Neither PDVSA nor its American subsidiary Citgo agreed to requests for interviews.

The challenges ahead are ever-present here in the vast oil fields of El Furrial, in northeastern Venezuela. Beneath the flat, grassy expanses lies the very grade of oil that Venezuela must now import to blend with its large reserves of heavy oil to ship them abroad.

At its peak, El Furrial alone produced 453,000 barrels a day, equivalent to about 80 percent of the national production of Ecuador. But in 2009, Mr. Chávez nationalized Wilpro, an American consortium that handled the complex natural gas injection at the site designed to coax more oil out of the ground. Production has declined by more than half.

Workers at El Furrial today tell a story of decline and mismanagement. There is not even enough drilling mud — the most basic fluid required to keep drill bits cool and well bores clear — to keep all of the rigs running.

At one PDVSA well pad here, China National Petroleum Corporation now fills the gap left by Wilpro. But the site had not been operating for several weeks because PDVSA had not delivered a vital piece of equipment that suspends tubing over the well.

Once completed, the well might produce 3,500 barrels of oil per day, but it was not clear when that would be.

“It’s the first time we’ve ever gone three weeks waiting this way,” said Nelson Ruiz, a manager. “Normally we would get the project going after one signature, and the drill would be in the ground.”

But it is the issue of food that is demoralizing the workers the most.

Workers at one production site described how they eat so little food now, they watch out for their co-workers in case they faint. Claudio Lezama, who has spent the past eight years at the site, said he weighed about 200 pounds several years ago. Between his manual labor and being able to afford only one meal a day, he is now 145 pounds.