Please write a brief summary of the article on petroleum industry with about 300 words

Petroleum Industry
Petroleum is vital to many industries, and is of importance to the maintenance of
industrial civilization itself, and thus is a critical concern for many nations. Oil accounts for
a large percentage of the world's energy consumption, ranging from a low of 32% for
Europe and Asia, up to a high of 53% for the Middle East.
Three main components
Today, the upstream sector includes more than 1,000 exploration and production
companies as well as hundreds of associated businesses such as seismic and drilling
contractors, service rig operators, engineering firms and various scientific, technical,
service and supply companies. The midstream sector includes oil and gas pipeline systems
that connect producing and consuming areas. Other facilities extract sulphur and natural
gas liquids, store oil and gas products and transport products by truck, rail or tanker. The
downstream sector consists of refineries, gas distribution utilities, oil product wholesalers,
service stations and petrochemical companies.
Finding oil and natural gas
• Exploration - The search for petroleum
Earth scientists in the petroleum industry, including geologists, geophysicists,
geochemists and paleontologists, study what has happened to rocks that may be buried
thousands of meters below the surface, how those rocks were formed and affected by
events stretching back millions of years, and how to identify traps where oil and gas have
accumulated within rock formations. A trap requires three elements: (1) a porous reservoir
rock to accumulate the oil and gas — typically sandstones, limestones and dolomites; (2)
an overlying impermeable rock to prevent the oil and gas from escaping; (3) a source for
the oil and gas — typically black waxy shales.
• Seismic surveys
In a seismic survey, the geophysical contractor's crew lays out a line or several lines of
sensitive receivers, called geophones or jugs, on the ground. Then explosions or
mechanical vibrations are created on the surface. The geophones record the energy
reflected back as seismic waves from rock layers at various depths. To reduce
environmental impact, many contractors today use the mechanical vibroseis method to
send energy waves from a heavy, vibrating vehicle into the Earth.
Like the rest of the petroleum industry, explorers have adopted ever-higher
environmental standards for seismic surveys. For example, improved methods for clearing
and using narrower cut lines have reduced the impacts on soil, water, plants and wildlife in
forested areas. In other sensitive areas such as mountainous terrain, seismic crews use
helicopters or even packhorses to limit surface disturbance. In offshore exploration, "air
guns" using compressed air have replaced dynamite as a better, safer energy source which
also minimizes the impact on marine life. A marine vessel records the reflected energy
from a towed array of hydrophones. In shallow waters, the hydrophones may be laid out on
the seabed.
• Drilling
Drillers turn theory into hard economic reality. Even when a development well is
located right between two producing wells, there is still a risk that nothing will be found
and also the possibility of greater-than-expected success. The stakes are much higher
when the well is a wildcat in unexplored territory.
The basic drilling process is simple. A revolving steel bit at the bottom of a string of
pipe grinds a hole through the rock layers. There are many different types of rigs. The
smallest are service rigs mounted on trucks, while the largest are installed on ships or
offshore platforms.
Some are specially equipped for sour gas exploration, slanted holes or horizontal
drilling. As a general rule, the bigger the rig, the deeper it can drill. About 75 workers are
directly employed in the drilling of one well, although only four to seven may be on duty at
the rig at any given time. The actual number can vary considerably, depending on the type
of wells being drilled.
Producing oil and natural gas
• Production - Recovering resources
After drilling has located a reservoir of oil or natural gas, the operating company's
production department takes over bringing the resource to the surface. Petroleum is not
produced from underground lakes. Rather, oil and gas are contained in the pores and
fractures of certain sedimentary rocks in the same way that water is held in a sponge. In
mature producing areas, recovering more oil and gas from old wells is an important job.
Getting the most petroleum, at the least cost, is also a key challenge in new production
areas.
• Oil recovery methods
In primary recovery — the initial approach to produce oil — natural reservoir pressure
or simple mechanical pumps are used to raise oil to the surface. Most oil wells in the world
today have to be pumped.
A number of methods can improve primary recovery. The most common is infill drilling,
which involves drilling more wells into the same pool so the oil does not have to travel as
far as through the rock to reach a wellbore. Directional wells are often used for infill drilling.
More than one directional well can be drilled from a common platform. Horizontal
drilling, which extends the wellbore into a much larger portion of the oil-bearing formation,
has been employed since the late 1980s to improve production and enhance recovery.
Further oil production can be obtained by injecting water (water flooding) or natural
gas to maintain reservoir pressure and push oil out of the rock. This is called secondary
recovery. More advanced methods are referred to as tertiary recovery. The most common
tertiary recovery method for light and medium crude oil is miscible flooding. In this
procedure, natural gas liquids (ethane, propane and butane) are injected into special
injection wells.When discovered, these liquids reduce surface tension and oil viscosity to
help release the oil from the reservoir rock. Carbon dioxide has also been used for miscible
floods.
Even with all these techniques, the average recovery in the light oil fields is slightly
more than 30 percent of the original oil in place (OOIP). The remaining resource represents
billions of cubic meters of oil that have been discovered in the world but can not be
produced economically with existing technology.
Processing - Making marketable commodities
 Most crude oil and natural gas require some processing to remove undesirable
components before the commodity goes to market. Some processing facilities are just
settling tanks for removing sand and water, while others are billion-dollar plants treating
large volumes of sour gas or bitumen. Processing facilities separate the raw petroleum into
the major products sold by the upstream sector: (1) crude oil, a mixture of liquid
hydrocarbons;
(2) market-ready natural gas, composed mainly of methane; (3) natural gas liquids (NGLs),
the heavier gaseous hydrocarbons, including ethane, propane and butane; (4) condensate,
liquid hydrocarbons obtained from processing natural gas for market; (5) sulphur, obtained
from processing natural gas and transported by truck or train as liquid, pellets or cakes.
• Gas processing
The natural gas purchased by consumers consists almost entirely of methane, the
simplest hydrocarbon. In gas reservoirs, however, methane is typically found in mixtures
with heavier hydrocarbons, such as ethane, propane and butane and pentane, as well as
water vapor, hydrogen sulphide, which is found in sour gas, carbon dioxide, nitrogen and
other gases.Almost all of these substances are removed from the gas stream at processing
plants located near production areas.
Moving oil and natural gas
Oil and natural gas supplies are mainly located in rural and remote areas. Supply and
demand are linked together by pipelines. Some are massive steel conduits more than a
meter in diameter, while others are plastic tubes a few centimeters across. They form
delivery systems as vast and complex as railroads, highways or electric utilities. However,
pipelines are largely invisible, buried a meter or more underground.
Crude oil, gas liquids and refined products are transported by tanker, barge, railway
and
truck. Pipelines are the only method used to deliver natural gas today.
Using oil and natural gas
Petroleum molecules come in a wide variety of sizes and shapes - strings and rings of
carbon and hydrogen atoms. The methane in natural gas is the simplest and smallest. By
comparison, the molecules in paraffin wax and asphalt are complex and enormous. These
hydrocarbon molecules are sorted, split apart, reassembled and blended at refineries and
petrochemical plants. There, they become part of a multitude of products, from gas lines to
synthetic rubber.
A versatile energy source
The petroleum industry exists because people have become accustomed to the
benefits oil products and natural gas provide - benefits like convenient, affordable
transportation, warm homes and thousands of synthetic materials. The production and use
of petroleum have altered the way in which we live. Petroleum and products derived from it
show up everywhere in our daily lives.