The majority new oil being developed are heavy, sour crude oils which have a high sulfur content, high viscosity, and high density.

FORBES: China's Not Going Green

Oil refineries use hydrogen to strip sulfur from sour crude supplies, especially those from Mexico and Venezuela, and to meet stringent clean-fuel regulations.

FORBES: Suddenly Sexy

World crude oil production has in some cases already peaked (sweet, light) while others (heavy, sour) it has yet to be will soon.

FORBES: China's Not Going Green