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Last Thursday, I spoke in the AAPG Academy Webinar on petroleum superbasins. I’ll share some key highlights in this edition, but if you’d like to receive a recording of the event, register here.
Let’s jump in!
Rasoul Sorkhabi
Editor, Core Elements
Back to Shale Gas: Stories from Australia and Pakistan
Deposition of the Velkerri striped shale in northern Australia – the world’s oldest shale gas (source: AAPG Bulletin, June 2026)
The U.S. shale revolution began with shale gas. The June issue ofAAPG Bulletin contains interesting studies of shale gas, each paper discussing particular aspects of these important hydrocarbon plays.
The Velkerri Formation dates to Mesoproterozoic times (about 1,500–14,000 Ma), making it the world’s oldest shale gas formation.
It is part of the Roper Group, consisting of interbedded sandstone and shale formations.
It is located in the Beetaloo Sub-basin of the McArthur Basin in Northern Australia.
Exploration history:
The McArthur Basin has a long history of exploration for minerals, conventional oil, and shale gas.
Amoco initiated petroleum exploration in the basin in 1984.
The Falcon Company investigated the shale gas potential of the Velkerri Formation in 2011 and drilled the first hydraulic fracture-stimulated well in the basin.
What they did:
The researchers used data from six drill cores that intercepted the Amungee Member of the Velkerri Formation.
The data came from core photographs, thin sections, and well logs.
What they found:
The dark-light-striped appearance of the Amungee Shale reflects alternating layers (millimeters to centimeters) of variable total organic carbon (TOC) contents (more than four percent for dark-colored layers and less than two percent for light-colored layers).
TOC-rich layers often show lenticular fabric, composed of sand-sized (0.1–1 millimeter) elongate fine-grained aggregates of variable composition.
Flume experimental studies of lenticular fabric suggest that these layers reflect seafloor erosion of soft muds in the form of sand-sized aggregates transported across the basin floor by bottom currents.
Why it matters: Deposition of organic-rich vs. organic-poor sediments 1,500 million years ago, when Earth was populated only with single-celled organisms, is a peek into the Deep Time of sedimentology.
The Goru Formation is interbedded shale, sandstone, and limestone. It is located in the onshore Middle Indus Basin of Pakistan.
It was deposited in a shallow-marine environment during the Early Cretaceous.
What they did:
The researchers measured TOC values from cuttings from two wells.
They compared the measured TOC values with those derived from well-log interpretations.
What they found:
Individual models for TOC estimation, the 1974 Kuster and Toksöz (KT) model and the 2009 Markov model for self-consistent approximation (SCA), showed correlations between 55 and 75 percent.
However, combining KT and SCA models significantly improved TOC estimation, achieving correlations of 90 to 98 percent compared to laboratory data.
TOC showed a negative correlation with compressional and shear wave velocities.
TOC showed no clear relation with pore geometries or shale porosity.
Why it matters:
TOC is a key geological indicator of resource richness and producibility of shale formations.
Well logs are often used for estimating TOC in shale formations.
Better-calibrated models would improve the well log interpretations.
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In case you missed it last Thursday, here is a brief recap of the AAPG Academy Webinar entitled “Global Superbasins: Geoscience Resources and Future Opportunities.” Speakers included Bob Fryklund (Chief Strategist,Upstream at S&P Global), Charles Sternbach (President of Star Creek Energy), and myself. Our presentation was hosted by Susan Nash (Director of Innovation and Emerging Science and Technology at AAPG).
What are superbasins?
As defined by Fryklund and Pete Stark in 2020 in the AAPG Bulletin, superbasins have the following features:
More than 5 billion barrels of oil equivalent (BOE) of cumulative production
More than 5 billion BOE remaining
Two or more source rocks
Stacked reservoirs
Mature infrastructure
Established service sectors
Large amounts of data
Access to market
Why are superbasins important?
About 90 percent of the world’s oil and gas production comes from nearly 50 superbasins.
Superbasins have provided the data and geological framework for training petroleum geoscientists for more than a century.
Superbasins have the potential to provide more than oil and gas, including carbon capture, geothermal and solar power generation, and metal elements extracted from produced formation waters.
Outside of the United States, shale plays remain largely untapped. This will be the greatest addition to the world’s portfolio of oil and gas resources.
Emerging superbasins: Frylund and Stark identified 62 superbasins in 2020.
Some emerging superbasins are located in the Equatorial and Southern Atlantic Margin, including the Guyana-Suriname Basin in South America and the Orange Basin offshore Namibia and South Africa.
The Black Sea may become another superbasin in the coming years.
AAPG Superbasin Initiative: From 2018 to 2023, AAPG organized 17 events related to superbasins, including four SuperBasin Leadership conferences.
AAPG Bulletin has published four special issues on superbasins:
December 2020 edited by Charles Sternbach and Claudio Bartolini
June 2021 edited by Charles Sternbach and Claudio Bartolini
March 2022 edited by Charles Sternbach and Claudio Bartolini
August 2023 edited by Charles Sternbach and Robert Merill
These special editions are available for purchase and are accessible for free to AAPG members.
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