This was not a happy year for American oil and gas workers.

U.S. oil and gas producers have managed to shed costs and maintain production by laying off tends of thousands of workers. Courtesy the Federal Reserve Bank of Dallas

In the fourth quarter alone, at least nine oil and gas companies – together accounting for more than $2 billion in debt – have filed for bankruptcy, and quarterly bankruptcies overall have risen to a level not seen since the Great Recession, the researchers said.

"If bankruptcies continue at this rate, more may follow in 2016," the report warns.

With Iran expected to bring millions more barrels per day of oil onto the market if sanctions are lifted next year – a result of an agreement to curb its nuclear ambitions – "market expectations have shifted toward a weaker price outlook," the report says.

While U.S. oil and gas companies have proved more resilient to low oil prices than expected, they've still been forced to take hundreds of rigs offline. Courtesy the Federal Reserve Bank of Dallas

Benchmark Brent and West Texas Intermediate crude were fetching about $37 per barrel Monday afternoon, down from peaks of $112 and $105, respectively, in June 2014.

Companies' spending has fallen by more than half from the end of 2014 to the third quarter of this year. Saudi Arabia, which previously drew as much as 90 percent of its budget from oil revenues, is also apparently feeling the pinch, announcing a 2016 budget that reduces the government's public subsidies.