L032 Haddon Downs experimental seismic survey, SA, 1957

Brief description

An experimental seismic survey was conducted at Haddon Downs, South Australia, during Octobor and November.1957. The area lies within the Eromanga Sub-basin of the Great Artesian Basin, and at least 5,500 feet of Mesozoic section are known to exist there, part of which is of a marine facies. Preliminary reconnaissance work by geologists of Santos Ltd. which holds an Oil Prospecting Licence over the area, revealed some large anticlines on the surface. The Company has already completed a limited amount of gravity work which gives promise of supplying useful information on both regional and detailed subsurface structure. Two important refractors were recorded which may be useful for semi-regional mapping. A refractor of velocity 10,250 ft/sec. was recorded from a depth of about 2,700 feet, and this may represent the top of the marine Cretaceous section. The second refractor of velocity 17,000 ft/sec. and aidoroximate depth 7,250 feet may be just below the base of the Mesozoic section. Large multiple geophone arrays and pattern shots were needed to obtain good quality reflections over most of the area, except when shooting on the alluvial plains of the larger creeks. The sedimentary section was shown to be at least 8,000 feet and possibly 16,000 feet thick, The base of the Mesozoic section is interpreted as being 7,250 feet deep on the refraction traverse and 8,600 feet at the south-east end of the reflecta.on traverse. The rest of the section probably consists of Palaeozoic sediments. If so, the high velocity (17,000 ft/sec.) suggests that a dense elastic or crystalline limestone is probably present near the top of them. The structure of the Mesozoic section is subhorizontal, but there may be minor structures with dips less than 1 degree which correlate with the surface structures.

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Maintenance and Update Frequency: asNeeded

Statement: From September 23rd to November 29th, 1957, the Seismic Group of the Bureau of Mineral Resources, Geology and Geophysics conducted an experimental seismic survey in the Haddon Downs area of the north-east of South Australia.The survey was requested jointly by the South Australian Mines Department and Santos Ltd, the latter company holding an Oil Exploration Licence covering the area. The request followed an increasing interest in this area when a preliminary geological reconnaissanoe carried out by Santos revealed that anticlinal structures of considerable size existed there. It is known that the Mesozoie secton is at least 5,50 feet thick, part of which consists of marine shales, The possibility of oil having accumulated in these structures warranted their further investigation. Firstly, the work was of an experimental nature to assist Santos in determining what success might be expected from a subsequent large scale seismic survey to locate a suitable drilling target. Secondly, it was hoped to learn something of the subsurface geology of the area from the survey.