After 20 years in the oil-and-gas industry, Eric Neece was used to its booms and busts. He wasn’t surprised when he was laid off by GE Oil & Gas in Conroe, Texas, in 2015 after oil prices plummeted. He figured his job would come back when prices crept back up.

He was almost right. The work came back. But Mr. Neece’s former job as a well logger—measuring well conditions thousands of feet underground—was gone. Those duties are increasingly being overseen remotely and handled by automation.

Technology has already transformed labor needs in most of the world’s manufacturing. It’s now upending the energy business, foretelling the end for one of the last sectors in America where blue-collar workers could depend on jobs paying six-figure salaries.

“Our industry has had a lot of people making $150,000 out in the field,” said Kathryn Humphrey, who spent two decades at BP PLC before retiring from the company’s digital oil field program in 2013. Those days are going away, she said.

For Mr. Neece, the changes could reduce the number of jobs he used to do by more than 25%, analysts said. Automated control systems can send commands to underground tools that capture data on a well’s geologic formations, flow rate and other variables. Smaller teams of technical specialists located in remote operations centers are replacing laborers on the ground, who in the past made adjustments manually.