PETROLEUM

Petroleum is mineral oil, organic in origin, and occurs in the pore spaces of sedimentary rocks. It is derived from the decomposition of marine or vegetative matter. It normally occurs in dome-shaped anticilines, between layers of non-porous rocks.

The oil is usually trapped in the crest of the anticiline with gas above and water below. Oil traps may also result from faults when porous and non-porous strata are brought into juxtaposition. In volcanic districts, when a resistant impermeable dyke is intruded into alternating layers of rocks, it may act as a cap rock imprisoning a pool of gas, oil and water.

Besides its liquid form, oil may also be extracted in its gaseous state as natural gas. This consists mainly of methane and ethane and is increasingly used for heating, lighting and the chemical industry. In America, Europe, Russia and New Zealand natural gas is pumped through pipes for use in households and industrial plants.

Another interesting product mined in connection with petroleum is asphalt or bitumen or pitch. It is, in fact, a highly viscous oil. The most important asphalt deposit is the Pitch Lake of Trinidad which has been dug for over a century, though only a fraction of its 87m (285 feet) depth has so far been removed. It is an excellent material for road surfacing. Large quantities of this natural asphalt are dug up, melted into barrels and exported.

Oil prospecting and drilling: The modern oil industry began in 1859 when the first oil-well was sunk by Laurentine Drake in Titusville, N.W. Pennysylvania. Today the number of oil-wells must be well over 700 000 and the annual oil output more than 2000 million tonnes.

In the early days of prospecting, fortune-seekers merely drilled randomly (called ‘wildcatting’), hoping to strike oil. They had practically no knowledge of the mode of oil occurrence, and if they did find oil, it was pure luck! But modern oil prospecting is a very technical job. A detailed survey of the geological structure of the area is carried out first and precise instruments that can register the density, permeability and complexity of the rocks beneath are used. It is then possible to draw a fairly accurate sketch of the subterranean structural pattern before drilling is recommended. Modern oil-wells are sunk to a depth of between a few hundred and 6 700 m (22 000 feet). To drill a well of average depth can cost as much as $125 000! So unless there is a fair chance of striking oil, it is a terrific waste of money to attempt ‘wild-catting’. Once a drilling site is decided, a steel derrick about 30 m (100 feet) high will be erected and equipment for drilling brought in. Steel tubes are inserted in the borehole and, once the drill reaches the oil-bearing strata, oil gushes out through the bore-hole and keeps ‘flowing’ for weeks or even years. When it ceases to flow naturally, it is pumped to the surface.

The main mineral oil producing country in West Africa is Nigeria, where there has been an intensive search for oil for many years. Prospecting has been concentrated in the Niger delta under very difficult physical conditions. Since 1956, when oil was first found in commercial quantity at Oloibiri and Afam, production has greatly increased and more areas have since been explored, including off-shore areas. Crude oil has become Nigeria’s leading export and by 1972, it accounted for about 82 percent of the total export value. Four refineries have been built at Alesa Eleme near Port Harcourt, Warri and Kaduna, to supply oil products for the country’s needs, and as export to the neighbouring states.

 

Oil transportation

The cheapest and the most efficient method of transporting crudeoil overland for great distances is by pipelines, which may be 610mm (24 inches) or 944mm (36 inches) in diameter. This involves the construction of pumping stations at intervals and the installation of pipes, hundred or thousands of kilometres long. The initial cost may be high, but in the long run, it is very economical. It saves time, money and labour and the operation is very simple. In this manner crude oil can be carried by pipelines direct to the refineries or to exporting distant countries. For internal use, oil trucks and rail-wagons are also used, mainly for the conveyance of refined petroleum products. For military and emergency requirements, barrels of oil are sometimes transported by aircraft. For sea transport, oil tankers which are often extremely large are used.

 

Oil Refining

A) Location of refineries: Oil refineries may be located.

1. In or near the oilfields: This is a temporary measure and applies only to small refineries. As oilfields are often located in remote or desert regions, there is little industrial demand for the refined products and they are not likely to be good locations for refineries.
2. At the port of export: Examples are the refineries in the Persian Gulf area, and the refineries at Port Harcourt, Nigeria, which serve local needs and protect the interests of the oil-producing countries. They provide employment for local people, but industrial demand is not very high.
3. At the port of import: Refineries, as in Southampton Yokohama, Singapore and Port Dickson, are normally owned by large international firms that have worldwide oil interests. It is cheaper to import crude oil and refine it locally for domestic and industrial use than to import refined products.

 

B) The distillation of oil: Mineral oils are made up of different hydrocarbons. Crude petroleum has little use unless it is refined, by a process known as distillation.

In distillation, the mechanism is simply to split the oil into its various ‘group’ of hydrocarbons or ‘fractions’ at a very high temperature. As each fraction boils at a different temperature, the various groups of hydrocarbons can be extracted at their own boiling points. The lighter fractions, such as petrol, paraffin or kerosene and benzene, will be evaporated and condensed first at temperatures probably below 38° C (100° F). The heavier fractions, such as diesel, lubricating and fuel oils, will condense later at temperatures between 38° C and 427° C (100° F.and 800° F). At the end of the line is the residue, comprising the heaviest fuel oils as well as vaseline, wax and asphalt. The process of distilling oils by fractions is referred to as fractional distillation.

