Frac Sand FAQ

What is frac sand?
Frac sand is a crush resistant sand for oil and gas wells.It is a high-purity sand with very durable and very round grains of a specific size. It is a highly specialized, crush-resistant material produced for use by the petroleum industry. It is used in the hydraulic fracturing process (known as "fracking") to produce petroleum fluids, such as oil, natural gas and natural gas liquids from rock units that lack adequate pore space for these fluids to flow to a well. Frac sand can be a natural material made from high purity sandstone. An alternative product is ceramic beads made from sintered bauxite.
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 will not flow to a well because the rock unit either lacks permeability (interconnected pore spaces) or the pore spaces in the rock are so small that these fluids can not flow through them.
The hydraulic fracturing process 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 has been treated with a chemical that creates a viscous gel. This gel facilitates the water's abillity to carry grains of frac sand in suspension.
Large pumps at Earth's surface increase the water pressure in the sealed portion of the well until it is high enough to exceed the breaking point of the surrounding rocks. When their breaking point is reached they fracture suddenly and water rushes rapidly into the fractures, inflating them and extending them deeper into the rock. Billions of sand grains are carried deep into the fractures by this sudden rush of water. Over one million pounds of frac sand can be used to stimulate a single well.

What Type of Sand?

Petroleum industry proppants must meet very demanding specifications. The characteristics of a high quality frac sand include:
*high-purity silica sand
*grain size perfectly matched to job requirements
*spherical shape that enables it to be carried in hydraulic fracturing fluid with minimal turbulence
*durability to resist crushing forces of closing fractures
Rock units such as the St. Peter Sandstone, Jordan Sandstone, Oil Creek Sandstone and Hickory Sandstone have been potential sources of frac sand material. These rock units are composed of quartz grains that have been through multiple cycles of weathering and erosion.
That long history has removed almost all mineral grains other than quartz and produced grains with very round shapes. This is why sand dredged from rivers, excavated from terraces or removed from beaches is unlikely to produce a good product.
Where these rock units are produced they are soft and poorly cemented. This allows them to be excavated and crushed with minimal damage to the quartz grains. High-purity sand from areas such as the Appalachians is often not suitable for frac sand because it has been subjected to tectonic forces which have weakened the sand grains.

To be continued...