An oil pump operates in the Permian Basin oil field near Carlsbad, New Mexico. Joe Raedle | Hulton Archive | Getty Images

Move over ExxonMobil, Chevron and ConocoPhillips— t here's a new "Big Three" in U.S. energy production. And they're not companies. In a new update to its drilling productivity report from last week, the Energy Information Agency said North Dakota's Bakken and Texas' Permian Basin and Eagle Ford Shale are quietly generating more than a million barrels of oil per day each–comprising at least a third of total U.S. daily oil production. Shale oil drilling generated the equivalent of nearly 90 percent of the U.S.'s total energy needs in 2013, according to EIA figures. Mark Perry, an economist at the University of Michigan and a scholar at the American Enterprise Institute, crunched the EIA's numbers even further. His analysis suggests the output of the combined three oil fields is actually exceeding 4 million bpd, which would make them the world's fifth largest oil producer by volume. "In all of human history, there have only been ten oil fields in the world that have ever reached the one million barrel per day milestone," the economist wrote in a recent blog post. "Three of those ten are now active in the US–thanks to the advanced drilling techniques that started accessing oceans of shale oil in Texas and North Dakota about five years ago." Read MoreShale upstarts merge in Big Oil's shadow

Naturally, the impetus behind the new Big Three is the relentless shale revolution that has sent the world's largest economy churning out more than 8 million barrels per day. In April, North Dakota also became a member of the one million bpd club as output soared by 2.5 percent from March alone. Yet of the major U.S. oil producing regions, the Permian Basin is the most unlikely cog in the machinery of the shale revolution. With little fanfare, it has assumed a more prominent role in the booming crude sector. The nearly 100-year old West Texas oil hub boasts 546 drilling rigs, more than 1/3 of the total onshore machines in the U.S. Four decades ago, the field's production was thought to have peaked around 2 million barrels a day.

