Basically, the higher oil prices are, the more oil and derivative products will be sold, which should increase profits.

FORBES: Peak Oil Plan

Service companies are a second derivative of rising oil prices.

FORBES: Magazine Article

The windfall profits of oil companies in recent months are derivative largely from their overseas investment - the North Sea, as far as BP is concerned, only accounts for 10% of its profits.

BBC: 'No plans' for oil windfall tax