The Perth-based joint venture of Quadrant Energy Ltd. and Carnarvon Petroleum Ltd. has made an oil discovery with its Dorado-1 wildcat well in permit WA-437-P in the Bedout subbasin off northwest Western Australia.
The JV said light oil has been recovered from a gross hydrocarbon package of 96.1 m and a net pay thickness of 79.6 m in the primary objective Caley member, which has excellent reservoir characteristics.
This result was confirmed by wireline testing undertaken after the well reached a depth of 4,044 m. Porosity in the reservoir averaged 20% with a hydrocarbon saturation of 82.5%. Permeabilities of 100-1,000 md were recorded in the Caley hydrocarbon zone.
The high quality of the reservoir was reinforced by the quick time taken to obtain oil samples and the high mobility recorded when doing formation tests.
Hydrocarbon-bearing sands also have been identified in the underlying Baxter member and, at the time of the announcement, the well was still in a hydrocarbon-bearing column and had not encountered water saturated sands. The wireline logging tools have not yet been able to assess whether this is part of the same accumulation or a new accumulation of oil.
The well will now be deepened to 4,550 m to fully evaluate the Baxter sand as well as the deeper secondary targets in the Crespin and Milne sandstones. The JV said it is likely that a 7-in. liner will be set prior to drilling into the Crespin and Milne members.
Dorado-1 is being drilled by the Ensco-107 jack up drilling rig less than 20 km south and updip from the previous Roc-1/Roc-2 discovery, which has an estimated 2C resource of 332 bcf and 19 million bbl of condensate, also in the Caley interval. The well also lies south of the neighboring Phoenix South-2 gas-condensate discovery in permit WA-435-P.
The Dorado structure is defined by 3D seismic as a shale-filled canyon, which has incised into the Caley and Milne sediments creating a large trap geometry in the target levels bounded to the west, south, and east.
Predrilling estimates for the Caley Member at Dorado suggested a prospective resource of about 545 bcf of gas and 30 million bbl of condensate. A new, revised volume estimate will be issued following completion of drilling, which will be a contingent resource of oil.
The JV is keen to add resources that could be combined with the potential development of the Roc and Phoenix South discoveries.
Pre-FEED work has commenced at Roc, including detailed reservoir modelling, to determine the most appropriate development concept. All the development scenarios being considered include options for tie-back of surrounding discoveries and appraisal successes.
Quadrant has 80% interest and operatorship. Carnarvon has the remaining interest.
