Unit 3: Natural Resources Part 3: Energy Resources

Hydraulic Fracturing and Natural Gas Hydraulic fracturing, also called fracking, is the process by which materials are pumped underground to break up rock and release oil or natural gas. Materials include large amounts of water, sand, and chemicals. At the time, most of the energy in the U.S. is generated using fossil fuels, such as natural gas extracted by hydraulic fracturing. The natural gas is primarily used to generate electricity and heat. This is a problem, because fossil fuels cannot be quickly replaced, and exist in limited amounts. Hydraulic fracturing has consequences.

Petroleum and Natural Gas Fossil fuels are compounds that contain hydrogen and carbon atoms formed from the remains of living things. Because of their organic origin, coal, petroleum, and natural gas are known as fossil fuels. Fossil fuels are considered non-renewable.

Petroleum and Natural Gas Petroleum is the largest source of energy used today, and is a fundamental component of many consumer and commercial products. The majority of petroleum recovered from Earth is used to produce gasoline and diesel fuels (transportation). Natural gas is the second largest source of energy, accounting for about 24% of energy in the U.S. It is used to generate electricity, but also for applications such as heating and cooking.

Petroleum and Natural Gas Petroleum and natural gas form in reservoirs, or pockets in Earth’s interior. Three components are required to produce these reservoirs. Heat Permeable Layer Must have large enough pores to serve as storage and migration sites for petroleum to accumulate. Impermeable Layer A dense layer of rock must be located above the permeable layer to prevent petroleum from moving to the surface.

Extracting Petroleum and Natural Gas Three techniques are commonly used to extract petroleum and natural gas from Earth’s interior. Primary recovery relies on underground pressure to drive petroleum to the surface. If the pressure falls, pumps are used to bring petroleum to the surface. Secondary recovery is when water is injected into the rock to bring petroleum to the surface. Enhanced recovery, such as thermal recovery, is when gas injection and chemical flooding are used to bring the remaining petroleum to the surface.

Environmental Impacts of Extraction Extracting fossil fuels can affect air quality. Refining petroleum releases toxins into the atmosphere. Oil spills produce environmental hazards. Advanced drilling processes can minimize the environmental impact of extracting petroleum from Earth’s interior. Horizontal drilling begins when a vertical hole is drilled into rock. Drilling is then turned horizontally to extract gas from a particular rock, with fewer drill holes. Multilateral drilling is when the drill hole accesses multiple layers underground to more efficiently remove natural gas through a single drill hole. Extended reach drilling is an advanced process that can cover great distances, exceeding those by vertical drilling methods. Complex path drilling extracts petroleum and natural gas from a single drill hole using several routes. Seismic images can also use to improve efficiency of extraction.

Coal, Tar Sands, and Oil Shale Coal is currently the largest domestically produced source of energy in the United States. It generates about 50% of the country’s electricity. The energy in coal is stored in the bonds of ancient plants that died millions of years ago. Coal is classified into different types: Anthracite Bituminous Lignite These are based on the carbon content and rated from highest to lowest. The highest carbon content produces the most heat energy when burned.

Consumption of Coal

Coal Mining Surface mining processes used to extract coal include strip mining, open-pit mining, and mountaintop removal mining. During these processes, topsoil, vegetation, and rock are removed and placed to the side, exposing coal on the surface. Coal can be mined underground. Room and pillar mining uses machines to dig into Earth’s surface, and large rooms are excavated along the coal seam. All three types of coal contain sulfur, which is a source of environmental pollution. Coal mining also results in land disturbance, soil erosion, noise pollution, water pollution, and mine subsidence Careful planning can minimize the impact of coal mining on the environment.

Tar Sands and Oil Shale Tar sand contains bitumen, a thick, sticky substance that does not flow like petroleum. It can be mined and processed to extract the petroleum-rich bitumen, which is then refined into oil. Much of the world’s petroleum is found in the subsurface as tar sands. Tar sands are found in the U.S., specifically in eastern Utah along public lands. Oil shale is a sedimentary rock that contains kerogen, a solid bituminous material. The kerogen formed millions of years ago when organic matter was deposited with fine-grained sediment on lake and ocean floors. The kerogen releases hydrocarbons when the rock is heated. The recovery of oil from oil shale comes at a high cost, and regulations prevent the leasing of land for oil shale production.

Extraction of Tar Sands and Oil Shale Because bitumen cannot be pumped from the ground like traditional petroleum reservoirs, it must be mined. Near-surface tar sands can be accessed by open-pit mining. The sticky sand is mixed with hot water and shaken to separate the bitumen from the sand, which then floats to the surface. It is skimmed off and mixed with chemicals so it can be processed further.

Extraction of Tar Sands and Oil Shale Mining tar sands and oil shale can have serious environmental consequences. The surrounding landscape and ecosystems are disruptive. One gallon of gasoline refined from tar sands produces more carbon dioxide than one gallon of gasoline produced from conventional petroleum. The extracting and refining processes require three times more water than conventional petroleum extraction processes do. The environmental consequences of extracting oil shale from the subsurface parallel those for tar sands. Hydraulic fracturing has similar consequences as well. Additionally, many chemicals used during fracturing are toxic to humans and animals. The chemicals can affect air quality. The disposal of the chemicals also poses a serious risk.