Case Study: Petroleum
Petroleum refineries are marvels of modern engineering. Within them a
maze of pipes, distillation columns, and chemical
reactors turn crude oil into valuable products. Large refineries cost
billions of dollars, employ several thousand workers, operate around the clock,
and occupy the same area as several hundred football stadiums. The U.S.
has about 300 refineries that can process anywhere between 40 and 400,000
barrels of oil a day. These refineries turn out the gasoline and
chemical feedstocks that keep the country running.
The Search
Locating an oil field is the first obstacle to be overcome. The
first explorers used Y-shaped devining rods and other supernatural, but
ineffective, means of locating petroleum. Today geologists and
petroleum engineers employ more tried and true methods. Instruments to aid
the search include; geophones (uses sound), gravimeters (uses
gravity), and magnetometers (uses the Earth's magnet field). While these
methods narrow the search tremendously, a person still has to drill a
exploratory well, or wildcat well, to see if the oil actually exists.
Success brings visions of gushers soaring skyward, however today wells are
capped before this happens.
Drilling
There are three main types of drilling operations; cable-tool, rotary,
and off-shore. Cable-tool drilling involves a jack-hammer approach
were a chisel dislodges earth and hauls up the loose sediment. Rotary
drilling works at much greater depths, and involve sinking a drill
pipe with a rotating steel bit in the middle. Off-shore drilling
involves huge semisubmersible platforms which lower a shaft to the ocean
floor, containing any oil which is located.
All crude oil contains some amount of methane or other gases
dissolved in it. Once the drilling shaft makes contact with the oil it
releases the pressure in the underground reservoir. Just like opening a
can of soda pop, the dissolved gases fizz out of solution pushing crude
oil to the surface. The dissolved gases will allow about 20% recovery of
oil. To get better recovery water is often pumped into the well, this forces the
lighter oil to the surface. Water flooding allows recoveries of about
50%. The addition of surfactant allows even more oil to be recovered by
preventing much of it from getting trapped in nooks and crannies. Yet, it is
impossible to get all of the oil out of a well.
Transportation
Because crude oil is a liquid it is much easier to move than
natural gas or coal. Coal is nice and dense, so it does not require large
holding containers, but it cannot be pumped. Conveyor belts and cranes
cannot compete with pipelines for economic efficiency. Natural gas can be
pumped using expensive compressors, but it requires enormous holding tanks.
A recent trick has been to inject huge amounts of water into salt strata. The
water dissolves the salt, leaving truly enormous caverns. The natural gas is
then pumped in and stored until needed. The ease in transporting oil is
one of the reasons we have become so dependent upon it. Pound for pound
natural gas and coal just cannot compete.
Reserves
The proven reserves of crude oil within the U.S. are about
3.9 billion cubic meters. This could cover the state of Minnesota
with a layer one half inch thick. A reasonable value for the total
amount of crude oil obtainable using current methods from around the
world is 350 billion cubic meters. This could cover Minnesota
with a layer of oil four and a half feet thick. Yet, at the rate we are
consuming oil, the nation's reserves will be depleted by 2010, and
the world's reserves will be depleted by the end of the 21st Century.
Yet, oil is not the only source of hydrocarbons. Natural gas and
coal are both available in much greater amounts . However, we may decide that it is not such a good idea
to burn all of these hydrocarbons. Carbon dioxide is a strong
greenhouse gas (along with water and methane), and the results to the global
environment could be catastrophic to human life. Nuclear fission, solar power,
hydroelectric power, and geothermal power offer immediate alternatives,
however energy produced by these methods would be more expensive than burning
oil, coal, or natural gas. The holy grail of power production, nuclear fusion,
continues to elude scientists and engineers. In any case, refining techniques
will remain vital to produce not only fuels but raw materials
for petrochemical industries (plastics, pharmaceuticals, agrochemicals,
etc.).
"The Kingdom of Heaven runs on righteousness, but
the Kingdom of Earth runs on OIL!"
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