What is Frac Sand?

Sand Sorting Tower

Sand Sorting Tower

Excellent article on a key component that makes  the shale oil revolution possible. – Rockpick

Article Credit – Geology.com

This special sand is one of the keys to producing oil and natural gas from tight shale formations

A Crush-Resistant Sand for Oil and Gas Wells

“Frac sand” is a high-purity quartz sand with very durable and very round grains. It is a 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. Most frac sand is a natural material made from high purity sandstone. An alternative product is ceramic beads made from sintered bauxite or small metal beads made from aluminum.

The demand for frac sand has exploded in the past several years as thousands of oil and natural gas wells are being stimulated using the hydraulic fracturing process. (See the production chart in the right column of this page.) A hydraulic fracturing job on one well can require a few thousand tons of sand. This surge of specialized drilling has created a billion dollar frac sand industry in a very short time. Between 2009 and 2012 the amount of frac sand used by the oil and gas industry has tripled.

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 is generally treated with a 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.

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. A few thousand tons of frac sand can be required to stimulate a single well.

Continue reading the rest of the article at Geology.com

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