OIL SEEPAGES

Evening Star, Issue 23135, 8 December 1938, Page 8

OIL SEEPAGES

THE MARTIN’S BAY DISCOVERY RESULTS OF GEOLOGISTS' SURVEY [Special to the ‘ Stak. 1 ] WELLINGTON, December 8. Two years ago great public interest was created by the report that oil seepages had been discovered at several points on the coast of North-west Otago, near Martin’s Bay, and prospectors sent samples to Wellington for analysis. The interest died down, and the reason is fully evident from a very thorough report on the geological conditions of the coastal area which was prepared by Messrs J. Healy, of the New Zealand Geological Survey, and R. W, Willett. This has been published in the Journal of Science and Technology, and the conclusion reached is that the geological conditions are negative for the existence of oil in commercial quantities. A long strip of the coast was examined, 25 miles in length, and explorations were made inland up the main water courses. The principal point of interest was, of course, Martin’s Bay, which Mr Healy states is bordered throughout the greater part of its length by sandhills backed by swampy ground and lagoons. The Hollyford River, by far the largest in the district, discharges into the bay a mile from the North Head. The details of the country in a geological sense are given so comprehensively that it is evident that the geologists did much arduous field work in country almost unexplored.' They reported that three oil-seepages are known, all occurring within a small area ’in the south of the district. Of these, one on Madagascar Beach was covered with sand, but from the other two, one in rocks exposed on the beach between tides, and the other five chains up the Wolf River, samples were collected. These were forwarded to-the Dominion Laboratory for analysis, and crude oil extracted from both samples. Both seepages are along small fault cracks separating limestone and calcareous sandstone near the base of the tertiary strata, and the quantity of oil coming away is small. “ The possible economic importance of any oil deposits which may be present,” writes Mr Healy, “is dependent on three factors. There must be a source bed, a reservoir bed, and a structure suitable for the retention of oil in large quantities. Apart from a slight development _ of shaly facies in the tertiary beds in Ruby Creek, no beds were seen which would be a likely source of oil.” Other geological features are mentioned which support the view that there is no large quantity of oil present, the writer expressing the opinion that the pressure and crushing movements to which the rocks have been subjected would be sufficient to generate small quantities of oil in the beds, and this may be escaping gradually to the surface along minor cracks caused by the movements.