“It’s a relief,” said Tom Kloza, chief oil analyst at GasBuddy.com, who estimates that American consumers collectively saved as much as $700 million a week through much of August compared with last year. “We can thank Texas, North Dakota and Canada.”

Image John and Beth Hughes stopping for gas in Three Rivers, Tex. They say low gas prices allowed them to take a “day-cation” to buy fish in San Antonio. Credit... Michael Stravato for The New York Times

Nowhere is the boom bigger than in Texas, home to two of three of the nation’s biggest shale-oil drilling frenzies. While oil rushes are nothing new to the state of J.R. Ewing and Spindletop, the new bonanza has doubled the state’s crude production over the last two years, suddenly making Texas a bigger producer than either Kuwait or Venezuela.

The Eagle Ford field surrounding this refinery town is responsible for more than half of Texas’ new bounty. The production frenzy here and other shale fields in West Texas and North Dakota, all made possible by horizontal drilling and hydraulic fracturing, techniques that crack oil and gas out of hard shale rock with blasts of water, sand and chemicals, has lowered the country’s dependence on imported oil by more than a third in recent years.

Most of the price of gasoline is determined by the world price of crude, now hovering around $100 a barrel. Turmoil in major producer countries like Iraq and Libya does matter. But the new source of American energy means more supply has been added to global markets — almost the exact amount that has been taken off the market at times because of unrest in the Middle East and Africa over the last five years.

“If it weren’t for that, we would be seeing $200 a barrel oil or higher and $7 to $8 gasoline prices,” said Scott D. Sheffield, chief executive of Pioneer Natural Resources, one of the most aggressive producers in the Eagle Ford shale field. “It would be another shock to the world economy at a time when we don’t need it.”