A CASE HISTORY OF ROUGH RANGE

Abstract

Rough Range No. 1 was the first well to be drilled for oil in Western Australia in the post-war period. It was spudded on September 5th, 1953. At a depth of 1100m, the well encountered a flow of oil at a rate of 500 bbls per day from the Early Cretaceous Birdrong Sandstone. This first discovery of flowing oil in Australia set off a boom in exploration for oil that rivalled the gold mining booms of the last century. The discovery well was drilled for a total of 20 months, encountering a section of Tertiary, Cretaceous, Jurassic, Permian, and Carboniferous -? Devonian rocks. By May 1955, when Rough Range No. 1 was terminated, a further seven wells had been drilled on the Rough Range Anticline and all were dry. Late in 1955, Rough Range -9 was drilled but also proved dry. Rough Range-10 was drilled less than 200m from the discovery well but only found a thin, non-commercial pay zone.

Studies of the Rough Range structure, incorporating data from all of the wells and the intense seismic mapping of the feature show that the area of closure is very small and the total accumulation could not be more than 282,000 bbls of oil in place in the reservoir.

Assuming a 30% recovery factor, the accumulation is capable of producing approximately 84,600 bbls. Of this, 16,900 bbls has already been produced in a 48-day production test of Rough Range-1 A in 1955. WAPET believes that the small remaining reserves, even at world parity pricing, are not economically viable.

Although the small accumulation at Rough Range No. 1 was a disappointment to WAPET, this first post-war oil well proved to be a "lucky break" and a big stimulus for oil exploration in Australia.