In unconventional resources like the Marcellus Shale, the natural gas is stored within the pores of the shale
and unable to flow because of the very low permeability of the shale. Therefore, extracting unconventional
resources requires both horizontal drilling and hydraulic fracturing to create pathways that increase the porosity and permeability of the shale, and allow the natural gas to travel to the wellbore. Because natural gas trapped in the Marcellus Shale has not migrated outside of the shale, gas companies drilling into the Marcellus are guaranteed to drill into commercial quantities of natural gas, however the extraction methods are more expensive and labor intensive.