Oil explorers idled rigs in US fields for the 20th straight...

Oil explorers idled rigs in US fields for the 20th straight week, extending a record retreat in drilling that has brought the country's shale boom to a halt.

Rigs targeting US oil slid by 31 to 703, the lowest level since October 2010, Baker Hughes said. The Permian Basin of Texas and New Mexico lost the most, dropping 13 to 242, the Houston-based field services company said. Texas's Eagle Ford shale declined by nine and the Williston Basin, home North Dakota's Bakken formation, fell by five.

Drillers have idled more than half of the country's oil rigs, eliminated tens of thousands of jobs and cut billions of dollars in spending since the price collapse that began last year. The retrenchment from shale formations has suspended an unprecedented era of output growth, with crude production falling three out of the past four weeks.

"We're not rolling downhill at a 70-rig drop a week, but 31 is still substantial, so we're not at the bottom yet," James Williams, president of energy consultancy WTRG Economics, said by phone from London, Arkansas, on Friday. "I think we'll hit bottom next month or mid-June."