October 27, 1923] 



NA TURE 



627 



The Origin 



UNLIKE most problems concerning origins, which 

 have but a philosophic or academic interest, 

 that of the genesis of petroleum has a distinctly practical 

 significance, for if solved, prospectors for mineral oil 

 would be provided with important data and chemists 

 might learn how to produce artificially valuable sub- 

 stances similar to, if not identical with, natural petro- 

 leum. Man's fertile imagination has spun not only an 

 embarrassing number of speculations and hypotheses 

 concerning the nature of the raw matiriul or materials 

 from which petroleum has been dtTi\ed, but also 

 innumerable explanations of the modus operandi of its 

 formation. Of these, only a tithe remains. Explana- 

 tions that af!irm a cosmic origin or postulate volcanic 

 activity as the effective cause, have long been abandoned, 

 and to-day there are only three which find scientific 

 support. The least popular of these, the inorganic 

 theory, affirms that petroleum originates from the 

 interaction of metallic carbides, presumed to exist 

 immediately below the earth's outer crust, and steam, 

 whereby various hydrocarbons are formed, and these 

 undergo further changes, including polymerisation, to 

 produce the compounds that are found in petroleum. 

 It has recently been suggested that the methane syn- 

 thesis from carbon monoxide or dioxide and hydro- 

 gen, in the presence of a catalyst, such as vanadium 

 or nickel, of which traces are found in petroleum, might 

 also explain the initial formation of hydrocarbons in 

 Nature, and the presence of methane in natural gas ; 

 t)ut tliese suggestions fail to interpret the occurrence 

 of optically-active substances in petroleum, and the 

 presence of nitrogen in some oils, while geologists have 

 met them with uncompromising hostility. 



The views that are uppermost to-day are that 

 petroh'um is derived from either animal or vegetable 

 sul)st;m((>, or from both of these sources, and ihe eliiet 

 direct evidence supporting this organic theory is the 

 occurrence in petroliferous strata of vegetable and 

 animal remains, indiHling. in a few cases, remains of 

 barleria. Important, if less direct, testimony is the 

 presence in petroleum of the optically-active substances 

 cholesterol and phytosterol, which are characteristic 

 ( onstitueiits (il animals and plants, respectiveK . The 

 various elaborations of this view are mainly concerned 

 with the nature of the chemical reactions involved, and 

 how they are influenced by the three determining factors 

 of pressure, temperature, and time ; it i>. liouc \{ r, not 

 casv to formulate any one hypothesis to i xpl.iin the 

 tnriiiat ion of such complex mixtures a^ niim i;il oils, and 

 still iiiori' (lil'ticult to aiiomii i(,r i1m L'lcal ili\ cisii \- in 

 chciiiirat ioiiij)osition (\liiiiiiril li\ minrial nils limn 

 (liffirciit loiahties. 



The (Aidenri' admitted li\ tii<.-.r ulio hclicxr m a 

 pureh animal origin inrhides the statements : that 

 petrolrum hiuiid in prmiar\ rocks is nuicli more often 

 accDhipauicd 1)\ annual th.m i)\" \c:it.dilc rrmaius ; 

 that i(.)rmai i^.n , , ,,111:011111 ■ , ,iih nl ,1,! ., , , n, ,1 ! ,ii ,, 

 minous ; tl 



those found m ,,. ^ .-,■,. ,11- , .n, , ,■ i,,,,. ,• ,, , 1 n,, ,,, ,, , , , , m 

 auuiial lal s. and 1 h,il sucli |)rodncni ,n < an lie ohsi ix ri| 

 in N.itnri- t,, ,l,i \ , untaMv in tlr ■ ' ' ' ' 



of 1 )jel)cl /cii in 1 /j\ pt . I ill 

 in net n ,i' cxiil.ina', | : - , ,1 i .liiUi.. t l;a ! ! i;c 



of Petroleum. 



fauna were either skeletonless, or, if not, their calcareous 

 coatings were dissolved by the carbon dioxide liberated 

 during their decomposition. Advocates of the vege- 

 table origin doubt if the supply of animal matter has 

 been sufficient for the purpose, plants being much more 

 plentiful than animals ; they comment on the absence 

 of phosphatic deposits from the vicinity of oilfields ; 

 and many trace relationships between coals and 

 petroleum. 



Mr. E. H. Cunningham-Craig is one of the foremost 

 supporters of the purely vegetable theory, and in open- 

 ing the discussion on the origin of petroleum, held by 

 the Institution of Petroleum Technologists in London 

 on October 9, he brought forward evidence in its favour 

 derived from recent researches. Geological evidence is 

 accumulating in support of the view that coals and 

 lignites are related to petroleum. Thus, in Trinidad, 

 the three main oil-bearing horizons have each a car- 

 bonaceous phase in some other district, and the petro- 

 liferous and carbonaceous phases approach each other 

 very closely in some localities. Similar evidence is 

 found in Venezuela, Burma, Assam, Hungary, and 

 Rumania. The D'Arcy well, near Dalkeith, was drilled 

 on the assumption that oil-shale deposits represent 

 petroleum that is " dead and buried," and therefore 

 that free petroleum nnglit he f^tfd beneath the oil- 

 shale series ; actualh it was disJK^red below the oil- 

 shale at each of two jjredicted depths. Dr. F. Bergius, 

 of Heidelberg, has hydrogenised coal by heating it in 

 free hydrogen in an autoclave at very high pressures and 

 at temperatures up to 455° C. As the result of an 

 exothermic reaction, a liquid was obtained that was 

 " almost identical with crude petroleum." The deter- 

 mining factors of the formation were the proportion of 

 volatile matter in the coal and the pressure. Nature, 

 it is thought, may act in a similar wa\ . but more slowly 

 and at lower temperatures, on \(m table matter before 

 it has reached the coal stage, /.< . while it still contains 

 much hydrogen in proportion to carbon. 



Supportersof theanimal theory, said Mr. Cunningham- 

 Craig. should endeavour to repeat Dr. Bergius's experi- 

 ments with animal matter in place of vegetable. 

 Cannel coals yield most oil on distillation : tlu\ contain 

 much inorganic matter ;ind are not highly carbonised. 

 Torbanites also give hiuh \ itlds of oil and are to be 

 regarded as cannels contamiiiL; colloidal innrcnnic 

 matter which has been heated m a natural autocla\e. 

 In this process it is assumed that the oil liberated Irom 

 the torbanite combines with tlu' colloidal inorganic 

 matter to form the i^els that can be seen in the micro- 

 scope ; but till' t on\ trsion into petroleum has not been 

 I omplete owing to j)artial carbonisation. I'tnl. A. V.. 

 1'1\ im has separated and in\(stiL;ated tla ;.( Is u, , uning 

 in torbaiute from Nova Siotia. .uid has piiued con- 

 ( lnsi\(l\ that thev are not \cgetal)le lossils ; s,i ihat if 

 oil sh.de is ]ietroleum "dead or buried, " torbaiute is 

 IietloleUUI ■' still born." 



\\ y . ( uuiuui'li.iiii ( raiu' 

 I I It a I ans, 1 lot ii hum ' '■■ 

 I >un -t.ui, and liom t i 

 I 'i'. 1 luustan r.H ' 

 Idl' example. li, 



s pa pel- met with many 



■ '-uusts. Kd i.N l»r. .\. K. 



Is. h (1 |.\ Mr. I )ew hurst. 



til more than one t heoiw ; 



iilmit that the laboratorv 



metiiods ot produt mu hxdroiarbons trom latl\- acids 



No. 



:.../, \oL. I 12J 



