Rossco-1 spuded on 14 December 2005 and reached total depth of 3050 m within the Tirrawarra Formation on 29 December 2005. Independent interpretation of wire-line logs and pressure data confirmed the likely presence of several combined gas bearing zones and, following a mechanical failure during DST #1, it was decided that the well be cased and suspended for testing during a future CHPT. Rossco-1 was operated by Great Artesian and 25% funded by Traditional Oil Pty Ltd, which will retain a 12.5% interest in any subsequent production licence.
CHPT commenced on 7 June 2006 with a program to test five sandstone intervals. This testing commenced on 7 June 2006 using Ensign Work-over Rig #5. The program entailed testing of five sandstone intervals interpreted as being hydrocarbon bearing on the basis of wireline geological data and engineering data at the time of drilling. Four of these sandstones lie within the Patchawarra Formation, and one within the overlying Toolachee Formation.
The lowermost two 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) on the 13 and 14 June 2006 during Cased Hole Drill Stem #1 (CHDST #1). No hydrocarbons flowed during this test. The 29-1 sandstone (2915 – 2922 m) was tested on 19 and 20 June during CHDST #2. Again no hydrocarbons flowed during this test. The two remaining sandstones 27-9 (2792.3-2794 m) and 25-2 (2523.7-2529.7m) were perforated on 23 and 25 June 2006. To-date only the 27-9 sandstone has been tested, during CHDST #3. The 25-2 sandstone will be evaluated at a later date, once production testing of the 27-9 sandstone is completed. The 27-9 sandstone has produced gas at a rate of approximately 4.2 million cubic feet per day with associated condensate at between 100 and 150 barrels per day. Subsequently the well was shut in for pressure analysis and extended flow testing. The Ensign Workover Rig #5 was released from site on 26 June 2006; however, testing will continue to ascertain stabilized pressure flows and productivity of the 27-9 sandstone. As at the end of June 2006 the well had been shut in for 3 days prior to at least a 7 day flow period.
Testing had to be temporarily abandoned due to wet weather and will resume in conjunction with testing programs for adjacent offset wells.