Esso Gippsland Shelf No. I, Australia's first offshore well, was drilled by Esso Exploration Australia, Inc., in the Gippsland Basin, about sixteen miles off the Ninety Mile Beach, south-eastern Victoria.
Gippsland Shelf No. 1 was spudded on 27th December, 1964, reached a total depth of 8701 feet on 31st May, 1965, and was completed as a suspended gas well on 5th June, 1965. The 268-foot drilling vessel "Glomar III" owned and operated by Global Marine Australasia pty Ltd was used to drill the well.
The well penetrated a Tertiary section to 5378 feet and an Upper Cretaceous section from 5378 feet to 8701 feet, total depth. 353 feet of gas column was logged in the top of the Eocene Latrobe Valley Coal Measures, which proved to be productive by subsequent tests. Minor hydrocarbon shows in the Upper Cretaceous section are considered to be noncommercial.
Three production tests were made through perforations opposite sandstones in the Latrobe Valley Coal Measures; one to confirm the gas-water contact and two for reservoir evaluation. On the first and lowermost test from 3809 to 3814 feet the well flowed gas at the maximum rate of 1.63 MMcf/D and fresh water at the rate of 750 barrels a day. On the other tests the maximum flow rates were 6.85 MMcf/D plus 75 barrels of consensate a day, and 5.36 MMcf/D plus 79 barrels of condensate a day.
The well was the first offshore discovery in Australia, and gave the first significant production from the Latrobe Valley Coal Measures. It was also the first occurrence of a porous sandstone member in the Gippsland Limestone; the first occurrence of porous sandstone members in the Upper Cretaceous section; and the first occurrence of a Mesozoic section younger than the Strzelecki Group in the Gippsland Basin.
A new and unknown sandstone section some 369 feet thick was encountered in the lower part of the Gippsland Limestone. The areal extent of this section is as yet unknown. Otherwise the lithology of the Tertiary sequence was as expected.
The stratigraphic drilling operation at Esso Gippsland Shelf No. 1 was subidized under the Petroleum Search Subsidy Act 1959-1964, from surface to total depth.
