How is natural gas extracted from a shale formation?

Natural gas is extracted from the shale through a two-step process of drilling and fracturing. To start, a production well is drilled thousands of feet downward and then gradually angled out horizontally through the shale deposit. The well is drilled horizontally to maximize the ability to capture gas once the shale is hydraulically fractured.
After the well is drilled, a mixture of water, sand, and chemical additives is injected at very high pressure to fracture the shale. This part of the process, called hydraulic fracturing (fracking), is a technique used in the oil and gas industry since the 1950s. The sand keeps the fractured shale open and serves as a conduit for extracting the natural gas.
The chemical additives reduce potential problems during drilling and gas production, since bacterial build-up and the formation of scale, mineral deposits and rust. It can take up to four million gallons of fresh water to fracture a single well. The water used in the fracturing process usually comes from a stream, river, reservoir or lake near the drill site, or in some cases, from a local municipal water plant.