From Australia to Argentina. From Indonesia to West Africa.
Take four compelling and distinct exploration areas around the world. Combine descriptions in one session. And present at AAPG’s upcoming International Conference and Exhibition in Oman. ICE 2024 runs from Sept. 30 to Oct. 2 at the Oman Convention and Exhibition Center in Muscat.
The oral presentation session, “Global Exploration Concepts II” on Oct. 1 offers a look at four diverse play areas:
- An unconventional resources play in northern Australia, with potential that’s been favorably compared to the Marcellus Shale
- A prospective area offshore Argentina with geological origins that mirror counterparts off West Africa
- A newly developed sub-thrust fault play in the proven onshore Kutai Basin area in Indonesian Borneo (Kalimantan)
- Prospects in the Namibe Basin offshore Angola and Namibia, which is probably the hottest and most-watched offshore exploration region in the world today
Velkerri Formation of Northern Australia
Alan Collins is professor of Earth sciences at the University of Adelaide and leads the school’s Tectonics and Earth Systems Group. He will present “A Very Unconventional Hydrocarbon Play: The Mesoproterozoic Velkerri Formation of Northern Australia” at ICE ‘24.
“The Beetaloo sub-basin and the Velkerri formation within it is incredible – it is by far the most unconventional field on the planet, in that the source shales are 1.4 billion years old,” Collins said.
“Despite this, the resource is huge and pressures look good … The companies that are leading here, Tamboran (Resources) and Empire (Energy), are aiming for production next year,” he noted.
This Beetaloo-Velkerri play could extend the unconventional resources revolution to a completely new area, finally pushing significant shale production beyond the United States and Argentina’s Vaca Muerta.
The Velkerri formation makes up the major deepwater facies of the Roper Group in the McArthur Basin in Australia’s Northern Territory, bordering the Gulf of Carpentaria. According to published research, it covers anywhere from 80,000 to 120,000 square kilometers and is up to 800-meters thick. Analysis of Velkerri oil content indicates organics from bacteria and primitive algae deposited in a marine environment.
Exploration for conventional oil in structural and stratigraphic traps in the McArthur Basin dates back to the 1980s. Numerous vertical wells showed the presence of hydrocarbons, but no commercial discoveries were reported.
Empire Energy has drilled a series of increasingly successful wells in the play with longer laterals, up to 2,640 meters, which the company claimed as an Australian record.
Examination of the Beetaloo-Velkerri as a potential petroleum province made its way into the AAPG Bulletin two years ago. At that time, it was considered an oil and gas shale play with somewhere between 8-118 trillion cubic feet of natural gas in place.
Later, that gas appraisal was increased a bit – to 500 trillion cubic feet, with more than 100 Tcf of recoverable dry gas. Collins said the new estimate was just a stab at a top number.
“The gas assessment is really because the source rock is so large and the extent of it is not well known,” he explained.
Potential for this Australian shale play has attracted the interest and participation of shale industry executives from the United States. That’s one cause for recent excitement. The other comes from new analysis of the Velkerri’s stacked pay zones. Collins said the Precambrian shale play is unusual, but hardly unique.
“I will be talking about the nature of the basin, what the tectonic geography of the basin was 1.4 billion years ago, what may have caused the bloom of bacteria that formed the source of the hydrocarbons and, also, how there are many other basins like this around the world that have never had a drill hole into them,” he said.
North Argentina Basin
Exploration drilling in the offshore CAN-100 block of the North Argentina Basin began earlier this year and immediately hit a hiccup. Equinor said its first operated ultra-deep test in the basin, the Argerich I, came up dry with no meaningful show of hydrocarbons.
Drilled to a reported depth of more than 1,500 meters, the Argerich well targeted Cretaceous reservoir potential. CAN-100 is one of several offshore exploration blocks southeast of Buenos Aires, in the northern sector of the Argentine Basin.
The presentation “North Argentina Basin (CAN): A New Frontier Offshore Basin Arising in the South Atlantic Margin” at ICE ‘24 examines shallow-water and deepwater realms in the Argentine continental margin.
Comparisons of the northern basin to West Africa geology offshore Angola and Namibia – especially the potential presence of Barremian to Aptian source rocks and Turonian age fluvial and littoral reservoirs – have generated excitement over the area’s exploration promise.
“The geological model is significantly influenced by analogies with Africa,” noted Luis Stinco, associate director of technical research for S&P Global Commodity Insights.
Recent discovery successes offshore Namibia, especially in the Orange Basin, prompted Equinor, Shell and YPF to begin an offshore program off Argentina, Stinco said.
Kutai Basin of Indonesia
Pertamina’s Sanga Sanga working area consists of seven onshore oil and gas fields in the Kutai Basin in eastern Borneo. This area has produced hydrocarbons for more than 50 years, with more than 1,000 wells to date.
“Success Story of Sub-Thrust Fault Play from New Era Exploration Phase in Sanga Sanga Area, Kutai Basin, East Kalimantan, Indonesia,” describes an effort to revitalize and extend output through a new development concept.
The company proposed a sub-thrust play based on the combination of faulting due to delta inversion and the possibility of sand-into-shale facies juxtaposition as a lateral seal. A mixture of coals and shales, including several rich organic shales, comprise the reservoir source rocks.
Asnanto Putranto, exploration geologist for Pertamina Hulu Sanga Sanga, said the most important facet of the area’s geology is “the relation between time of hydrocarbon migration and the juxtaposition of sand to shale, due to the thrust system during Miocene to Pliocene.”
Earlier drilling to test the sub-thrust play concept led to a series of dry wells without any show of hydrocarbon accumulation. But new modelling revealed a previously overlooked play sweet spot, with a promising gas discovery and oil indication.
Putranto said the new development concept “is very important because it acts as a play opener in this area. Also, several prospects and leads have been identified.”
Namibe Basin of Namibia
The northernmost of a series of highly prospective basins offshore Namibia, the frontier Namibe Basin covers more than 100,000 square kilometers off southern Angola and northern Namibia, north of the Walvis Ridge.
Recently, Atlantic Margin exploration has targeted post-rift deepwater clastic reservoirs with underlying mature Upper Cretaceous marine source rocks. Namibe Basin mapping shows extensive marine source facies with stacked, overlying clastic fairways.
“The frontier basin offers a wide range of exploration targets that will likely be drilled over the coming years. Target plays include the pre-salt in syn-rift and sag sections and post-salt/post-rift deep marine plays, analogous to those successfully recently explored and exploited in other areas of the South Atlantic,” said Matthew Plummer, principal geoscientist-AMME for geophysical and energy data company TGS.
“ExxonMobil’s Arcturus-1 well, currently drilling, is being closely watched prior to the drilling of three further wells planned in the Angolan sector of the basin by industry peers. The Arcturus-1 well, should it succeed in proving a petroleum system, could open a play with significant follow-on potential,” Plummer added.
The ICE ‘24 presentation “Hydrocarbon Potential of West Africa’s Final Frontier: The Namibe Basin” examines this almost unexplored area. Extensive broadband 3-D seismic has now been acquired in both the northern and southern sectors of the basin, revealing a wide range of exploration possibilities.
“In my talk I currently plan to highlight potential targets, showcasing the geology revealed by the widespread 3-D data and relating this to similar proven plays elsewhere in the South Atlantic,” Plummer said.