The Process of Hydraulic Fracturing
Jake McTavish
Introduction
Hydraulic fracturing, or fracking, has drawn a lot of attention over the last several
decades for its highly economic extraction of natural resources, and its potentially
hazardous environmental impact. Hydraulic fracturing is the process of drilling and
injecting fluid into the ground at high pressure in order to fracture shale rock to
release natural gas and oil trapped inside. As a country that depends on oil and gas
resources to operate, these drilling techniques are seen as highly desirable in the
energy market. However, with this efficient drilling technology come potentially
harmful environmental effects, such as groundwater pollution.
The purpose of this document is to discuss the process of hydraulic fracturing with a
general audience who has interest in the subject. Familiarity with the oil and natural
gas drilling industry will benefit the reader in understanding some of the concepts
within the document. However, the content discussed will be written to ensure a
general audience reader with no background knowledge will still gain a significant
understanding of the process.
Key concepts discussed will include:
 Key natural resources and their purposes
 The process of hydraulic fracturing
 The advantages and disadvantages of the process
Natural Gas, Oil and Marcellus Shale
Natural gas has emerged as a necessity in the energy industry. It is responsible for
roughly a quarter of the U.S. energy demand and heats over half of the U.S.
households.1 Natural gas has become increasingly desirable because it is a clean
burning source of fuel that can be used for a variety of applications, such as heat and
electricity. It is a colorless, odorless gas made up of hydrocarbons (compounds
containing only hydrogen and carbon elements), the most significant one being
methane, CH4.
Another part of the fossil fuel family is oil. Rather than being in the form of a gas, oil
is a hydrocarbon that is in liquid form. When burned, oil produces a concentrated
flame, making it ideal for heating purposes. Oil plays a significant role in the energy
demand because it can be refined into petrol, commonly referred to as “gasoline,” to
power automobiles. A downside of oil is that it produces a more significant amount
of harmful emissions such as greenhouse gases and other harmful chemicals.
Natural gas and oil are both fossil fuels, which means they are produced naturally
from prehistoric plant and animal remains. These remains settled into the seas
along with sand, silt, and rocks, and over time this organic matter became trapped
within pressurized layers of sedimentary rock, such as shale. Underground traps of
oil and gas are known as reservoirs. These reservoirs can be anywhere from
hundreds of feet to miles below the ground surface. The hydraulic fracturing
process utilizes layers of Marcellus shale rock, which can house deposits of natural
gas or oil, usually found between 1 to 2 miles underneath the surface. The Marcellus
shale is fractured, or broken, in order to free these trapped energy resources.2
Hydraulic Fracturing Process
Figure 1
Hydraulic fracturing is a multi-step process that takes a few months to establish, but
can pump oil and gas for 20 to 40 years. Typically, it takes a few weeks to prepare
the drilling sight, a month to drill the well, and one to three months of collection and
completion activities, which will be discussed later on.
Drilling
To begin the process, a location must be chosen where Marcellus shale is accessible.
Once a well site is established, a drilling rig will drill a large bit down through the
earth until the Marcellus shale layer is reached. As shown in Figure 2, the key parts
of the diagram to focus on are boxed in red. This includes the casing, cement, and
drill bit. However, it is to be noted that the other mechanical and structural parts of
the rig are essential to ensure that the bit is driven, and do serve a purpose. The drill
bit is the metal cutting element that is rotated and driven through the layers of earth
well below the groundwater table and through several layers of rock until the oil
and gas reservoirs are
reached. As the drill bit is
entering the earth, the
Figure 2
casing, which is a heavy
steel pipe, lines the walls
of the hole to prevent
caving in, and also serves
to prevent any fluid used
from polluting any
groundwater supply. The
cement is then used to fill
the void space between
the wall of the hole and the
metal casing. This serves
to supply structural
support to the casing and
to further protect any
fluids from contaminating
groundwater supply.
When the Marcellus shale
layer is reached, the drill is
turned horizontal, as
shown in Figure 1, and
extended for anywhere up
to a few miles in the
horizontal direction. The
horizontal drilling is useful
because it allows the same
well site to reach natural
resources up to miles
away, reducing the need
for additional drilling sites in the area.
