Generally, hydraulic fracturing refers to a process of stimulating tight rock formations, often drilled a mile or more below the earth’s surface, to enable the release and extraction of crude oil and natural gas.

Unlike with most other types of rock formations, the gas and oil in black shale stayed in place for millions of years – until hydraulic fracturing and horizontal drilling made access to this hydrocarbon-rich trove possible.

While hydraulic fracturing has cracked open an economic bonanza at the Bakken and dozens of other production sites worldwide, it has also created concerns over its environmental impact.