Dating back to 1910, Wisconsin has been the number one producer of cheese in the United States. Wisconsin is so well recognized for its cheese production that fans of the Green Bay Packers have been referred to as “Cheeseheads” since the late 1980s. Although California’s production of cheese has recently posed a threat to Wisconsin’s historic lead, our state has grasped the title as the number one producer of a different commodity: frac sand.
The process of hydraulic fracturing has been around since the 1980s, but Wisconsin’s valuable sand deposits have attracted the attention of the oil and natural gas industry just within the past 10 years. Reaching from the Northwestern part of the state and extending down into Dane County, a large portion of Wisconsin contains the sandstone formations in demand.
While Packer fans probably don’t have to worry about trading their Cheeseheads in for sand heads, many people who live in the affected regions are concerned about the recent demand for Wisconsin’s valuable sand deposits.
What is frac sand? What makes Wisconsin sand so special? How will the mining process affect Wisconsin’s natural landscapes? And what is being done to protect the people who are starting to see these sand mines come to their backyards? These are only a few concerns on the minds of many Wisconsin residents.
Hydraulic fracturing is a technique used during the drilling of oil and natural gas to increase the amount of resources extracted from the source rock. According to Professor Alan Carroll of the UW-Madison Department of Geoscience, “The old way to capture resources was to drill into a large natural concentration of hydrocarbons. They would flow out through the well very easily.”
Access to extremely cheap accumulations of hydrocarbons is what powered the United States in the 20th century, but is also what has been in decline since the 1970s as many of the large natural concentrations have been drilled dry. Professor Carroll emphasizes that this is why the introduction of hydraulic fracturing has been revolutionary in the United States.
Smaller accumulations of ‘tight’ oil and gas were previously trapped by low permeable rocks that prevented their flow into the larger concentrations of hydrocarbons. By inducing small fractures into the source rock, these hydrocarbons are now accessible.
Wisconsin’s valuable sand deposits have attracted the attention of the oil and natural gas industry just within the past 10 years.”
The benefits of hydraulic fracturing can be seen on UW-Madison’s campus in the conversion of the Charter Street Heating Plant, which previously burned coal. “It wouldn’t have been predicted that the conversion would be to natural gas, but the increase in natural gas production as a result of hydraulic fracturing is what has made that possible,” says Carroll.
The process of hydraulic fracturing starts with a well being drilled to a scientifically determined location in the rock formation. Next, a perforation gun is guided through the wellbore, is detonated in the desired pay zone and fractures are created in the source rock. Simultaneously, a group of trucks with diesel pumps send a proppant mixture down into the well at extremely high pressures to not only ‘prop’ open the newly created fractures, but also enhance fractures that naturally exist in the source rock.
Frac sand is an important component of the proppant because it holds the cracks open, allowing the oil or natural gas to freely flow down into the well bore. “If the proppant did not contain frac sand,” Professor Carroll says, “the fluid would flow back out of the fractures as the pumping is stopped, and the fractures would instantly snap shut due to the high pressures of the earth at that depth.”
The Wisconsin sand deposits settled into their formations approximately 450 to 500 million years ago and date back to the Cambrian and Ordovician ages. Prior to settling, they were subjected to approximately one billion years of erosion, chemical weathering and redeposition resulting in the modern day deposits with an ideal set of characteristics to be used as a proppant for hydraulic fracturing.
According to Michael Parsen, a hydrogeologist for the Wisconsin Geological and Natural History Survey (WGNHS), there are three main factors that have made Wisconsin’s frac sand so appealing to the drilling industry: strength, uniform size and shape and accessibility.
Strength is a necessity for a sand grain that is tasked with propping open fractures in rock formations up to five miles under the surface of the earth. Professor Carroll says, “The silica quartz has a three dimensional lattice structure without natural cleavage, making it very mechanically strong.” Without a natural cleavage, a term used in geology for describing the direction the specimen will naturally break, this pure silica quartz sand is able to withstand five to ten thousand pounds per square inch.
