REPORT ON THE PETROLEUM FOUND AT TARANAKI:

Appendix to the Journals of the House of Representatives, 1866 Session I, A-16

A.—No. 16.

REPORT ON THE PETROLEUM FOUND AT TARANAKI:

BY DR. HECTOR.

PRESENTED TO BOTH HOUSES OF THE GENERAL ASSEMBLY, BY COMMAND OF HIS EXCELLENCY.

WELLINGTON. 1866.

A.—No. 16.

BY DR. HECTOR. Geological Survey of New Zealand, 'Sib,— Wellington, 18th June, 1866. I have the honor to furnish the following information respecting the Eock oil, or Petroleum, that is found at Taranaki, various specimens of which, along with the associated rocks, have been sent to this Department for examination. It appears that an exhalation of gas, and bubbles of bituminous matter, has been observed since the earliest days of the settlement, at about half-a-mile from high water mark, between the main-land and Moturoa, the highest of the Sugarloaf islands; and, according to Dieffenbach, "was whimsically attributed by the Maoris to the decomposition of an Atua, or spirit, who was drowned there." It was not, however, until November last, that any attempt appears to have been made to search for this oil, by boring or sinking wells on land, and as these experiments have to a certain extent proved successful, much attention has been recently attracted to this natural production, which it is hoped may yet prove a valuable and important article for export. The petroleum is described as oozing in small drops from cracks and fissures in the rock that forms the Sugarloaf promontory, but it does not appear that the solid rock itself contains any appreciable traces of oil. All the rock specimens sent are either of the common superficial sand beds of the coast, or of a hard gray rock that proves to be the same trachytic breccia which forms the Sugarloaves, and which can be traced only a short distance inland towards Mount Egmont. This rock is of volcanicorigin, being composed of fragments of still older igneous rocks, ejected under the sea in the tertiary period, and cemented together by the feldspathic mud which usually accompanies such eruptions. Trachytic breccia of similar character is of frequent occurrence in other parts of New Zealand, encircling the districts where energetic volcanic action once prevailed, either as rudely stratified masses of immense thickness, which overlie the deposits that were forming in the sea at the time of their eruption, or as massive dykes that have pierced through and consolidated among these same strata. When the nature and origin of this rock is taken into consideration, it is evident that the petroleum it contains can be only accidentally present having been originally derived from some distant source, and indeed it is probable that this rock has only acted as a condenser and absorber of gaseous vapour produced by the natural distillation of deep-seated strata of carbonaceous matter. It should be remarked that among the recent superficial deposits along the same coast, there are found considerable beds of lignite and decomposing vegetable matter, and though such deposits cannot account for the dissemination of the oil in the rock to a depth of 115 feet (at which depth I understand decided indications of its presence have been obtained), still it is well to bear in mind the existence of such superficial deposits, as it is quite possible that they may give rise to small quantities of bituminous oil, and to other indications that might tend to mislead explorers in searching for true oil wells. The real source of the oil is most probably to be looked for in the coal seams that belong to the Brown Coal Formation, that is believed to form the base of the series of tertiary strata that extends under Mount Egmont, and the valleys of the Wanganui and other rivers which enter the sea along the coast between Mokau and Otaki. This coal formation, which is probably not a continuous sheet but occupies issolated depressions in the Paleozoic rocks, is overlaid by marine strata of various kinds, comprising clay shales, sandstones, and limestones that were accumulated during a gradual depression of the land beneath the sea. The volcanic eruptions seemed to have commenced at the period of the greatest depression, most probably with the eruption of volcanic rock, like that which forms trachytic breccia that' now yields the petroleum. The volcanic action, at first submarine, was continued with the re-emergence of the land, becoming gradually more feeble and more localized, until the great cone of Mount Egmont was piled up in the atmosphere. The total thickness of the submarine strata which in the deepest part of the basin overlie the brown coal formation, cannot be less than 2,000 feet, and to this must bo added at least an equal thickness of submarine volcanic formations, above which rises the true volcanic cone of Mount Egmont to a height of 8,270 feet, composed principally of lavas and scoria beds of recent date. Under this immense accumulation any brown coal beds that exist in the deeper part of the basin must have been subject throughout a lengthened period of time to the combined action of heat from the frequent injection of igneous dykes, and moisture from the percolation of water to supply that which was carried off in the form of steam during the volcanic eruptions ; and one of the most probables results of the chemical action produced would be the formation of bituminous vapours that would ascend through the strata along lines occupied by dykes and fissures until they reached rocks sufficiently cool to cause their condensation into the form of oil. In the foregoing endeavour to account for the remarkable fact of the presence of petroleum in the volcanic rock at Taranaki, it has been necessary to rely greatly on the analogy of geological structure which may reasonably be expected to exist between the district in question and other

REPORT ON THE PETROLEUM FOUND AT TARANAKI:

