Oil characteristics

Historical research has proven that petroleum, or mineral oil (petrae = stone and oleum = oil, in Latin) has been known since ancient times. With bitumen, asphalt derived from petroleum, the bricks of the tower of Babel were settled and Noah's ark was caulked. The Egyptians used it in embalming at least from 7000 a. In the 3rd century the Chinese dug wells and used it as an illuminator. However, the first modern exploitation took place in 1854 when DRAKE, assisted by a blacksmith, drilled a 21-meter-deep well in Titusville (Pennsylvania, USA).

2. Chemical composition and properties of oil

Chemical analysis reveals that oil is almost exclusively made up of hydrocarbons, compounds made up of two elements: carbon and hydrogen. This simplicity is apparent because, as oil is a mixture, and not a pure substance, the number of hydrocarbons present and their respective proportions vary within very wide limits. It is chemically incorrect to refer to "oil", in the singular; There are many "oils", each with its chemical composition and characteristic properties. Indeed:

They are insoluble liquids in water and of lower density than her. Said density is comprised between 0.75 and 0.95 g / ml.

Its colors vary from brownish yellow to black.

Some varieties are extremely slimy while others are quite fluid.

It is common to classify oils into three main types considering their specific attributes and the by-products they supply:

1) Asphalt oils

Black, viscous and high density: 0.95 g / ml. In primary distillation they produce little naphtha and abundant fuel oil, leaving asphalt as residue. Asphalt oils are extracted from the southern flank of San Jorge (Chubut and Santa Cruz).

2) Paraffinic oils

Light colored, fluid and low density: 0.75-0.85 g / ml. They yield more naphtha than asphalt. When its lubricating oils are refined, paraffin separates. Mendoza and Salta have paraffinic oil deposits.

3) Mixed oils

They have characteristics and yields between the other two main varieties. Although not equal to each other, oils from Comodoro Rivadavia (Chubut) and Plaza Huincul (Neuquén) are of mixed base.

3. Geological origin of oil

During the tertiary era, the remains of fish, invertebrates and, probably, algae accumulated at the bottom of the seas, being buried by sand and sedimented clays. The decompositions caused by microorganisms, accentuated by high pressures and high subsequent temperatures, gave rise to hydrocarbons. At the beginning of the Quaternary era, the orogenic movements convulsed the earth's crust and shaped new mountains, the Andes mountain range between them. The sedimentary strata collapsed and the oil migrated through the porous rocks, such as the sandstones, until it was stopped by anticlines, capital A-shaped folds, and by faults that interrupted the continuity of the strata.

The site should not be imagined as a large underground "lake". Oil occupies the interstices of highly porous sedimentary rocks, usually accompanied by natural gas and salt water.

It is worth noting similarities between coals and oils:

• both fuels had organic origin but were formed in different geological epochs, • and, as non-renewable natural resources, human consumption will inevitably exhaust them.

Location of oil basins

The discovery of oil fields is not a work done at random and obeys a scientifically organized task, which is planned well in advance. High precision instruments and specialized technicians must be transferred to often uninhabited regions, in the desert or in the jungle, forcing to build roads and communication systems, have helicopters, install camps and laboratories, etc. The studies carried out are carried out according to the following order:

• Geographical survey, which includes aerial photography.

• Geological survey to identify sedimentary lands with the possibility of containing oil.

• Application of geophysical methods: with gravitometers the acceleration of terrestrial gravity is measured: g, which decreases slightly where there is oil of lower density than the rocks that surround it. With magnetometers, variations in the magnetic field can be seen. There are also electrical conductivity determinations of the terrain. And, finally, seismic waves caused by the detonation of explosive charges are detected with seismographs. All these procedures are concurrent and allow determining the direction, extension and inclination of the presumably petroleum strata.

• Test drilling: Rock samples taken at different depths are analyzed chemically and geologically. Argentina not only explores its territory, but thanks to a semi-submersible mobile platform, the cost of which was 200 million dollars, it has begun the study of the seabed at the mouth of the Río de la Plata and in the Gulf of San Jorge (Chubut). On average it takes ten years and a huge capital is invested before deciding if the exploitation can be faced with relative success.