Another ideal characteristic of this sand grain is its degree of roundness versus sphericity. The ancient sand dunes were subjected to perpetual high-velocity collisions that resulted in geometrically uniform sand grains. Professor Carroll says, “For hydraulic fracturing, they are looking for sand with maximum penetration. They don’t want sand with jagged edges which will get caught and not reach into the fractures.” The sandstone formations of Wisconsin contain deposits with slightly different, yet well sorted properties which are ideal for different applications within hydraulic fracturing.
Drilling companies may selectively use a different grain size based on the stage of hydraulic fracturing or resource they are extracting. A smaller and finer grain would be beneficial in the early stages of the process to reach the narrow tips of the fracture, while larger grains should be pumped at the final stages where the fractures start and are the largest. Oil requires a larger grain size as it is more viscous than natural gas and has to move through larger pore spaces before it can be accessed whereas shale gas is capable of traveling through smaller pore sizes.
The accessibility of Wisconsin’s frac sand is another major factor that makes its formations attractive to drilling companies. “Wisconsin’s sandstone is very close to the surface,” says Parsen. “There is not a lot of overburden or glacier material that needs to be removed before the sand can be mined.”
According to Professor Carroll, “There are similar deposits of this type of sand across the world, but it is particularly attractive from Wisconsin in that they are not too deeply buried, and they are close to both river and rail transportation.”
Wisconsin’s combination of ease of transporting the material plus near perfect geological conditions is very positive from the standpoint of mining and drilling companies, but many Wisconsin residents who are being affected by the recent demand do not feel as fortunate.
At the WGNHS, Michael Parsen and coworkers are frequently contacted by the public, industry and various media outlets. The mission statement of the WGNHS is to “provide objective scientific information about the geology, mineral resources, water resources, and soil of Wisconsin… and support informed decision-making by government, industry, business, and individual citizens of Wisconsin.”
Parsen’s role is in accordance with the mission statement of the WGNHS, however he is frequently contacted by citizens across Wisconsin and listens to their concerns. “Many people have concerns about the nuisance related side of things including truck traffic, noise pollution and light pollution. They are more than just a nuisance; they are real legitimate concerns,” says Parsen.
With a majority of the frac sand mines opening near rural communities, local citizens are worried about how their infrastructure is not suited for the type of traffic the mines require. Usually this is one dump truck carrying about one ton of sand every fifteen minutes. Another large concern is the amount of light and noise that is caused by such a large industrial activity in quiet rural towns, as many of the mines operate 24 hours a day, 365 days a year.
The common qualm of groundwater contamination associated with most mining operations is also on the minds of Wisconsinites. According to Professor Carroll, however, “sand mining of quartz is chemically inert. It does not share the problems of iron and copper mines in that there is not the serious potential threat of ground water contamination.” A frac sand site will require the removal of all the trees, top soil and overlying bedrock as well as 50 to 100 feet of sand. The sites will be reclaimed, meaning the plant vegetation will be restored similar to the pre-frac site conditions, but there is no denying the landscapes of many beautiful regions of Wisconsin will be drastically transformed.
Reclaiming the sites may result in other potential impacts, will rain and runoff recharge the aquifer like it always has? Is recharge going to increase and cause flooding or decease and cause draught and other problems? Parsen says, “It is a possibility that reclaiming a mining site could essentially be like putting a geomembrane or cap on the reject material which could increase runoff and potentially damage different habitats.”
While some residents are excited about the economic and employment perks the appearance of frac sand mines would create, others are extremely frustrated and disgusted at how their communities will be negatively affected. Discussions surrounding the opening and operation of frac sand mines are taking place across Wisconsin. It is important to provide an economic foundation by creating jobs and bringing money into the state, but to what extent is that balanced by protecting Wisconsin’s air, water, soil and charm of rural communities?
Parsen encourages citizens that feel strongly about the possibility of frac sand mines coming to their regions of the state to become active and focus their energy into local conversations. “It is important for Wisconsin citizens who think there will be large impacts on their communities to reach out to their administrators and start the necessary discussions in their towns.”