Fractional distillation is one of the oldest and most universal forms of oil refining, but of the total oil distilled, the motor fuel fraction is only 15 percent. With the rapid rise of the automobile industry, which demands enormous quantities of the lighter oils such as petrol or gasoline, it has been found necessary to adopt the thermal cracking process in which the heavier fractions are heated to much higher temperatures until they break down or ‘crack’ into the lighter fractions such as petrol. In recent years, oil chemists have found that by adding a catalyst, such as powdered platinum, to speed up the cracking process, more and better motor fuels can be extracted. This is the catalyst cracking process.

 

The uses of oil

The many uses of oil may best be grouped under four categories

1. As an indispensable motor fuel: This is the greatest use of oil, ‘the servant of the automobile age’. As petrol and diesel oil, petroleum drives all the motor vehicles and aircraft of the world as well as a large proportion of trains and ships. The modern communication complex would simply break down if petroleum were exhausted. At the rate that the hundreds of millions of automobiles consume petroleum daily, scientists willhaveto find a substitute for oil in the future.
2. As a lubricant: Petroleum in the form of grease and lubricant is absolutely essential in lubricating machine parts to reduce friction to the minimum. Our ‘machine age’ with its high speed machines would grind to a standstill if lubricants were not available.
3. As a vital source of power: Vast amounts of mineral oil are being burnt daily in heaters, boilers and furnaces to provide power in factories and to generate thermal electricity. Its great calorific capacity and its convenience for handling and transporting has made petroleum the most extensively used fuel.
4. The many uses of its by-products: Kerosene has long been a domestic fuel for cooking, lighting and heating. Bitumen or asphalt is used for roofing, road-surfacing and water-proofing purposes. Paraffin and wax are used as illuminants and lubricants and for the manufacture of candles, seals and polishes. Its various byproducts form the basic raw materials of a host of industrial items such as plastics, synthetic rubber, detergents, insecticides, and pharmaceutical and organic chemical products such as drugs, varnishes, solvents and diluents.

 

World oil production and distribution

Although over two-thirds of the world’s oil reserves are estimated to be in the Middle East, the present major oil-producing countries are the Russia and the USA. The Russia with 23 percent of world production is the greatest oil nation. The oldest oil wells are located in the Caucasus region of which the Baku fields are the most productive. Fresh sources are being exploited around the Urals, the Caspian Sea, the Russian Turkestan and Siberia. The oil reserves of Siberia are said to be enormous and the exploitation of this oil is responsible for the Russia’s rise to prominence in world crude oil production.

The United States accounts for about 16 per cent of world crude oil production. It used to account for 25 percent. The relative fall of the United States in crude oil production is due to the rise of other oil producers such as the Russia, Mexico, Norway and the United Kingdom.

The United States oil comes mainly from the mid-continental states of Kansas, Oklahoma and Texas as well as the Gulf Coast region of southern Arkansas, Louisiana and California,the Rocky Mountains and the old, now almost exhausted, fields in the Appalachians.

Apart from the Russia and USA, none of the other oil producing countries accounts for up to 10 percent of world output. In the Middle-East, there have been marked changes in the relative importance or the different countries in crude oil output. Kuwait which used to be the leading producer, accounting for 7 percent of world output in the late 1960’s, now produces only 2 percent of the world output.The oil, first discovered there in 1946, comes mainly from the Burgen fields near Kuwait town. The leading oil producer in the Middle East now is Saudi Arabia which accounts for 8.5 percent of world output. The oil comes mainly from the Dahran oil fields, opposite the oil-rich island of Bahrain. The other major crude oil producing countries are Iran (4 percent), Iraq (2.2 percent), and the United Arab Emirates (2.1 per cent).

In Iran, oil production began in 1913, well before oil was found in any other part of the Middle East. The chief oilfields are at Masjid-i-Salaiman, at the foot of the Zagros Mountains. The refinery at Abadan is one of the largest in the world. Another oil-rich state is Iraq. The pipelines from the oilfields at Kirkuk and Mosul run across the deserts to the tanker terminals at Tripoli in Lebanon and Banias in Syria. Another oil producing area of Iraq is the swampland of the Shatt-al-Arab. The North Africa countries of Libya (1.9 percent) Egypt (1.5 percent) and Algeria (1.1 percent) are also important oil producers.

Venezuela used to account for as much as 11 percent of world crude oil output but its share has now fallen to 3.5 percent. Oil is found around Lake Maracaibo and in the Orinoco Basic. Some of the crude oil is refined at the nearby Dutch islands of Aruba and Curacao, some of it is refined locally while the bulk of the output is exported.

Mexico (5.3 percent), China (4.2 percent), UK(4.5 percent) and Norway (1.3 percent) are the new up-and-coming crude oil producers outside the Middle East. Indeed, the rise of these countries has greatly reduced the dependence of the world oil market on the Middle East producers. British and Norwegian oil comes mainly from the North Sea where oil was discovered in the early 1970’s. The major oil producers in tropical Africa are Nigeria (2.5 percent) and Gabon. The oil comes mainly from deltaic swamps and offshore locations.

In the other parts of the world, the other notable oil producers are Canada and Indonesia.

Canada’s oil comes from the Prairie provinces of Alberta and Saskatchewan while the Indonesian oilfields are in Sumatra and Borneo.