Georgina Basin

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This page is currently being authored by a student at the University of Oklahoma. This page will be complete by Dec. 15, 2021.

The Georgina Basin, a large basin that spans across the Northern Territory and Queensland in northern Australia. It is approximately 330 000 km shown in Figure 1. [1] It is prospective for both petroleum and mineral resources. In the southern Georgina Basin, petroleum prospectively is associated with a thick Cambro-Ordovician succession of marine carbonates that host several prospective source rocks with multiple oil and gas shows.[2] With being in Northern Australia, heavy rainfall from December to March can isolate road network and restrict access to rigs.

History of the Georgina Basin

The basins are under-explored by any standard with most serious exploration being undertaken in the 1960s and 1970s. Regional coverage of seismic data is available to enable an assessment of the potential regional geological setting. While only 29 wells drilled from 1961-1991, the number told has only increased to 40 wells drilled, and most of these wells are in the southern region. The Georgina Basin is a Neoproterozoic to Palaeozoic basin which formed on a basement comprising three major Proterozoic blocks, the Arunta Complex, the Mount Isa Inlier and the ‘Aljawarra Craton’.[3] Barka Energy and Resources is currently a big player in this region as well as Hess Corporation and PetroFrontier Corp. [4] Only vertical wells had been drilled up to that point because Australian companies have not had the technology to do anything else until North American companies with the technology came to the Georgina Basin and started drilling. [4]

Petroleum System

The Georgina Basin is the most prospective undeveloped onshore petroleum province in the Northern Territory, particularly in the southern part of the basin. The Northern region has not been explored, this region has shown oil and gas prospects are not there. Most previous petroleum exploration has focused on depocentres on the southern margin, now marked by the Dulcie Syncline and Toko Syncline. Shown in Figure 2, the key source rock units are in the middle Cambrian Narpa Group: the Thorntonia Limestone, the Arthur Creek Formation and, to a lesser extent, the Chabalowe Formation. The Georgina Basin is a broad Neoproter-ozoic to Paleozoic intracratonic sedimentary basin that over-lies the North Australian Craton in north central.[2] This basin was formed after the supercontinent Rodinia broke apart. This would explain the Cambrian marine shales as we see lots of those in North America where Australia was believed to be before the plates moved.

Figure 2: The formations in the southern region of this basin http://www.mdcampbell.com/QldPetroleumExplorNov2006.pdf

Seal/Trap

Anticlinal traps occur adjacent to the Toomba Fault and in the Burke River Structural Belt. Stratigraphic traps are likely where the carbonate units thin to the north-west in the Toko Syncline area and a shelf-to-slope transition may occur.[5] Siltstones and mudstones of the Mithaka and Nora Formations are suitable cap rocks in the Toko Syncline. Within carbonate units, zones lacking in permeability may occur locally to form effective seals. In the Burke River Structural Belt, the fine-grained units such as the Chatsworth Limestone lack permeability and would be good cap rocks.[5]

Source Rock/Migration/Reservoir

There are three aquifer types in the Georgina Basin — sandstones, fractured reservoirs and carbonate reservoirs. The Carlo Sandstone is the best reservoir but is also a major aquifer. Porosities and permeabilities are generally very low in carbonate rocks but are higher in some dolomites. Vugular porosity in dolomites offers the best chance of carbonate reservoirs with the Ninmaroo and Kelly Creek Formations and Thorntonia Limestone. There are also oolitic sedimentary rocks and interbedded sandstones in the carbonates that contain porosity. Fracture porosity is another possibility but the prediction of its distribution is difficult.[5]

Arthur Creek "Hot Shales"

Figure 3: Bakken vs. Arthur Creek "Hot Shales" shows the similarities between both these basins leading to believe finding the shale in the Georgina Basin will produce massive amounts oil and gas. https://www.searchanddiscovery.com/pdfz/documents/2010/80125bennett/ndx_bennett.pdf.html

