straight down into oil reservoirs, the water was simply pumped back into the reservoir from which it came. But horizontal drilling, which cuts across shale rock that will be fracked to release oil and gas, requires companies to find other places to dispose of the water, typically in disposal wells that are drilled deep underground.
Since the fracking boom got underway, earthquakes have occurred in areas that rarely experienced them before. Oklahoma, for example, experienced fewer than two earthquakes a year between 1978 and 1999. Between 2014 and 2016, more than 2,100 earthquakes occurred.
Making the link between oil and gas operations and increased earthquakes was controversial, with both industry officials and regulators expressing skepticism that disposal wells were causing earthquakes.
The Texas Legislature, in its 2015 and 2017 sessions, established the TexNet Seismic Monitoring Program, which includes a network of seismic sensors overseen by the University of Texas’ Bureau of Economic Geology.
The program’s responsibilities include “helping to locate and determine the origins of earthquakes in our state and, where possibly caused by human activity, with helping to prevent earthquakes from occurring in the future.”
But mounting scientific evidence is removing lingering doubts. The University of Texas study built on several other studies that connected the injection of water underground with increased earthquake activity in Oklahoma.
The UT study, funded by nonprofit foundations and universities, got underway in summer 2017. It examined data from the research firm IHS Markit, U.S. Geological Survey, and state oil and gas regulators in Texas, New Mexico and North Dakota, including the Texas Railroad Commission, and the U.S. Geological Survey, among other sources.
Disposing of water at shallower depths to avoid basement formations is unlikely to provide a simple solution for oil and gas companies, the study concluded, as it could make it harder to tap oil and gas reservoirs further below and increase the risk of aquifer contamination. That is leading more companies in places like the Permian to look to drilling deeper to dispose of water, which could add enough pressure to basement formations to cause earthquakes.
Wastewater disposal is becoming a particular problem for oil and gas companies, which are using increasing volumes of water to frack wells. The Trump administration is examining whether to adjust federal clean water rules to allow drillers to discharge wastewater directly into rivers and streams as concerns grow that the underlying geology in the Permian Basin and other shale plays are reaching capacity for disposal wells.
Todd Staples, the president of the Texas Oil and Gas Association, said the trade group supported establishing TexNet and that the state’s oil and gas regulator, the Railroad Commission, has “the authority to address existing and proposed disposal wells where historic, geologic data indicates pressurization concerns.”
Railroad Commissioner Wayne Christian said his agency takes the issue seriously, noting that the Railroad Commission was commended by the Environmental Protection Agency for efforts to change disposal well permitting and other requirements aimed at reducing earthquakes.
“We have some of the most stringent rules on disposal wells — the type of wells some link to earthquakes — in the country,” he said.
Such words ring hollow for Barbara Brown, a former resident of Reno, west of Fort Worth. Brown says she had to abandon her home after a series of earthquakes linked to nearby natural gas drilling in the Barnett shale.
At least 27 earthquakes shook Reno and neighboring communities in a three-month period between November 2013 and January 2014. Many residents blamed the earthquakes on wastewater disposal wells in the area, but Brown said the Railroad Commission ignored those concerns, discounting a 2015 Southern Methodist University study that found saltwater production and wastewater disposal were the likely causes of the earthquakes.
“I get Texas was founded on oil and cattle, I understand that — I am a true Texan,” Brown said. “But at the same time, we have so much technology today that surely if someone would just really look at the problem they could find a way to fix it. Basically we were just told, well, thank you for your time.”
The Railroad Commission has received 304 disposal well applications in areas with histories of earthquakes, said Railroad Commission spokeswoman Ramona Nye. Of those, at least 149 permits were approved, the vast majority with special conditions.
Brown moved 230 miles south to Columbus, near Katy, choosing the area because, she said, “It was the only place I could really find in the state that didn’t have a lot of wells.”
But she still thinks of her home in Reno.
“Our families would come from all over Texas and have holidays there,” she said. “That was the country house, and it’s just gone.”
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