McArthur Basin

The Palaeo- to Mesoproterozoic McArthur Basin contains an unmetamorphosed and relatively undeformed succession of sedimentary and minor volcanic rocks with a preserved thickness of up to 15km in the northeastern Northern Territory.

It contains elements of at least two Proterozoic petroleum systems:

  • The oldest within the Palaeoproterozoic McArthur and Nathan groups,
  • The other within the Mesoproterozoic Roper Group.

Other petroleum systems may also be present in equivalent and older groups of the basin.

Conventional and unconventional gas and oil resources have been the target of exploration in the McArthur Group within the Batten Fault Zone in the southern McArthur Basin.

Armour Energy Ltd

In 2012, Armour Energy Ltd reported gas in Cow Lagoon-1 and Glyde-1 ST1, and this was followed-up by significant oil and gas shows in Lamont Pass-3 in 2013. Glyde-1 is a shallow conventional gas accumulation within brecciated Coxco Dolostone Member (Teena Dolostone), underlying Barney Creek Formation source rocks.

The Barney Creek Formation is a significant shale gas and -oil prospect and unconventional gas is also reservoired in relatively low-permeability rocks in the Lynott Formation and Reward Dolostone.

Roper Group

Roper Group petroleum occurrences are primarily located within the Beetaloo Sub-basin, which hosts substantial shale gas resources, and which is the most advanced shale gas play in the Northern Territory.

Reports

A more detailed description of the petroleum potential of the McArthur Basin can be found in NTGS Report 22.

There is extensive seismic coverage over the Beetaloo Sub-basin and relatively sparse over the broader McArthur Basin and across to outcropping age-equivalent stratigraphy in the Birrindudu Basin. Petroleum wells are also focussed on the Mesoproterozoic Roper Group stratigraphy within the Beetaloo Sub-basin and the Palaeoproterozoic McArthur Group stratigraphy across the McArthur Basin. Open file petroleum company reports and all NTGS data and information on the McArthur Basin is available from the GEMIS website.

The sub-surface Beetaloo Sub-basin represents a structural sub-basin of the McArthur Basin that preserves the thickest sequences of highly prospective Mesoproterozoic Roper Group stratigraphy. The Sub-basin is the Northern Territory’s premier shale gas play, with substantial shale gas resources in place.

Drilling

The most prospective shale units in the Roper Group occur within the Velkerri and Kyalla formations. Drilling of the middle Velkerri Formation has demonstrated the consistent presence of gas saturated, quartz-rich shale source rocks that are mature for gas over extensive areas, and which appear to meet all of the physical and chemical parameters for a successful shale gas play (see Revie 2017). The shallower Kyalla Formation also has high potential as a productive shale play, with large areas within the wet gas window.

Wells

Wells drilled to date by industry indicate a P50 Gas-In-Place Resource for the Velkerri B-shale alone of at least 500 Tcf, with the additional potential for liquids-rich gas in the basin. Following the successful hydraulic fracturing and production testing of the Amungee NW-1H well in 2016 (see Close et al 2017), Origin Energy announced a 2C Contingent Gas Resource Estimate for the Velkerri B-shale pool in 2017. With the 2018 lifting of the moratorium of hydraulic fracturing in the Northern Territory, shale gas exploration and appraisal of the sub-basin recommenced in 2019.

The Beetaloo Sub-basin has the most extensive seismic coverage of all Northern Territory onshore basins and has had 20 exploration wells drilled. Open file petroleum company reports and all NTGS data and information on the Beetaloo Sub-basin can be found on the GEMIS website.