Rick Wilkinson
OGJ correspondent
MELBOURNE, Dec. 7 -- Origin Energy Ltd., Sydney, has made a gas discovery with its Trefoil-1 wildcat on Bass basin Permit T/18P off Tasmania. It's one of two recent gas finds in Bass Strait.
In Trefoil-1, wireline logs, formation testing, and sampling confirmed 50 m of net gas pay over eight zones in the well in the Eastern View Coal Measures formation productive in Origin's nearby Yolla field.
Analysis so far indicates high-quality gas with a carbon dioxide content of about 3%, which is less than one sixth of the CO2 level at Yolla. Liquids content is 50-100 bbl/MMcf of gas.
Initial estimates suggest an in situ resource of 100-300 bcf of gas and 7-21 million bbl of associated liquids.
Origin will test production over two intervals: 3,040-47 m and 3,141-50 m. The company says these are across lower-quality reservoir sands.
In addition to Yolla field, which is nearing completion as part of the BassGas project to pipe gas to onshore facilities in Victoria, Origin has a smaller gas find in the White Ibis vicinity. Good results from Trefoil could see it developed along with White Ibis, with both fields' production funneled through Yolla and the BassGas system.
Holding interests in Trefoil-White Ibis-Yolla are Origin 41.4%, Sydney-based Australian Worldwide Exploration Ltd. 22.6%, the UK's CalEnergy Gas (Aust) Ltd. 23.5%, and Mitsui subsidiary Wandoo Petroleum Pty. Ltd. 12.5%.
Apache group discovery
Apache Energy Ltd., Perth, and partners made the second significant gas find in Bass Strait with its Longtom-2 appraisal well on Gippsland basin Permit Vic/P54 to the north of the Esso-BHP Billiton main producing area.
Longtom-2 flowed gas on test at the rate of 18-19 MMcfd gas from intervals 2,184-2,192.5 m deep and 2,212.5-2,243.5 m. The gas flowed through a 1 in. choke for 11 hr.
This is the first significant gas flow from the Tertiary Emperor formation in the Gippsland basin, and it confirms the potential of this zone, which had been a major concern before drilling.
The Longtom-2 well appraises an old Esso-BHP Petroleum Pty Ltd. discovery from the 1980s that was then considered noncommercial.
Apache is revisiting the well in light of recently more-favorable economics for gas production in southeastern Australia.
The well is being prepared for a production test of a separate zone in the reservoir section.
Apache holds a 62.5% interest, and Nexus Energy Ltd., Melbourne, 37.5%.
