A joint venture of Santos Ltd. and Carnarvon Petroleum Ltd. has confirmed a “major” oil and gas discovery with the Dorado well, drilled in the Bedout subbasin about 160 km offshore Port Hedland, Western Australia.
The JV reported that the Dorado-2 appraisal well encountered 85 m of net reservoir in the primary Caley formation containing 40 m of net oil pay. An additional 11 m of pay was encountered in the Upper Caley sands. Initial analysis indicates this upper zone is also oil-bearing, but further study is needed to confirm this.
The oil-water contact in the well was intersected at 4,003 m measured depth.
Operator Santos said another 32 m of net pay was encountered in the underlying Bazter and Milne sandstones with no fluid contacts intersected. Both these sands are interpreted to be gas-bearing, but again, the Milne hydrocarbons will require further analysis to confirm the hydrocarbon phase.
Wireline pressure testing has confirmed that all reservoirs are in pressure communication with the equivalent intervals in Dorado-1. Wireline sampling has also recovered hydrocarbons from each reservoir. The initial indications are that the fluid compositions are like the light oils and gases found in the discovery well where condensate yields ranged from 190-245 bbl/MMcf in the Upper Calley, Crespin, and Milne formations. The yields from the Baxter in Dorado-1 were 70-90 bbl/MMcf, again similar to initial results in Dorado-2.
Dorado-2 was drilled down-dip about 2 km from the Dorado-1 discovery made in permit WA-437-P in July 2018 (OGJ Online, July 20, 2018).
Kevin Gallagher, Santos managing director and chief executive officer, said the appraisal result points to the Dorado discovery as being larger than anticipated and significantly derisks a future development project.
The reservoirs are of high quality in a shallow-water setting of about 95 m. The result upgrades prospects in the surrounding Bedout subbasin permits where acquisition of a new 3D seismic survey is under way.
Dorado-2 will be plugged as planned on completion of wireline work and the rig moved on to the nearby Rock South-1 location. It will then come back to drill a third well in the 2019 program at Dorado-3.
Santos has 80% interest with Carnarvon holding 20%.