POVERTY BAY OILFIELDS.

Poverty Bay Herald, Volume XXXVII, Issue 12199, 15 July 1910, Page 5

POVERTY BAY OILFIELDS.

THE WHATATUTU SUBDIVISION

(From Our Parliamentary Reporter.) WELLINGTON, this day. The ninth bulletin dealing with the geology of the Whatatutu subdivision, compiled by Mr James Henry Adams, under the direction of Dr J. M. Bell, Director of the Geological Survey Department, and dealing exhaustively with tne Poverty Bay oilnolds, has just been published under the authority of the Hon. R. McKenzie, Minister of Mines. | The bulletin deals with a retangular area of 312.5 square miles of country, 2b miles from east to west, and 12£ miles from north to south, comprising the Mangatu and Waingaromia- survey districts. The southern boundary of the area is 16 miles north of Gisborne,, and its eastern boundary ten miles Avest of Tolaga Bay. It contains the most prominent petroleum seepage so far discovered in this portion ol New Zealand, viz., the oil springs at Waitangi hills and tho scene of the Gisborne Oil Co.'s present operations. !

"The surface indications of oil which occur in various localities throughout the llaukumara. division (of which the Whatatutu subdivision is the first portion to be geologically surveyed) are," remarks the assistant geologist, "suggestive of the existence of hidden mineral wealth. Many thousands of pounds sterling have already been expended in boring for oil, without, however, any return to the investors. Apropos of this point, it might be stated that these past operations M r ere carried on without any knowledge of the underlying rock masses, and. the geological examinations , forming .the subject of ; the present re- ; port were . undertaken ,'with. a view toj giving direction to future boring opera- j tions. •'. . HISTORY OF OIL PROSPECTING. !

In 1874 Waitangi Hill _. became the sdene of active prospecting operations for petroleum," remarks Mr Adams, in, sketching the history of past attempts to establish the petroleum industry. x "To, many of those who first commenced work near the prominent oil seepages occurring there it seemed necessary only "to dig a pit of shallow depth to* obtain an abundant supply of oil. That their expectations were not realised is only too well known, and the reported yield of eight to gallons per diem from one, •of -the pits was probably the maximumobtained.''.' j Mr Adams then details the subsequent; boring operations of the South Pacific and the Minerva Petroleum Companies, carried on until 1888, entailing the. ex-, penditure of £25,000. In 1903' a well; was sunk at the head of the Totangi stream, but was abandoned at sCoft. ' Following this came the present operations of the Gisborne Oil Company at Waitangi Hill, located upon the site. proposed in the second annual report of tlio Department. ! The bulletin contains a large amount of valuable, information as to the physical geography, geological sequence, and history, besides'dealing exhaustively with tlie general geology of the subdivision. It is interspersed with useful illustrations arid maps. - - „ . PETROLEUM INDICATIONS. 7

"The number of purposes for which petroleum is used in the : w6rld to-day, and the still increasing' demand f.or it, as a fuel, places it' in the first rank of economic minerals," remarks the Geologist, in the opening of chapter 3, which deals Avith the phase of economic geology. ' Tho petroleum indications occurring are .described under the following .heading .:—QiL: Good surface indications of oil occur at Waitangi Hill at a point 69 chains slightly south-west from trigonometrical station 138, on a headwater branch of the Te Hau o to' Atua' stream named Petroleum stream. - In a length of 16 chains of its course seepage of oil may be seen at fourteen different points. The main oil spring stands at an elevation above sea, level of 1413ft, on the jjouth-west corner of a very slightly undulating area, about 100 acres in extent. The. oil from tho pool was permeating the sandy clay surrounding it from lft to sft from its circumference; Proceeding the report sets out hi; detail' various other seepages* and indjjicationsi of the presence of petroleum underneath the surface, ; adding, that outsido the subdivision, but at no very great distance from its surface, indications of oil have been found towards tho head of the Totangi stream a branch of the Wharekopae river, five miles south of tho southern boundary of the Whatatutu subdivision. There is an oil seepage on the line of a probable anticline- some distanco inland from Tuparoa. On the last of the Raukutnara division oil springs also occur, i 1 A VALUABLE OIL.

