A key metric of the shale drilling boom

Data: U.S. Energy Information Administration; Chart: Axios Visuals

A short new Energy Information Administration report offers a vivid look at the rise of horizontal drilling, which works in concert with hydraulic fracturing to unlock huge oil and natural gas pockets in shale formations.

Why it matters: The drilling and fracking surge in regions like the Permian Basin of Texas and the Marcellus shale in Pennsylvania have transformed the U.S. into the world's largest oil-and-gas producer. Advances in horizontal drilling tech have helped enable the boom.

By the numbers: "In 2004, horizontal wells accounted for about 15% of U.S. crude oil production in tight oil formations. By the end of 2018, that percentage had increased to 96%," EIA notes. The numbers are similar for shale gas.

Go deeper: Oil investor warns of "energy crisis" for U.S. producers