The amount of water – both flowback fluid and formation water – that returns to the surface after hydraulic fracturing varies among different formations being drilled, and from well to well within the same formation. The specific characteristics of the target formation and the combination of chemicals used in the fracturing fluid, both of
which can vary from drill site to drill site, determines how much water returns to the surface. In Marcellus
Shale drilling, most of the water that is used to stimulate (the industry term for cracking the shale through
hydraulic fracturing to release the natural gas - for more information, see Marcellus Shale Issue 6: Drilling
Technology) a well will not return to the surface. For example, Marcellus drillers in Pennsylvania find
that between 9% and 35%
of the
hydraulic fracturing fluid returns
to the surface over the lifetime of a
well, with an average of about 10%
returning