From the results of the analysis of the samples of oil from Waitangi Hill, adds the report, it would soem that tho kero. sene or burning oil averages about 40 per cent. Tho oil is therefore valuable as a- fuel, and can be used in its crude state for- various purposes, amongst which not the least in the generation of steam power. It resembles the oil from Kotuku more than the oils of Taranaki. The latter have a higher percentage of the lighter variety of qils, benzine and kerosene. It must, however, bo borne in mind, when making such comparisons, that the samples from Waitangi have ,I^6^ taken from -oil^appearing- at the surface, while those from Taranaki have been taken from some depth below, the surface. From" tho reports made by the late Mr W. Skey, formerly Public Analyst, it would appear that he considered that should oil be obtained from a bore hole of some .d-^-Vi -t Waitangi it would havo a higher percentage of the lighter oils, and consequently .•». greater value as a heating agent, than the sucfacfl oii.

Dr. 801l adds the following note : "Subsequent to the writing of .this report, a flow of oil of two or three barrels per day was struck at 655ft in the Gisborne Oil Company's bore at Waitangi Hill, located 'by Mr Adams and myseli." , The following analyses are given : — Taranaki oil: Nantha 20.2 per cent., kerosene 42.8, lubricating oil paraffin 22.1. pitch 4.6. Waitangi oil : Naptha 34, kerosene 40.5, heavy lubricating oil paraffin 25.5. "The results of tho Waitangi analysis," remarks Dr. 8011,, "fully bear out Mr Skey's surmise." A comparison of tho analysis of New Zealand oil shows that the Waitangi oil is mostly richer in the valuable lighter oils, benzino and naptha, showing as it does 34 per cent., whilst Kotuku is sat down at 4.1 per cent., Greymouth 2.1 per cent., New Plymouth 20.2 per cent, and 14.0 per cent. (Breakwater borehole). GAB. "The strata yielding gas arc ideologically identical with those yielding oil," proceeds tho rcpnrt. "Gas is the invariable accompjMiiiunt, of oil where conditions favor its accumulation ; that is where the reservoir or porous stratum is overlain by an impervious one, which will prevent tho escape of tho gas to the, surface. A small number of gas occurrences have been noted within and close to the boundaries of the subdivision. In the Waitangi bore gas was struck at 311ft, while a considerable quantity of gas was reported to have been struck in the South Pacific and Minerva bope holes. • Numeroiui gas vents, which are now no longer active, exist within the subdivision, peveivil of which' aro detailed in the report, whilst at Waimata, four miles outside the- boundary, the pressure of the gas emanations is at tinieß sufficient to produce a considerable extravasation of mud anVT stones. . ■.'.,.

j PROBABLE OIL ZONE. } ,0f the ten or more bore-holes which have been sunk within the subdivision, in not one instance are samples of the wjck' .bored through - available, reports the. Geologist, and in only one instarico is a log available for information. Thbre-for-e v regarding the probable oil zona of this area., tho geologist is entirely dependent on the rocka which have been •exposed ■ by disintegration in stream beds, cliffs, landslides, etc. fo a re»v\t of the examination it seems- certain tlfat tho clay shales which form the ip'west beds of tho Whatatutu scries are the. upper portion of or form, an impervious cover for the "oil Ssoirie or the area. From its character the clay shale is admirably, suited for a cover for a stratum containing oil. This rock is exposed at the surface in the head water valleys. of : the Mangatahu and WaiUuigirua

streams, and will occur at some- perhaps considerable depth at Waitangi Hill. From this one exposure at the head waters mentioned, it is not possible to estimate the depth at which it occurs at the boring sites which have been recommended, since the overlying beds of chalky limestone and glaucanitic sandstone, etc., probably vary to some extent in thickness; also one or more of these overlying beds may be absent at the particular site chosen. SITE FOR BORE-HOLES. In the case of the Whatatutu subdivision it cannot be definitely stated, remarks the Geologist, that oil may be found, and moreover the most favorable sites for drilling may be pointed out, but it must be borne in mind that the writer does not say that it will certainly bo successful. In the recommendation of sites for bore-holes which is made in this report, it has been assumed that a domal arrangement of beds is the most favorable for the maximum accumulation O£ Oil.