4. Oil extraction

Located a deposit, the land is drilled until reaching it. A 40-50 meter high metal tower is erected to support the equipment and the subsoil is drilled with a drill bit that performs a double movement: advance and rotation. Both the trephine and the bar that actuates it have internal conduits for circulating an aqueous suspension of bentonite, yellowish clay of appropriate adhesiveness. That suspension cools the bit and pulls the crumbled material to the surface.

In its mouth the wells are 50 cm in diameter but it is from less to greater depth. Before it was drilled vertically but now it works in any direction using articulated bars. These devices allow the drill bit to be "steered", bypassing obstacles. Thus, in Comodoro Rivadavia, oil is extracted from fields located under the city without the need to erect towers in the urban core.

In Mendoza there are wells from 1,500 to 1,800 meters, but in Salta it has been necessary 4,000 meters of depth. As the drilling progresses, steel pipes, attached to the ground with cement, are inserted to prevent crumbling and infiltration of water. In the proximity of the deposit gases escape. Then precautions are extreme. On some occasions, the great pressure of these gases causes natural, spontaneous and uncontrolled upwelling, with risks of inflammation. Then the oil flows slowly being led to deposits. When the natural pressure decreases the oil is mechanically pumped.

The average yield of Argentine wells is not high, it is between 10 and 20 m3 / day. In exceptional cases up to 500 m3 / day are recorded. Anglo-Saxon countries value the volume extracted in a conventional unit: the barrel. A barrel is equivalent to 36 gallons, each one of 4.5 liters, of where:

1 barrel = 36 x 4.5 liters = 162 liters = 0.162 m3

Crude oil treatment and transportation

The oil extracted from the well is called crude oil. As it is not consumed directly, already in the site itself undergoes some treatments:

• Gas separation: Four gases, which are dissolved under pressure in the crude oil, are easily separated.

Methane: CH4, and ethane: C2H6, make up the dry gas, so called because it does not liquefy by compression. Dry gas is used as fuel in the reservoir or injected into gas pipelines, mixing it with natural gas.

Two other hydrocarbons, propane: C3H8, and butane: C4H10, constitute the wet gas that liquefies by compression. The liquid gas is packaged in 42-45 kg. Steel cylinders, marketed as «Supergas» and also in 10-15 kg bottles. The valve opening, which resets them to atmospheric pressure, converts it into gas.

• Dehydration: Decanted in large tanks, the crude oil removes the emulsified water.

The crude is sent from the fields to the distilleries that, in our country, are in the consumption centers and not in the producing region. Various means are used:

• By land: rail tank cars or trucks with trailers.

• By sea: oil tankers, also called tankers or tankers, with large-capacity holds. Japan has launched gigantic tankers, "super tanks" 400 meters long, carrying up to 500,000 m3.

• Mechanically, the crude oil is transported by pipelines 30-60 cm in diameter with stations along the way to pump it, heating it to decrease its viscosity. The pipelines are used for the alternative transport of the different by-products.

Primary distillation of crude oil

In distilleries, it is fractionally distilled into oil. As it is made up of more than 1,000 hydrocarbons, the separation of each one is not attempted. It is sufficient to obtain fractions, of approximately constant composition and properties, distilling between two predetermined temperatures. The operation requires several stages; The first of these is primary distillation, or topping.

The crude oil is heated to 350ºC and sent to a 50-meter-high metallic fractionation tower, inside which there are numerous "bubbling dishes". A bubbler plate is a perforated sheet metal, mounted horizontally, with a small capped tube in each hole. In this way, the hot gases that rise inside the tower pass through the colder liquid retained by the plates. As soon as said liquid overflows a plate, it falls to the immediate bottom.