Fluid Injection
The key ingredient to fracturing the shale is the pumping fluid. Once the well has
been drilled and cased, an explosive perforating tool is sent down the casing to the
point of the targeted gas or oil. The perforating tool creates holes through the
casing, cement and into the shale so that it allows the hydrocarbons to exit the shale
and enter the well stream. This can be repeated in several different horizontal
locations. At this point the pumping fluid comes into play. Water and sand make up
roughly 99.5% of this fluid; with the rest of the mixture coming from chemicals that
serve to improve the flow rate.3 This fluid mixture is highly pressurized and forced
down the casing to the hydrocarbon sites created by the perforating tool. Once the
pressurized fluid hits the shale, it opens up tiny fractures, or fissures (as seen in
Figure 1), within the shale. The water is then removed, but the sand remains
embedded within the fractures, forcing them to remain open and allowing the gas to
travel out into the well.
Retrieval
After the shale has been fractured and the gas can now enter the casing, it is
pumped back to the surface. Initially water flows up the well bore, followed by the
natural gas or oil. The gas is retrieved and sent into storage tanks where it can be
distributed to the market by piping (as seen in Figure 1). The water used in the
fracturing process can prove to be a bit more of hassle. A huge drawback from
hydraulic fracturing is the vast amount of water required to complete the process. A
well site can use up to 5 million gallons of water to successfully retrieve the oil or
gas. While being pumped back up the well, anywhere from 15-50% of this fracturing
fluid is recovered. This fluid can either be recycled, for more fracturing operations,
or sent to a well pit, and distributed to a wastewater treatment facility.3
Advantages and Disadvantages
Environmental Impact
There is heavy speculation that there are harmful side effects associated with
hydraulic fracturing. First and foremost, the process requires creating a drilling site,
which requires building a well site, and therefore may result in wildlife being
affected. Additionally, if the process is not done carefully, the groundwater supply
can be contaminated by allowing the gas or pumping fluid to enter the aquifer. If the
drilled hole is not cased and cemented properly, the underground layers of earth
can be exposed to the hazardous materials by leaking through the flow channel. The
recovered pumping fluid can also pose a threat if not successfully distributed to a
wastewater treatment facility. Furthermore, certain studies have found correlations
between hydraulic fracturing and earthquakes, leading to the belief that the process
is actually leading to man-made earthquakes. All potential issues continue to be
researched and debated between environmental and drilling companies.
On the other hand, natural gas is the cleanest fossil fuel used for energy. It emits
much lower levels of carbon dioxide, nitrogen oxides, and sulfur dioxide compared
to coal or oil. Hydraulic fracturing has given us the potential to access vast amounts
of this clean-burning natural gas.
Economic Impact
Hydraulic fracturing is proving to be the most efficient way to retrieve desirable
fossil fuels from the earth. This industry can lead to helping solve the potential
energy crisis, boasting an estimated 1,000 trillion cubic tons of natural gas
recoverable in shale rock in the U.S. alone.3 This would allow the U.S. to produce
100% of our own natural gas, as opposed to paying for it to be transported from
different parts of the world. Additionally, energy experts anticipate 200,000 new
jobs by 2020 in the Marcellus shale industry.4
Conclusion
The process of hydraulic fracturing has been accompanied by increases in natural
resource availability, but also with troublesome questions in the areas of
environmental safety. By utilizing advanced drilling techniques and the injection of
pressurized fluid down into the earth, obtaining oil and gas trapped within shale
reservoirs is now a very feasible concept. The process of hydraulic fracturing has
evolved and will continue to evolve in hopes to be more efficient and safe.
References
[1] "Natural Gas and Its Uses." Energy API. American Petroleum
Institute, 2013. Web. 25 Mar. 2014.
http://www.api.org/oil-and-natural-gas-overview/exploration-andproduction/natural-gas/natural-gas-uses
[2] "Petroleum – Oil and Natural Gas." Energy4Me. N.p., 2006.
Web. 24 Mar. 2014.
http://www.energy4me.org/energy-facts/energy-sources/petroleum/
[3] "Fracking Fluids." Energy From Shale. N.p., 2013. Web. 25
Mar. 2014.
http://www.energyfromshale.org/hydraulic-fracturing/hydraulic-fracturing-fluid
[4] "What They're Saying About the New Penn State Marcellus
Shale Economic Impact Study." Marcellus Shale Coalition.
N.p., 26 May 2010. Web. 26 Mar. 2014.
http://marcelluscoalition.org/2010/05/what-theyre-saying-about-the-new-pennstate-study/
[Figure 1] "What Is Hydraulic Fracturing?" Propublica, 2013. Web.
23 Mar. 2014.
https://www.propublica.org/special/hydraulic-fracturing-national
[Figure 2] "Oil, Gas & Geothermal - Picture of a Drill Rig."
Department of Conservation, 2013. Web. 26 Mar. 2014.
http://www.conservation.ca.gov/dog/picture_a_well/Pages/qh_drill_rig.aspx