In this lesson, students investigate sources of fossil fuels, particularly oil. Students will learn how engineers and scientists look for oil by taking core samples from a model of the Earth. Also, students will explore and analyze oil consumption and production in the United States and around the world.

Finding fossil fuels below the Earth's surface is a challenge for geological and petroleum engineers. Much investigation is done before drilling expensive wells: They examine core samples, look for natural fractures in the reservoir rock, and learn the size and porosity of the reservoir rock and how fast oil droplets move through these pores. Engineers also design special machines and tools for extracting and transporting oil, and complex refining processes to convert the crude oil into many forms of usable energy. fossil fuel Earth oil energy sedimentary rock geology core methane Identify the origin of fossil fuels Know the important role that engineers have in gathering and finding oil Understand how humans use oil in their everyday lives What is as precious as gold? Oil! Have you ever wondered where oil comes from, or what its use is? Well, the United States gets about 40% of their energy from oil, a fossil fuel that is also referred to as petroleum, which comes from sedimentary rocks under the Earth's surface. It takes millions of years to create oil. The process started much before the times of dinosaurs, but it is estimated that humans will use all the oil that is left in 40 to 60 years. Americans have been drilling for oil since about 1859, when the first oil well was constructed out of wood (see Figure 1). How do oil companies extract (pull out) these tiny droplets away from the rock thousands of feet underground? How does this oil move through the dense rock and into wells that take it to the surface? How do the tiny droplets combine into the billions of gallons of oil that the United States and the rest of the world use each day? Where should engineers drill oil wells to ensure that the most oil is contacted? How should machinery be built and used to get oil? So many questions exist about oil. Fortunately, scientists and engineers know the answers to these questions. First, to harvest oil, we have to find it. But, how do you know where is it if you cannot see under the ground? Geological and petroleum engineers drill holes in the Earth to get core samples of the underground layers. If oil is found in the core, then the chances are good that there is a lot more oil in the area surrounding the core. Next, the oil must be extracted and transported to a location where it can be used. Unfortunately, most of the steps involved in getting oil to our homes and cars can cause pollution. Pulling oil up to the surface of the earth can pollute the ground, moving oil to other locations can sometimes cause an oil spill, and burning oil to get energy for automobiles or at energy plants produces air pollution. Despite the potential for pollution, oil provides energy for most of the United States. Most cars run on gasoline, which is made from oil, and many houses are heated by oil. Engineers need to know about oil reservoirs before they begin the process of drilling wells, which is very costly. Any incorrect prediction could be a very expensive error for oil companies. They need to know about the size and number of pores in a reservoir rock. They need to know how fast oil droplets will move through these pores. They need to know where the natural fractures are in a reservoir so that they know where to drill their wells. Finding the answers involves research that is a mix of fluid mechanics, thermodynamics, applied mathematics and geology, which are all engineering principles. Engineers develop the machines and tools used for all steps for the extraction, transportation and use of oil for energy. Fossil fuels are energy-rich substances that have formed from the Earth's long-buried plants and microorganisms. Crude oil, one common fossil fuel, is formed in sedimentary rocks. Sedimentary rocks are rock layers formed from sediments, such as pieces of sand or organic matter that are transported, deposited and then cemented together over time. Sedimentary rocks normally have visible layers of different kinds of sediment (see Figure 2). The Sediment layers are always deposited in horizontal layers, one on top of the other. Therefore, sedimentary rocks always have horizontal layers initially, and the layers closest to the bottom, or found deeper under the Earth's surface, are the oldest. Over time, however, Earth's processes, such as erosion or plate tectonics can change the rocks. Plate tectonics cause rocks to fold and fault, as seen in Figure 3 (refer to the Earthquake Formation lesson of this unit for more information). Millions of years ago, in certain parts of the world, there were thriving marine communities with lots of different organisms. When these organisms died, they became organic matter (sediments) on the ocean floor. Over time, more sediment was deposited on top, and both layers solidified into sedimentary rock. The layer with a lot of organic matter has the potential to become oil, provided a couple of other things happen. Usually, microorganisms consume the organic matter in rock layers; however, if the rocks happen to be in a low-oxygen environment, different microorganisms — called anaerobic organisms — will turn the organic matter into methane. Methane, also called natural gas, is a gas made of hydrogen and carbon that can itself be used for energy or it can be turned into oil. Methane will become oil if it is created deep below the Earth's surface and trapped there by an impermeable rock, which it cannot pass through. Impermeable rocks, such as granite, that trap methane and oil under the ground are called cap rocks. When the cap rock is faulted, or folded, large oil deposits can be found (see Figure 4). Oil can also found in