Compared to the “Bakken Style Oil Shale” in the Northern part of North America (Montana up to Canada). The Bakken Oil Shale favorably produces over 4.7 million barrels of oil a year. Due to this comparison shown in Figure 3, the Arthur Creek “Hot Shale” has become one of the most wanted places to be drilling. Between 20m and 100m thick, the shale has been estimated to produce possibly 76.65 billion barrels of oil. This is a Middle Cambrian coarsening-upward sequence comprised of sands/silts, shales, dolomites and “hot shale.” Mostly found in the Toko and Dulcie Syncline and on the southern side of the basin.[4]

Toko Syncline

Located in the Simpson Desert the Toko Syncline, shown in Figure 4 has Palaeozoic sediments progressively thicken in a south-southeasterly direction, rarely exceeding 400 metres in the northern half of the basin and becoming significantly thicker. In the deeper part of the Toko Syncline, maturity for oil is reached in the mid-Ordovician, and that the Middle Cambrian was still in the gas generation zone. The time of peak hydrocarbon generation could not be determined. This considered that the Georgina Limestone in the northern Toko Syncline was marginally mature to mature and of poor to fair organic richness.[5] The Toko Syncline is considered by oil companies as having good potential for hydrocarbon discoveries due to the Arthur Creek Hot Shales but the remote location and lack of infrastructure has discouraged exploration of the major structures along the syncline. Most companies that drill their wells are in this area.

Figure 4: Shows the location and the big players of the Toko and Dulcie Syncline Locations https://riscadvisory.com/wp-content/uploads/2019/04/RISC_Good_Oil_2015_Georgina_Basin_Steve_Newman.pdf

Future of the Georgina Basin

The Southern Georgina Basin in the Northern Territory represents one of the few remaining virtually unexplored onshore oil and gas basins in the world. Yet the rewards are potentially vast to the company that threads the needle in the Basin.[4] Hydrocarbon generation has occurred in the Georgina Basin and overmaturity has not been reached. Traps, reservoirs and seals are present.[5] There is still much to explore in this basin as there is still lots to discover in this basin in the Southern region.

Petroleum and Facility Engineering

In the past, only vertical wells had been drilled up because Australian companies have not had the technology to do anything else until North American companies with the technology came to the Georgina Basin and started drilling, but when the North American companies came to explore this basin they brought along their technology of horizontal drilling. [4] This basin is an incredibly under explored with lots of great potential to find oil and gas.

References

  1. “Georgina Basin.” Northern Territory Government, December 5, 2006. [1]
  2. 2.0 2.1 Tenthorey , E., and B. Ayling. “Geomechanical Evaluation of a Middle Cambrian Unconventional Oil and Gas Play in the Southern Georgina Basin, Northern Australia.” Taylor & Francis, December 9, 2020. [2]
  3. GJ, Ambrose, and Putnam PE. “Abstract: Carbonate Ramp Facies and Oil Plays in the Middle-Late Cambrian, Southern Georgina Basin, Australia.” AAPG Datapages/Archives. Petroleum Exploration Society of Australia (PESA), January 1, 1970. [3]
  4. 4.0 4.1 4.2 4.3 4.4 McCrea, Andrew. “Baraka Energy & Resources: Bakken Style Oil Shale Play Goes down under in Southern Georgina Basin.” Proactiveinvestors UK, May 17, 2011. [4]
  5. 5.0 5.1 5.2 5.3 5.4 “Adavale and Georgina Basins Opportunities 2007.” Queensland Opportunities for petroleum exploration 2007 Geological assessment for potential tenderers. The State of Queensland (Department of Mines and Energy) , November 2006. [5]

[1] [2] [3]

  1. Howard, Peter F. “Exploration for Phosphorite in Australia; a Case History.” Economic Geology. GeoScienceWorld, 1972. [6]
  2. Greene, David C. “Neoproterozoic Rifting in the Southern Georgina Basin, CentralAustralia: Implications for Reconstructing Australia in Rodinia.” Advancing Earth and Space Science, September 17, 2010. [7]
  3. Icons Atlas.” AUS - Georgina Basin. Accessed December 1, 2021. [8]