The temperature inside the fractionation tower is progressively graduated from 350ºC at its base, to less than 100ºC at its head. As it works continuously, the entry of hot crude is continued while various fractions are extracted from dishes located at convenient heights. These fractions are given generic names and respond to well-defined characteristics, but their relative proportion depends on the quality of the distilled crude, the dimensions of the fractionation tower and other technical details.

Gases emerge from the heads of the towers. This «distillery gas» receives the same treatment as the reservoir gas and the dry gas joins the natural gas while the liquefied gas is dispensed as Supergas or in bottles.

The three most important liquid fractions are, from top to bottom, that is, from lowest to highest distillation temperature:

• Naphtha: These fractions are very light (density = 0.75 g / ml) and have a low distillation temperature: less than 175ºC. They are composed of hydrocarbons with 5 to 12 carbon atoms.

• Kerosenes: Kerosenes distill between 175ºC and 275ºC, being of medium density (density = 0.8 g / ml). Its components are hydrocarbons of 12 18 carbon atoms.

Gas oil: Gas oil is a dense liquid (0.9 g / ml) and oily, which distills between 275ºC and 325ºC. There is a residue that does not distill: fuel oil, which is extracted from the base of the tower. It is a black and viscous liquid with excellent calorific value: 10,000 cal / g. An alternative is to use it as fuel in thermoelectric plants, ships, cement and glass factories, etc. The other is to subject it to a second fractional distillation: conservative distillation, or vacuum distillation, which is carried out under very low pressure, on the order of a few millimeters of mercury. With fractionation towers similar to those described, new fractions are separated which, in this case, turn out to be lubricating oils, light, medium and heavy, according to their density and distillation temperatures. The final residue is asphalt, impossible to fractionate.In Argentina there are almost one million cubic meters of asphalt per year, used for paving and waterproofing of roofs and pipes.

Secondary distillation, or cracking

The Argentine oils, in general, produce little quantity of gasoline. The average percentage regarding distilled crude is 10%. To increase it, a third procedure is used: secondary distillation, destructive distillation or cracking. The "heavy" fractions such as gas oil and fuel oil are heated to 500ºC, at pressures of the order of 500 atm, in the presence of auxiliary substances: catalysts, which help in the process. Hence "catalytic cracking" is mentioned. Under these conditions, the hydrocarbon molecule with many carbon atoms breaks down, forming "lighter" hydrocarbons, that is, with fewer carbon atoms in its molecule. The following equation illustrates the event:

C18H36 = C8H16 + C8H18 + CH4 + C

The breakdown of the molecule of 18 carbon atoms creates new hydrocarbons, two of them with 8 carbon atoms each, the same as those that make up naphtha. Another hydrocarbon formed is methane: CH4. And there is a carbonaceous residue: petroleum coke.

The fractions obtained through cracking are sent to fractionation towers to separate:

• gases, • gasoline and eventually kerosene, • and residues that can be incorporated into new portions of gas oil and fuel oil.

Thanks to cracking, the naphtha yield increases to 40-50%.

5. Naphtha

The fractions obtained in the distillations are refined undergoing physical and chemical treatments that adjust their composition, eliminate harmful components and improve the technical characteristics of each by-product. Thus, for example, the refining of naphtha consists of:

• Redistillations to separate varieties of different density and distillation temperature, related to volatility.

• Treatment with sulfuric acid and subsequent neutralization with alkaline solutions.

• Filtration through absorbent clays.

One of the objectives of refining is to free naphtha from sulfur compounds, which communicate bad odors and produce corrosive gases. Another is to avoid the deposit of semi-solid "gums" caused by the action of air and light on some hydrocarbons, which clog filters and carburettors.

In our country two types of naphtha are manufactured for automotive: common naphtha and special naphtha. The difference lies in anti-knock, a property linked to the operation of explosion engines.

These motors go through a cycle of four successive stages:

• Intake: The carburetor supplies a mixture of naphtha and air vapors with the exact proportions for its total combustion. This mixture penetrates into the engine's cylinders.

• Compression: The piston compresses the fuel mixture.

• Explosion: At the moment of maximum compression, the spark plug, connected to a synchronized electrical system, explodes a spark that starts combustion.