Three sites are recommended, viz., (1) The dome of the Toromiro anticline ; (2) the dome of the Waitangi anticline at Wailangi Hill (site of the Gisborne Oil Company's well), and (3) the dome of the Waitangi anticline on the western side of the Mangatu river, each being located on an accompanying map. Number 1 site is situated at an alti lurlo of 800ft and is about 300ft lower down than the apex of the dome. The track from the Gisborne inland Waiapu leads to this point. ' The Waitangi site is on an elevation of 1450ft and 5 miles from Whatatutu. Its recommendations are that it lies at or near the rest of a longitudinal fold and near the point of traverse folding on the longitudinal ; in other words at or fiear th'o point of doming in the strata. It is apparently removed from "slip" country. It appears, to be removed from the possible line of fault along the petroleum springs. Indications of oil, and possibly a small amount of oil, may be obtained within the glauconitic sandstone and chalky limestone beds, but the absence of such should not be taken as a proof that no oil will be obtained until the supposed oil lode has been reached. Their absence should rather be taken as proof that the underlying beds are sufficiently impervious and so little fractured as not to allow of the escape of oil from its proper zone. - Dr. Bell adds that the- deductions as •to strata mado by Mr Adams have been borne out to a remarkable degree by the records of the Waitangi bore. Number 3 site is directly overlain by gravels and boulders which form a low terrace, with an elevation of about 6ft above the ordinary water level of the river. It is abotit 3 miles from Whatatutu, the Mangamaia road passing within half a mile of it.

A detailed geological survey of those portions of the Arohoa, Ngateretcre, and ATo'tu Biirvey district, which immediately adjoin the north-western portion of Mangatu survey district, will be necessary to prove whether the greater elevation of the beds is due to the occurrence of a dome, or at least an 'anticlinal fold, coincident with or in the v vicinity of the crest of the Raukauma range. Unfortunately the exposures of clay shale examined in the Mantratu and Waitangirua streams do not show stratification. If the existence of a dome in this vicinity is proved then it is without doubt the most favorable position' in the whole area for the accumulation of oil and for drilling a well to penetrate the probable oil zone. In any cose, since it is almost certain that, these clay shales are a portion of or an impervious cover for an oil zone, a \ycll drilled here, though it proved- non-productive would supply very valuablo information as regards prospects: of obtaining oil, sinco clay shales are here exposed at* tho surface. Tho well would commence in beds which can only be reached at somo perhaps considerable depth on tho other boring sites recommended, therefor o tho chances of penetrating them and reaching' the probable oil zone aro (he better.

The fact that oil springs and gas vents havo not u)v'to now been discovered in this locality does not at all detract from the possibility of obtaining oil here, but if an oil zone irxists at some depth, it i; a proof that th<vfhiv shale- covering it has not been frftqturfcd sufficiently to allow of its pscapc. ',', It. -is impossible from , tho amount of information^ .available to suggest any particular •spot in this locality at which drilling should bo undertakno and still more impossible to predict that oil will bo obtained here. Nevertheless the general geological structure of tho ares, which has been examined suggests that it may bo a. most favorable locality for oil accumulation. ,

The bulletin also deals with the location of a, mineral spring and material for macadamising purposes and cement maleGOLD' AND .QOAL. As regards gold, Mr, Adams says "iSmall pieces of quartz containing gold arc reported to have boon . TouJkl. but attempts mado to locato , an, auriferous vtin hav-3 proved unsuccessful. The general rock formation of fhu area certainly suggests thai tho i specimens of auriferous quartz h;i.yo been derived from a vein situated in somo 'cither district, and it is indeed highly -improbable that quartz veins carrying gold . will ever be located within t lie area covered by the subdivision. Dishes of material were carefully washed but in no case was even a color of gold obtained. • No evidence of the occurrence of payable, coal seams was obtained. If such do occur they aro not exposed at the surface and will probably only be detected, by deep boring.