Chapter #15 Guided Reading
15.1 FOSSIL FUELS
Fossil energy resources include petroleum (crude oil), natural gas, coal, and some others. Petroleum is a complex mixture of organic molecules that are purified or refined into numerous products like gasoline, kerosene, heating oil, asphalt, synthetic fibers, plastics, etc. Natural gas is also a complex mixture that consists mostly of methane. Fossil fuels were formed millions of years ago from the debris of plants. The energy in fossil fuel originally came from the sun (recall the 1st law of thermodynamics), and is essentially stored sunlight. The major fossil fuels provide 90% of energy consumed in the world, mostly for transportation and industrial uses. Usage is increasing, mostly due to coal burning.
15.2 CRUDE OIL AND NATURAL GAS
Fossil fuel is formed from organic matter made by plants that was trapped in the earth without a chance to decompose. The exact chemistry of the process is not fully understood. Most deposits are found at plate boundaries in depositional basins that were buried (source rock), although several important exceptions exist. Petroleum and natural gas formed during 1000s of years of heat and pressure. Petroleum and gas are light and will migrate to the surface (reservoir rock) and evaporate unless they are trapped by a confining layer of rock or a trap, known as a cap rock usually consisting of shale. In other words, the geological requirements are exacting. If the cap develops cracks, the oil will migrate to the surface, the light fractions will evaporate, and the remaining, oily residue is known as tar sand. As crude oil ages, it eventually decomposes. The two end products or maturation products are graphite and methane.
● Petroleum Production
Production can be by primary or enhanced extraction methods. Primary production involves pumping the oil from wells, a method that can recover only about 25% of the oil in the field. Enhanced production methods, in which steam, water, or compressed gases are pumped into the field, can improve the efficiency up to 60%. Most proven reserves are located in only a few fields. One percent of all fields contains 65% of the oil, and the largest is located in the Middle East. Enormous trade imbalances have grown as world users purchase this oil.
● Oil in the 21st Century
At present production rates, petroleum will last only a few decades. Consider the following signs:
1. We are approaching the time when 50% of total crude oil from known fields is gone (peak oil).
2. Proven reserves are about 1 trillion barrels. World consumption is 27 billion barrels/yr. (1012/27 x 109/yr = 37 yr). Forecasts predict the amount of oil that may ultimately be recoverable is in the order of 2-3 trillion barrels. We are not finding new oil as fast as we are depleting known oil.
4. While we can not possibly get all the oil out of the Earth, oil exploration will end when the energy cost of exploration approaches the energy content of the
discoveries.
3. U.S. oil reserves will be depleted by 2090, world oil will be depleted by about 2100.
● Natural Gas
Natural gas is a complex mixture of organic gases (e.g. propane) that consists mostly of methane.
● Coal-Bed Methane
There is a considerable amount of methane associated with coal beds that can be tapped by drilling. The technology is developing. This gas is clean burning and produces lower amounts of carbon dioxide than other fossil fuels. There are significant problems with the disposal of polluted water that is produced when the methane is recovered, along with foul smells and nuisance noise.
● Environmental Effects of Oil and Natural Gas
These effects arise from processes associated with the extraction and refining stages, and the delivery and use stages.
15.3 COAL
Coal is the world’s largest conventional source of fossil fuel. There are may different types of coal that vary greatly in energy and sulfur content. Those most commonly used a fuel, in order of increasing energy per ton, are lignite, bituminous, and anthracite. The high sulfur content of some types of coal pollute the atmosphere. Sulfur can be removed from coal as it burns, but this produces toxic pollutants as well.
15.4 OIL SHALE AND TAR SANDS
These are currently being explored for future use but currently do not contribute much to overall energy production.
Fossil energy resources include petroleum (crude oil), natural gas, coal, and some others. Petroleum is a complex mixture of organic molecules that are purified or refined into numerous products like gasoline, kerosene, heating oil, asphalt, synthetic fibers, plastics, etc. Natural gas is also a complex mixture that consists mostly of methane. Fossil fuels were formed millions of years ago from the debris of plants. The energy in fossil fuel originally came from the sun (recall the 1st law of thermodynamics), and is essentially stored sunlight. The major fossil fuels provide 90% of energy consumed in the world, mostly for transportation and industrial uses. Usage is increasing, mostly due to coal burning.
15.2 CRUDE OIL AND NATURAL GAS
Fossil fuel is formed from organic matter made by plants that was trapped in the earth without a chance to decompose. The exact chemistry of the process is not fully understood. Most deposits are found at plate boundaries in depositional basins that were buried (source rock), although several important exceptions exist. Petroleum and natural gas formed during 1000s of years of heat and pressure. Petroleum and gas are light and will migrate to the surface (reservoir rock) and evaporate unless they are trapped by a confining layer of rock or a trap, known as a cap rock usually consisting of shale. In other words, the geological requirements are exacting. If the cap develops cracks, the oil will migrate to the surface, the light fractions will evaporate, and the remaining, oily residue is known as tar sand. As crude oil ages, it eventually decomposes. The two end products or maturation products are graphite and methane.
● Petroleum Production
Production can be by primary or enhanced extraction methods. Primary production involves pumping the oil from wells, a method that can recover only about 25% of the oil in the field. Enhanced production methods, in which steam, water, or compressed gases are pumped into the field, can improve the efficiency up to 60%. Most proven reserves are located in only a few fields. One percent of all fields contains 65% of the oil, and the largest is located in the Middle East. Enormous trade imbalances have grown as world users purchase this oil.
● Oil in the 21st Century
At present production rates, petroleum will last only a few decades. Consider the following signs:
1. We are approaching the time when 50% of total crude oil from known fields is gone (peak oil).
2. Proven reserves are about 1 trillion barrels. World consumption is 27 billion barrels/yr. (1012/27 x 109/yr = 37 yr). Forecasts predict the amount of oil that may ultimately be recoverable is in the order of 2-3 trillion barrels. We are not finding new oil as fast as we are depleting known oil.
4. While we can not possibly get all the oil out of the Earth, oil exploration will end when the energy cost of exploration approaches the energy content of the
discoveries.
3. U.S. oil reserves will be depleted by 2090, world oil will be depleted by about 2100.
● Natural Gas
Natural gas is a complex mixture of organic gases (e.g. propane) that consists mostly of methane.
● Coal-Bed Methane
There is a considerable amount of methane associated with coal beds that can be tapped by drilling. The technology is developing. This gas is clean burning and produces lower amounts of carbon dioxide than other fossil fuels. There are significant problems with the disposal of polluted water that is produced when the methane is recovered, along with foul smells and nuisance noise.
● Environmental Effects of Oil and Natural Gas
These effects arise from processes associated with the extraction and refining stages, and the delivery and use stages.
15.3 COAL
Coal is the world’s largest conventional source of fossil fuel. There are may different types of coal that vary greatly in energy and sulfur content. Those most commonly used a fuel, in order of increasing energy per ton, are lignite, bituminous, and anthracite. The high sulfur content of some types of coal pollute the atmosphere. Sulfur can be removed from coal as it burns, but this produces toxic pollutants as well.
15.4 OIL SHALE AND TAR SANDS
These are currently being explored for future use but currently do not contribute much to overall energy production.