Oil at $100 a barrel is a bane for fuel consumers. But it isn't entirely a boon for major oil companies, either.
The rub: The economics of the production deals governing some of the world's biggest oil fields stipulate that the higher the oil price, the less production and reserves oil companies get. Host countries such as Nigeria, Angola and Azerbaijan gain a bigger share.
Investors and analysts judge oil giants in part by their ability to pump more crude and find new reserves. So a decline can have an impact on the way markets perceive Exxon Mobil Corp., BP PLC, Total SA and others.