Researchers find leak in West Texas injection well

A diagram from the study, showing possible causes of wastewater leakage to a shallower depth (which caused the “uplift” observed by radar). Graphic courtesy of Weiyu Zheng at Southern Methodist University

FAR WEST TEXAS — After oil companies frack a well, federal and state regulations require the companies to pump any fracking wastewater deep underground into an “injection site” to prevent contamination. But new research suggests these sites could nonetheless be leaking into freshwater supplies.

In a study, published this year in Scientific Reports – a division of the journal Nature, researchers at Southern Methodist University used radar imaging to study a wastewater injection site in the Ken Regan oilfield in Reeves County.

The ground around the injection site had “uplift” — meaning it was raised due to underground pressure. And the uplift got more dramatic from 2007 to 2011, when the well was most active.

The researchers ran these observations through mathematical models, which showed the well had an “effective injection depth” far shallower than the depth reported to the Texas Railroad Commission. That may sound complicated, but the implications are pretty simple: The well was releasing pressure, and possibly wastewater, at a shallow depth — possibly just a few hundred feet deep.

The researchers cited “leakage due to casing failures and/or sealing problems” as the “most reasonable explanation.” Further research, which showed an increase of sodium in the Pecos Valley Aquifer, seemed to confirm this. Sodium compounds are often included in the “brine” used for fracking.

Taken together, the findings left researchers “very confident that something was wrong with this wastewater injection well,” Zhong Lu, a researcher on the project, said in a phone interview.

To simplify the science, Lu compared the ground to a sponge. It can hold some water, but inject too much and, eventually, it will get saturated. The water then needs to find somewhere else to go.

That’s when problems like leaking and earthquakes can occur, he said. And while uplift itself isn’t the problem, the phenomenon is “associated with problematic wastewater injection.”

Lu was wary of drawing any broad conclusions from his research — including whether oil companies should find other ways besides injection wells to store fracked wastewater. Petrochemical engineers, he said, were better qualified to decide the safest and most economical practices to handle that waste.

“I don’t want people to say, ‘We went from paying $2.50 per gallon of gas to $6 or $7,” he said, laughing. “They wouldn’t be happy.”

Instead, he hoped that oil companies and the Railroad Commission of Texas, which regulates oil and gas drilling in Texas, would treat his research as a starting point — a cost-effective way to monitor wastewater wells that does not require on-site inspections.

“It’s not a cure-all medicine,” he said, but “this technology is very, very cheap.”