• Expulsion: Combustion gases cause the piston to recoil and exit through the exhaust. The cylinder is ready to restart the cycle.

A gasoline "detonates" when its combustion is premature and begins during the compression period, before the piston completes its journey. The driver perceives a "knock" because, braking the piston movement, the engine vibrates unnecessarily. This defect is exacerbated in high compression engines fed with common naphtha: their power and speed are lowered.

Detonation by compression alone is linked to the molecular structure of the hydrocarbons present in naphtha. Two of them are particularly interesting:

Heptane: C7H16 has 7 carbon atoms aligned, one after the other. It is very explosive and explodes easily by compression.

And the isooctane: C8H18, its 8 carbon atoms form a short chain, with lateral ramifications. It does not explode by compression and is therefore anti-knock.

Anti-knock is measured on a conventional scale: octane degrees. Pure heptane is assigned zero anti-knock: 0 degrees octane. While the highest value on the scale: 100 degrees octane, corresponds to isooctane, a good anti-knock. The percentage of isooctane in a mixture of both hydrocarbons expresses the octane degrees of it.

Common gasoline is 80-82 degrees octane. Special gasoline increases its anti-knock to 90-92 degrees octane. The aircraft, with a slightly different chemical composition than the common ones, reach 120-130 degrees octane. The octane rating is significantly improved with the addition of lead-tetra-ethyl. A tiny amount of this additive: 0.03%, transforms a common naphtha into special naphtha. However, it offers a drawback: metallic lead is deposited inside the cylinder. To obviate this problem, a second additive is incorporated: dibromo-ethylene, in charge of converting lead to lead bromide, a volatile substance that comes out of the cylinder dissolved in the combustion gases. The automotive contribute significantly to environmental pollution:

• evaporate naphtha from deposits and spills during loading and unloading;

• the expelled gases, when the combustion is incomplete, contain carbon monoxide, toxic gas, Petroleum ether, solvent naphtha and "benzine" are varieties of naphtha consumed in industry and in dry cleaners, due to their solvent power. In particular, they dissolve oils and fats, both edible and lubricating, and chub well.

Other petroleum by-products

With the refining of kerosenes it is possible to burn without smoke and without odor, being suitable for kitchens, stoves and lanterns. Their volatility is conveniently reduced to inflame after being heated. The ignition temperature has been regulated and will always be higher than 40ºC. Some varieties are consumed by jet planes and farm tractors.

Gas oil is used in DIESEL, or internal combustion, engines. Fuel oil, meanwhile, is the "heavy" fuel of the industry: thermoelectric plants and factories. Its calorific value is very high: 10,000-11,000 cal / g. 12 million cubic meters of fuel oil and 6 million cubic meters of gas oil are dispatched annually in the country.

Lubricating oils interpose a very thin liquid layer between two moving metal surfaces, reducing wear due to rubbing. Its refining is complicated due to the diversity of prepared qualities that are identified by the SAE number (acronym taken from Society of Automotive Engineers). This number, which ranges from 10 to 10, from 10 to 250, is set based on density, viscosity, freezing and flash temperatures, and other physical and chemical properties. The automobile engine requires 40 SAE oil. For machinery gears 80 SAE will be used, denser and more viscous.

Lubricating greases are semi-solid. They are prepared by filling lubricating oils with soaps, resin, glycerin, graphite, etc.

All lubricating oils are dewaxed during refining. For this, they are cooled to -30ºC, filtering afterwards. Paraffin, semi-solid and low melting point, is separated. It is used in matches, candles, waterproofed cardboard, electrical insulation and other minor uses. Petroleum jelly is similar but soft and smooth to the touch.

6. World and Argentine oil production

Based on known reserves and the rate of extraction, experts predict that natural oil would be depleted by 2030. A first symptom of the energy crisis was manifested in 1973 when the Organization of Petroleum Exporting Countries -OPEP- decided to regulate production and quadruple the price within a year, shaking the world economy. There are many proposals to face the situation:

• Intensify the search for deposits, not ruling out Antarctica or the bed of the seas.

