Applegate became one of the founders of UK-based Overseas Energy Holdings, a junior that is one of the few explorers to ever drill a dedicated petroleum well in Tasmania, and the company with the deepest ever well.

OEH has flown under the radar for most of its life, but the company remains resolute that it wants to push ahead with its exploration plans in northern Tasmania as long as it can.

Founding CEO Michael Roberts told Energy News Applegate became convinced of the oil potential on his frequent visits, and that led to the formation of OEH, where he was the company's geologist.

"As one of the UK's leading practical geologists his understanding of the geology from bore holes he drilled and other evidence led him to that belief," Roberts said.

Roberts admits OEH is an outlier, and that a positive view of the prospectivity of Tasmania for hydrocarbons is not widely shared among Australian geologists, and there have been just a handful of permits for exploration over the past few decades as proof of that.

"In world oil terms the proposition is simple: there is a source kitchen and a producing basin in the Bass Strait," Roberts explained.

"To the north lie the onshore Gippsland and Otway basins [that] have produced a significant portion of Australia's oil and gas over the last 40 or so years.

"Oil is normally found up-dip from the producing basins and so while the north side of the basin has been explored, onshore Tasmania, which is the southern lip of the basin, has not."

OEH's objective is to test that proposition.

"Migration of the oil is expected in the older sedimentary rocks that lie beneath the dolerite but, due to differential lifting and fracturing, [which] are thought to be aligned with the younger rocks in which the Bass Strait hydrocarbons have been generated and are migrating," Roberts said.

So, OEH was established to secure and explore SEL5/2005, drilling its first well, Westwood-1, in late 2009.

Roberts says Westwood-1 was the first real wildcat oil and gas exploration in Tasmania.

The drilling, 12.5km southwest of Launceston in the northeastern portion of the Longford Sub-basin, had a target depth of 2000m, terminating in the Late Carboniferous Stockers Formation, however drilling ceased at 1670m.

OEH says the directional drilling sub-contractor, Hunt Minerals and Energy, failed to maintain control of the drill bit and the well deviated off-course due to an unexpected and very sharply dipping fault plane.

"The problems of drilling dolerite and the extremely hard metamorphic rocks that we believe form the cap over the oil results in a technical challenge and high well costs," Roberts explained.

"The rig employed at Westwood-1 was not powerful enough to cope with the demands put on it by the strata which it was drilling.

"So, the main lessons of Westwood-1 is that there is exactly the type of seal rock in place that would secure an oil field and that a much more powerful rig is required to penetrate to the target depths."

Since completing the well OEH has conducted a number of small gravity surveys and the 42km Devonport 2D seismic survey in 2012, spending more than $US10 million to date.

The company then completed some seismic reinterpretation, and has since been undertaking geological and geophysical work to improve the quality of the data, but it has been hampered by the lack of capital.

It was a tough ask to raise the cash to drill just one of the three proposed wells, and the lack of encouragement has made it that much tougher.

Re-entry and deepening of Westwood-1 remains on the wishlist, and it is one of the top five sites that would be drilled if OEH had the funds.

Roberts stressed that OEH was not looking primarily for unconventional targets, although the rich Tasmanite shale source rocks is in the area, so fraccing would not be an issue, and said the feeling back in 2010 generally supported the drilling at Westwood for the potential benefits it could bring.

SEL5/2005 expires soon and the company intends to renew those high-graded areas of the existing licence and apply for smaller licences.

Mineral Resources Tasmania rules mean OEH cannot simply ask for a further extension of the existing licence, but it can peg out new areas.

OEH's current investors remain interested in the area, but doors remain generally shut to investment, Roberts said.

"We continue to mount an investor program with a specialist adviser and once the new licences are confirmed we hope that we will be able to attract new funding, although events in the global oil market will be influential," Roberts told Energy News.

Ideally the company is seeking up to $US20 million for a three well program and further seismic.

A number of other prospective sites have been defined including the 20MMbbl or 34Bcf Bass Highway-1 and the 30MMbbl/37Bcf Westbury prospect, near Davenport and Exton respectively.

A third location, Weymouth Road-1, has potential for 30MMbbl of oil or 45Bcf of gas.