Art. XXXVI.—The Oil Prospects of Poverty Bay and District.
[Read before the Hawke's Bay Philosophical Institute, 12th Nov., 1888.]
During the present year a good deal of interest has been aroused throughout New Zealand and the neighbouring colonies by the reported “striking of oil” at one of the many springs which are to be found along the east coast of this island. It is now twenty-three years since the first reported discovery of oil in the Poverty Bay district was made known in Napier. Ten years ago I visited the site of an abandoned well in the vicinity of Poverty Bay, where it had been anticipated that oil would flow like water; but at that time few traces remained of what had once been a scene of activity and hope. Since the date of my visit a number of attempts have been made to find a payable field in several places, but without success until early in the present year, when news reached Gisborne that oil had been struck in a new sinking, and that the engine-house, derrick, and adjoining buildings had been destroyed by an explosion of gas and oil from the new well.
Being in the Poverty Bay district shortly after the reported “striking of oil,” I took the opportunity to visit the site of the South Pacific Company's well, so that I might judge for myself whether the oil prospects are equal to what had been reported in the papers. The locality of the South Pacific Company's well, and of another well in course of sinking, and known as the Minerva Company's well, is about twenty-eight
miles from Gisborne in a north-west direction, and at a height of about 450ft. above sea-level. The well belonging to the former company is situated on the Wairangamea Stream, five miles above its junction with the Waipaoa River, which empties its waters into Poverty Bay. The Minerva well is situated on the Waipaoa River, a mile or so to the west of the Pacific Company's well. Work had been stopped at the Pacific Company's well at the date of my visit, but I was enabled nevertheless to gather a good deal of information from the gentleman in charge, who is an experienced American well-sinker. As already remarked, the engine-house and derrick at this well had been destroyed, and in order to provide against further accidents a cap had been fixed on the pipe or tube-bore of the well, and this was kept locked. This cap was taken off, and I saw for the first time an oil-well, having a pipe or tube 6in. in diameter, and passing down into the earth more than 1,300ft., and as far as one could judge it was full of oil to the brim. Specimens of the oil were obtained by me, and I have no doubt whatever that they are genuine.
The oil appears of a grey-amber colour when held against the light, and its specific gravity in its crude state is greater than the American oil. As to its illuminating qualities, it is impossible to speak with certainty, but the tests hitherto made have been very satisfactory. The exact depth of the well is 1,321ft. This is the depth at which oil has been struck, so that the oil-rock or oil-beds are about 870ft. below sea-level. The oil in the tube rises 3ft. or so above the surface, but, curiously, the height varies according to the direction of the winds and the character of the tides. Before the great eruption at Tarawera when the terraces were destroyed it was noticed that one of the great cauldrons of boiling water varied in its intensity according to the direction of the winds, and we know as a fact that the artesian wells in Hawke's Bay rise about 2ft. higher at high tide than at low tide. It hardly seems credible that wells—and those oil-wells—so far from the sea could be influenced by the action of the tides, as is the case with our local artesian wells; but such would appear to be the case: this could only be possible, as far as I can judge, on the supposition that the oil-bearing strata are similar in arrangement and plan to an artesian basin.
When the explosion took place in the well under notice the tools were lost, and they have remained in the well ever since. When the machinery is once more in working-order, and the tools have been recovered, it may be that the boring-tool will be able to penetrate still further into the oil-bearing strata, and that the flow will be largely increased; for unless the well be a flowing one I do not see how it is possible to make it a paying concern, which, after all, is the practical test
of the capitalists. The sinking at the Minerva well has not reached more than 750ft., but the prospects are reported as being good, and the working manager anticipates reaching the oil-beds at 1,000ft., or 1,100ft. at the furthest. I fear the manager is too sanguine on this point; but in any case the working of this second well, and of a third well midway between the Minerva and Pacific Company's wells, will provide data of great importance as to the dip and character of the oil-bearing strata along the east coast. At present everything in connection with the oil industry is tentative. Facts have to be gathered together and careful observations made before inferences can be drawn as to the future success of the east coast as an oil-producing district. But the subject is of special interest to this colony, for the question as to the employment of petroleum as a fuel is growing into prominence every day, and I look upon it that no opportunity should be lost by the Government in providing for the accumulation of facts and statistics bearing on the question of sinking and the production of oil, which might prove of great value in the near future.
The east coast district north of the Kidnappers is mainly composed of rocks of tertiary age, and it is among the tertiary rocks that evidence is forthcoming as to the existence of oil.
In America the oil is found in the silurian rocks; but in Burmah, in Galicia, in Austria, in France, and in the celebrated district south of the Caucasus, the oil is found in rocks of tertiary age, as in this country.
