The formation of petroleum, or crude mineral oil, took place long ago when great seas covered most present-day land masses. As the seas came and went with the shifting of the earth's surface, organic materials from plants and animals were buried with sediments from oceans and rivers. These sediments were subjected to great pressure and bacterial action, thus slowly becoming petroleum.
As a result of folding of the earth's crust. pockets or reservoirs of gas, oil, and salt water formed in the rock layers—valuable resources awaiting man's discovery. The earliest known use of petroleum was during Biblical times when surface-seeping pitch was used to seal the seams of ships. Often men dug for salt water to get edible salt. and found black oil instead. Knowing no use for the oil, the wells were abandoned.
In the mid-nineteenth century, a salt-maker, Samuel Kier of Pittsburgh, bottled and sold petroleum as medicine. Samples of this "rock oil" reached Professor Benjamin Silliman of Yale University in 1855. He analyzed it and separated out light-weight fractions that burned in lamps better than the commonly used sperm whale oil.
The chief oil-producing countries are: The United States, Venezuela, Russia, Saudi Arabia, Kuwait, Iraq, Indonesia, and Iran.
The most important early product of oil was kerosene, and the lighter gasoline which would explode in kerosene lamps was thrown away. Today, the chief products are: natural gas, gasoline, kerosene, lubricating oil, fuel oils, asphalts, and oil coke.
Much of the oil recovered from oil deposits today is found off shore along the sea coasts where special drilling rigs are set up.
Crude oil recovered from the ground is separated in the gas-oil separator. Then it is sent through a network of pipelines throughout the country to be refined.
