What is oil made of

Hydrocarbon Composition

Crude oil is fundamentally a complex mixture of hydrocarbons—organic molecules composed of carbon and hydrogen atoms bonded together. The primary components are alkanes (straight and branched-chain hydrocarbons), cycloalkanes (ring-structured hydrocarbons), and aromatic hydrocarbons (containing benzene rings). The specific balance of these compounds varies dramatically between different oil fields.

Formation Process

Oil formed from the remains of microscopic organisms and plants that lived in ancient seas millions of years ago. When these organisms died and accumulated on the ocean floor, layers of sediment buried them. Over millions of years, intense heat, pressure, and chemical reactions converted this organic material into crude oil and natural gas.

Non-Hydrocarbon Content

Beyond hydrocarbons, crude oil contains valuable and problematic trace elements. Sulfur compounds range from less than 0.5% to over 3% depending on the source, creating environmental concerns during refining. Nitrogen and oxygen compounds, along with trace metals like nickel and vanadium, influence refining processes and the quality of end products.

Refining and Separation

Oil's usefulness comes from separating its components. During fractional distillation, different hydrocarbons separate based on boiling points—lighter molecules like propane and gasoline separate at lower temperatures, while heavier molecules remain as fuel oil and bitumen. This separation process is crucial for producing the diverse petroleum products we use daily.