fossil fuels reading part 1

US has for many years relied heavily on imported oil to meet part of its oil demand. Without it, U.S. reserves would dwindle more quickly. The United States consumes about

7.5 billion barrels of oil per year, to supply about 40% of all the energy used. Currently, almost two-thirds of the oil consumed is imported from other countries.

The production of a large deposit of any fossil fuel requires a large initial accumulation of organic matter, which is rich in carbon and hydrogen

Another requirement is that the organic debris be buried quickly to protect it from the air so that decay by biological means or reaction with oxygen will not destroy it.

There is an abundance of organic matter rapidly buried by sediment. Oil and much natural gas are believed to form from such accumulated marine microorganisms.

Continental oil fields often reflect the presence of marine sedimentary rocks below the surface. Additional natural gas deposits not associated with oil may form from deposits of plant material in sediment on land.

The United States alone consumes about 25% of the oil used worldwide, more than all of

Europe together, and about three times as much as China or Japan, the next-highest individual-country consumers

Primary and secondary recovery together extract an average of one-third of the oil in a given trap, though the figure varies greatly with the physical properties of the oil and host rocks

Recovery using no techniques beyond pumping is primary recovery. When ow falls off, water may be pumped into the reservoir, filling empty pores and buoying up more oil to the well (secondary recovery)

In the United States, drilling for oil or gas in 2006 cost an average of $324 per foot; drilling costs in some areas of future resource potential, notably Alaska, are far higher than the average

The average oil or natural gas well drilled was over 6400 feet deep (it was about 3600 feet in 1949); nearly half of exploratory wells come up dry of hydrocarbon deposits

Cracking

The breaking down of long-chained saturated hydrocarbons to form a mixture of shorter-chained lighter, smaller molecules

Since virtually no petroleum is found in rocks younger than 1 to 2 million years old, geologists infer that the process is comparatively slow; the world's oil and gas is being used up far faster than significant new supplies could be produced

Therefore, oil and natural gas are among the nonrenewable energy sources. We have an essentially nite supply with which to work.

Worldwide, over one trillion barrels of oil have been consumed, according to estimates by the

U.S. Geological Survey. The estimated remaining reserves are about 1.2 trillion barrels (42 gallons=1 barrel)

Despite a quadrupling in oil prices between 1970 and 1980 (after adjustment for inflation), U.S. proven reserves continued to decline.

Yield from producing wells is also declining, from a peak average of 18.6 barrels of oil per well per day in 1972 to 10.2 barrels in 2007.

The United States initially had perhaps 10% of all the world's oil resources. Already over 400 billion barrels have

been produced and consumed; remaining U.S. proven reserves are only about 21 billion barrels. net U.S. oil reserves have generally been decreasing year by year as well as domestic production

Examples of fossil fuels

coal, oil, natural gas

U.S. oil production peaked at 9.64 million barrels per day in 1970, and has

declined steadily since then, dipping to 5.10 million barrels per day in 2007.

As burial continues, the organic matter begins to change. Pressures increase with the weight of the overlying sediment or rock; temperature increase with

depth in the earth; and slowly, over long periods of time, chemical reactions take place. These reactions break down the large, complex organic molecules into simpler, smaller hydrocarbon molecules

fossil fuel

energy sources that formed from the remains of once- living organisms. These include oil, natural gas, coal, and fuels derived from oil shale and tar sand.

natural gas

flammable gas, consisting largely of methane and other hydrocarbons, occurring naturally underground (often in association with petroleum) and used as fuel.

Most of the maturation process occurs in the temperature range of 50° to 100°C (approximately 120° to 210°F). Above these temperatures,

he remaining hydrocarbon is almost wholly methane; with further temperature increases, methane can be broken down and destroyed in turn

The large portions of the continents underlain predominantly by

igneous and metamorphic rocks are, for the most part, very unpromising places to look for oil. Some such areas are now being explored, but with limited success.

most regions not yet explored have been neglected precisely because they are unlikely to yield appreciable amounts of petroleum. The high temperatures involved in the formation of

igneous and most metamorphic rocks would destroy organic matter, so oil would not have formed or been preserved in these rocks. Nor do these rock types tend to be very porous or permeable

petroleum

not a single chemical compound. Liquid petroleum, or oil, comprises a variety of liquid hydrocarbon com- pounds (compounds made up of different proportions of the elements carbon and hydrogen

Commercially, the most valuable deposits are those in which a large quantity of

oil and/or gas has been concentrated and con ned (trapped) by impermeable rocks in geologic structures

Natural gas presently supplies close to 25% of the energy used in the United States. The United States has proven natural gas reserves of just over 200 trillion cubic feet. However,

roughly 20 trillion cubic feet of these reserves are consumed per year, and most years, less is found in new domestic reserves than the quantity consumed

The majority of petroleum source rocks are fine- grained clastic

sedimentary rocks of low permeability, from which it would be difficult to extract large quantities of oil or gas quickly

Most oils and all natural gases are less dense than water, so they

tend to rise as well as to migrate later- ally through the water- filled pores of permeable rocks.

In the early stages of petroleum formation in a marine deposit, the deposit may consist mainly of larger hydrocarbon molecules ("heavy" hydrocarbons), which have the thick, nearly solid consistency of asphalt, as the petroleum matures, and as

the break- down of large molecules continues, successively "lighter" hydrocarbons are produced. Thick liquids give way to thinner ones, from which are derived lubricating oils, heating oils, and gasoline

the most conservative estimate of the supply of an energy source is the amount of known reserves,

the supply of an energy source is the amount of known reserves, "proven" accumulations that can be produced economically with existing technology

As with minerals, estimates of energy reserves are thus sensitive both

to price fluctuations and to technological advances.

In the final stages, most or all of the petroleum is further broken down into

very simple, light, gaseous molecules—natural gas.

Some of the heavier hydrocarbons may also be broken up during refining into smaller, lighter molecules through a process called cracking,

which allows some of the lighter compounds such as gasoline to be produced as needed from heavier components of crude oil.

At many known oil and gas seeps, these substances escape into the air or the oceans or ow out onto the ground. These natural seeps,

which are one of nature's own pollution sources, are not very efficient sources of hydrocarbons for fuel if compared with present drilling and extraction processes