conventional energy sources

1. CHAPTER 8
Oil
Introduction
The terms oil and petroleum have been used interchangeably by industry since
the early 1900s. However, there are some who refer to petroleum as the crude
oil prior to any treatment/refinery, with oil reserved as the definition of “any of
the various kinds of greasy, combustible substances obtained from animal,
vegetable, and mineral sources, and liquid at ordinary temperature.”
The viscosity of the oil in these formations may be as thin as gasoline or as thick
as tar.
Oil is an entirely separate substance from the rock in which it was formed. Oil,
in its liquid form, is very mobile and tends to move upward as the heat in the
Earth’s crust causes it to expand. Rising oil frequently penetrates surrounding
rock formations and continues its upward journey until it meets a layer of rock
that is so tightly compressed that passage is not possible.

2. CHAPTER 8
Oil
Introduction
Because the gases are lighter than the oil, they gradu- ally separate and gather
at the top of the oil reservoir. Similarly, oil is lighter than water and will float
into the pore spaces above it. However, in most oil- fields, there is not enough
space for all three substances as they expand in the high temperatures deep
within the Earth’s crust. This explains why pressure builds up and drives oil to
the surface when a well is drilled.
Oil, like coal, is a fossil hydrocarbon fuel. The particular combination of
hydrogen and carbon determines whether the fuel takes the solid form of coal
or the liquid form of oil or the gaseous form of natural gas.

3. CHAPTER 8
Oil
Availability/Distribution
Regarding availability/distribution, every estimate of oil reserves represents and
is based on current knowledge. It is possible to increase reserves by new
discoveries and by enhanced recovery methods. However, oil is a nonrenewable
resource, the end of the age of oil may be reached sooner rather than later.
Regarding distribution, individuals and companies called jobbers handle the
wholesale distribution of oil. Approximately 15,000 jobbers in the United States
handle orders for petroleum products from gasoline stations, industries, utility
companies, farmers, and other consumers of oil. The last step involves a retailer.
A retailer may be a gasoline station or a home heating oil company.

4. CHAPTER 8
Oil
Characterization
Regarding fuel oil characterization, fuel oils contain virtually all petroleum
products that are less volatile than gasoline. They range from light oils, suit-
able for use in internal combustion or turbine engines, to heavy oils requiring
heating. The heavier fuels are primarily suited for steam generation boilers. The
ASTM specifications for fuel oil properties are given in Table 8.1.
Fuel oils can be divided into two classes: distillate and residual. Distillate fuels
are those that are vaporized in a petroleum refining operation. They are
typically clean, essentially free of sediment and ash, and relatively low in
viscosity.
The residual fuel oils are those that are not vaporized by heating. They contain
virtually all the inorganic constituents present in the crude oil. Frequently,
residual oils are black, high-viscosity fluids that require heating for proper
handling and combustion.

5. CHAPTER 8
Oil
Characterization
A typical analysis of a fuel oil provides the following information:
1. Ultimate analysis
2. API gravity
3. Heating value
4. Viscosity
5. Pour point 6. Flash point
7. Water and sediment
Details for each are provided below.

6. CHAPTER 8
Oil
Characteriza6on
1.Ultimate analysis. The ultimate analysis for an oil is like that for a coal. The
results indicate the quantities of sulfur, hydrogen, carbon, nitrogen, oxygen,
and ash.
2. API gravity. The petroleum industry uses the API gravity scale to determine
the relative density of oil.
3. Heating value . The heating value of a liquid fuel indicates the heat released
by the complete combustion of one unit mass of fuel (pound or kilogram).
4. Viscosity. The viscosity of a liquid is the measure of its internal resistance to
flow.

7. CHAPTER 8
Oil
Characterization
5. Pour point. The pour point is the lowest temperature at which a liquid fuel
flows under standardized conditions.
6. Flash point . The flash point is the temperature to which a liquid must be
heated to produce vapors that flash but do not burn continuously when ignited.
There are two instruments used to determine the flash point: the Pensky–Martens or
closed cup flash tester, and the Cleveland or open cup tester. The closed cup tester
indicates a lower flash point because it retains light vapors that are lost by the open cup
unit.
7. Water and sediment. The water and sediment level, also called bot- tom
sediment and water, is a measure of the contaminants in a liquid fuel. The
sediment normally consists of calcium, sodium, magnesium, and iron
compounds. For heavy fuels, the sediment may also contain carbon.