reservoir rocks, which are permeable rocks were methane got stuck as it was migrated up and turned into oil (see Figure 5). First, to harvest oil, we have to find it. But, how do you know where is it if you cannot see under the ground? Geological and petroleum engineers drill holes in the Earth to get core samples of the underground layers. If oil is found in the core, then the chances are good that there is a lot more oil in the area surrounding the core. Engineers then set up the equipment to drill in the exact area that their tests show will result in a lot of oil coming out of the ground. Next, the oil must be extracted. The oil is extracted mostly through oil wells that pump the oil up to the surface. Extracting oil and using oil can be potentially harmful to the environment. Sometimes when the oil is brought to the surface it contains sediments that cannot be used for energy. If these sediments are not disposed of properly they could pollute the environment. Once extracted, the oil must be properly transported to where it will be used. During transport, oil could also potentially pollute the environment. For example, disastrous oil spills have occurred when tankers transporting oil have run aground or leaked into the ocean. Finally, burning oil to produce gasoline for automobiles increases air pollution — and that is in addition to automobiles using that gas for energy. Despite the potential for pollution, oil provides essential energy for most of the United States. Most of our nation's cars run on gasoline, which is made from oil, and many houses are heated by oil. Because the predicted decrease in oil production and the increase in pollution, engineers are continually searching for more efficient ways to power automobiles and heat houses that use less oil. Energy-rich substances that have formed from the Earth's long-buried plants and microorganisms. There are three commonly-used fossil fuels: coal, oil (petroleum) and natural gas. A rock formation with special kinds of porous rocks that contain oil droplets. Open spaces in rocks. Very hard, impermeable rocks that trap methane and oil under the ground. Tiny cracks in rock layers. Layers of rock that were formed by accumulation of rock fragments, shell fragments, plant material, mud and sands, which were transported to their present locations by water, air, wind or ice. A long, thin sample of rock taken from deep below the Earth's surface. What's Down There? A Closer look at Oil and Energy Consumption What is oil used for? (Answer: Oil is burned to create energy for a variety of uses: so that automobiles can run, to heat houses, for oil-burning lamps, for maintenance of moveable parts — such as motors, door hinges, swings, etc.) Where does oil come from? (Answer: Oil is a fossil fuel that is created from plants and animals that were alive millions of years ago.) Ask students to describe how oil can contribute to pollution. (Possible answers: automobiles, industry/factories, the extraction of and transportation of oil from the Earth.) Can they think of any ways to help reduce the pollution caused by the drilling and transport of oil? Do they have any ideas of ways to conserve oil so we do not run out of it in 40 to 60 years? Brainstorming: Have students generate a number of possible ideas about the following question. Remind students that no idea or suggestion is "silly." All ideas should be respectfully heard. Ask the students: What are some of the many uses for oil? (Answers: cars, lamps, heat for houses, to make a hinge work smoothly, etc) Question/Answer: Ask questions and have students raise their hands to answer. Discuss answers as a class. Where does oil come from? (Answer: It is found in between the layers of sedimentary rocks.) How fast will humans use all the oil? (Answer: It is estimated that humans will use all the oil left in 40 to 60 years.) What are the two types of engineering that work to gather oil? (Answer: petroleum and geological engineering) How do engineers get oil from the ground? (Answer: They drill for it after they have verified its existence through core samples obtained from areas that are predicted to contain oil.) After oil is found, what else must be done with it before it can be used in our homes and cars? (Answer: It must be extracted and transported.) Can oil cause pollution? (Answer: Yes, pulling oil up to the surface of the earth can pollute the ground, moving oil to another location can sometimes leak and cause an oil spill, and burning oil to get energy in cars or at energy plants produces air pollution.) What types of things do engineers need to know before drilling for oil? (Answer: The must know the size of oil reservoirs and how oil moves through the reservoirs.) Numbered Heads: Break the class up into teams of three to five. Students on the team number off so each has a different number. Ask the students a question (give them a time frame for solving it, if desired). The members of each team should work together on the question. Everyone on the team must know the answer. Call a number at random. Students with that number should raise their hands to answer the question. If not all the students with that number raise their hands, allow the teams to work on the question a little longer. Pick a student to answer. Continue until you get the right answer. Questions from the Post-Introduction Assessment can be used as well. How is oil formed? (Answer: From plant and animal microorganisms, or sediments.) When was oil made? (Answer: Over millions of years ago.) Where is oil found? (Answer: Deep below the Earth's surface, in reservoir rocks.) Make a core sample using cupcakes: http://www.coaleducation.org/lessons/wim/4.htm See the following web site for a fun activity on what rocks contain: http://www.schoolscience.co.uk/content/4/chemistry/findoils/index.html Keller, Edward A. Environmental Geology, 7th Edition: New York: Prentice Hall, 1996.