A key limitation of a vertical wellbore is its limited contact with the hydrocarbon-bearing, or production, zone. A relatively recent technical advancement, horizontal drilling, has overcome this limitation by permitting greater wellbore-production zone contact. See illustration below. This advancement has been augmented by multiple perforations of the production zone casing (and its encasing cement), thereby allowing greater flow of hydrocarbons from the production zone into the wellbore. This hydrocarbon flow results from the pressure difference between the production zone (high) and the wellbore (lower).

The porosity of shale, however, is less than that of sandstone, so hydraulic fracturing is employed to both increase pre-existing pore diameter and create new fractures. These modifications to the shale reservoir improve natural gas flow from the production zone to the wellbore and have proven to be revolutionary. Recovery of available gas has increased from as little as 2% to as much as 50%; 15-35% is the usual recovery range.