The problem of the origin of petroleum has been the subject of considerable scientific controversy for many years. Not a few of the leading scientists hold to the theory that petroleum is derived from metallic carbides lying far beneath the porous strata in which the oil is stored by Nature, and that even at the present time the process is in operation. This idea, which may be termed the inorganic theory of petroleum origin, was considered to have received substantial support when it was found that the action of water on the carbides of certain metals resulted in the liberation of hydrocarbons.
The view that petroleum is of organic origin is to-day almost universally accepted, although there is no general agreement either as to whether petroleum is derived from vegetable or animal matter, or as to the forms of life that provided for its genesis. In certain places in the world—notably on the eastern side of the Caspian Sea and also near the Mediterranean—there is some conversion of organic matter into petroleum actually to be seen to-day. It is not difficult, as the late Sir Boverton Redwood, Bart., pointed out in an address before the Royal Institution of Great Britain in 1918, to account for the formation of adequate deposits of the necessary material. In the comparatively deep and quiescent water along the margin of the land in past ages, there would be abundant opportunity for the deposition not only of the remains of marine animals and plants, but also of vegetable matter brought down to the coast by the water courses, and the changes which the earth has undergone would result in the burial of these substances under sedimentary mineral matter, the deposits thus formed being ultimately, as the result of further alterations in the earth’s surface, frequently found occupying positions far removed from the sea, and sometimes beneath immense thicknesses of subsequent deposits.
That vegetable matter may be the source of certain petroleums is an opinion that has found increasing evidence to support it. There are two kinds of vegetable matter which are possible, terrestrial and aquatic, and in the deltaic conditions that characterize so many oil-fields, either could be equally well appealed to as a source of accumulation. The extensive coal and lignite deposits in many geological periods bear eloquent testimony to the presence of carbonaceous matter far in excess of that required to provide proved supplies of petroleum. Every important coal-field demonstrates the fact that vegetable matter can be partially converted into bituminous compounds or hydrocarbons by natural processes. Marsh gases often occur in great quantities in faulted zones in the coal measures, though the bituminous substances found in coal are not true bitumens that dissolve in the usual solvents, while the tars derived from the destructive distillation of coal in no way resemble natural petroleums or the products of oil-shale distillation.
In spite, however, of the outstanding differences between petroleum, oil-shales and coal, I might here point out in favour of the vegetable theory of origin, that actual petroleum and true bitumens have been found in some coals, though in small quantities, while solid paraffins have been extracted by means of pyridine and chloroform. Again, low temperature distillations have yielded petroleum hydrocarbons, all of which appear to indicate that even when coal was the overwhelming product, at certain times and places the conditions were merging into those which could yield petroleum. There is no doubt that each of the various views expressed as to the organic origin of petroleum contains elements of truth, and it is reasonable to assume that a substance so varied in its physical and chemical properties as petroleum has not in all cases been created under precisely the same conditions, or from an exactly similar source.
Summing up the whole question of origin, however, the balance of opinion points to its being the result of organic action, and that the petroleum which we now find in the Palaeozoic and Tertiary rocks is substantially of the same geological age as the rocks themselves.
Volumes of technological literature have been written upon this complex question of petroleum origin, and though these may be of intense interest to the student of geology, the brief references which I have already given to the question are sufficient for the purpose of this little publication.
The geographical distribution of petroleum throughout the two hemispheres is no less wide than the geological. The deposits mainly occur along well-defined lines, often associated with the mountain ranges. This is chiefly due to the formation, in the elevatory process, of minor folds which have arrested and collected the oil in richly productive belts.
CHAPTER II
THE OIL-FIELDS OF THE WORLD
Ever since petroleum and its products entered the realm of commercial commodities, there has been a ceaseless search throughout the two hemispheres for crude oil, and to-day there are comparatively few countries in the world where the presence of petroleum has not been proved. The ever-expanding uses of petroleum, which in their train have called for a continually increasing demand for crude oil, have given an impetus to the search for commercially productive oil-fields, which, in mining history, has no parallel. On the one hand, we have those important oil-producing regions which embrace enormous regions of the United States, Mexico, Russia, Roumania, the Dutch Indies, India, and Galicia; on the other, we find comparatively recent enterprise which is bringing into prominence the newer oil-producing regions of Egypt, Trinidad, Canada, the Argentine, Algeria, and various parts of Australia and Japan, though in several of these latter mentioned countries, the production of petroleum has been carried on by private means for not only many years, but even for centuries.
It naturally follows that, with the constant withdrawal of large supplies of crude oil from Mother Earth, Nature’s stores must be growing less, and it is not surprising, therefore, to hear, with persistent regularity, alarming rumours of the coming dearth of crude oil. Experts have devoted considerable time and thought in an endeavour to arrive at a conclusion as to the length of time it will take for the withdrawal of practically the whole of the crude oil from the known deposits in the more developed fields: their conclusions, however, are widely different, for while some assert that in the United States, for instance, the known fields will cease to be commercially productive within forty years, others there are who declare that centuries must elapse before the question of a failing supply need call for serious consideration.