Crude Oil: From Formation to Products
What is Crude Oil?
Crude oil is a viscous black liquid, collected at great depths within sedimentary rocks. The term ‘petroleum’ means ‘rock oil’. It is a complex mixture of liquid hydrocarbons and contains dissolved solid and gaseous hydrocarbons, along with oxygen, nitrogen, and sulfur compounds. Its appearance varies from a less dense liquid to a thick, tarry substance.
Understanding Hydrocarbons
Hydrocarbons are organic compounds containing hydrogen and carbon. They are classified into series such as alkanes, alkenes, alkynes, aromatic compounds, and cycloalkanes. The most prominent hydrocarbons include:
- Methane
- Ethane
- Propane
- Butane
- Ethylene
- Benzene
- Phenol
How Oil Forms
It is thought that millions of years ago, the remains of billions of animals, plants, and microorganisms were slowly deposited on the seabed. There, covered by mud and under strong pressure in the absence of oxygen, they were decomposed by anaerobic bacteria and processed into the huge masses of hydrocarbons that form oil fields.
The First Commercial Oil Well
The first commercial oil well was drilled in Pennsylvania, USA, in 1859 by the American Edwin L. Drake.
Extracting Crude Oil
It is extracted by drilling using long steel pipes. A drill bit at the end rotates, drilling the hole through which oil is obtained by pumping.
Fractional Distillation Process
This process involves heating crude oil in a furnace to temperatures exceeding 400°C. Gaseous components are distilled into liquid form, yielding products such as:
- Kerosene
- Gasoline
- Fuel Oil
- Diesel
- Lubricants
Fractions with high boiling points undergo a process called “cracking,” or the breaking of molecules by heating in the presence of catalysts. This aims to obtain other products like ethylene and propylene and is widely used in producing additional gasoline.
Importance to Petrochemical Industry
Crude oil is of great importance to the chemical derivative industry (petrochemicals), allowing the production of an enormous variety of products such as:
- Detergents
- Synthetic fibers
- Fertilizers
- Food packaging
- Plastics
- Rubber
- Paints
- Textiles
Major Petroleum Derivatives
- Gas
- Gasoline (or Benzine)
- Kerosene (or Paraffin)
- Gas oil (or Diesel)
- Lubricating Oil
- Semisolids (Vaseline, wax, paraffin wax)
- Solids (Asphalt, petroleum coke)
Gasoline is a volatile mixture of hydrocarbons, mainly alkanes, aromatic hydrocarbons, and some cycloalkanes.
Types of Crude Oil
- Paraffinic Oil: Composed of molecules where the number of hydrogen atoms is always two more than double the number of carbon atoms (CnH2n+2).
- Asphaltic Oil: Their molecules contain naphthenes, where the number of hydrogen atoms is approximately twice the number of carbon atoms (CnH2n).
- Mixed-Base Oil: It consists of a mixture of paraffinic and naphthenic hydrocarbons.
Petroleum Exploration Methods
Geological Exploration
This involves the observation and examination of the upper layers of the Earth’s crust to identify areas most conducive for drilling.
Geophysical Exploration
This is based on various physical properties of the Earth’s crust and rocks, such as elasticity, density, and magnetism.
Seismic Exploration
This method studies underground structures by measuring the transit time of acoustic waves generated by a surface explosion (an artificial earthquake).
Magnetic Exploration
This allows for the indirect identification of sedimentary basins.
Crude Oil in Chile
Chilean oil is typically low density and contains a low percentage of sulfur. The first oil field was discovered on December 29, 1945, in Isla Grande de Tierra del Fuego and was named ‘Springhill’.
ENAP’s Role
ENAP focuses on the exploitation of existing fields, the search for new deposits, and oil refining.
What is Natural Gas?
Natural gas is a mixture of hydrocarbon gases, primarily methane, with lesser proportions of ethane, propane, and butane. It is often found above oil deposits.