|Location||Operator||CTP Consolidation Entity||Other JV Participants|
|ATP 909||1,254||Georgina Basin QLD||Central||100||100||–||–|
|ATP 912||2,679||Georgina Basin QLD||Central||100||100||–||–|
|EP(A) 132||9,564||Georgina Basin NT||Central||100||100||–||–|
Description and Geology
The Southern Georgina Basin comprises a succession of Neoproterozoic, Cambrian, Ordovician and Devonian carbonate and clastic sediments up to 5,000 metres in thickness deposited in a broad northwest–southeast depression. Several structural phases have shaped the basin, the most important of these events being the Petermann and the Alice Springs orogenies. The Toko Syncline formed in the later part of the Alice Springs Orogeny by northerly thrusting of the Arunta Block. The basin was extensively eroded after uplift in the east. The basin has two established Middle Cambrian source rocks, one developed at the base of the Lower Arthur Creek Formation, and the other within the Thorntonia Limestone. These source rocks are responsible for ubiquitous oil and gas shows in some 30 wells drilled in the basin. A sub-commercial gas flow of ~200 Mcfd from the Coolibah formation was recorded in the exploration well Ethabuka 1.
A primary target in the Southern Georgina Basin (SGB) is the unconventional gas resource potential of the lower Arthur Creek Formation.
The first phase of exploration commenced in 2013. Exploration activities included acquisition of 974 km of 2D seismic, followed by the drilling of two wells, Whiteley-1 and Gaudi-1.
Whiteley-1 Well, ATP 912
The Whiteley-1 unconventional gas well was drilled in July 2014. This well was the first of a two well programme of unconventional gas exploration operated by Central. The planned depth for this well was 1,920 metres but for operational reasons the well was suspended above the target section at 1,141 metres.
Gaudi-1 Well, ATP 909
The unconventional gas well, Gaudi-1, was drilled in September 2014. As with Whiteley-1, the primary objective was the Lower Arthur Creek Formation. A total of 282 metres of core were successfully retrieved from the Lower Arthur Creek Formation and Thorntonia Limestone, before the well reached a total depth of 2,430 metres in basement. Good gas shows were recorded in the Lower Arthur Creek Formation during drilling and selected core segments were placed into sealed canisters for desorption analysis, from which the adsorbed gas content of the Lower Arthur Creek Formation has been determined. A comprehensive wireline logging suite was run to TD and the well was cased and suspended. Ongoing integration of core and log data will progress the understanding of the unconventional potential of the Lower Arthur Creek Formation.
Exploration efforts have included analysis of legacy wells in conjunction with the drilling of Gaudi-1 and Whiteley-1. These studies confirm there are at least four play types operating in the SGB, being:
- Lower Arthur Creek unconventional gas target. The company aims to complete the drilling of Whiteley-1 well to better understand distribution of key unconventional reservoir parameters;
- Tight gas target, as demonstrated in Gaudi-1 where gas is reservoired in tight carbonates. The extent and variability of the play is to be determined;
- Hydro-Thermal Dolomite play: A new play has been identified, bearing a good resemblance to analogues in the US; and
- Conventional gas such as discovered in Ethabuka-1, which is a large structure requiring appraisal by flank wells to determine the extent of the gas column and reservoir distribution.