The major oil companies did not seem to know how good they had it.

Despite crude oil hovering around $100 a barrel for three years between 2011 and 2014, the five so-called supermajor oil companies kept growing their debt. As oil started to fall, cost-cutting, cuts in capital expenditures, and decreased dividend-payments were not enough: The debt kept rising.

By the end of 2016, aggregate debt for ExxonMobil (XOM) - Get Report , Chevron Corp (CVX) - Get Report , Total S.A. (TOT) - Get Report , Royal Dutch Shell PLC (RDS.A) , and BP PLS (BP) - Get Report increased to more than $375 million from under $200 million in 2009.

All of the companies are over-leveraged for their credit ratings, according to a report released Wednesday, June 12 by S&P Global Market Intelligence.

"[The] supermajors' balance sheets weren't well prepared for the 2014 and ongoing sector downturn," the report authors wrote.

Major commitments to investment projects hurt companies such as Chevron as oil fell, with the company forced to continue investing as prices declined and stayed low.

"I am not surprised that Majors continued to make bullish investments 2011 to 2014 rather than deleverage," Morningstar director of research, commodities and energy Sandy Fielden said in an email. "I think there was a sense that oil prices would stay high because supplies were running out. Shale was seen as an expensive marginal production rather than a solution to the search for new oil."

Payments to shareholders, which some companies continued to increase despite the downturn, have been a "drain on company cash," the report authors note.

"Keeping up the dividends is seen as a necessary tax on big oil companies to preserve stock prices in a downturn - a rule that dare not be broken," Fielden said. 

Dividend payments have been an ongoing problem for the supermajors, some of whom have spent more than 100% of their profits on dividends in recent years. 

"We continue to see reduced investment in the long-term cash generating assets of a company in order to maintain shareholder distributions as a negative factor for ratings," the report authors write.

Capital expenditures by the supermajors have declined each of the past three years, down to almost half their 2013 peak. On Monday, July 10, Saudi Aramco's CEO said declining investments in new projects could lead to an oil shortage over the next few years. 

S&P downgraded all five of the supermajor oil companies in 2016 by one notch, after assigning negative outlooks in 2014 and 2015. S&P continues to have a negative outlook on three of the five, including Exxon, Chevron, and Total.

Despite the negative outlooks, S&P noted that most of the major oil companies had succeeded in driving down costs, with most likely to reach breakeven prices of about $50 to $55 a barrel.

Chevron Chief Financial Officer Patricia E. Yarrington said her company was looking to reduce its debt over time. 

"We're at a 24% debt ratio, which is an okay place to be, I would say," the executive told analysts during the company's first quarter earnings call in May. "But over time, I'd like to see us move a little bit lower in the debtprofile when cash flow permits us to do that. Maintaining a AA is important to us."

The price of a barrel of benchmark WTI crude oil is down about 16% this year, to $45.07. Analysts estimate the price of benchmark WTI to reach $52 in 2017, $55 in 2018, and to approach $60 the year after, according to FactSet data.