Petroleum is a marketable item, and a raw material. Petroleum is used to produce Oil.
Players can obtain Petroleum by:
Petroleum production in a company is boosted by 20% if the company is located in a region which contains an Petroleum deposit.
Producing 1x Petroleum in a company consumes 1 Production Point.
Players can use Petroleum to create Oil, by owning a Oil production company.
Producing 1x Oil in a company consumes 1 Production Point and 1 Petroleum.