The U.S. shale-oil industry has made another enemy: Europe’s largest crude explorers.

Standard & Poor’s Ratings Services revised its outlook to negative for Shell, Total and BP as the oil-market rout driven by weakening demand and a flood of supply from American shale fields threatens cash flow into 2016.

The credit-rating company also cast a dim eye on Houston- based ConocoPhillips, saying it’s facing similar cash flow pressure, and said it may cut the ratings on Eni SpA and BG Group’s BG Energy Holdings. S&P cited “the dramatic deterioration in the oil price outlook” and the 50% increase in debt loads for the biggest European oil producers since the end of 2008.

Oil has slumped about 21% since the Organization of Petroleum Exporting Countries (OPEC) decided against cutting its production target last month. United Arab Emirates Energy Minister Suhail Al Mazrouei said non-OPEC suppliers should cut “irresponsible” output. Prices of Brent, the European benchmark crude, have fallen about 45% this year, setting the stage for the largest annual drop since 2008.

The major European oil explorers are hamstrung by heftier investor payouts than their U.S. rivals that leave them less room to maneuver during cash crunches.

Dividend Payouts

BP has an indicated dividend yield of 6.85%, followed by 5.7% for Total and 5.25% for Shell. By comparison, Exxon Mobil Corp. and Chevron Corp.’s dividend yields are 2.95% and 3.83%, respectively.

The European companies also are burdened with relatively inflexible capital spending budgets because most contracts require cash infusions into oil and gas projects, S&P said.

ConocoPhillips was among the first oil producers to slash its 2015 spending plan two weeks ago when it announced a 20% budget cut and plans to defer some projects. Even with those cuts, ConocoPhillips’s net debt may balloon during the next two years as it funnels some cash into “its sizable common dividend,” S&P said in a separate note to clients.

ConocoPhillips’s indicated dividend yield is 4.2%, higher than its biggest U.S. competitors but below that of the three European major producers also reassessed by S&P.