|
|
Petroleum products are probably the most widely studied and measured type of energy in the global economy. They come in many different forms, though this is not immediately obvious from news reports that lump them all together under the banner of “oil.”
Crude oil is extracted through wells that tap into underground reserves where oil has been discovered. The extraction process is facilitated by the intense pressure found beneath the earth’s surface. The release of natural gas often occurs alongside oil removal. Once this initial pressure has been relieved, concentrated streams of water, steam, gas or other pumping mechanisms help displace the oil remaining in reservoirs. 1
Source: http://www.eia.doe.gov/kids/energyfacts/sources/non-renewable/oil.html
Although these techniques have been improved over the last 100 years, significant inefficiencies remain. Using the latest technologies, the average reservoir recovery rate has risen from 20 percent to a still modest 35 to 45 percent.2 This jump in efficiency has greatly increased the global supply of oil, but there is still plenty of room for improvement, which has been evident in the recent disastrous oil spill in the Gulf of Mexico.
Types of Oil
The quality of crude oil can be assessed in several ways and is an important determinant of how the oil can be used. Depending on the level of the chemical sulfur, crude is classified as either sweet (low sulfur content) or sour (high sulfur content). The ease with which the oil flows during the extraction process indicates whether the oil is heavy (flows with difficulty) or light (flows smoothly). Because heavy crude and sour crude are rawer forms, they are more difficult to process and refine. As a result, lighter and sweeter crudes are generally preferred, and are used to manufacture gasoline and diesel fuel for cars.
Source: EIA Energy
To read more about oil refining, see Appendix A, “The Refining Challenge.”
The density of the oil distinguishes gasoline from diesel fuel. Diesel does not require as much refining as gasoline and is therefore cheaper to produce. Its greater density allows diesel to release more energy when burned, making it a more efficient fuel. On the other hand, this density also results in increased emissions of sulfur and greenhouse gases that are harmful for the environment. 3
Diesel is the preferred automobile fuel in Europe, where rigorous government emissions standards and generous tax incentives have led to the development of diesel engines that are cleaner and more efficient than their gasoline-fueled counterparts. The vast majority of American passenger automobiles, on the other hand, use gasoline, although there has been a movement in recent years to take advantage of the improved performance of the latest generation of diesel engines.
|
HOW MUCH ENERGY IS IN A GALLON OF GASOLINE? A gallon of gasoline provides enough energy to:
|
3 Brain, “Diesel Fuel;” “National Clean Diesel Campaign”
Further Reading
For more on oil exploration, see “A Petroleum Prospecting Primer,” Chevron, <http://www.chevron.com/products/learning_center/primer/>.
Next: Oil Markets