SHALE DEPOSITS IN SOUTH
RESULTS OF SURVEY Probable reasons why the Orepuki shale works closed down were discussed by Mr R. W. Willett, of the Department of Scientific and Industrial Research, in an address to the Southland branch of the Royal Society last night. The lecturer indicated that he did not subscribe to the sensational stories in circulation that the works had been closed down by competitive firms. Petrol shortages had focussed attention on the shale deposits in Otago and Southland with a view to ascertaining whether petrol could be produced in the country, Mr Willett said. The Department of Scientific and Industrial Research had undertaken a survey of the deposits in the south during the last three years. The results had not yet been published and some of the findings could not be released.
The shale deposits at Orepuki had been worked between 1899 and 1903 and 14,000 tons of shale had been processed in that time. The company had refined the oil as far as kerosene, there being no demand then for anything finer. The company’s plant had cost £lOO,OOO, which was a very considerable sum for those times.
Many wild sthtements had been made about the reasons for the company closing, said Mr Willett. One was that an overseas firm had closed it down to restrict competition. He believed, however, that the chief reasons for the works closing down were the removal of the duty on imported kerosene, which was a political matter; the cost of mining, which was originally estimated at 3/6 a ton, but which ultimately ranged up to 18/- a ton; mining difficulties; the reaching of exhaustion point; and retorting difficulties. There were extensive mining difficulties because the shale was covered with a poor roof, which required timbering. It lay on coal which was subject to spontaneous combustion. The lead appeared to dip down fairly deeply both towards and away from the sea, being closest to the surface at the point where the deposit was worked. EXTENT OF DEPOSITS Laboratory yields of the Orepuki shale averaged 42 gallons of crude oil to the ton. In commercial practice that average would probably not be reached. The high percentage of sulphur in the yield was considered to be a serious bar against success in the production of gasoline, and some authorities argued that the cracking of Orepuki shale oil for high quality gasoline was practically impossible. The probable minimum quantity of shale available was 1,500,006 tons, and it might range up to a maximum of 6,500,000 tons. On the basis of mining at the rate of 100 tons a day the deposits might last 55 years, but at the rate at which it was considered most economical to operate a cracking plant, the deposits would be exhausted in six years. The Freshford deposits were estimated as being very limited in quantity, totalling about 750,000 tons. It was a high-grade shale, but the quantity was insufficient to establish an industry. The Nevis deposit was the largest in New Zealand, the possible quantity ranging from 19,000,000 tons to 1,800,000,000 tons. A lot of it would be available to open cast working. The yield was not high and the deposit was probably a border-line case from the commercial point of view. The Cambrian and Waitati deposits were too small for commercial exploitation. All five deposits broke down on some vital point on examination. Mr Willett concluded. The vast quantity available at Nevis might offset the low yield. A vote of thanks to the speaker was moved by Dr G. H. Uttley.
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Southland Times, Issue 24882, 23 October 1942, Page 3
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592SHALE DEPOSITS IN SOUTH Southland Times, Issue 24882, 23 October 1942, Page 3
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