What is Fracking Sand in Hydraulic Fracturing?

Hydraulic fracturing equipment at gas shale well site
••• Photo (c) W.L. Sunshine

Fracking sand (or frac sand) refers to sand and similar small materials used during the process of hydraulic fracturing, a method for extracting underground natural gas from shale gas formations. Fracking sand is a proppant—a material used to prop open the underground cracks from which natural gas is harvested during the fracturing process. These gases include petroleum fluids such as oil, natural gas, and natural gas liquids from rock units that don't have enough pore space to allow fluids to flow to a well.

Proppants are blasted under pressure into a shale gas well along with large quantities of water and industrial fluids. This process stimulates gas production. 

What is Fracking Sand Made Of?

Typical proppants include actual sand crystals, such as sand from high-quality quartz sand with very durable and very round grains. Most frac sand is from this natural material made from high-purity sandstone. The sand then goes through the process of being industrially coated with resin, ceramic crystals, or other suitable materials. It then is known as resin-enhanced sand. An alternative to sandstone is tiny ceramic beads made from sintered bauxite or small metal beads made from aluminum. Most grains, or beads, of fracking ​sand are between 0.1 millimeter and 2 millimeters wide.

How is Frac Sand Used?

Some subsurface rock units such as organic shale contain large amounts of oil, natural gas, or natural gas liquids that will not flow freely to a well. They won't flow because the rock unit either lacks permeability or the pore spaces in the rock are so small, these fluids can't flow through them.

Hydraulic fracturing solves this problem by generating fractures in the rock. This is done by drilling a well into the rock, sealing the portion of the well in the petroleum-bearing zone, and pumping water under high pressure into that portion of the well. This water is generally treated with chemicals and thickeners such as guar gum to create a viscous gel. This gel facilitates the water's ability to carry grains of frac sand in suspension.

How Much Fracking Sand is Used?

Industry experts estimate that each shale gas well requires approximately 5 million pounds of sand or other proppant for the​ hydraulic fracturing process. The quantity of proppant can vary from as low as 2.5 million pounds to about 7 million pounds, depending on specific geological variations and characteristics of a shale formation. An estimated 95 billion pounds of fracking sand and ceramics were pumped into the ground in the U.S. in 2014 alone.

What Are the Side-Effects of Fracking Sand?

According to government warnings, exposure to high levels of fine quartz fracking sand can lead to silicosis and other respiratory problems for workers. The fracking industry acknowledges the hazards, and the Occupational Safety and Health Administration (OSHA) updated new standards that became enforceable in June of 2018. The new standards require employers to implement practices such as wetting down work operations to limit silica-containing dust that could be inhaled. Exposure also is limited to 8 hours and a permissible exposure limit (PEL) of 50 micrograms per cubic meter.