Oil and Petroleum: The Liquid Fuel That Shaped the Modern World

Petroleum — from the Latin petra (rock) and oleum (oil), the rock oil that seeps to the surface in hundreds of locations around the world — is the most economically and geopolitically consequential energy resource in human history. In fewer than 170 years since the first commercial oil well was drilled in 1859, petroleum and its refined products have become the foundation of the global transportation system, the feedstock for the chemical and pharmaceutical industries, the basis of modern warfare, and the center of international politics. No other substance has done more to shape the geography, economy, politics, and daily life of the modern world.

Oil is a mixture of hydrocarbons — molecules composed entirely of carbon and hydrogen atoms — formed from the remains of marine organisms (primarily plankton and algae) that accumulated on the floors of ancient seas over hundreds of millions of years, were buried by sediment, and were transformed by heat and pressure into liquid and gaseous hydrocarbons. The specific mixture of hydrocarbons in crude oil varies considerably by origin, determining the "crude quality" — its density (measured in API gravity), sulfur content, viscosity, and the proportion of different products it yields when refined.

The energy density of petroleum is exceptional. A liter of gasoline contains approximately thirty-four megajoules of chemical energy — roughly equivalent to the energy a healthy adult consumes in food over five days. This extraordinary energy density, combined with petroleum's liquid state at room temperature (enabling easy storage, pumping, and dispensing), made it ideal for transportation applications. A gasoline-powered automobile can carry enough fuel for several hundred kilometers of travel in a tank that occupies a fraction of the vehicle's volume. No alternative energy carrier has yet replicated this combination of energy density, convenience, and ease of handling for transportation applications.

Petroleum's non-energy applications are almost equally important. The petrochemical industry converts petroleum feedstocks into plastics, synthetic fibers, fertilizers, pharmaceuticals, lubricants, solvents, adhesives, and thousands of other materials that pervade modern life. A substantial fraction of the world's food production is enabled by nitrogen fertilizers synthesized from natural gas (which is closely associated with oil production) using the Haber-Bosch process. The clothes on most people's backs contain synthetic fibers derived from petroleum. The casings of electronic devices, the insulation on electrical cables, the packaging of food and consumer goods — all depend on petroleum-derived plastics and chemicals.

The Ancient World and Petroleum: Bitumen, Naphtha, and the Eternal Fires

Human beings have been aware of petroleum and its properties for thousands of years. Naturally occurring oil seeps — places where petroleum oozes to the surface through fractures in the rock — are found in many parts of the world, and the ancient peoples who lived near them found practical uses for the viscous black liquid long before the first oil well was drilled.

Bitumen — the heaviest fraction of petroleum, a thick, tar-like substance that occurs naturally in oil sands and as the residue of evaporated oil seeps — was one of the most useful materials of the ancient world. In Mesopotamia, where bitumen seeps were common in the region around present-day Iraq, it was used as a waterproofing material for boats, baskets, and jars; as a construction mortar; and as an adhesive for attaching stone blades to wooden handles. The famous walls of Babylon were constructed partly with bitumen mortar, and the city of Babylon itself stood above one of the world's most extensive bitumen deposits — the Tar Pits of Hit on the Euphrates River, where seeping petroleum had created thick bitumen deposits exploited for thousands of years.