Llanberis' unfinished business

THERE'S yet more evidence of a modest resurgence of interest in the Gippsland Basin, with start-up Llanberis Energy being awarded a wildcat block, VIC/P71, on the unloved Southern Platform.
Llanberis' unfinished business Llanberis' unfinished business Llanberis' unfinished business Llanberis' unfinished business Llanberis' unfinished business

Llanberis, which was founded by explorationists John Mebberson and Chris Carty, is a vehicle developed to continue an exploration program that was truncated in 2013 when Larus Energy surrendered the permits to focus on Papua New Guinea.

They believe that since the Barracouta discovery in 1965, that people have been looking for the easy oil and neglecting what they is the next major oil and gas region in Australia.

They first started looking at the Southern Platform of the Gippsland Basin more than a decade ago when with Drillsearch Energy, back when Carty was the junior's technical director, but a change in direction under Brad Lingo saw the permits sold to Larus for $700,000. Larus later merged with Newport Energy to explore PNG.

The three former permits covered around 8300sq.km of the Bass Strait, straddling the Victorian/Tasmanian border.

Work to date involved reprocessing more than 2000km of vintage 2D seismic data to delineate the exploration play and identify potential leads.

That led to the identification of a series of anomalous high amplitude reflections in the shallow section near the basin margin in the former T/46P, which Drillsearch considered was a Hydrocarbon-Related Diagenetic Zone along the edge of the Bassian Rise.

That makes a convincing argument that oil migrated out of the Kingfish source kitchen and out up to the Bassian Rise, and that the orthodox view there was "just one big sandy beach heading up to the Bassian Rise" were incorrect and that hydrocarbons have migrated through the area as the HRDZ indicates hydrocarbon leakage.

Migration

Migration into the Southern Platform is, for many, the first thing that kills interest in the area, because Esso (now ExxonMobil) and others have had no luck in the area Carty, told Energy News.

"We don't regard the lack of shows as evidence that there is no oil that has migrated out to the southern platform," he said.

The former targets have been remapped and all the wells appear to have failed to intersect valid traps, and so the prior drilling has not damaged the prospectivity of the new block.

"Exploration in the rest of the basin shows that the Latrobe sands are so clean there are no traces of hydrocarbons below the oil water contract," he said.

"It would defy the laws of physics for oil and gas not to have migrated up onto the southern platform of the Gippsland Basin.

"Just common-sense says that it has to have gone there. There is no evidence of seeps or leakage at the edges of the basin and hence the hydrocarbons must still be trapped there somewhere.

"We have picked this block as the best of the three we had, in this whole prospective southern area.

"We are focusing on an area that has some structural nosing that allows the migration to focus, and it is closest to Kingfish."

The one billion barrel Kingfish field, which is the largest in the Bass Strait, is just 30-60km away.

He said if oil is proven in the southern side of the basin it would open up the whole area.

That kind of thinking has been successful elsewhere.

The western flank of the Cooper Basin was written off by Santos, and it wasn't until companies such as Beach Energy and Great Artesian Oil & Gas started looking for oil beyond the Permian edge that the Jurassic fairway was proven, and it is now the exploration focus.

Aside from the overlooked nature of the area, Llanberis is not attempting to re-invent the wheel.

"We have a couple of different styles of prospect, one of which is the straight four-way dip closure at the Top Latrobe," Carty said.

Mebberson explained: "The Latrobe Group reservoir is too high in quality to leave any hydrocarbon shows outside a valid trap and the Lakes Entrance Formation regional seal persists to the basin margin, where it onlaps basement."

Work to date has highlighted a portfolio of structural and stratigraphic trap Top Latrobe and early Eocene prospects and leads, typically pinch-out plays and fourway dip closures, some of which are capable of containing billions of barrels of oil or trillions of cubic feet of gas.

The range of leads range from just 5MMbbl of oil-in-place up to 700MMbbl OIP in Tasmanian waters, south of VIC/P71.

All the leads in VIC/P71 can be drilled with a jack-up rig.

Llanberis now needs to raise money to shoot a planned 3D seismic survey, which is the largest commitment in the primary term for the 1960sq.km block, which covers a larger area than the former VIC/P64.

The proposed 550sq.km 3D survey, which will likely be conducted with others in the Gippsland when a vessel becomes available, will be split over the main four-way dip closure and a basement high where there appears to be a potential stratigraphic trap.

"In the rest of the area there is a big embayment, which was the type of trap that Esso was trying to drill back in the 1960s, but that requires serious 3D because of the basement topography, so we are saving that for phase two," Carty said.

The blocks have a handful of nearby wells: Mudskipper-1 was drilled right on the edge of VIC/P71, while Pisces-1 was drilled just to the west, and Mullet-1 just to the south.

Mullet-1 was drilled by Esso 1969 66km from Kingfish-3 and was a duster.

Pisces-1 was drilled by Union Texas Australia and its partners in 1983. While the well proved to be dry, probably due to the lack of adequate vertical seal, the JV's structural-stratigraphic model was essentially vindicated.

Mudskipper-1 was drilled by Petrofina in 1990 and plugged and abandoned as a dry hole. No tests were undertaken, however the report submitted by the operator was considered to be poor and did not include results, lithology or geology.

To the north of Llanberis is VIC/P70 where US-based Liberty Energy Corporation has defined the giant Dory gas prospect on the Central Platform, a large Top Latrobe structural closure that is a lookalike to the 4.4 trillion cubic feet Pluto discovery made by Woodside Petroleum on the North West Shelf.

VIC/P70 also contains the Archer-1 Intra-Latrobe oil discoveries and multiple Golden Beach gas discoveries Anemone-1 (120PJ and 14MMbbl), Angler-1 (140PJ and 6MMbbL) and Archer (155PJ and 8MMbbl oil, with untested upside in Archer Deep and other follow-up targets.

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