In 2004, horizontal wells accounted for roughly 15% of U.S. crude oil production in tight oil formations. By the end of 2018, that percentage had skyrocketed to 96%.
Drilling horizontally allows producers to access more of the oil- and natural gas-bearing rock than drilling vertically.
The lateral length of horizontal wells has also increased, allowing for more exposure to oil- and natural gas-producing rock from a single well.
Presently, essentially all (99%) hydrocarbon production from the Marcellus has been from horizontally drilled wells.
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