The Rossco Block joint venture operator said the flows were achieved during cased hole production testing of the 27-9 sandstone of the Patchawarra Formation.

Rossco-1, which was drilled late last year, was cased and suspended as a potential future gas-condensate discovery well subject to further cased hole production testing.

Managing director Raymond Shaw said the Ensign Rig 5 workover rig on June 7 started testing five sandstone intervals interpreted as being hydrocarbon bearing, based on wireline geological data and engineering data at the time of drilling.

Four of these were within the Patchawarra Formation, and one within the overlying Toolachee Formation.

On June 13 and 14, the lowest sandstones were tested together – the 29-9 (2991.5–2993.2 m and 2995.2-2997.5m) and 29-7 (2978.9-2981.95 m) – during the cased hole drill stem test-1 (CHDST-1). However, no hydrocarbons flowed.

Then on June 19 and 20, the 29-1 sandstone (2915–2922m) was tested during CHDST-2 and again, no hydrocarbons flowed.

Lastly, on June 23 and 25, the two remaining sandstones – 27-9 (2792.3-2794 m) and 25-2 (2523.7m-2529.7m) – were perforated.

To date, only the 27-9 sandstone had been tested during CHDST-3. The 25-2 sandstone would be evaluated later, once production testing of the 27-9 sandstone was completed.

Shaw said although the Ensign workover rig was released last Monday, testing would continue to ascertain stabilised pressure flows and productivity of the 27-9 sandstone.

That zone had been shut in for three days in preparation for flow testing scheduled to last at least seven days.

Participants in the Rossco-1 well are operator Great Artesian (50%), Energy Investments (37.5%) and Enterprise Energy (12.5%), conditional on a commercial discovery.