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PETROLEUM (Lat. Petra, rock, and oleu...
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See also:PETROLEUM (See also:Lat. See also:Petra, See also:rock, and oleuin, oil)
, a See also:term which, in its widest sense, embraces the whole of the See also:hydrocarbons, gaseous, liquid and solid, occurring in nature (see See also:BITUMEN)
.
Here the application of the term is limited to the liquid which is so important an See also:article of See also:commerce, though references will also be made to natural See also:gas which accompanies See also:petroleum
.
Descriptions of the solid forms will be found in the articles on See also:asphalt or asphaltum, See also:albertite, See also:elaterite, See also:gilsonite, See also:hatchettite and See also:ozokerite
.
Particulars of the shales which yield oil on destructive See also:distillation are given in the article on See also:paraffin
.
See also:Ancient See also:History.—Petroleum was collected for use in the most remote ages of which we have any records
.
See also:Herodotus de-See also:scribes the oil pits near Ardericca (near See also:Babylon), and the See also:pitch See also:spring of Zacynthus (See also:Zante), whilst See also:Strabo, Dioscorides and See also:Pliny mention the use of the oil of See also:Agrigentum, in See also:Sicily, for See also:illumination, and See also:Plutarch refers to the petroleum found near See also:Ecbatana (See also:Kerkuk)
.
The ancient records of See also:China and See also:Japan are said to contain many allusions to the use of natural gas for See also:lighting and See also:heating
.
Petroleum (" burning See also:water ") was known in Japan in the 7th See also:century, whilst in See also:Europe the gas springs of the See also:north of See also:Italy led to the See also:adoption in 1226 by the See also:municipality of See also:Salsomaggiore of a See also:salamander surrounded by flames as its See also:emblem
.
Marco See also:Polo refers to the oil springs of See also:Baku towards the end of the 13th century; the medicinal proper-ties of the oil of See also:Tegernsee in See also:Bavaria gave it the name of " St See also:Quirinus's Oil " in 1436; the oil of Pechelbronn, Elsass, was discovered in 1498, and the " earthbalsam " of See also:Galicia was known in 15o6
.
The earliest mention of See also:American petroleum occurs in See also:Sir See also:Walter See also:Raleigh's See also:account of the See also:Trinidad pitch-See also:lake in 1595; whilst See also:thirty-seven years later, the account of a visit of a Franciscan, See also:Joseph de la See also:Roche d'Allion, to the oil springs of New See also:York was published in Sagard's Histoire du See also:Canada
.
In the 17th century, See also:
A See also:Russian traveller, See also:Peter Kalm, in his See also:work on See also:America, published in 1748, showed on a See also:map the oil springs of See also:Pennsylvania, and about the same See also:time Raicevich referred to the " liquid bitumen " of See also:Rumania
.
See also:Modern Development and See also:Industrial Progress.—The first commercial exploitation of importance appears to have been the distillation of the oil at See also:Alfreton in See also:Derbyshire by See also:
See also:Sumatra, See also:Java and See also:Borneo, where active development began in 1883, 1886 and 1896, bid See also:fair to See also:rank before See also:long among the See also:chief See also:sources of the oil supplies of the world
.
Similarly, Burma, where the Burmah Oil Company have, since 189o, rapidly extended their operations, is rising to a position of importance
.
Oil fields are being continually opened up in other parts of the
world, and whilst America still maintains her position as the deposited on See also:compression. largest petroleum producer, the world's supplies are now being derived from a steadily increasing number of centres
.
See also:Physical and Chemical Properties.—Although our See also:information respecting the chemical See also:composition of petroleum has been almost entirely gained since the See also:middle of the 18th century, a considerable amount of empirical knowledge of the substance was possessed by chemists at an earlier date, and there was much See also:speculation as to its origin
.
In his Sylva sylvarum (1627), See also:Francis See also:
This See also:report has become a classic in the literature of petroleum
.
The physical properties of petroleum vary greatly
.