A.—No. 16.

parts of New Zealand where similar superficial features prevail, as the information which has been derived from actual observation of the district is yet very limited. It must be distinctly understood that there is no similarity between the mode of occurrence of the rock oil, so far as it has yet been found at Taranaki, to that which prevails in the oil-bearing districts in the United States of America and Canada; for although it is held by some geologists that in these countries the oil has also been produced by destructive distillation of coal seams, which are now represented by seams of anthracite coal, or have been wholly removed by denudation ; still the nature and arrangement of the condensing rock has been very different, and this, of course, will completely alter the case so far as the practical search for petroleum is concerned. In the United States the wells are sunk principally in very ancient strata —older, perhaps, than many of the slate rocks of New Zealand, but lying in an undisturbed and nearly horizontal manner over immense areas. In Oil Creek Valley, according to Professor Draper, these strata consist of clay shale in beds of about one hundred feet in thickness, separated by layers of sandstone of twenty to thirty feet. The borings are carried through alternate beds of this description to a depth of 400 feet before the oil is obtained plentifully, although it also exists in the upper strata in small quantity. In this case it undoubtedly percolates through the more porous layers of sand rock, so that the process for obtaining it is like ordinary well-sinking, and a continued supply can be calculated on with considerable certainty. In Canada the oil is also obtained much in the same way by piercing horizontal beds of limestone and shale of Silurian and Devonian age, the oil being found in the cracks and fissures of the former rock. In that district there are also surface wells sunk in the superficial gravel and clays that have been saturated with the oil rising to the surface by natural springs. The steady supply of rock oil from the American wells is no doubt due to the great extent and regularity of the porous strata in which it has been accumulated, and through which it percolates in the same manner as water supplying artesian wells. The petroleum wells of Italy, Asia Minor, and the Crimea, have more resemblance to what may be expected in New Zealand, in so far that the oil escapes from strata of tertiary age and is always more or less distinctly connected with active or extinct volcanic agency. Professor Ansted in a recent article on this subject, describes the petroleum in the Crimea as springing from blue clay shales that underlie a crust of marine limestone of recent tertiary formation. The petroleum wells up in the bottom of valleys that have been eroded through the limestone and so exposed the shales, and evidence of deep-seated chemical action is indicated by mud volcanos from which liquid mud accompanied with an escape of gas, slowly oozes and forms conical mounds and hillocks. In these tertiary strata we have a marked resemblance to the older tertiary rocks of New Zealand which overlie the brown coal formation, and as I have already described, underlie the eruptive rocks of such volcanic centres as Mount Egmont; and I am inclined to think that the proper place to expect petroleum to occur in large quantities may be in connection with lines of dislocation at some distance from the centre of disturbance, and where the older tertiary rocks come up to the surface. In the Taranaki district this would be to the north of New Plymouth, and in localities where perhaps there might be no surface indications excepting those which everywhere mark dislocations of tlie strata. From the above considerations it is probable that, in the neighbourhood of Sugarloaf Point, where these explorations are being made, the boring will have to be carried to a very great depth before a constant or abundant supply of oil can be looked for, unless, as is not improbable, when sinking through a rock which appears to be in parts saturated with oil, an open cavity or fissure be accidentally struck in which a large quantity of oil has accumulated. Such natural cavities are frequently struck when boring in the sandstone in America, the result being a sudden and forcible discharge of gas, oil, or water, according to whether the upper, lower, or middle part of the cavity be first tapped ; but before long this spontaneous overflow always ceases, and then the ordinary method of pumping has to be resorted to. If, however, the oil has been condensed in the fissures that traverse the trachyte breccia at Taranaki, from the form of vapour, and if it does not percolate freely through the substance of the rock, as it does between the layers' of sandstone and shale m America, I fear that the pumping will not be of much avail. The specimens of petroleum submitted have been carefully analysed in the laboratory of this department, by Mr. Skey, and from the result of his examination it would appear that the nature and value in relation to other petroleum oils, of the samples as yet obtained, has been somewhat overestimated, and that they must only be looked upon as a good indication that really valuable oils may exist in the neighbourhood. All the various samples which have been submitted have the same physical characters, having a dirty green color by reflected light and being opaque, unless examined in thin films, when it has a deep red color by transmitted light. At GO ° Pah. it is quite liquid, and though at lower temperatures it has considerable consistency, yet when reduced to 25 ° Fah. it docs not become solid. It has a mawkish but not unpleasant odour, being very different in this respect from most rock oil, and is especially free from all traces of sulphuretted hydrogen gas. Minute flakes of a white substance, probably allied to paraffine, float in the oil, and are gradually deposited, when it is allowed to remain quiet at a low temperature, nearly the whole of this solid substance becoming dissolved when the oil is gently heated. The temperature at which the oil boils is 340° Fall., and it does not appear to evaporate much at ordinary tetnnerature for when exposed to the air it remains unchanged, neither thickening, nor acquiring a skin on the surface.