• Reactivate closed wells for poor performance with better techniques.

• Rationalize consumption, returning to coal in fixed installations and replacing gaseous hydrocarbons with hydrogen and carbon monoxide.

• Increase the exploitation of hydroelectric energy and accelerate studies related to solar energy, geothermal energy and energy derived from tides, as they are renewable sources.

• Renew the production of synthetic naphtha, attempted during the Second World War.

Meanwhile, production has stabilized at 3.1 billion cubic meters per year. The ex-Soviet Union, with 20% of said total, and the US, with another 15%, lead the payroll of producers. But this last country needs import to satisfy its needs. The third producer, Saudi Arabia, although it only extracts 10%, is the world's largest exporter, given its small domestic consumption. A similar situation is observed in its neighbors in the Middle East: Iran, Iraq, Kuwait and the United Arab Emirates.

Argentina extracts around 30 million m3 of oil annually. It is not a great production since it does not reach 1% of the world total but it has been sufficient for self-sufficiency. Crude oil has not been imported since 1984 and there is an incipient export of fuel oil and other derivatives. The decisive factor for this achievement has been the supplanting of liquid fuels by natural gas.

Since the end of the last century, there was knowledge of the existence of oil in the Argentine subsoil. Incipient works in Mendoza and Salta failed. In 1907, while looking for drinking water for Comodoro Rivadavia (Chubut), oil accidentally came up. Subsequently, other basins were discovered forcing the creation of a state division: Yacimientos Petroliferos Fiscales (YPF).

Today, with 60,000 technicians, employees and workers, it has become the first national non-agricultural industry. Among the many functions it performs include:

• Systematic exploration of the territory.

• Extraction, transportation and storage, building pipelines and pipelines and managing an oil fleet of 500,000 tons of capacity.

• Obtaining and distributing by-products.

• Scientific research with a large laboratory in Florencio Varela (Buenos Aires).

• Negotiations and control of private companies, national and foreign, that extract and distill oil for themselves or for YPF. Private participation covers 30% of production and has been governed by different laws.

• The social, economic and cultural promotion of the areas under its dependency. An eloquent index is the transformation of Comodoro Rivadavia (Chubut), an insignificant hamlet in 1907, into a progressive city of 100,000 inhabitants today.

• In his opportunity, he started the extraction of coal in Río Turbio (Santa Cruz) and took charge of natural gas.

There are five current oil basins:

1. Patagonian basin: It extends around Comodoro Rivadavia (Chubut) and includes Pico Truncado and Cañadón Seco, in the north of Santa Cruz. It produces 45% of the total.

2. Mendoza Basin: Mainly in Barrancas and La Ventana since the initial district: Tupungato, is almost exhausted. It contributes 25% of the total but with the Malargüe deposits it exceeds this percentage. As a province, Mendoza is the first producer in the country.

3. Neuquén basin: 20% is divided between Plaza Huincul (Neuquén) and another area further north, which reaches Catriel (Río Negro) and Medanito (La Pampa).

4. Salta Basin: Promising thirty years ago, Tartagal, Madrejones and Campo Durán have stagnated and Caimancito (Jujuy) is in danger of extinction.

5. Austral basin: Located on both banks of the Strait of Magellan: El Cóndor and Cerro Redondo, in Santa Cruz, and the bay of San Sebastián, in Tierra del Fuego and probably in the vicinity of the Malvinas islands.

The cubed reserves are estimated at 500 million cubic meters, enough for the next 15 years. But the future is not bleak since:

• the mainland has not yet been fully disclosed, • and the South Atlantic and, eventually, Antarctic underwater platform could contain 20 billion m3.