As far as I can judge from the sections (see Plate XXIV.), the sinking at the South Pacific well shows no rocks except tertiary; but it is a curious circumstance that what are known in the American oil-fields as the first, second, and third sand-rocks are reported as having been passed through in the South Pacific well, and latterly in the Minerva well. These sand-rocks vary in structure, depth, and thickness in the different localities of the American oil-regions, but from each bore oil is obtainable, the best flow, though not the most valuable oil, being in the third or lowest sand-rock. The manager of the South Pacific well has had an extensive experience in America, but he is no doubt mistaken, notwithstanding, as to the similarity between the sand or oil-producing beds in America and the rocks passed through in this country. There may be some likeness between the sand-rocks, or what are called sand-rocks by some oil-sinkers, in America and in the Poverty Bay district; but in America the sand-rock is the true oil-bearing rock, whilst in the South Pacific well, according to the sections shown on the manager's plan, the so-called sand-rocks simply
gave a show of gas and oil where passing through them, and oil has been struck 170ft. below the third sand-rock, as shown by him. No instance, as far as I am aware, has as yet been found of oil below the third sand-rock.
Between the American oil-wells and that sunk by the South Pacific Company there is one point of similarity worthy of special notice. In all the American wells brackish or salt water is found immediately overlying or in connection with the oil. The two liquids have been found in almost immediate contact very generally in the first, second, and third sandstone (?), the rule being in some districts “No brine, no petroleum,” for while the brine usually manifests itself first in order when the pump is applied, it never forsakes the oil; the two clinging to each other like brother and sister. I understand that similar appearances are met with in Burma and in Galicia, but whether they occur in France or in the district south of the Caucasus I have been unable to ascertain.
At the South Pacific well salt water was everywhere met with below 470ft., so that in this particular the appearances are encouraging. The existence of brackish water along with oil is of great interest as probably giving a clue to the extent of the oil - bearing strata along the east coast. I have watched for a long time past, as opportunity offered, a number of salt springs which are to be found scattered over a large extent of country extending from the Mahia Peninsula to Poverty Bay, and thence onward north-west or north-northwest in the direction of the oil-wells. These springs resemble miniature volcanic cones, the crater being occupied by water and mud instead of lava. This water rises and falls as the gas-bubbles rise to the surface, and the bursting of the bubbles causes a bluish-grey mud to be thrown out, which forms a conical mound of bare ground. The gas-bubbles explode if a lighted taper is held over the surface of the water just as they rise to the top. At Tua Motu, near Gisborne, and on what is known as the Kaiti Block, the springs are somewhat numerous; and inland, some miles to the west of Wangara, fifteen miles or so north of Gisborne, very large salt springs are met with.
The appearances observable in the oil-fields of different localities and countries may prove by comparison of great value in discussing the prospects of the east coast as an oil-producing district. Surface-appearances may not afford proof positive that payable oil will be struck, nor is it to be expected that they should; but they may be indicative, nevertheless, of similar causes operating to produce the appearances: and it seems to me that the origin of the oil may by this means be inferred. Many theories have been put forth as to the origin of oil, one being that it results from the distillation of vegetable remains not yet turned into coal, another that it
is produced from the destructive distillation of coal, another that it is derived from the animal remains collected at the bottom of seas; whilst latterly a chemist has put forth the theory that oil is purely a mineral product, that it is due to the action of water on masses of carburets of metal, chiefly iron, at high temperatures far down in the earth, and that its production is going on day by day.
It is well known, however, that oil is found in the tertiary rocks in close connection with lines of volcanic phenomena. In the oil-region of Burma mud-volcanoes and hot springs are met with in close proximity to the oil, and it is certain that similar phenomena have been seen to the south of the Caucasus, between Baku and Tiflis, since the days of Marco Polo, who in his book of travel refers to a well of flowing oil suitable for use as lamp-oil.
Now, there are hot springs and mud-cones within the limits of the oil-wells of the east coast district; and, although these may probably exist in the absence of an oil-field, they still form what may be termed very favourable indications as far as the district under notice is concerned. But the indications grow in importance in face of the fact that oil has been struck; and the time may not be distant when the position of hot springs, salt springs, and mud-cones may become of commercial importance, for the reason that wherever the salt springs and mud-cones are found the rocks are identical with those where the oil-wells are situated. It is true that the country north of the Mahia Peninsula is rough and broken in places, and great flexures are to be met with on the coast to the north of Poverty Bay; but I see no reason why oil should not exist in basins as in the case of artesian wells, and flow accordingly. I am aware that flowing oil-wells are supposed to be due not to hydrostatic pressure, like an artesian well, but rather to the elastic force of the gas (carburetted hydrogen) which accompanies the oil in the majority of the wells; but this does not appear to be essential in the case of all flowing wells, and it is clear that some flowing wells must be due to hydrostatic pressure.
The east coast oil-district is surrounded by enormous beds of porous fossiliferous sandstones, which trough under Poverty Bay and underlie all the younger tertiaries, and it may be that these sandstones are the oil-bearing rocks of the district. At present, however, the data available are not sufficient to affirm with any degree of certainty either the character of the oil-beds or the actual existence of a payable oil-field; but, still, the prospects are encouraging and are worthy of careful attention even from a geological standpoint. The Minerva well is now within 300ft. of the oil-bearing strata, and another well is being put down at the point where the
Wairangamea Stream enters the Waipaoa River. Should these wells strike oil—as there is every prospect of their doing—the undertaking will be in a great measure assured, for facts will be available of much geological value, and the east coast district will have a great future before it.
The sections accompanying this paper (Pl. XXIV.) show the character of the rocks passed through at the South Pacific Company's well. The thickness of the several sections is also given, as taken from the working-sheets of the manager in charge, who kindly placed all available information at my disposal.