The two wildcats lie in permit Vic/P47. The first to be drilled, Gilbert, has a target depth of 910m; Maclean is programmed for 770m. Each will take less than 12 days to reach total depth.

But the wells have the potential to make a significant contribution to new petroleum development in Bass Strait outside the traditional ExxonMobil/BHP Billiton production system.

On completion of its current work at the Basker-2 appraisal for Anzon/Beach Petroleum, the semi-submersible Ocean Patriot will move to the Gilbert-1 location early in October. This prospect lies immediately inshore from the Santos-owned Patricia/Baleen gas fields and the pipeline to Santos’ Marlo treatment facilities runs right across the Gilbert structure.

It is an anticlinal nose plunging to the south-west with the Tertiary-age Top Latrobe reservoir faulted against basement. Gilbert is being touted as an oil play, the theory being that oil originally trapped in structures further downdip has been displaced to the north and hopefully into the Gilbert structure.

To support this idea, geologists point to Tuna and Kipper gas fields deeper in the basin, both of which have small oil legs. The bulk of original oil in these structures could have been displaced updip to the north, passing through Baleen gas field (which has remnant oil traces) and on into the next structure, which is Gilbert.

The Gilbert Block is actually a farm-out segment in the northwest part of Vic/P47. Interests are: Lakes Oil Ltd 26%, Gippsland Offshore Petroleum 51%, Moby Oil & Gas Ltd 10%, Eagle Bay Resources NL 10% and Gravity Capital Ltd 3%.

BSOC has no direct interest in this sector of the permit, but the company will be acting as operator and drilling the well for a fee.

But at the Maclean-1 wildcat BSOC has a 40% participating interest and will be operating on behalf of Moby Oil & Gas (35%) and Eagle Bay Resources (25%).

The Maclean prospect is due east of Patricia/Baleen fields. It is located on the southern flank and downdip of the company’s Moby gas field on the large Flathead Anticline.

The original 1960s Esso/BHP Flathead-1 well drilled on the crest of this anticline found oil shows in a veneer of Tertiary-age Kingfish Formation sandstone.

Interpretation of high quality seismic data acquired in a recent 3D survey indicates the presence of a much thicker Kingfish Formation reservoir pinched out on the faulted flank of the main feature and sealed by the overlying Gurnard Formation. This pinchout or anticlinal rim play is the target for Maclean-1.

BSOC believes that the occurrence of oil shows in Flathead-1, as well as in nearby Moby-1 and Whale-1, indicates that the Flathead Anticline did receive migrating oil in the past.

The absence of amplitude anomalies over the deeper parts of the structure suggests that any petroleum found in the Maclean feature is likely to be oil rather than gas.

Both Gilbert-1 and Maclean-1 will have a single casing string and be drilled to their total depths in 121/2-inch hole. The results will be known by the end of October.