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REPORT ON THE PETROLEUM

A.—No. 16.

Its temperature requires to be raised to 260° Fab. before its vapour inflames ; and eyen with a wick it does not burn so freely as common animal oils. The specific gravity is very high as compared with other hydro-carbons, being no less than 962 (water being 1000) or 14| degrees of Gesner's hydrometer scale. There does not appear to be any instance on record of a rock oil having so high a, specific gravity, the usual range being from "814 to 930 for crude oil. It may be explained that all the varieties of petroleum are composed of carbon and hydrogen and only differ in their quality according to the proportion which these two elements bear to one another, the heavier, and inferior oils for illuminating purposes having the larger proportion of carbon. There is therefore no test of the quality of the oil which is so reliable and so easy of application as that of the specific gravity, and the above results are quite sufficient to show that the samples of oil examined have a much larger proportion of carbon in their composition than the common petroleum from which the kerosene of commerce is manufactured. This was still further proved by the examination of the oil by distillation as in the production of kerosene. A measured quantity of the crude oil was distilled with a very gentle heat which was gradually raised until 80 per cent, of the original quantity was obtained in the receiver, which is about the average proportion of kerosene obtained from the American petroleum. The oil obtained which had a faint yellow color and pleasant odour, was of specific gravity '930, which is denser than the commercial proof that has been fixed for heavy lubricating oils ('927). As the lighter oil would distil over first and at a lower temperature, the experiment was repeated and the process stopped when 25 per cent, of the original quantity operated on had been obtained in the condenser. The distilled oil obtained on this occasion had a specific gravity of -889 or slightly over the proof fixed for light lubricating oils ("881). By further experiments it was found that the lightest oil that could bo drawn over had the specific gravity of '874 and of this quality only a i oz. could be obtained from 12 oz. of the crude oil after it had been carefully purified by filtration. The next lj oz. obtained had a specific gravity of '893, and the next ounce "917, which would give to the remainder of the 80 per cent, of distilled oil obtained in the first experiment a specific gravity of '941. The first two samples were quite clear and colorless, but the last had a pale yellow tinge. The average specific gravity of the 2i oz. thus obtained from the original quantity of 12 oz. was "900, or that of a lubricating oil of medium quality, while the oil left in the retort had a consistency of tar. The ordinary density of the kerosene of commerce should be '819 (although it is often made lighter, in order to improve its color, which however renders it liable to explode), and it has been found impossible to obtain oil of this low density from Taranaki petroleum. The lightest distilled oil which was obtained burns freely with a wick, but has a lurid flame and, though not adapted for use in the ordinary kerosene lamp, might possibly be used in a lamp suitable for paraffine oil. The residuum left in the retort when 80 per cent, of oil was drawn over was a hard brittle pitch, which can be obtained from the crude oil in the proportion of 73 grs. to the fluid ounce. This pitch when further examined gave 28 per cent, of hydro-carbon evolved at a high temperature, and 62 per cent, of a lustrous vesicular coke, which contains 777 per cent, of ferruginous ash. The general results of these experiments may be tabulated as follows : — One hundred parts of the crude oil, as obtained from the wells, having a specific gravity '962, gives— Distilled oil of specific gravity-874 ... ... ... ... ... 2 •893 10 •917 8 ■941 60 Solid bitumen ... ... ... ... ... ... ... • 6"1 Fixed carbon ... ... ... ... ... ... ... 124 Ash 1-5 1000 It may perhaps be considered premature to form an opinion as to the prospect of these wells from the result of the analyses of the small samples yet obtained, which, I understand, are only collected as drippings from the boring rods and pumps ; but it must be remembered that it is usual to strike the lightest oils first when boring, and it may be expected with more certainty if in this case the oil has been condensed in the rock from a state of vapour, that the lightest and most valuable oils should be met with nearest the surface. It, however, occasionally happens that petroleum obtained in one part of an oil-bearing district is much denser than in others, and sometimes even passes gradually into semi-solid bitumen, so that the occurrence of this heavy oil at Taranaki does not necessarily indicate the total absence of the finer oils, but only that the locality in which the borings have been made may not be the most favorable. A remarkable instance of this gradual change of the quality of the oil occurs at Baku, on the shores of the Caspian Sea, where the petroleum is obtained over a tract of" country twelve square miles in extent, the strata being a porous argillaceous sandstone, full of fossil shells of the tertiary period. The oil obtained from the centre of this district is very light and colorless, and accompanied by quantities of inflammable vapour; while towards the sides of the district it becomes darker iv color and more dense, and gradually passes into asphaltum. In concluding these remarks, I would remind explorers for oil wells in New Zealand that petroleum is to be found in nearly all parts of the world, and has been recognized and worked from time immemorial for illuminating purposes. The only novelty in connection with it in the present age is the discovery of large natural

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EOUND AT TAEANAKI.

