Technology & Process
Hydrocarbon exploration
It is the search by petroleum
geologists for hydrocarbon deposits beneath the Earth's surface, such
as oil and gas. Oil and gas exploration are grouped under the science
of petroleum geology.Visible surface features such as oil seeps, natural gas seeps,
pockmarks (underwater craters caused by escaping gas) provide basic
evidence of hydrocarbon generation (be it shallow or deep in the
Earth). However, most exploration depends on highly sophisticated
technology to detect and determine the extent of these deposits using
exploration geophysics. Areas thought to contain hydrocarbons are
initially subjected to a gravity survey, magnetic survey or regional
seismic reflection surveys to detect large scale features of the
sub-surface geology. Features of interest (known as leads)
are
subjected to more detailed seismic surveys which work on the
principle of the time it takes for reflected sound waves to travel
through matter (rock) of varying densities and using the process of
depth conversion
to create a profile of the substructure. Finally, when a prospect has
been identified and evaluated and passes the oil company's selection
criteria, an exploration well is drilled in an attempt to conclusively
determine the presence or absence of oil or gas.Oil exploration is an
expensive, high-risk operation. Offshore and
remote area exploration is generally only undertaken by very large
corporations
or national governments. Typical Shallow shelf oil wells (e.g. North
sea) cost USD$10 - 30 Million, while deep water wells can cost up to
USD$100 million plus. Hundreds of smaller companies search for onshore
hydrocarbon deposits worldwide, with some wells costing as little as
USD$100,000.
Extraction
The most
common method of obtaining petroleum is extracting it from oil wells
found in oil fields. After the well has been located, various methods
are used to recover the petroleum. Primary recovery methods are used to
extract oil that is brought to the surface by underground pressure, and
can generally recover about 20% of the oil present. After the oil
pressure has depleted to the point that the oil is no longer brought to
the surface, secondary recovery methods draw another 5 to 10% of the
oil in the well to the surface. Finally, when secondary oil recovery
methods are no longer viable, tertiary recovery methods reduce the
viscosity of the oil in order to bring more to the surface.
Drilling
Because of the subterranean origin of petroleum it must be extracted by means of wells.
Until an exploratory well, or wildcat, has been dug, there is no sure
way of knowing whether or not petroleum lies under a particular site.
In order to reduce the number of exploratory wells drilled, scientific
methods are used to pick the most promising sites. Sensitive
instruments, such as the gravimeter, the magnetometer, and the
seismograph, may be used to find subsurface rock formations that can
hold crude oil. Drilling is a fairly complex and often risky process.
Some wells must be dug several miles deep before petroleum deposits are
reached. Many are now drilled offshore from platforms standing in the
ocean bed. Usually the petroleum from a new well will come to the
surface under its own pressure. Later the crude oil must be pumped out
or forced to the surface by injecting water, air, natural gas, steam,
carbon dioxide, or another substance into the deposits. Enhanced
recovery techniques have increased the percentage of oil that can be
extracted from a field.
Transportation
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.
Refining
The
physical properties and exact chemical composition
of crude oil varies from one locality to another. The different
hydrocarbon components of petroleum are dissolved natural gas,
gasoline, benzine, naphtha, kerosene, diesel fuel and light heating
oils, heavy heating oils, and finally tars of various weights (see tar
and pitch). The crude oil is usually sent from a well to a refinery in
pipelines (see under pipe) or tanker ships.The
hydrocarbon components are separated from each other by various
refining processes. In a process called fractional distillation
petroleum is heated and sent into a tower. The vapors of the different
components condense on collectors at different heights in the tower.
The separated fractions are then drawn from the collectors and further
processed into various petroleum products. One of the many products of
crude oil is a light substance with little color that is rich in
gasoline. Another is a black tarry substance that is rich in asphalt.As
the lighter fractions, especially gasoline, are in the greatest demand,
so-called cracking processes have been developed in which heat,
pressure, and certain catalysts are used to break up the large
molecules of heavy hydrocarbons into small molecules of light
hydrocarbons. Some of the heavier fractions find eventual use as
lubricating oils, paraffins, and highly refined medicinal substances such as petroleum.
The Pillars of Refining
While
distillation can separate oil into fractions, chemical reactors are
required to create more of the products that are in high demand.
Refineries rely on four major processing steps to alter the ratios of
the different fractions. They are; Catalytic Reforming, Alkylation,
Catalytic Cracking, and Hydroprocessing. Each of these methods involves
feeding reactants to a reactor where they will be partly converted into
products. The unreacted reactants are then separated from the products
with a distillation column. The unreacted reactants are recycled for
another pass, while the products are further separated and mixed with
existing streams. In this way complete conversion of reactants can be
obtained, even though not all of the reactants are converted on a given
pass through the reactor.
1.Catalytic Reforming
Catalytic
Reforming produces high octane gasoline for today’s automobiles.
Gasoline and naphtha feedstocks are heated to 500 degrees Celsius and
flow through a series of fixed-bed catalytic reactors. Because the
reactions which produce higher octane compounds (aliphatic in this
case) are endothermic (absorb heat) additional heaters are installed
between reactors to keep the reactants at the proper temperature. The
catalyst is a platinum (Pt) metal on an alumina (Al2O3) base. While
catalysts are never consumed in chemical reactions, they can be fouled,
making them less effective over time. The series of reactors used in
Catalytic Reforming are therefore designed to be disconnected, and
swiveled out of place, so the catalyst can be regenerated.
2.Alkylation
Alkylation
is another process for producing high octane gasoline. The reaction
requires an acid catalyst (sulfuric acid, H2SO4 or hydrofluoric acid,
HF) at low temperatures (1-40 degrees Celsius) and low pressures (1-10
atmospheres). The acid composition is usually kept at about 50% making
the mixture very corrosive.