8. CHAPTER 8
Oil
Characterization
The basic analyses described above are important in designing oil-fired boilers.
The HHV determines the quantity of fuel required to reach a given heat input.
The ultimate analysis determines the theoretical air required for complete
combustion and, therefore, indicates the size of the burner throat. Also available
from the ultimate analysis is the carbon/hydrogen ratio, which shows the ease
with which a fuel burns. This ratio also indicates the expected level of carbon
dioxide emissions.
Compared to coal, fuel oils are relatively easy to handle and burn. There is less
bulk ash to dispose of and the ash discharged is correspondingly small.

9. CHAPTER 8
Oil
Extraction
Companies today searching for oil use many methods to investigate possible
sites before drilling even begins. Underground rock formations are carefully
surveyed to determine the best place to explore.
1- Variations in the Earth’s natural magnetism
which can provide a clue to the type and thickness of rock that will be found
below the surface. Underground rocks containing iron cause a distortion in the
Earth’s magnetic pull, which can be recorded on very sensitive instruments.
However, the influence of these rocks deep in the Earth’s crust is reduced if
they are covered by thick layers of nonmagnetic, oil-bearing rocks.
Possible oilfields can therefore be detected by measuring the distortions in
magnetic pull caused by the rock pattern, a job usually carried out by aircraft
equipped with devices that can quickly record magnetic variations over large
areas.

10. CHAPTER 8
Oil
Extrac8on
2- Seismic surveying
A more detailed picture can be obtained by sebing off a small explosion at or just
below ground level and recording the time the shock waves take to bounce off the
deep rock layers and return to a series of sensing devices strung out along the
ground at regular intervals. This method is known as seismic surveying.
The speed at which the shock waves travel back varies according to the type and
thickness of the underlying rocks. The echoes that return to the surface are
recorded by the sensing devices and the information is fed into a computer to
produce a picture, known as a seismograph, which indicates possible oil reservoirs.

11. CHAPTER 8
Oil
Extraction
3- Drilling
Drilling techniques have advanced a long way since the early days of oil
prospecting.
The natural pressure that causes oil to gush to the surface will normally keep an
oilfield flowing for months or even years after the first well has been drilled. But
eventually, the pressure will drop to a level where it is no longer sufficient to
produce a flow, and at this stage up to three-quarters of the total volume of oil
may remain in the rocks. When this happens, the flow of oil can be boosted by
reproducing the natural pressure of the water and gas between which it is
sandwiched. Extra wells can be drilled to inject water into the zone below the oil,
or gas into the area above. The gas can be collected at the surface after bubbling
out with the oil and compressed to boost its pressure before being returned to the
natural underground reservoir. Water injection, however, demands a ready
supply of pure water, which may be difficult to obtain at oilfields in the desert or
other arid zones.

12. CHAPTER 8
Oil
Oil exploration at sea
During the last few decades new techniques have been developed to tackle oil
exploration at sea.
1- One of the earliest was the jack-up rig. It gets its name from a set of steel legs
that rest on the seabed and can be extended to jack up the drilling platform above
the reach of the waves. The legs can also be raised through the deck so that the
platform can be towed to another location. Jack-up rigs can also operate in deep
water.
2- Another drilling rig has been specially designed for exploration in deeper
water. This has huge buoyancy tanks that enable it to float out to the drilling site.
There, the tanks are partly filled with water, making the rig sink lower in the sea
and giving it more stability in stormy weather. Anchors are also used to keep it in
place above the well. This type of rig, known as a semisubmersible rig, allows
exploration in water depths of more than a thousand feet.

