Seal + Reservoir + Source, page-13

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The Amadeus Basin

Subsalt plays in the southern Amadeus Basin are of particular interest given that two thick regional salt horizons are present across wide areas of this highly structured geological terrane. Potential reservoirs below the middle Cambrian Chandler salt have yet to test positive for helium but exploration is extremely sparse.

Conversely, of the two wells to penetrate the older Proterozoic Gillen Salt, both recovered very significant helium contents in small gas flows from reservoirs directly sub-cropping this blanket salt seal.

These occurred at Magee-1 from the Heavitree Quartzite (6.2 per cent helium was recorded from a small gas flow emanating from a significant fracture in the quartzite) and also from small gas flows from fractured granite basement in Mt Kitty-1 (up to 12 per cent helium recovered).

These are extremely high concentrations by world standards and constitute an exploration success rate of 100 per cent for pre-salt helium targets in the southern Amadeus Basin. The future for additional deposits over this very large area is thus very bright.

The Magee-1 discovery (discovered and tested in 1992 by Pacific Oil and Gas Limited)

This discovery occurred in the first well and penetrated the Gillen salt and the underlying Heavitree Quartzite in the Amadeus Basin. The well flowed 63.1 thousand standard cubic feet per day (Mcfd) on test from a large fracture in the lower part of the quartzite. The flow included nitrogen, wet gas and helium (6.2 per cent).

The Mt Kitty -1 discovery – 2014

This well was 6.3 m thick and contained 4.5 m of net sand with an average porosity of 9.0 per cent.

Careful analysis of well data – only the second well to penetrate the Gillen salt – indicates the gas flows emanated from fractured granitiod rocks of the Musgrave Province, with high helium contents derived from radiogenic basement.

Progress reports from the operator (Santos) indicate a flow test at 2144 m produced 500 Mcfd before declining to 70 Mcfd after ten minutes. A second test at 2156 m produced 530 Mcfd, decreasing to 420 Mcfd after 18 minutes.

The original primary target at Mt Kitty-1 (Palmer and Ambrose, 2012) was Heavitree Quartzite, while helium/gas charged fractured basement was a secondary target, however –as a result of pinch-out –the Heavitree Quartzite was absent. The palaeo-high appears ‘bald’ of this unit which now presents as a downdip ‘halo’ play. The exact vertical extent of mobile inert basement gases into granitoid basement remains uncertain as is the nature of fracture distribution in the structure.

In a general sense, structuring in the southern Amadeus Basin was largely manifested as thrust belts generated by major crustal shortening along the northern margin of the Musgrave Basement Block during the late Neoproterozoic. Basinward, the thrust belts are generally linear but domal structures such as Mt Kitty are also common.

Seismic coverage in this terrane is extremely sparse as is the structural definition, but a multitude of Magee/Mt Kitty ‘look alike’ structures can be expected in this vast, complex structural domain. In addition to the afore-mentioned helium deposits, there are two other instances of noteworthy levels of helium in the northern portion of the Amadeus Basin