The See also:colour ranges from See also:pale yellow through red and See also: It is found that transparent oils under the influence of light absorb oxygen, becoming deeper in colour and opalescent, while strong acidity and a penetrating odour are See also:developed, these changes being due to the formation of various See also:acid and phenylated compounds, which are also occasionally found in fresh oils . The residues from petroleum distillation have been shown to contain very dense solids and liquids of high specific gravity, having a large proportion of carbon and possessed of remarkable fluorescent properties . Natural gas is found to consist mainly of the See also:lower paraffins, with varying quantities of carbon dioxide, carbon monoxide, hydrogen, nitrogen and oxygen, in some cases also sulphuretted hydrogen and possibly See also:ammonia . This mixture dissolves in petroleum, escaping when the oil is stored, and conversely it invariably carries a certain amount of water and oil, which is Occurrence.—Bitumen is, in its various forms, one of the most widely-distributed of substances, occurring in strata of every See also:geological See also:age, from the lowest Archean rocks to those now in process of deposition, and in greater or less quantity throughout both hemispheres, from Spitzbergen to New See also:Zealand, and from California to Japan . The occurrence of commercially valuable petroleum is, however, comparatively limited, hitherto exploited deposits being confined to rocks younger than the See also:Cambrian and older than the See also:Quaternary, while the majority of developed oil-fields have been discovered north of the See also:equator . The See also:main requisites for a productive oil or gas field are a porous See also:reservoir and an impervious See also:cover . Thus, while the See also:mineral may be formed in a stratum other than that in which it is found, though in many cases it is indigenous to it, for the formation of a natural reservoir of the fluid (whether liquid or gas) it is necessary that there should be a suitable porous rock to contain it . Such a rock is typically exemplified by a coarse-grained See also:sandstone or See also:con-glomerate, while a See also:limestone may be naturally porous, or, like the Trenton limestone of See also:Ohio and See also:Indiana, rendered so by its See also:conversion into See also:dolomite and the consequent production of cavities due to shrinkage—a change occurring only in the purer limestones . Similarly it is necessary, in view of the hydrostatical relations of water and mineral oils, and the volatile character of the latter, that the porous stratum should be protected from water and See also:air by an overlying shale or other impervious See also:deposit . Water, often saline or sulphurous, is also found in these porous rocks and re-places the oil as the latter is withdrawn . In addition to these two necessary factors, structural conditions See also:play an important part in determining the See also:accumulation of oil and gas . The main supplies have been obtained from strata unbroken and comparatively undisturbed, but the occurrence of anticlinal or See also:terrace structure, however slightly marked or limited in extent, exerts a powerful influence on the creation of reservoirs of petroleum . These tectonic See also:arches often extend for long distances with great regularity, but are frequently crossed by subsidiary anticlines, which themselves play a not unimportant part in the See also:aggregation of the oil . Owing to difference of density the oil and water in the anticlines See also:separate into two layers, the upper consisting of oil which fills the anticlines, while the water remains in the synclines . Any gas which may be See also:present rises to the summits of the anticlines . When the slow folding of the strata is accompanied by a See also:gradual See also:local descent, a modified or " arrested " anticlinal structure, known as a " terrace " is produced, the up-heaving See also:action at that part being sufficient only to See also:arrest the descent which would otherwise occur . The terraces may thus be regarded as See also:flat and extended anticlines . They need not be See also:horizontal, and sometimes have a See also:dip of a few feet per mile, as in the See also:case of the Ohio and Indiana oil fields, where the amount varies from one to ten feet . These slight See also:differences in level, however, are found to have a most powerful effect in the direction already mentioned . It is evident that accurate knowledge of the character and structure of the rock-formations in petroliferous territories is of the greatest importance in enabling the See also:expert to select favourable sites for drilling operations; hence on well-conducted petroleum-properties it is now customary to See also:note the character and thickness of the strata perforated by the See also:drill, so that a See also:complete See also:section may be prepared from the recorded data . In some cases the depths are stated with reference to See also:sea-level, instead of being taken from the See also:surface, thus greatly facilitating the utilization of the records . Oil and gas are often met with in drilled See also:wells under great pressure, which is highest as a See also:rule in the deepest wells . The closed pressure in the Trenton limestone in Ohio and Indiana is about 200–300lb. per sq. in., although a much higher pressure has been registered in many wells . The gas wells of Pennsylvania indicate about See also:double the pressure of those drilled in the Trenton limestone, 600–800 lb. not being unusual, and even moo lb having been recorded . The extremely high pressure under which oil is met with in wells drilled in some parts of the Russian oil fields is a See also:matter of See also:common knowledge, and a See also:fountain or spouting well resulting therefrom is one of the " See also:sights" of the See also:country . A famous fountain in the See also:Groznyi oil field in the See also:northern See also:Caucasus, which began to flow in August 1895, was estimated to have thrown up during the first three days 1,200,000 poods (over 4,500,000 gallons, or about 18,500 tons) of oil a day . It flowed continuously, though in gradually diminishing quantity, for fifteen months; afterwards the flow became intermittent . In See also:April 1897 there was still an occasional outburst of oil and gas . Three theories have been propounded to account for this pressure:- 1 . That it results from the weight of the overlying strata . 2 . That it is due to water-pressure, as in artesian wells (" hydro-static " or " artesian " theory) . 3 . That it is caused by the compressed See also:condition of the gradually accumulating gas . Of these the first has been proved untenable, and while in some instances (e.g. certain wells in Ohio), the second has held See also:good, the third appears to be the most widely applicable . The conditions of formation and accumulation of petroleum point to the fact that the principal oil fields of the world are merely reservoirs, which will become exhausted in the course of years, as in the case of the decreasing yield of certain of the American fields .
But new deposits are continually being exploited, and there may be others as yet unknown, which would entirely alter any view that might be expressed at the present time in regard to the probable duration of the world's See also:supply of oil and gas
.
As already stated, every one of the great geological systems appears to have produced some See also:form of bitumen, and in the following table an See also:attempt has been made to classify on this basis the various localities in which petroleum or natural gas has been found in large or small quantities:
See also:Recent.—See also:Lancashire (Down See also: |