A.—No. 16.

reservoirs, that seem to yield an inexhaustible supply, of a quality that can be purified by an inexpensive process, in districts where its presence had not been previously expected. The occurrence of mineral oil in New Zealand must not, therefore, be looked upon as an exceptional and uncommon phenomenon, but as one of the productions natural to a country where extensive deposits of carbonaceous matter have been involved in volcanic disturbances. Whether mineral oil of fine quality has been accumulated in accessible positions and in sufficient quantity to exert a marked influence on the future prosperity of this country, is the problem now being solved, and even if the boring now carried on at Taranaki should not prove successful, the question will not be set at rest. The presence of petroleum has been reported, and may be expected, in many other parts of New Zealand; and now that attention has been directed to the subject I have no doubt it will be found, at least in small quantities, throughout both islands, wherever volcanic disturbances have affected deep basins containing tertiary strata overlying the brown coal formation. Mention should not be omitted, however, of the circumstance that in the lower secondary rocks of New Zealand, which consist of sandstones and shales that have undergone great mechanical disturbance and chemical change, there are thin seams of graphite and anthraeitic coal, and probably from these also there has been produced a certain amount of" bituminous oils. These beds, as yet discovered, are of very insignificant extent and cannot have yielded a large quantity of oil in their conversion to their present state. As I intended in the present report merely to furnish general information respecting the origin and mode of occurrence of the petroleum at Taranaki, and to give the results of the chemical examination which has been made of it, I have deferred attempting to give any detailed description of the workings or the immediate locality where they are being carried on, as all the information I possess regarding what is to be seen on the spot since the workings were commenced has been gathered from the newspapers or from Mr. Grayling's letter (copy herewith enclosed) forwarded for my information along with a box of specimens which were only received a few days since. I have also to acknowledge with thanks information which I have received verbally from Mr. Balfour, C.E., and Mr. James Hacket, both competent observers, who have recently visited the locality of the oil wells. I have, &c, James Hector, M.D., F.G.S., The Hon. the Colonial Secretary, &c. Director of New Zealand Geological Survey. Copy of a Letter from Mr. Grayling. Sin,— Taranaki, 30th May, 1866. Having been requested by Mr. Hacket to forward you a box of specimens from the neighbourhood of the Sugarloaves, I write to inform you that a small box has been placed in the hands of the agent, with directions to forward the same by the first vessel, and should the weather moderate it will in all probability reach you by the " Storm Bird." You will see by the enclosed index that oil is to be mot with on the eastern side of the Sugarloaves, for some half-a-mile in distance, wherever a fissure is perceptible. At such a spot, a blow from the hammer will cause water, when poured on the fractured portion immediately to be coated with a film of petroleum, which is easily recognized by its smell. I would particularly ask your attention to the fact that the more solid portions of the reef yields no appearance of oil. This, coupled with the fact that out at sea, where the water is upwards of 100 feet in depth, large bubbles of the diameter of an ordinary tumbler, are constantly bursting on the surface, induces the belief that petroleum is to be found in large quantities by deep boring. I might ask your attention to another significant fact. Carter, prior to boring, sunk a shaft between fifty and sixty feet in depth, this is now nearly filled with water, from which gas is constantly evolved, some thousands of cubic feet being daily given off, whilst the surface of the water has a layer of oil some inches in thickness. Again, during the time the men were engaged in sinking, the gas at times disenabled them from continuing operations. Another point worthy of record is, that the quantity of oil in the tube down which the boring rods work varies with the weather. I have only found surface indications where the rocks are exposed to view, by being protected from the prevailing winds which would otherwise cover them with sand. On the westward side of the Sugarloaves the reef is covered with several feet of sand. In an unstratified country such as Taranaki actual experiment alone can throw light on the lay of the rock. It will give me great pleasure to send you at any time specimens of rocks; and would it be of any service to send you a gallon or more of oil. I have, &c, W. E. Grayling. The specimens referred to in Mr. Grayling's letter were found to be as follows: — No. 1. Gray trachyte breccia, containing fragments of gray and blue trachyte, with crystals of feldspar and hornblende imbedded in a feldspathic ash. Some of the surfaces were stained with petroleum. Nos. 2, 3, and 4. Decomposed feldspathic sand containing rolled gravel, evidently from superficial deposits. No. 5. Fragments of trachytic breccia from the bottom of the deep bore, contains fragments of crystals of hornblende. Nos. 6, 7. and 8. All trachyte fragments from the breccia rocks. These rocks, with the exception of 2, 3, and 4, are of volcanic origin. James Hectoe.

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REPORT ON THE PETROLEUM FOUND AT TARANAKI.