Gayathri Vaidyanathan, E&E reporter, EnergyWire, August 5, 2013
When
a geyser of oil and fracking fluid spewed out of an oil well on a
farmer's field in Innisfail, Alberta, it coated 100 trees with a fine
mist. About 20,000 gallons of oil and fluid collected on a snow-covered
field and had to be cleaned up.
The
spill was caused by hydraulic fracturing -- not the activities
surrounding drilling. A series of similar incidents are being reported
across the United States and Canada.
Drillers call it a "frack hit" or "downhole communication," and it could also contaminate groundwater aquifers.
A basic review by EnergyWire of
oil spill reports from various states, as well as phone interviews with
regulators, revealed more than 10 cases of frack hits that have
resulted in spills ranging from 300 gallons to 25,700 gallons. The
events were recorded in states from Montana to Texas.
The
incidents are called frack hits because they happen when the fractures
of two wells intersect. The communicating wells have, in cases, been as
far apart as 1.8 miles, though it is more common for the wells to be
less than 3,000 feet apart. That is too close for comfort because most
states allow adjacent horizontal well bores to be about 600 feet from
each other.
"Our
concern is where the communication results in a loss of well control,"
said Ron Gusek, vice president of an Alberta-based oil and gas company
and chairman of an Alberta industry task force set up to examine frack
hits.
"In other words, there's a fluid spill on the surface or loss of
well control underground that could lead to contamination of a water
aquifer."
The
incidents generally go unrecorded by state regulators, but traces are
found in oil spill databases as instances where operators report an
overflowing production tank that spilled a few barrels into the
environment.
Frack hits will be more common in the future as companies drill multiple wells in close proximity on each well pad.
They
are a result of technological advancements in the industry since
companies began combining directional drilling and fracking to split
apart shale rock and extract oil and gas. The oil and gas development
brought concerns about groundwater, set off by Josh Fox's "Gasland," a documentary
that showed water from a tap being set on fire due to the presence of
methane. Since then, contamination worries have surfaced in Pavillion,
Wyo., where U.S. EPA and the U.S. Geological Survey have found propane,
methane and ethane -- all components of natural gas -- in groundwater
aquifers.
Some frack hits
New Mexico: A
horizontal well being fracked communicated downhole with an older
producing well on February 22, 2012, leading to a spill of 9,000 gallons of
oil. The wells were separated by 600 feet. The spill was cleaned up.
New Mexico: Two
vertical wells, both fracked, communicated across a distance of 2,000
feet on July 7, 2010, causing a spill of 19,000 gallons of produced
water. The spill was cleaned up.
Oklahoma: A
well being fracked communicated with a neighboring well on October 10,
2012, spilling 420 gallons of oil. The spill was cleaned up.
Oklahoma: A
well being fracked communicated with a neighboring well on June 7,
2012, spilling 714 gallons of oil and produced water. The spill was
cleaned up.
Arkansas: A
well being fracked hit another well on November 2, 2012, spilling 3,300
gallons of produced water. The spill was contained in the berm and
cleaned up.
Montana: Two
wells communicated during fracking on January 3, 2012, spilling about
35,000 gallons of oil and water. The spill was cleaned up.
West Virginia: Two
frack hits have come to the attention of the DEP since 2011: one where a
company was fracking in the Marcellus Shale and communicated with
producing wells, and another where a company was fracking in the Berea
sandstone formation and communicated with an abandoned well.
Industry
has argued that fracking is not a threat to groundwater resources and
that there is no path for methane or fracking fluid in formations deep
underground to contaminate groundwater aquifers. And surface spills are
generally tied to human carelessness rather than drilling.
Frack hits could be a path of contamination, particularly in cases where the cementing is below standards.
In
New Mexico on February 9, 2012, Devon Energy Corp. was fracking a well when
an older producing well 600 feet away started spouting 7,000 gallons of
oil and wastewater. The fracks had hit the older well and pushed fluids
out.
If
the well had not been properly cemented -- a possibility with older
wells -- the fluids could have migrated outside the well bore and
directly entered groundwater aquifers.
"Everyone
thinks cement is this magic; it's not," said Michael Beck, president of
Surface Solutions Inc. and a consultant for the oil and gas industry in
Canada who is helping companies including Encana Corp. deal with
downhole communication issues. "Cement is not 100 percent perfect, it
cracks."
The mechanism
Fracking involves pumping water, sand and chemicals into the well bore
at high pressures to fracture shale. The well bores are horizontal,
extending thousands of feet at times, and fractures extend a few hundred
feet into the surrounding rock, like cracks embedded in an ice cube.
That's the assumption, at least.
The
truth can be messier. Some fractures get away from the drillers,
extending even as far as adjacent formations. Using microseismic
technology, researchers in Pennsylvania recently found one extending as
far away as 1,800 feet, as reported by the Associated Press.
