Timor Sea prospect a gem, says Finder

FINDER Exploration has joined Total securing a new block in the western Bonaparte Basin immediately to the east of AC/P60 in an area rich with production history and potential.
Timor Sea prospect a gem, says Finder Timor Sea prospect a gem, says Finder Timor Sea prospect a gem, says Finder Timor Sea prospect a gem, says Finder Timor Sea prospect a gem, says Finder

Haydn Black


Finder commercial offshore manager Craig Gumley has said the junior has already defined a "gem" of a prospect.

AC/P61 covers a mere 335sq.km and was released in the 2015 acreage release as AC15-1.

It joins Finder's existing interests in the Timor Sea: 100% of the contiguous AC/P45, AC/P55 and AC/P56 and the 20% owned AC/P52 that has been farmed out to Shell (50% and operator) and Sasol (30%).

The new Vulcan Sub-basin block has water depths between 50-350m and flanks a Jurassic depocentre with oil and gas prone source rocks.

Geoscience Australia says there is the potential for structural and stratigraphic Triassic-Jurassic, Cretaceous and Paleogene plays.

The Vulcan Sub-basin is a proven Jurassic hydrocarbon province containing the producing Montara oil field and several depleted oil fields, including the Jabiru oil field, which sits just outside AC/P61.

That field, discovered in 1983, was the first FPSO development in Australian waters, and produced more than 120 million barrels from the Jurassic Montara Formation until 2013 when PTTEP decommissioned it.

The province also includes PTTEP's Cash/Maple oil and gas accumulation, which is currently under development consideration, and several sub-economic oil and gas accumulations, including the Oliver gas-condensate field immediately to the north, the Audacious pool immediately to the east and the Tenacious and the Pengana gas accumulation to the west.

Oliver has a potential recoverable resource of 19.2 million barrels, but in 2010 PTTEP drilled the Oliver-2 appraisal well, finding an 81m gas column and has yet to release updated numbers.

PTTEP owns Oliver, Audacious and Tenacious.

Hydrocarbons at Oliver and Pengana are reservoired in the Plover and Nome formations, respectively.

AC/61 sits on the flank of the Paqualin Graben, about 100-120km from the Montara platform and the Ichthys pipeline.

The major risks in the block are the structural complexity of the Vulcan Sub-basin that has meant adequately imaging reservoir, trap and seals has historically proven challenging, although 3D seismic can help reduce the subsurface uncertainty.

There is also a risk of water washing. Both Jabiru and Tenacious showed moderate water washing, Audacious-1 showed significant water washing, however Oliver-1 showed no evidence of water washing

AC/P61 contains six wells: Douglas-1, Augustus-1, Hadrian 1, Audacious-3 and Audacious -4 and Cockell-1. The Ponderosa-1 oil shows are on its southern edge.

Augustus-1, the only well with shows within the block, was drilled on the eastern flank of the Cartier Trough by Western Mining Corporation in 1990.

It found the poor to fair reservoir quality in the Plover Formation and a 3m residual oil column.

The oil samples had different biomarker characteristics and were more mature than the source interval suggesting migration of a more deeply buried Upper Jurassic source rock to the west.

WMC considered a sidetrack, however, probability of encountering a commercial hydrocarbon accumulation updip from the location seemed "very low", and it was instead decided to plug and abandon Augustus-1.

The earlier Douglas-1 was dry, but intersected rreservoir quality sandstones in the Jurassic through Triassic-ages rocks and good source rock potential in the Echuca Shoals Formation, with some background gas below2108m immediately above the Palaeocene-Cretaceous boundary.

Finder's initial exploration targets will be the petroleum systems currently identified within the permit.

These are Tithonian fluvio-deltaic to basin floor fans sandstones of the Upper Vulcan Formation charged from Oxfordian to Kimmeridgian and Plover oil prone source rocks; the Middle Jurassic fluvio-deltaic sandstones of the Plover Formation charged from Plover Formation source rocks; the Lower Jurassic to uppermost Triassic fluvio-deltaic sandstones of the Nome Formation charged from Plover Formation source rocks; and the Upper Triassic deltaic sandstones of the Pollard Formation charged from Plover Formation source rocks.

There is already a prospect in the permit, Gem, an intra-graben Jabiru/Challis look-a-like horst block.

The prospect is mapped with closure over the Jurassic Oxfordian formation over 8sq.km with some 190m of vertical relief.

Other leads are identified within the permit, such as the Douglas Updip lead and a possible extension of the Tenacious oil field into the permit.

The permit is fully covered by the Innia 3D seismic survey, so Finder will undertake a broadband pre-stack depth migration reprocessing effort of 650sq.km to include the adjacent offset well ties from Oliver, Tenacious and Audacious.

A critical focus of the reprocessing will be using new and improved technologies such as the broadband de-ghosting, shallow water de-multiple techniques, Full Waveform Inversion or refraction tomography modelling of the near surface with the application of an amplitude variation with offset friendly Kirchhoff migration.

The techniques will be applied to improve the signal to noise ratio and gather flatness while preserving the frequency spectrum for prospect AVO screening and input into reservoir characterisation studies.

Further to the west, Finder has conducted new 3D seismic over AC/P 45 and AC/P 55 along the Browse/Bonaparte basinal edges with hydrocarbon charge de-risked by 2014 seabed sampling survey and it has a full carry in the Cronus-1 well within AC/P 52 with Shell.

Drilling of Cronus-1 will test the Montara, Plover and Nome sandstone reservoir targets with an unrisked gas-in-place high side resource estimate of 7.8 trillion cubic feet.

Cronus sits near the Argus and Prelude fields.

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