Examiners: Company Not To Blame For Quakes

The Texas Railroad Commission appears poised to clear a second oilfield company of responsibility for a series of earthquakes that rattled two North Texas towns — despite research suggesting otherwise.

In a preliminary report issued Thursday, two agency hearing examiners concluded that evidence “does not support” a finding that a wastewater disposal well drilled by Houston-based EnerVest contributed to the burst of seismic activity that riled up residents in Reno and Azle from late 2013 through early 2014.

It follows a nearly identical report absolving another disposal well operator, ExxonMobil subsidiary XTO Energy, of ties to the quakes.

More than two-dozen mini earthquakes during that period shook towns atop the gas-rich Barnett Shale, and put pressure on regulators to address concerns that oil and gas activities — namely disposal wells, deep resting places for liquid oil and gas waste —triggered those and other temblors across the state.

The railroad commission ordered hearings after a team of researchers led by Southern Methodist University concluded that industry activity “most likely” unleashed the earthquakes. The peer-reviewed research, published in April, linked the earthquakes to wells operated by XTO Energy and EnerVest.

The commission’s June “show cause” hearings required the companies to offer evidence rebutting the researchers’ findings, showing why the operators should keep their permits. No other parties presented evidence. The commission invited the SMU study’s authors to participate in the hearing, but they declined, saying they did not want to wade into policy decisions and that their research speaks for itself. The researchers continue to stand by their study.

The SMU study said the operators’ withdrawal of brine – naturally salty water removed during oil and gas drilling – and the high-pressure injection of huge volumes of wastewater from gas wells likely spurred the quakes. 

It added to the growing body of research linking disposal wells, and to a lesser extent some oil and gas production, to mostly small earthquakes in Texas and other states. The number of disposal wells has surged amid Texas’ drilling bonanza. Drilling areas in South and West Texas have also seen more earthquakes.

Scientists have known for decades that injecting fluid deep underground could trigger earthquakes. Neighboring Oklahoma has seen an increase in earthquakes even greater than Texas, and has surpassed California as the country’s most quake-prone state. The USGS and Oklahoma Geological Survey say wastewater disposal probably contributes to the trend.

But in two rulings — XTO’s in August and now EnerVest’s  — commission examiners have sided with the energy companies, ruling that “natural tectonic processes” surprised North Texans unaccustomed to shaky ground.

The SMU study is a “commendable first-order investigation” of the issue, the examiners wrote in both decisions, but “presents data indicating a weak temporal correlation between injection and seismic activities — too small, however, to imply a causal relationship without further corroborating evidence.”

The examiners recommended the commission take no action on either company’s well permit.

The decision is not quite final. Parties in the case — just the company and the Railroad Commission — have 15 days to file exceptions, and the examiners have 10 days to reply to those filings.

Disclosure: ExxonMobil is a corporate sponsor of The Texas Tribune. Southern Methodist University was a corporate sponsor in 2013. A complete list of Tribune donors and sponsors can be viewed here.