Frac Sand and Hydraulic Fracturing
Discussion of the material known as “frac sand” has become increasingly common in recent years, especially in Wisconsin. This leads to the question, "What exactly is frac sand, and why is it so significant?" Frac sand is used for oil and natural gas extraction in a process known as hydraulic fracturing. Hydraulic fracturing involves pumping a slurry of water, chemicals, and sand under high pressure, deep into oil and natural gas wells in order to expand naturally-occurring or explosive-induced fractures within shale formations. After the pressure is released, the frac sand grains remain behind, acting as pillars that keep the fractures propped open and permit oil and gas to flow more freely from the formation. This technology has been known for the last 75 years. However, its potential has only recently been realized with advancements in horizontal drilling. Combining the two techniques (Fig. 1) has drastically increased oil and gas extraction abilities and allowed formations that were previously too expensive to drill to become profitable (WDNR, 2012).
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| Figure 1. An illustration of combining hydraulic fracturing and horizontal drilling to enlarge fractures in shale formations to more easily remove oil and natural gas (WDNR, 2012). |
The hydraulic
fracturing process requires a very specific type of sand. Effective frac sand must be almost pure
quartz, so it is strong enough to hold the weight of the overlying material.
Additionally, the sand grains must be well rounded, uniform, and sufficiently
coarse to create openings in the fractures that are large enough for the oil
and natural gas to flow through (WDNR, 2013). Sand meeting these specifications is only
formed in specific geologic environments. Wisconsin has multiple sandstone
formations that meet the requirements for frac sand and are close enough to the
surface to be mined (WDNR, 2012).
Frac Sand Mining in Wisconsin
Mining of frac sand in Wisconsin
has primarily been focused in the west-central part of the state (Fig. 2). In this region, the Jordan, Wonewoc, Mt.
Simon, and St. Peter formations all contain sand with the desired traits and
are accessible from hilltops and hillsides (WDNR, 2012). Because of the recent surge in
demand for frac sand, both nationally and internationally, and Wisconsin’s
abundant supply, frac sand mining has become a major contributor to the state’s
economy. There are over 100 frac sand
operations active in Wisconsin. These mines and processing facilities have
resulted in the creation of over 2,000 jobs, which generate millions of dollars
in income and tax revenue. Communities across the state have benefitted from
the money brought in by the frac sand industry. Future prospects show no signs
of slowing down, but not all Wisconsin residents are excited about this
reality (Nichols, 2013).
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| Figure 2. Locations of sandstone formations, frac sand mines, and frac sand processing plants across Wisconsin (WDNR, 2013). |
Concerns with Frac Sand Mining
Frac sand mining in
Wisconsin comes with certain disadvantages and risks. Many citizens are concerned about mining away
the hills that serve as aesthetic icons of the region and how that could affect erosional
patterns. Additionally, explosives are used to remove sand for processing, where
it is crushed and sorted. These
processes generate significant dust, which can lead to respiratory issues,
particularly if the dust is silica-rich. The most common concern is silicosis, an
irreparable respiratory disease caused by the inhalation of fine silica
particles. In an effort to control dust, most frac sand operations use a notable
amount of water to spray down the plant. Add this to water already being used to wash the mined material, and the
water toll on a region can be considerable, even if the plant is using a
closed-loop system. Beyond this, chemicals are used throughout the mining
process as flocculants. If mishandled,
these chemicals have the potential to contaminate local groundwater resources. Furthermore,
operating such large facilities can generate substantial air emissions. If not
properly filtered, this can reduce local air quality, as well as release greenhouse gases. In addition to health and safety issues, frac sand
facilities can be inconvenient for facility neighbors in other ways (WDNR, 2012).
Removal, processing,
and transportation of frac sand creates ongoing inconveniences typically not
experienced in many rural communities.
Facility, equipment, and train operations often generate ongoing noise and
light that can last throughout the night.
Also, frac sand is commonly transported in large dump trucks on roads
that previously saw very little traffic (WDNR, 2012).
This is a change locals have to adjust to and has the potential to generate
a higher number of serious accidents in the area. Because of these issues, along with the other health concerns discussed, many locals fear the
value of their homes will decrease drastically if a frac sand plant is opened
nearby (Nichols, 2013).
In-Class Risk Assessment
Clearly, frac sand
mining is an important issue in Wisconsin.
It has high-risk potential, but high-reward potential as well. Because of this, it is important to build a
thorough suitability/risk model for frac sand mining in Western Wisconsin. This will be the focus of our class project,
with a particular emphasis on Trempealeau County. To complete this task, we
will download data from a variety of sources, such as the National Atlas, the
USGS, and the USDA. Using these resources and a variety of data analysis methods, we will hopefully be able to generate a useful, accurate model.
Sources
Nichols, M. (2013, April). Mining success. Wisconsin Interest, 22(1), Retrieved from
http://www.wpri.org/WIInterest/Vol22No1/Nichols22.1.html
WDNR. (2012, JANUARY). Silica sand mining in wisconsin. Retrieved from
http://dnr.wi.gov/topic/Mines/documents/SilicaSandMiningFinal.pdf
http://dnr.wi.gov/topic/Mines/documents/SilicaSandMiningFinal.pdf
WDNR. (2013). Frac sand in wisconsin: Fact sheet 05. Retrieved from
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