A Practical Treatise on Petroleum

IT may readily be supposed that as long as questions concerning the geological relations of petroleum remain unanswered, equally perplexing difficulties will attend the solution of the problem of its origin. If it were positively ascertained, for example, that vast deposits of organic remains had been formed at a certain geological period; if it could be clearly shown that at another period of time such deposits had been subjected to destructive distillation; if the track of the distillate could be traced from its parent bed to the porous sandstone reservoir-if conditions like these could be clearly shown to have existed, we could approach the subject of the origin of petroleum with reasonable hope of arriving at a satisfactory conclusion. But in the present stage of the controversy, when any one of the above-mentioned conditions, which at present appear to be essential to its formation, is controverted, we are

placed at a great disadvantage in entering upon the discussion of any theory. Indeed, so grave are the difficulties and objections which beset the path of any theory that our best geologists, while leaning at times, it may be, to one or the other of the various solutions which have been offered in explanation, confessedly prefer to wait for more light upon a matter literally so hidden and obscure. Professor Lesley, the State Geologist of Pennsylvania, says: "The origin of petroleum is still an unsolved problem. That it is in some way connected with the vastly abundant accumulations of palæozoic sea-weeds, the marks of which are so infinitely numerous in the rocks, and with the infinitude of coralloid sea animals, the skeletons of which make up a large part of the limestone formations which lie several thousand feet beneath the Venango oil-sand group, scarcely admits of dispute; but the exact process of its manufacture, of its transfer, and of its storage in the gravel beds, is utterly unknown. That it ascended into them rather than descended seems indicated by the fact that the lowest sands hold oil when those above do not, and that the upper sands hold oil when they extend beyond or overhang the lower."

An opinion at one time extensively prevailed among certain oil prospectors, that petroleum was in some way associated as a product with the bituminous coal measures. Some have supposed that it was a resultant of distillation of this variety of coal, others that it was "the natural drainage” of the coal beds; both classes were equally ignorant and careless as to whether the oil ascended or descended after

its formation. As might be expected, wells drilled upon hopes so illusory and baseless failed to respond to the projector's expectations. The oil-bearing sands lie many thousand feet beneath the lowest of the coal strata, and no well ever drilled in that section has pierced them. The opinion, however, was not an unreasonable one in view of the ignorance then existing among all classes as to the true sources of the oil, and, in the absence of correct information respecting the geology of that section of country. It was an acknowledged fact that an oil almost identical in appearance and chemical composition had been artificially produced by the distillation of certain bituminous shales. Why could not Nature in her vast subterranean laboratory produce a corresponding product from bituminous coal? The existence of marsh-gas, the fire-damp of the mines, and a constant associate of petroleum belonging chemically to the same paraffine series of hydrocarbons, as petroleum, seemed also to point to an identity of origin. Two considerations, however, have satisfied both the oil miner and the scientist that bituminous coal is not the real source of the petroleum of commerce. The miner has been satisfied because he can find no oil anywhere near the coal beds, and the geologist has been satisfied because he has a more correct knowledge of its origin and formation. We, therefore, hear very little at the present time about petroleum being either the product of distillation from the coal beds, or of its being "the natural drainage" therefrom.

Lesquereaux has furnished some interesting views on

this subject. He is of the opinion "that petroleum is the result of the decomposition of marine plants, as coal is the result of terrestrial vegetation. The conclusion is natural, for there exists an evident correlation between the formation of both kinds of deposits of bitumen.

"There is no doubt that the marine vegetation of the palæozoic ages can be compared for luxuriance, and in some measure for its composition also, to the terrestrial vegetation of the coal epoch. From the upper Devonian down to the lower Silurian, some strata of shales are not only covered, but, indeed, filled sometimes for hundreds of feet in thickness with fossilized forms of hydrophytes." As illustrating the extent of such deposits "the great bank of Sargassum, which extends between the 20th and 45th parallels of latitude, covers, according to Humboldt's computation, a space of more than 260,000 square miles. In places the floating bank is so thick as to arrest the progress of vessels, and it appears at present to be of the same extent and to occupy the same place as when it was first noticed by navigators. What can we then infer to have been the result of a vegetation whose force was at least double what it is now, and which has written its history in whole strata of great thickness? Thus also the

remains of marine plants in the shales of the Devonian point out, I think, not only the fecundity of an ancient marine vegetation but its result in the contemporaneous deposit of petroleum.

"The Chlorosperm of the palæozoic times with their simple bladdery conformation and their green color were

« Previous Continue »

Books

A Practical Treatise on Petroleum: Comprising Its Origin, Geology ...