During a fracturing treatment, a clean fracturing fluid is pumped first to create a fracture with adequate width, and then a mixture of proppants and fracturing fluids (often called slurry) follows.
Proppants are designed to fill in the fracture space and strong enough to hold the walls of the fracture apart so that a conductive path to the wellbore can maintain after the treatment has completed and the fracturing fluid has leaked off.
There are basically two types of proppants used for hydraulic fracturing applications: either naturally occurring silica sands or made-made ceramic proppants.
Sands represent the majority of proppants used in the industry.
A subclass called resin-coated proppants is manufactured to improve proppant performance.
The majority of resin-coated proppants are sands.
Frac sand, or naturally occurring sand-type proppant is generally irregular in shape, although this depends on the source. Compared to other types of proppants it has a low strength and packs together closely in fractures, resulting in a lower permeability when compared to other proppant types.
Resin-coated sand is more smooth and round in shape, and is stronger than traditional frac sand. As a result of this shape and texture, resin-coated sand does not pack as closely together and thus is more permeable than frac sand.
Ceramic proppant is the most uniform shaped and most round proppant. It has a high strength, and as a result of its properties it is also very permeable, allowing trapped oil or natural gas to flow easily out of the fractures.
Recently, demand for proppants has increased as oil and natural gas wells are being made to yield more oil and gas using hydraulic fracturing.
How much proppant is needed for fracking?
It varies by well, depending on the overall length of the wellbore and the physical characteristics of the rock.
For exampe, a typical Wolfcamp well drilled in the Permian Basin features an 8,500-foot lateral and requires 13 million pounds of frac sand.