Concurrently with the increasing price of natural gas and the exponential growth of estimated gas extraction potential in the Marcellus, two separate existing drilling technologies – hydraulic fracturing and horizontal drilling – began to be successfully
combined for extracting natural gas from low permeability, ‘tight’ shales like the Marcellus. Horizontal drilling
allows a well to be drilled along nearly horizontal layers of rock. Hydraulicfracturing is a method of cracking
the rock with high volumes of water along the well bore to release the natural gas from the shale, a process
sometimes called “stimulation.” Water used in hydraulic fracturing contains chemicals that play an important role
in the extraction of the natural gas, and a large quantity of water (3 to 5 million gallons) is used per well during the process. Together, the process is called high-volume, slickwater hydraulic fracturing.