Big oil companies such as BP, Shell, Total and Exxon Mobil have weathered the storm by cutting back on billions of pounds of investment, and thousands of jobs have been cut.
However, Jeremy Batstone-Carr, chief economist at Charles Stanley, warns that further price falls could really start hurting the big firms.
The first clue that they are starting to suffer, he suggests, will be cutting dividend payments to investors - something they have avoided so far.
Meanwhile, Alan Gelder, of oil analysts Wood Mackenzie, says many North Sea oil operators are "beginning to really feel the pain" at current prices.
He says firms can just about survive as many North Sea operators have already cut costs. But Mr Gelder warns that "there is no money left for future investment".