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.