Geologist: Site Injection Wells Away from Critical Infrastructure

The State Journal
5 January 2012
By Pam Kasey

Mapping critical infrastructure could help the West Virginia Department of Environmental Protection minimize the risk of damage to structures from earthquakes stimulated by underground wastewater injection.

It's a question of growing importance as the gas industry need to dispose of hydraulic fracturing flowback increases.

"It would seem prudent to ensure that all large volume frackwater disposal wells are located a ‘safe' distance from major infrastructure that might be damaged (bridges, dams, urban areas)," wrote West Virginia University geologist Tom Wilson in an e-mail to The State Journal.

The topic drew attention in the region with the suspension of activities at underground injection disposal wells outside Youngstown, Ohio, in late December after the area was hit by an extraordinary tenth and eleventh minor earthquake for the year.

The well was used largely for the disposal of wastewater generated by hydraulic fracturing of horizontal gas wells, according to media reports — a use that some of West Virginia's 50 or so private and 13 commercial injection wells serve.

Geologists contact by The State Journal affirmed that underground injection of fluids can cause earthquakes.

"If you took a brick in each hand and tried to slide them past one another, the rough surface along the boundary would represent a fault and the frictional resistance that is present," explained Marshall University geologist Ronald Martino. "When you build pore fluids up in faults, you decrease the resistance. The fault will slip at lower thresholds than it would naturally so you're triggering movement along the fault — it's occurring sooner and more frequently than it would if left alone under natural conditions."

Earthquakes caused by injection have been registered as high as magnitude 5.0, according to Martino, a level he said could damage bridges and dams.

A series of eight smaller tremors in 2010 near a Chesapeake Appalachia injection well in Braxton County subsided when the company agreed, in cooperation with DEP, to scale back its injections from the permitted 2,100 pounds per square inch. Chesapeake has since been able to gradually ramp its injections back up to the permitted level without incident.

DEP's current plan for future incidents is to scale back injection as was successful in Braxton County, according to spokeswoman Kathy Cosco.

Suggestions from geologists for other ways DEP might prepare for or respond to future incidents included seeking proprietary subsurface information from oil and gas companies, placing temporary seismic devices around an area to get an accurate reading on depth for comparison with the injection depth, and establishing a higher density of permanent devices.

But on further thought, West Virginia University geologist Tom Wilson had two suggestions for proactively minimizing the likelihood of earthquakes and of damage to important structures.

One is to avoid siting injection wells near known faults.

"The state might consider development of more comprehensive subsurface mapping effort to locate at least the major faults that might be reactivated," Wilson wrote in an e-mail message to The State Journal.

In fact, DEP's Office of Oil and Gas does consult a map of faults before permitting injection wells, according to Cosco.

Wilson also suggested including in the mapping effort any significant infrastructure to avoid siting wells where earthquakes, if they did occur, might have catastrophic effects.

"The state could also seek input from the United States Geological Survey's Seismic Hazards program," Wilson wrote, "specifically those familiar with eastern seismicity and critical infrastructure (pipelines and power lines)."

That effort is one the DEP has not undertaken, according to DEP spokesman Tom Aluise.

The issue may not be pressing at this time. The number of horizontal, hydraulically fractured wells drilled in the state appeared to be low in 2011, based on DEP data — 148 completed in 2010, but only 47 reported completed through Dec. 1, 2011, with not all reports yet in.

And with gas prices so low that national media report the expectation that some wells will be shut in, the waste stream of hydraulic fracturing flowback may not increase soon.

On the other hand, Aluise points out that a good mapping effort takes time.

"Some rough maps could probably be assembled in about a year," he wrote.