Hydraulically fractured wells provide two-thirds of U.S. natural gas production

"For decades, hydraulic fracturing had been referred to as an unconventional completion technique, but over the past 10 years it has become the technique by which most natural gas is produced in the United States. Based on the most recent data from states, EIA estimates that natural gas production from hydraulically fractured wells now makes up about two-thirds of total U.S. marketed gas production. This share of production is even greater than the share of crude oil produced using that method, where hydraulic fracturing accounts for about half of current U.S. crude oil production.

Hydraulic fracturing, often in combination with horizontal drilling, involves forcing a liquid (primarily water) under high pressure from a wellbore against a rock formation until it fractures. The fracture lengthens as the high-pressure liquid in the wellbore flows into the formation. This injected liquid contains a proppant, or small, solid particles (usually sand or a manmade granular solid of similar size), that fills the expanding fracture. When the injection is stopped and the pressure is reduced, the formation attempts to settle back into its original configuration, but the proppant keeps the fractures open. This allows hydrocarbons to flow from the rock formation back to the wellbore and then to the surface..."

Fractured wells

Hydraulic Fracturing: Chemical Disclosure Requirements

"Hydraulic fracturing is a technique used to free oil and natural gas trapped underground in low-permeability rock formations by injecting a fluid under high pressure in order to cause cracks in the formations. The composition of a fracturing fluid varies with the nature of the formation, but typically contains mostly water;a proppant to keep the fractures open, such as sand; and a small percentage of chemical additives. Some of these additives may be hazardous to health and the environment. The Shale Gas Production Subcommittee of the Secretary of Energy Advisory Board(SEAB) has recommended public disclosure, on a well-by-well basis, of all of the chemical ingredients added to fracturing fluids, with some protection for trade secrets..."