Removing and Refining Fossil Fuels
Geologists use a variety of sophisticated instruments to locate underground petroleum, natural gas, and coal deposits. These instruments allow scientists to interpret the geologic composition, history, and structure of sedimentary basins in the earth’s crust. Once located, petroleum and natural gas deposits are removed by wells drilled down into the deposit, while coal is removed by excavation.
Petroleum and Natural Gas
To locate deposits of petroleum and natural gas, exploration geologists search for geologic regions containing the ingredients necessary for petroleum formation: organic-rich source rock, burial temperatures sufficiently high to generate petroleum from organic material, and petroleum-trapping rock formations.
When potentially petroleum-rich geologic formations are identified, wells are drilled into the sedimentary basin. If a well intersects porous reservoir rock containing significant petroleum and natural gas deposits, pressure inside the trap may force the liquid hydrocarbons spontaneously to the surface. However, pressure inside the trap typically declines to the point where the petroleum must be pumped to the surface.
Once petroleum has been extracted from the ground, it is transported by pipeline, truck, or tanker to a refinery to be separated into liquid and gas components. Raw petroleum is heated to distill hydrocarbons by molecular weight. Lighter molecules are separated and refined into gasoline and other fuels, while heavier molecules are processed into engine lubricants, asphalt, waxes, and other products. Because demand for fuel far exceeds demand for the products made from the heavier hydrocarbons, refiners often break apart the heavy molecules into lighter ones that can be refined into gasoline. They do so by means of processes called thermal cracking and catalytic cracking.
Coal
Because of their enormity, the world’s most extensive coal beds have already been identified. Modern underground mining commonly employs machines called longwall miners to remove coal. These machines use rotating drums studded with picks to rip coal from seams in large chunks.
Surface-mine operators use mammoth earth-moving shovels to mine coal. These shovels first remove overlying soil and rock so the coal beds can be blasted apart. The blasted coal is scooped up and loaded into the beds of huge trucks for transport.
Petroleum and Natural Gas
To locate deposits of petroleum and natural gas, exploration geologists search for geologic regions containing the ingredients necessary for petroleum formation: organic-rich source rock, burial temperatures sufficiently high to generate petroleum from organic material, and petroleum-trapping rock formations.
When potentially petroleum-rich geologic formations are identified, wells are drilled into the sedimentary basin. If a well intersects porous reservoir rock containing significant petroleum and natural gas deposits, pressure inside the trap may force the liquid hydrocarbons spontaneously to the surface. However, pressure inside the trap typically declines to the point where the petroleum must be pumped to the surface.
Once petroleum has been extracted from the ground, it is transported by pipeline, truck, or tanker to a refinery to be separated into liquid and gas components. Raw petroleum is heated to distill hydrocarbons by molecular weight. Lighter molecules are separated and refined into gasoline and other fuels, while heavier molecules are processed into engine lubricants, asphalt, waxes, and other products. Because demand for fuel far exceeds demand for the products made from the heavier hydrocarbons, refiners often break apart the heavy molecules into lighter ones that can be refined into gasoline. They do so by means of processes called thermal cracking and catalytic cracking.
Coal
Because of their enormity, the world’s most extensive coal beds have already been identified. Modern underground mining commonly employs machines called longwall miners to remove coal. These machines use rotating drums studded with picks to rip coal from seams in large chunks.
Surface-mine operators use mammoth earth-moving shovels to mine coal. These shovels first remove overlying soil and rock so the coal beds can be blasted apart. The blasted coal is scooped up and loaded into the beds of huge trucks for transport.
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