Oil and natural gas are the remains of living organisms that inhabited the sea millions of years ago. They sank to the sea bed and became buried by layers of mud and sand, in a similar way to the plants that formed coal. As the remains became more deeply buried, they were broken down by bacteria, heat and pressure and gradually turned into oil and gas. These fuels are trapped in layers of porous rock, either beneath the sea bed or deep below land that was once covered by sea. Geologists call oil and natural gas “petroleum”.
Oil and natural gas are naturally occurring chemicals that are made up of just two elements — carbon and hydrogen. The class of chemicals based on carbon and hydrogen are called hydrocarbons.
The simplest hydrocarbon, methane, is made up of one carbon atom and four hydrogen atoms. Other hydrocarbons like octane and octadecane have more complicated structures. Plastics are made of molecules called polymers that are very long chains of hydrocarbons.
Stage 1 – All of the oil and gas we use today began as microscopic plants and animals living in the ocean millions of years ago. As these microscopic plants and animals lived, they absorbed energy from the sun, which was stored as carbon molecules in their bodies. When they died, they sank to the bottom of the sea. Over millions of years, layer after layer of sediment and other plants and bacteria were formed.
Stage 2 – As they became buried ever deeper, heat and pressure began to rise. The amount of pressure and the degree of heat, along with the type of biomass, determined if the material became oil or natural gas. More heat produced lighter oil. Even higher heat or biomass made predominantly of plant material produced natural gas.
Stage 3 – After oil and natural gas were formed, they tended to migrate through tiny pores in the surrounding rock. Some oil and natural gas migrated all the way to the surface and escaped. Other oil and natural gas deposits migrated until they were caught under impermeable layers of rock or clay where they were trapped. These trapped deposits are where we find oil and natural gas today.
Oil and natural gas reserves are found in many parts of the world. In the past, demand was low and reserves were easy to find. In fact, the first users of oil depended on surface seepage for their supplies. However, as demand has increased, all the easy-to-find oil has been used.
Today, oil exploration takes place in some of the most challenging places on earth. We are now looking for new oil reserves thousands of feet under the ocean and in areas of climatic extremes.
We don’t have to worry about running out of oil or natural gas any time soon. At our current rate of use, we have oil and natural gas reserves to last 60-90 years. And while the total amount of oil and natural gas isn’t increasing, our ability to find and extract oil and natural gas from new sources expands almost every day!
We now produce natural gas from buried coal seams, oil and natural gas from deep deposits located miles beneath the surface of the earth, and in the deep ocean, hundreds of miles offshore and in water depths greater than 10,000 feet.
Finding economical ways to extract oil from coal tars and oil shales could provide supplies for hundreds of years. The oil and natural gas industry is also investing in alternative energy such as wind, solar, geothermal and biomass to make these potential energy resources more reliable and affordable to meet the growing need for energy.
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