https://www.eurekalert.org/pub_releases/2019-08/uoa-fhl081519.php
[Despite other headlines this week distorting this story, the real
message here is that conventional oil and gas drilling - including
abandoned wells - are a considerable source of groundwater
contamination, in addition to the issues associated with fracking.]
15-Aug-2019
Fracking has less impact on groundwater than traditional oil and gas
production
Both types of oil and gas production activities inject water underground
University of Arizona
Conventional oil and gas production methods can affect groundwater much
more than fracking, according to hydrogeologists Jennifer McIntosh from
the University of Arizona and Grant Ferguson from the University of
Saskatchewan.
High-volume hydraulic fracturing, known as fracking, injects water, sand
and chemicals under high pressure into petroleum-bearing rock formations
to recover previously inaccessible oil and natural gas. This method led
to the current shale gas boom that started about 15 years ago.
Conventional methods of oil and natural gas production, which have been
in use since the late 1800s, also inject water underground to aid in the
recovery of oil and natural gas.
"If we want to look at the environmental impacts of oil and gas
production, we should look at the impacts of all oil and gas production
activities, not just hydraulic fracturing," said McIntosh, a University
of Arizona professor of hydrology and atmospheric sciences.
"The amount of water injected and produced for conventional oil and gas
production exceeds that associated with fracking and unconventional oil
and gas production by well over a factor of 10," she said.
McIntosh and Ferguson looked at how much water was and is being injected
underground by petroleum industry activities, how those activities
change pressures and water movement underground, and how those practices
could contaminate groundwater supplies.
While groundwater use varies by region, about 30% of Canadians and more
than 45% of Americans depend on the resource for their municipal,
domestic and agricultural needs. In more arid regions of the United
States and Canada, surface freshwater supplies are similarly important.
McIntosh and Ferguson found there is likely more water now in the
petroleum-bearing formations than initially because of traditional
production activities.
To push the oil and gas toward extraction wells, the conventional
method, known as enhanced oil recovery, injects water into
petroleum-bearing rock formations. Saline water is produced as a
by-product and is then re-injected, along with additional freshwater, to
extract more oil and gas.
However, at the end of the cycle, the excess salt water is disposed of
by injecting it into depleted oil fields or deep into geological
formations that don't contain oil and gas. That injection of waste water
has changed the behavior of liquids underground and increases the
likelihood of contaminated water reaching freshwater aquifers.
Some of the water injected as part of oil and gas production activities
is freshwater from the surface or from shallow aquifers. McIntosh said
that could affect groundwater and surface water supplies in
water-stressed regions such as New Mexico or Texas.
"There's a critical need for long-term -- years to decades -- monitoring
for potential contamination of drinking water resources not only from
fracking, but also from conventional oil and gas production," McIntosh said.
The team published their paper, "Conventional Oil--The Forgotten Part of
the Water-Energy Nexus," online June 30 in the journal Groundwater.
Global Water Futures funded the research.
McIntosh has been involved in studies about the environmental impacts of
hydraulic fracturing. She started wondering how those impacts compare to
the impacts of the conventional methods of oil and gas production --
methods that have been used for about 120 years and continue to be used.
Both fracking and conventional practices use groundwater and surface
water when there isn't enough water from other sources to continue
petroleum production.
To see how all types of oil and gas production activities affected water
use in Canada and the U.S., she and Ferguson synthesized data from a
variety of sources. The published scientific studies that were available
covered only a few regions. Therefore, the scientists also delved into
reports from state agencies and other sources of information.
The researchers found information for the Western Canada Sedimentary
Basin, the Permian Basin (located in New Mexico and Texas), the states
of Oklahoma, California and Ohio, and the total amount of water produced
by high-volume hydraulic fracturing throughout the U.S.
"What was surprising was the amount of water that's being produced and
re-injected by conventional oil and gas production compared to hydraulic
fracturing," McIntosh said. "In most of the locations we looked at --
California was the exception -- there is more water now in the
subsurface than before. There's a net gain of saline water."
There are regulations governing the petroleum industry with regard to
groundwater, but information about what is happening underground varies
by province and state. Some jurisdictions keep excellent data while for
others it's virtually nonexistent. Despite this, Ferguson said he and
McIntosh can make some observations.
"I think the general conclusions about water use and potential for
contamination are correct, but the details are fuzzy in some areas,"
Ferguson said. "Alberta probably has better records than most areas, and
the Alberta Energy Regulator has produced similar numbers to ours for
that region. We saw similar trends for other oil and gas producing
regions, but we need better reporting, record keeping and monitoring."
Oil and gas production activities can have environmental effects far
from petroleum-producing regions. For example, previous studies show
that operating disposal wells can cause detectable seismic activity more
than 90 kilometers away. Conventional activities inject lower volumes of
water and at lower pressure but take place over longer periods of time,
which may cause contamination over greater distances.
Another wild card is the thousands of active, dormant and abandoned
wells across North America. Some are leaky or were improperly
decommissioned, providing possible pathways for contamination of
freshwater aquifers.
While there is some effort to deal with this problem through
organizations such as Alberta's Orphan Well Association, there is little
consensus as to the size of the problem. Ferguson said depending on
which source is cited, the decommissioning price tag ranges from a few
billion to a few hundred billion dollars.
A 2017 report from Canada's C.D. Howe Institute indicates that there are
155,000 wells in Alberta yet to be remediated. A 2014 paper by other
researchers suggest Pennsylvania alone has at least 300,000 abandoned
wells, many of which are "lost" because there are no records of their
existence nor is there surface evidence that an oil well was once there.
"We haven't done enough site investigations and monitoring of
groundwater to know what the liability really looks like," Ferguson
said. "My guess is that some wells probably should be left as is and
others are going to need more work to address migration of brines and
hydrocarbons from leaks that are decades old."
###
Researcher contact:
Jennifer McIntosh
University of Arizona
520-626-2282
mcintosh@xxxxxxxxxxxxxxx
Grant Ferguson
University of Saskatchewan
306-966-7429
grant.ferguson@xxxxxxxx
Media contacts:
Mari N. Jensen
University of Arizona
520-626-9635
mnjensen@xxxxxxxxxxxxxxxxx
Mark A. Ferguson
University of Saskatchewan
306-966-7135
m.ferguson@xxxxxxxx
--
Darryl McMahon
Freelance Project Manager (sustainable systems)
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