Udacha-1, an exploration well, was drilled to test a faulted anticlinal structure on the western margin of the Patchawarra Trough, about 12km northwest of the Moonanga gasfield and 17km east of the Sellicks Oilfield. The structure straddles the PEL 106 and PEL 91 boundary and the actual surface location of the well is in PEL 91 as this is the optimum position to address the play.
The primary objective of the well was the Patchawarra Formation (gas and/or oil) and had secondary potential in the Toolachee and Epsilon formations and the Tirrawarra Sandstone.
Udacha-1 spudded on the 11th January 2005 (11:30 hrs). TD was reached at 08:00 hrs on 4th February 2006. Two inflate straddle drill stem tests were attempted after acquiring wireline logs. DST-1 was conducted over the Patchawarra Formation but was a misrun due to tool malfunction. The test was repeated over the Patchawarra Formation as DST-1A resulting in gas to surface after 20 minutes and recovering 360m of water cushion from the drill string. The final flow after a 90 min flow period was recorded as 0.5 MMscfd. Samples collected during the reversal phase comprised very slightly mud cut water with a thin oily surface film exhibiting a strong petroliferous odour.
Udacha-1 was cased and suspended as a new field gas discovery and the rig released on 11th February 2006 at 03:30 hours. Development options are under consideration for the Udacha Gasfield.