3.Catalytic Cracking
Catalytic
Cracking takes long molecules and breaks them into much smaller
molecules. The cracking reaction is very endothermic, and requires a
large amount of heat. Another problem is that reaction quickly fouls
the Silica (SiO2) and alumina (Al2O3) catalyst by forming coke on its
surface. However, by using a fluidized bed to slowly carry the catalyst
upwards, and then sending it to a regenerator where the coke can be
burned off, the catalyst is continuously regenerated. This system has
the additional benefit of using the large amounts of heat liberated in
the exothermic regeneration reaction to heat the cracking reactor. The
FCC system is a brilliant reaction scheme, which turns two negatives
(heating and fouling) into a positive, thereby making the process
extremely economical.
4.Hydroprocessing
Hydroprocessing
includes both hydrocracking and hydrotreating techniques. Hydrotreating
involves the addition of hydrogen atoms to molecules without actually
breaking the molecule into smaller pieces. Hydrotreating involves
temperatures of about 325 degrees Celsius and pressures of about 50
atmospheres. Many catalysts will work, including; nickel, palladium,
platinum, cobalt, and iron. Hydrocracking breaks longer molecules into
smaller ones. Hydrocracking involves temperatures over 350 degrees
Celsius and pressures up to 200 atmospheres. In both cases, very long
residence times (about an hour) are required because of the slow nature
of the reactions.
Alternative methods
During
the last oil price peak, other alternatives to producing oil gained
importance. The best known such methods involve extracting oil from
sources such as oil shale or tar sands. These resources are known to
exist in large quantities; however, extracting the oil at low cost
without negatively impacting the environment remains a challenge. It is
also possible to transform natural gas or coal into oil (or, more
precisely, the various hydrocarbons found in oil). The best-known such
method is the Fischer-Tropsch process. It was a concept pioneered in
Nazi Germany when imports of petroleum were restricted due to war and
Germany found a method to extract oil from coal. It was known as Ersatz
("substitute" in German), and accounted for nearly half the total oil
used in WWII by Germany. However, the process was used only as a last
resort as naturally occurring oil was much cheaper. As crude oil prices
increase, the cost of coal to oil conversion becomes comparatively
cheaper. The method involves converting high ash coal into synthetic
oil in a multi-stage process. Ideally, a ton of coal produces nearly
200 liters (1.25 bbl, 52 US gallons) of crude, with by-products ranging
from tar to rare chemicals. Currently, two companies have
commercialised their Fischer-Tropsch technology. Shell in Bintulu,
Malaysia, uses natural gas as a feedstock, and produces primarily
low-sulfur diesel fuels.[8] Sasol[9] in South Africa uses coal as a
feedstock, and produces a variety of synthetic petroleum products.
The
process is today used in South Africa to produce most of the country's
diesel fuel from coal by the company Sasol. The process was used in
South Africa to meet its energy needs during its isolation under
Apartheid. This process has received renewed attention in the quest to
produce low sulfur diesel fuel in order to minimize the environmental
impact from the use of diesel engines. An alternative method of
converting coal into petroleum is the Karrick process, which was
pioneered in the 1930s in the United States. It uses high temperatures
in the absence of ambient air, to distill the short-chain hydrocarbons
of petroleum out of coal. More recently explored is thermal
depolymerization (TDP), a process for the reduction of complex organic
materials into light crude oil. Using pressure and heat, long chain
polymers of hydrogen, oxygen, and carbon decompose into short-chain
petroleum hydrocarbons. This mimics the natural geological processes
thought to be involved in the production of fossil fuels. In theory,
TDP can convert any organic waste into petroleum.
Technology
Oil Shale Technology
The
fine-grained sedimentary rock known as oil shale contains significant
amounts of kerogen (a solid mixture of organic chemical compounds),
from which technology can extract liquid hydrocarbons.The
extraction of the useful components of oil shale usually takes place
above ground (ex-situ processing), although several newer technologies
perform this underground (on-site or in-situ processing). In either
case, the chemical process of pyrolysis converts the kerogen in the
shale to synthetic crude oil and shale gas. Most conversion
technologies involve heating shale in the absence of oxygen to a
temperature at which kerogen decomposes (pyrolyses) into gas,
condensable oil, and a solid residue. This usually takes place between
450 °C (842 °F) and 500 °C (932 °F).The process of decomposition begins
at relatively low temperatures (300 °C/570 °F), but proceeds more
rapidly and more completely at higher temperatures.Hundreds of patents
for oil shale retorting technologies exist;however, only a few dozen
have undergone testing. As of 2006, only four technologies remained in
commercial use: Kiviter, Galoter, Fushun, and Petrosix.
Thermal depolymerization (TDP) is a process using hydrous pyrolysis for the reduction of complex organic materials (usually waste products of various sorts, often known as biomass and plastic) into light crude oil. It mimics the natural geological processes thought to be involved in the production of fossil fuels. Under pressure and heat, long chain polymers of hydrogen, oxygen, and carbon decompose into short-chain petroleum hydrocarbons with a maximum length of around 18 carbons.Thermal depolymerisation is similar to other processes which use superheated water as a major step in their processing to produce fuels, such as direct Hydrothermal Liquefaction and hydrous pyrolysis.
Thermochemical conversion (TCC) can mean conversion of biomass to oils using superheated water, although it more usually is applied to fuel production via pyrolysis. The Thermal Conversion Process is another name for thermal depolymerisation. A company called Renewable Environmental Solutions (RES) was formed as a joint venture between ConAgra Foods and Changing World Technologies to operate the plant at Carthage, Missouri and the name of the process was changed.