DEVELOPMENT OF NEW PLYMOUTH OILFIELD

Sun (Auckland), Volume II, Issue 387, 22 June 1928, Page 12

DEVELOPMENT OF NEW PLYMOUTH OILFIELD

Dr. Leon Bossard, the well known Swiss Geologist and Petrologist, to whom the credit of selecting the Omata Area is entirely due, and which ultimately lead to the location of oil accumulations by geophysical investigations, reports as follows to Coal-Oil (N.Z.), Ltd. The geological survey in the Omata District, which has been carefully examined by me prior to my directing of the geophysical group to proceed to this area, has disclosed the presence of structural conditions favourable for accumulation of commercial quantities of oil. The oil has been primarily generated under tho aid of tectonic movements and heat supplied by nearby volcanic vents. The main oil horizons are in the Urenui Formation, of Upper Miocene (Tertiary) Age, although minor horizons may occur in the tertiary strata immediately above and below this formation. The oil seems to be concentrated in several independent layers of a fine grained porous sandstone separated from each other by an impervious mudstone, which forms also the capping and the bottom of the oil horizons. These standstone layers, which have a thickness up to 100 feet, occur mainly at a depth varying between 1,000 and 4,000 feet. Their repetition means the probability of repeated success in the same bore, which adds considerably to the merits of a. boring enterprise in this area, supposing the most suitable location for the bore could be found. The nearly entire absence of outcrops in the area under review which is covered by volcanic debris did not allow for the exact location of oil accumulations by surface indications alone. The geophysical investigations have succeeded in pointing out the exact locality of the oil accumulations in the extended area held by your company, thus confirming also my previous recommendation. The New Plymouth petroliferous area can be considered an established oilfield, although most of the bores did not yield oil in satisfactory quantities. This is not necessarily due to lack of presence of oil in commercial quantities. After my careful examination of all available data, I can say that the following facts are responsible for the said:— (1) No drilling on structures. (2) The employment of non.-expert drillers had the consequence that the water was not properly shut off, resulting in the watering of the oil-sands at Moturoa. The penetrated oilsands were not recognised, shut off, and drilling continued. Also, all kinds of tools were dropped in the casing, which got plugged. (3) All bores were concentrated on a very small area of a few acres at Moturoa, so that each bore influenced the other in its production. All bores outside the Moturoa area, which lays a few miles north-east of Omata, have never been drilled deep enough to reach the oil-bearing sands. It is surprising, that under these circumstances, oil ever has been obtained. and indicates the excellent opportunities of the structural area held by your company, provided the above- , mentioned mistakes of the past will be omitted. Your area has never been touched by bores leaving oil-horizons undisturbed, there being also no watering of the oilsands. The fact that the Now Plymouth oil is very valuable and being close to a deep-water harbour obviates the construction of a pipe-line, thus materially increasing the value of this product. You are fortunate in possessing an area where the geological conditions are most favourable for obtaining oil in commercial quantities. The geophysical findings which have now been furnished by the Elbof Geophysical survey confirm in every respect my geological conclusions. —2.