OIL FOUND NEAR GREYMOUTH

Press, Volume LXXIV, Issue 22414, 30 May 1938, Page 10

OIL FOUND NEAR GREYMOUTH

. ♦ SEEPAGES AT KOTUKU TESTING WILL BE COMPLETED i SOON [THE PRESS Special Service.] GREYMOUTH, May 29. Very strong natural seepages of oil have been found near the township of Kotuku, 21 miles by road south-east of Greymouth. Thick, black, crude oil is bubbling from the ground, and a Vigorous prospecting programme will soon be, commenced. Although prospecting for oil by a Government party of three men commenced last year over an area of many square miles near Kotuku, little or no publicity has been given to their work. Presumably because of instructions, Mr Norbert Modriniak, an Austrian geophysicist attached to the Department for Scientific and Industrial Research, who is in charge of operations, when approached by a..reporter of "The Press,’’ declined courteously to be interviewed. “I am not able to give you, or anyone, information.” he said. *

That testing for oil is being carried out on an extensive scale is certainly known, however, to residents for miles round Kotuku, because of the loud reports and violent tremors from the “shots” of 1001b of gelignite fired by the party at least once every day. Windows many miles distant rattle because of the discharges. In spite of the secrecy that has been observed, it is plain that the results sq far obtained by Mr Modriniak and the members of his party are, quite definitely, such as to demand the fullest possible investigation. For many years before coming to New Zealand, about 10. years ago, Mr Modriniak was engaged in oil-prospecting and research in Germany, Rumania, and South Africa.

While it is too early for any confident opinion to be expressed about the ultimate success of the search by Mr Modriniak, whose work may have immensely important economic results to the Dominion by the winning of oil in commercial quantities, definite seepages are to be seen in the area. Most of the seepages, it is understood, have been tested by Dr. R. S. Allan, lecturer in geology at Canterbury University College. According to official records of the Department of Mines, the mining prospecting warrants formerly in the vicinity by the Kotuku Oil and Gold Fields; Ltd. (in liquidation), were transferred to Maoriland Oil Fields, Ltd., towards the end of 1934; but no drilling v/as done nor was oil production carried out during 1935. In that year 312 gallons of oil were collected from seepages, and it is indisputable that a very much larger quantity must have been lost in the process. In 1936, 1188, gallons were collected from five shallow borcholes.At an early date it is anticipated that the present testing of the area will be completed. Only then will Mr Modriniak advise whether or not costly boring operations should commence, and, if boring be advised, where it should be done. However, even should boring be decided upon, no guarantee is given that anything in the nature of a “flow” or of a “gusher” will result. To aid him, Mr Modriniak has assembled a large amount of-equipment, including many costly and extremely delicate instruments, the value of which is conservatively estimated as several thousand pounds. Moranic gravel to a depth of several hundred feet having prevented the use of surface methods of geology, recourse has been taken to geophysical methods, using the instruments referred to. Both the seismic refraction and reflec--tion methods are employed. In the former, the discharge of 1001b “shots" of deeply buried gelignite sets up vibrations in the ground, which travel in waves and are picked up by geophones, or recorders, buried in the ground. From these records is determined the speed of wave-transmission and the depth at which the waves travel. From this, in turn, is learned the formation of the ground below, a factor which is of the utmost importance in assisting the geophysicist to form an opinion. Below ground, sound waves travel at amazing speeds which vary according to the nature of the formation they meet. For example, in gravel they travel at the rate of 3000 to 5000 ft a second, in blue clay at 7000 to 8000 ft a second, in sandstone at 9000 ft a second, in limestone at 12.000 ft a second, and in greywaeke, which it met With extensively at Kotuku, at the rate of 15.000 ft a second. A study of these records reveals the nature, depth, and formation of the strata below and determines if favourable conditions, such as anticlines, or buried domes and hills, commonly known as “oil-traps,” exist below.

OIL POSSIBILITIES AT KOTUKU

RESEARCH DEPARTMENT’S , REPORT The possibilities of oil in the Kotuku district are discussed in a bulletin issued by the Department of Scientific and Industrial Research on “Petroleum in New Zealand,” by Mr J. Henderson, director of the geological survey branch of the department. The bulletin states: “The thick dark calcareous mudstone (2000 to 3000 feet) outlying the 4000 feet is a much more likely source of petroleum than the latter, which consist of terrestrial beds. Still higher in the sequence are middle Tertiary coal-measures, mudstones, sandstones, and limestones, and late Tertiary mudstones, sandstones, and comglomerates—in all close on 3000 feet thick. The limestone has been considered as a storage bed and is itself a possible source of oil, for at several localities the rock when freshly broken yields an evanescent smell of oil.

“At Kotuku tour bores at least, and probably six, * have penetrated the altered old rocks below the Tertiary cover. Late Cretaceous and early Tertiary beds are absent, and if the oil is derived from these beds and is migrating along the contact with the old rocks one would expect petroleum in the jointed limestone and the porous underlying deposits. These, however, contain but a trace of oil, and much the greater quantity is found within 150 feet of the surface, hundreds of feet above the limestone horizon which at the seepage is about 500 feet in depth. On this evidence the oil is derived from Pliocene • mudstone and carbonaceous shale. In this region the older Tertiary strata have nowhere been tested by a bore in the structure that is suitable for the accumulation of petroleum. Such favourable structures may well exist in the large areas of the graben covered with gravel and moraine.’*