13. CHAPTER 8
Oil
Processing
Distillation may be defined as the separation of the com- ponents of a liquid feed
mixture by a process involving partial vaporization through the application of
heat. In general, the vapor evolved is recovered in liquid form by condensation.
In continuous distillation, a feed mixture is introduced to a column where vapor
rising up the column is contacted with liquid flowing downward (which is
provided by condensing the vapor at the top of the column). This process
removes or absorbs the less volatile (heavier) components from the vapor, thus
effectively enriching the vapor with the more volatile (lighter) components.

14. CHAPTER 8
Oil

15. CHAPTER 8
Oil
In order to provide fuels, crude oil must be refined. It is the distillation column
that is the workhorse of this process. As portrayed in Figure 8.2, the liquid is
first boiled to turn it into a light vapor, which is passed into a tower where it
rises and cools. Each of the components of crude oil has a different boiling
point, so at each stage of the cooling a different liquid, or fraction, can be
drawn off at different heights in the column. Parts of the mixture that are not
fully vaporized at first will be collected as a liquid at the bottom of the tower
and recirculated.
At the end of this stage, known as fractional distillation, the crude oil mixture
will have been separated into several distinct substances.

16. CHAPTER 8
Oil

17. CHAPTER 8
Oil
Transportation/Transmission
Pipelines are the safest and cheapest way to move large quantities of either
crude oil or refined petroleum across land. Other transport methods include
ships (and barges) and trains. Details follow:
1- Pipelines
- Oil (and natural gas) can be transported in their natural states through
pipelines buried underground or even on the seabed.
- Some of the earliest pipelines used to move fuel were made from wood.
- Main distribution lines for crude oil (and gas) are nowadays almost always
made of steel.
- Most land pipelines are buried at least 3 feet underground
- Underwater pipelines may also be buried in a trench on the seabed.
- All oil and gas pipelines are coated with a layer of bitumen or fiberglass to
prevent corrosion while underwater pipelines have an additional coating of
concrete for extra protection against the effects of seawater.

18. CHAPTER 8
Oil
2- Ships
Much of the world’s oil comes from areas such as the Middle East that are too
distant from the main markets to make transport by pipeline either eco- nomic
or practicable. Oil from these regions is shipped to North America, Europe, and
Japan in specially built tankers. The first oil tanker, the Glückauf, launched in
1866, could carry just 300 tons of oil, but modern vessels can carry 500,000 tons.
These supertankers are more than 1,300 feet long and hide their bulk beneath
the surface like icebergs.
3- rains
Oil is transported by train in small quantities, usually across short distances.
This mode is employed when the receiver is not near pipelines or major
terminals. As noted earlier, jobbers handle the wholesale distribution of most
petroleum products. The retailer—a gasoline station or a home heating oil
company—then receives the product. The last stage is when a car receives
gasoline and/or the home receives fuel oil for heating purposes.

19. CHAPTER 8
Oil
Environmental Issues
As with coal, environmental concerns will continue to exist for the petroleum
industry.
• Drilling for and transporting oil can endanger wildlife and the environment
if it spills into rivers or oceans.
• Leaking underground storage tanks can pollute groundwater and create
noxious fumes.
• Processing oil at the refinery can contribute to air and water pollution.
• Burning gasoline to fuel cars contributes to air pollution.
• Even the careless disposal of waste oil drained from a car can pollute rivers,
lakes, and estuaries.
• Power plants burning all the various grades of oil produce SO2. The
combustion of any carbon- bearing compound also produces CO2, a gas that
may contribute to global warming.

20. CHAPTER 8
Oil
Future Prospects and Concerns
The increasing dependence on petroleum presents a continuing challenge for
the future. This dependence must be balanced by the growing demand for
petroleum products, increased costs, the depletion of this resource, and the
protection of the environment.
Dependence on imported petroleum is a major problem that reduces not only
energy security and the ability to withstand the disruption of oil supplies, but
also economic stability and national security. These factors need, therefore, to
be considered when developing an energy management policy that heavily
relies on oil.
There are steps that need to be taken in the future to help ensure oil energy
resources and reduce high oil prices. Some believe the most important step is to
decrease demand for oil through increased conservation (e.g., reducing the oil
used by increasing the efficiency of vehicles and transportation).