7. Synthetic gasoline and fuels

Solving the shortage of liquid fuels is not new. Since the 1930s, the possibility of manufacturing naphtha "artificially" through synthesis, combining carbon and hydrogen, was studied. Methods based on coal and lignite dispersed in coal tars were perfected. Under the effect of high temperatures, high pressures and in the presence of catalysts, products are obtained that, fractionally distilled, give naphtha, gas oil and lubricating oils. Germany applied these procedures en masse during the Second World War, but was later abandoned for economic reasons: the cost of synthetic naphtha is several times higher than that of natural naphtha. The progressive increase in the price of the latter has revived the prospects for this industry.

Another experience, previously rehearsed, that has been proposed in Tucumán. To increase the volume of naphtha, up to 10% absolute alcohol is added, free of water. The alcohol content and the degree of humidity are essential in these "fuel mixtures" since, beyond a certain limit, the liquid fuel is segregated into two different layers. Of course, for this fuel to be profitable, abundant and cheap alcohol must be produced, thanks to the fermentation of sugar molasses.

Additional questions:

1) What do you understand by oil refining?

Oil refining is understood as physical and chemical treatments that adjust its composition, eliminate harmful components and improve the characteristics of by-products. In naphtha, for example, refining is used to free it from sulfur compounds, which communicate bad odors and produce corrosive gases; it is also used to prevent them from depositing semi-solid "gums" caused by the action of air and light on some hydrocarbons, which clog filters and carburettors.

2) Make a table showing the name of the different fractions, the boiling range, the number of carbons of the hydrocarbons that make them up and their applications.

3) Explain what is thermal and catalytic cracking.

This is a process by which heavy fractions such as gas oil and fuel oil are heated to 500ºC, at pressures of the order of 500 atm, in the presence of auxiliary substances called catalysts. This is used to break the hydrocarbons of the gas oil and fuel oil and to form lighter hydrocarbons to obtain naphtha, gases and kerosenes.

4) What does it mean that the octane number is 85?

This means that the anti-knock of the naphtha is 85. This is due to the fact that there is 85% isooctane and 15% heptane in the naphtha mixture.

5) What compound is added to increase the octane number in a gasoline?

To increase the octane number of a naphtha, you can add lead-tetra-ethyl, although with drawbacks: metallic lead is deposited inside the cylinder. To solve this problem, dibromo-ethylene is incorporated, which converts lead to lead bromide, a substance that comes out along with the combustion gases. This substance is toxic.

6) What is the petrochemical industry?

The petrochemical industry is the one based on the chemical transformation of petroleum products, given the great diversity and importance of the raw materials obtained from them for other industries.

7) What does the "Fisher Tops" process consist of?

The process, known as TOPS (based on Thermal Oxidation and Gasification of Waste) is a leading method in reducing medical, industrial and municipal waste from its original form of deposit to achieve a small volume (approximately 5%) of metals. recyclable and aluminum, glass and fine and inert ashes. This represents a volume reduction of the order of 95%, and in most applications, where glass, metal and ash recycling occurs, you will not need to send anything to the landfill. The TOPS system does not require prior separation of incoming waste. Municipal waste, car and truck tires, oils, medical waste, industrial papers and plastics etc. can be directly deposited in the system.

The emissions to the atmosphere produced by the process have been repeatedly verified in a wide spectrum of parameters since 1988. The results have been extraordinary: Particles in suspension, Carbon Monoxide, Nitrous Oxides Sulfur and other chemical emissions, have been much lower than the new and restrictive requirements of the European Union regarding air quality. There are practically no heavy metal emissions.

The TOPS system reduces any type of waste including:

• Medical waste / Pathogenic waste

• Municipal solid waste.

• Tires • Remains of packaging.

• Polypropylene contaminated by oils and natural absorbents.

• Diesel filters for boats, vehicles and locomotives.

• Industrial waste.

• Paper and Pulp.

• Rubber Polymers.

• Paint residues.

• Railroad ties

• PVC pipes.

At the end of the process only a fine and inert ash remains, metals, glass, dust and gravel. These materials will be separated and recycled after the process.

It is important to note that this is not an "experimental technology". The TOPS system has been under scientific investigation and has been developed by its discoverers for over ten years, and tested through evaluation by scientific laboratories as well as commercially and industrially experienced since 1992.