Fracking: The Controversy Over its Safety for the
By: Adam H. Love, Ph.D.
Fracking (v): Abbrev. “Hydraulic Fracturing”,
process of initiating and subsequently propagating a fracture in
a rock layer, employing the pressure of a fluid as the source of
energy. (From Wikipedia)
While the environmental impacts of fracking have been big news
stories over the last couple of years, it is important to note that
hydraulic fracturing has been used by the oil and natural gas
industry in the United States since 1947, and was first used
commercially by Halliburton in 1949. Today, fracking is used
worldwide in thousands of oil and natural gas wells annually. Figure
1 (from Daily Kos) shows worldwide petroleum formations in red where
fracking would be potentially applied.
The growth of the practice and surge in attention
is a result of certain recent developments which have made the
process more commercially viable. These developments include:
Lower net drilling costs resulting from improvement in
horizontal drilling technology
Wells now reach 1,500 to 5,000 feet horizontally in the
formation compared to 50-300 feet in vertically drilled wells.
This results in greater productivity for each well drilled.
Energy Policy Act of 2005 provided for exclusions to
Underground Injection Control (UIC) program authority from the
Safe Drinking Water Act (SDWA) for natural gas well fields.
The fracking process involves creating fluid-driven fractures at
depth in a borehole and extending into targeted formations. Figure 2
(from S.F. Chronicle) shows the basics of the fracking process.
Fracturing equipment operates over a range of pressures and
injection rates, and can reach up to 100 MPa (15,000 psi) and 265
L/s (100 barrels per minute). Such pressure creates underground
fractures that extend thousands of feet.
The fracking process has raised a number of
concerns about the safety of the process for the environment. The
following section describes several of the key environmental
concerns with the use of hydraulic fracturing.
1. Pollution of groundwater and surface/near-surface water
The fluid injected into the rock is typically a slurry of water,
proppants, and chemical additives. There are a wide variety of
chemicals used in the fracking fluids in order to achieve an array
of objectives, such as biocides, stabilizers, scale inhibitors, etc.
A number of these chemicals present in fracturing fluid are
While the initial concern expressed is typically regarding fracking
fluid leaking through geologic formation fractures and into drinking
water aquifers, drilling experts and many fracking critics generally
agree that this pathway is improbable. Instead, fracking fluid leaks
are more likely to result from fluids entering the aquifers directly
through well construction defects or deteriorated or improperly
abandoned wells. Estimates suggest the existence of ~ 2.5 million
abandoned oil and natural gas wells in the United States.
Surface and Near-surface Water
Usually, injected fracking fluids are recovered and stored in pits
or containers. These fluids contain the fracking chemicals described
earlier that may be harmful to the environment. Improper disposal or
leaks in storage systems can cause surface water or near-surface
2. Methane penetration into water wells
Instances of methane gas bubbling from fracked sites into nearby
water wells have been extensively documented. A Duke University
study (PNAS 2011) found that methane levels in private water wells
are, on average, 17 times higher in wells that are within 1,000
yards of a natural gas drilling site. The Duke researchers suggested
that the most likely cause is leaky gas well casings – a mechanism
that is also consistent with groundwater pollution vulnerabilities.
3. Water usage leading to air and noise pollution
While drilling a well typically requires between 65,000 and 600,000
gallons of water, fracking typically requires an average of 5
million gallons of water per well. Companies drill as many as 16
wells from a single well pad, therefore a single drilling pad may
require up to 80 million gallons of water. To provide so much water,
a single driller might subcontract its water delivery and wastewater
hauling work to numerous hauling companies. The trucking water
supply and removal activities have caused noise and air pollution
concerns to local residents.
4. Seismic events and subsidence
The evidence for a link between fracking and earthquakes is
incomplete, but in more than one area where fracking has been
practiced, a noted increase in earthquakes has been recorded.
Examples include a magnitude 5.5 earthquake in 1967, near Denver,
Colorado and a magnitude 4.8 quake in 2011 in Arkansas. Fracking
operations in Great Britain were halted in 2011 as a result of
Subsidence is not directly caused by hydraulic fracturing but may
occur after considerable production of oil or utilization of ground
water. Subsidence of ground surface result from removing fluids from
the reservoir and lowering the pore pressure.
What is being done to better understand the environmental impact
EPA has a report on fracking that it issued in 2004 “Hydraulic
Fracturing of Coalbed Methane Reservoirs Study”. This report focused
on coalbed methane reservoirs because they are typically closer to
the surface and in greater proximity to drinking water aquifers
compared to conventional natural gas reservoirs. This study
concluded that hydraulic fracturing posed “little or no threat” to
underground drinking water supplies.
Critics claimed that the Bush Administration officials influenced
the 2004 EPA study and so recently Congress has requested that the
EPA undertake a new study of hydraulic fracturing. This study is
expected to evaluate broader risks regarding well construction
defects and abandoned wells serving as conduits for contamination.
Current research results are expected by the end of 2012 with a goal
for a report in 2014.
There is a clear trend worldwide toward increased exploration and
production of natural gas from shale and coal formations. Hydraulic
fracturing is a critical technology for the petroleum industry and
is not likely to disappear as a viable technological approach.
Recent environmental concerns associated with fracking technology
are putting heavy scrutiny on the industry. Such scrutiny is
expected to lead to regulatory and industry practice changes that
provide additional information, safeguards, and oversight that
assures the technique is executed in a responsible manner.
For more information, please contact
Dr. Adam H. Love, Principal