In
the case of the Alberta spill, regulators found that an oil well 3,000
feet away was being fracked, and it had communicated with the well that
lost control. About 20,000 gallons of fracking fluid and oil had to be
cleaned up.
The
fractures move toward the regions of lowest pressure, which can be a
nearby well bore. Once a channel is established, the pressures of around
10,000 pounds per square inch travel rapidly across the formation to
the older well. It pushes fracking fluid and whatever is at the bottom
of the producing well -- oil, gas and produced water -- up the old well
bore, which is not equipped to handle high pressures.
"The
frack fluid crosses the path of least resistance," said James Amos,
supervisory environmental protection specialist with the Bureau of Land
Management in New Mexico. It runs up the well bore and can cause the
production tank that's collecting the oil to overflow.
To
the lay observer, it appears to be a surface spill. But in reality,
such spills are caused by fracking hundreds or even thousands of feet
away.
Communication
between wells is not always bad. Sometimes companies want the fracks to
communicate to effectively stimulate the rock. But problems arise when
the communication is unintended and unexpected.
The
worst-case scenario is when the fluids, propelled by high pressure,
travel outside the steel pipe casing the producing well, through a bad
cement job, and the brine enters groundwater aquifers. The risk is high
when the frack hits communicate with older producing wells or abandoned
wells.
In
the New York State Department of Environmental Conservation alone,
there are 4,000 unreported or abandoned wells to be plugged and 35,000
wells for which there are no records.
"If
it doesn't get inside the well bore, it can migrate up the outside of
the well bore; there are water aquifers up there," Beck said. He
described aging cement as a layer of bubble gum wrapped around the steel
pipe casing a well. It separates from the well bore with time,
especially in areas where the geology is sandy or swampy, and provides a
path to the groundwater aquifer.
How probable is it?
EnergyWire documented
more than 10 cases of frack hits that resulted in blowouts or spills
since 2010, and most state regulators said they are rare but would be
more common in the future as additional wells get drilled.
"We've
drilled 4,500 wells in our particular area, the wells are all closely
spaced, you are drilling in areas where there are pre-intersecting
fractures in the rock; I wouldn't expect it not to happen," said
Lawrence Bengal, director of the Arkansas Oil and Gas Commission.
In
the Montney Formation of Alberta, about 30 percent of the well bores
that are up to 1,500 feet apart experience frack hits, Beck said. The
Montney is similar in geology to the Bakken Shale of North Dakota.
The
hits are common enough on New Mexico federal lands that some operators
are temporarily shutting down their producing wells while new wells are
being fracked, Amos said. They install cast-iron plugs downhole to
prevent the fracking fluid from shooting up the well bore and damaging
the producing well, he added.
Predicting frack hits
Industry is getting better at predicting the behavior of fractures
underground, but the challenge will only increase as more wells get
drilled, Pat Handren, an engineer with Denbury Resources Inc., wrote in a
brief to EPA, which is conducting a study on fracking.
"As
well density increases, it becomes increasingly probable that wells
will communicate either through previously created fractures or through
adjacent wellbores and then into previously created fractures," he
wrote.
Anthony
Ingraffea, an engineering professor at Cornell University and a critic
of the oil and gas industry, described communication, and any resulting
environmental impact, as a matter of probability.
"The
industry can say there is less than a 1 percent probability this is
going to happen," he said over the phone. "If you roll the dice 100
times, it is going to happen once. If you roll the dice 1,000 times, it
is going to happen more than once."
Regulation
Frack hits are usually not reported to state regulators unless there is a spill of fracking fluid from the producing well.
In such cases, the incidents masquerade in state databases as production
tank overflows due to an unexpected increase in pressure -- a "kick."
That seems innocuous until one pauses to examine why, exactly, a
producing well that should experience stable pressures would experience a
kick.
"They
[frack hits] periodically occur, but they don't necessarily put down
the exact or the surmised cause. Most of the time we'll just get a spill
report that says all of a sudden we overran the tanks 100 barrels to
the bermed area," said Steve Sasaki, chief field inspector at the
Montana Board of Oil and Gas.
State
regulators disagree on whether a frack hit is a significant problem.
Most, such as Bengal of the Arkansas Oil and Gas Commission, believe
they are an issue for companies to resolve among themselves because it
affects production. If there is a surface spill, it will be cleaned up
and contained, he said. Additional regulation is not necessary,
especially because wells are cased and cemented very stringently in his
state, he added.
He acknowledged there could be a problem with fracks communicating with older wells.
Other regulators, such as Amos with the BLM in New Mexico, see all
spills, including ones that can be contained at the surface, as a
problem.
In Canada, the industry has put together a set of best practices to deal with the problem before it gets more prevalent.
"We just want to make sure that people have taken steps to ensure that
they eliminate the risk of anything happening," said Gusek of the
Alberta task force. "We saw that it has a potential to be a
high-consequence event when and if it happened."
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