Hydraulic Fracturing, Quartz Sand and the Dairy State

- An overview of sand mining in the state of Wisconsin and hydraulic fracturing -

Figure 1: Illustration of hydraulic fracturing
http://dnr.wi.gov/topic/Mines/documents/SilicaSandMiningFinal.pdf

Also know as hydrofracking or fracing, hydraulic fracturing is a technique used for resource extraction from with rock formations. To obtain the desired resource, a well is drilled into the earth, explosives are detonated, then water, sand, and chemicals under high pressure are pumped down the well to expand and maintain the cracks formed by the explosives which allows for the resource to be removed (Figure 1).  This technique has been used for over 60 years but recently, with technological improvements in horizontal drilling, allowing for new areas of economical extraction, and a desire for new fuel deposits, an interest in hydraulic fracturing for oil and natural gas has increased dramatically. With an increase in hydraulic fracturing comes an increase in demand for sand, but not every kind of sand is appropriate for fracing purposes.



Figure 2: Wisconsin quartz sand
http://wcwrpc.org/frac-sand-factsheet.pdf

Sand for hydraulic fracturing goes by different names: quartz sand, silica sand, or frac sand. Regardless of the name, the sand is the same; it needs to be very well rounded, almost entirely quartz, and have uniform grain size (Figure 1). The largest deposits of this type of sand are found in Cambrian sandstone formations in Western Wisconsin (Figure 2, 3).

Figure 3: A snipping of a USGS Geologic map of the USA.
Areas in red are Cambrian quartz sandstone, where quartz sand is mined
http://dnr.wi.gov/topic/Mines/documents/SilicaSandMiningFinal.pdf
 

Figure 4: Cambrian sandstone and mining site locations in Wisconsin
http://wcwrpc.org/frac-sand-factsheet.pdf

As seen in Figure 4, mining of quartz sand is primarily located in western Wisconsin ranging from Barron County to Monroe County. Special emphasis will be given to Trempealeau County in subsequent analyses and blog posts. Typically, a quartz sand mining operation will engage in seven stages: overburden removal, excavation, blasting, crushing, processing, transportation and reclamation.  Overburden is the undesired soil on top of the sought after sandstone formations. These soils and materials are removed with scrapers or excavators and dumped around the edges of the mining site creating berms that act as a noise, light, and visual barrier to the possible irritants of the mining operation for local residents. Excavation and blasting at times go hand-in-hand. During these stages the sand is removed either by straight excavation or by blasting heavily cemented sandstone. If blasting occurs, noise, vibrations, and airborne dust can become sources of contempt for local residents. After blasting, the chucks of sandstone are hauled by trucks to be crushed, either on site or elsewhere, until they become nothing more than grains. The small grains of sand are then processed in four steps: washing, drying, sorting, and storing. The is done to ensure the sand is pure and uniform in size. Once the sand is sorted it can be transported to hydraulic fracturing sites, mainly shale gas formations, around the country (Figure 5). Now that the sand has been mined, the reclamation process can be started, if it has not already. Each county has different rules to determine how the land should be treated to be considered reclaimed, though the general policy is to return the land to a proper condition for land use such as farming or residential building.

Figure 5: Areas in red depict shale gas formations
http://dnr.wi.gov/topic/Mines/documents/SilicaSandMiningFinal.pdf

Throughout the mining process, fossil fuels are burned in most, if not all, stages. Groundwater is used for washing and dust control. Noise is generated through explosive detonations and use of heavy machinery. Hauling of sand and materials via trucks cause degradation of infrastructure. The removal of tons of sand will permanently alter natural landscapes causing potential ecological issues. Some of these issues have been addressed by use of  Wisconsin Department of Natural Resources (WDNR) permits and regulations, electrical equipment and generators when applicable, and pollution modeling. Though measures have been taken to reduce negative impacts of an increase in mining operations, the results have yet to be seen.

The issues related to quartz sand mining in Wisconsin are spatial in nature and GIS will be used to analyze and interpret them. As the semester continues, additional blog posts will discuss these issues in more detail.

- Sources -

Wisconsin Department of Natural Resources. (2012). Silica Sand Mining in Wisconsin. Accessed via web: http://dnr.wi.gov/topic/Mines/documents/SilicaSandMiningFinal.pdf

Wisconsin Geological and Natural History Survey. (2012). Frac Sand in Wisconsin. Accessed via web: http://wcwrpc.org/frac-sand-factsheet.pdf