How Are Fossil Fuels Obtained?

Fossil Fuel Basics

Fossil fuels are combustible hydrocarbons which were formed millions of years ago. Plants and animals died, began to decay, and were buried under sediment. Over eons, these decaying remains were covered by layers and layers of silt and buried deep underground. The pressure and heat at those depths, transformed them into the fossil fuels oil, natural gas and coal.

Coal Mining

Coal is a solid, fossil fuel--basically it's a flammable rock. When the coal is deep underground, a tunnel must be dug to reach it. In shaft mining, this tunnel goes straight down to the coal. Sometimes, if the coal is near the surface or buried in a mountain, it can be reached by a diagonal shaft instead of a vertical one and it is called a slope mine. Sometimes, the coal is harvested directly from a tunnel near the surface in a drift mine, or the ground is dug away to expose the bed of coal in a surface mine.

Gas and Oil

Most natural gas and oil comes from underground reservoirs. The heat and pressure underground often force fossil fuels up through the earth. If the coal and gas encounter a solid, dome-shaped rock structure, they may become trapped under it, unable to continue upwards. Often, the same well will contain both a layer of oil and a lighter layer of gas on top of it.

Drilling the Reservoirs

To get at the gas and oil, a company will drill into a hole in the reservoir. Sometimes, the oil and gas are under so much pressure that they will actually shoot out of the hole, and all the company needs to do is to collect them. As the fossil fuels flow out, however, the pressure will decrease. Sometimes, the driller will inject water or gas into the reservoir to increase the pressure and propel the gas out. Other times, they will use large pumps to remove as much oil and gas as possible.

References

• Fossil Fuels Guide
• Natural Gas
• Coal Mining