Some of the world’s largest energy companies are saddled with their highest debt levels ever as they struggle with low crude prices, raising worries about their ability to pay dividends and find new barrels.

Exxon Mobil Corp., Royal Dutch Shell PLC, BP PLC and Chevron Corp. hold a combined net debt of $184 billion—more than double their debt levels in 2014, when oil prices began a steep descent that eventually bottomed out at $27 a barrel earlier this year. Crude prices have rebounded since, but still hover near $50 a barrel.

The soaring debt levels are a fresh reminder of the toll the two-year price slump has taken on the oil industry. Just a decade ago, these four companies were hauled before Congress to explain “windfall profits” but now can’t cover expenses with normal cash flow.

Executives at BP, Shell, Exxon and Chevron have assured investors that they will generate enough cash in 2017 to pay for new investments and dividends, but some shareholders are skeptical. In the first half of 2016, the companies fell short of that goal by $40 billion, according to a Wall Street Journal analysis of their numbers.

“Eventually something will give,” said Michael Hulme, manager of the $550 million Carmignac Commodities Fund, which holds stakes in Shell and Exxon. “These companies won’t be able to maintain the current dividends at $50 to $60 oil—it’s unsustainable.”