“Working on a hunch that the true extent of the Beetaloo had yet to be defined, Santos commissioned a survey of the basement topography and discovered an even thicker sediment pile had been overlooked to the east of … what had previously been regarded as the core of the Beetaloo.”
The Velkerri B shale, which hosts the rocks behind Origin Energy’s 2C contingent resource of 6.6 Tcf (gross), is 1.4 billion years old.
“The shallower Kyalla formation, which is liquids rich and will be the target of Origin’s upcoming wells, is about 1.2 billion years old.
“Both formations are almost a billion years older than most of the world’s hydrocarbon-producing rocks.
“The exploration text books say the Beetaloo is too old to be worth exploring. Time works against preservation of hydrocarbon systems. And the further one goes back in the geological record, the less life existed on earth, which means less organic matter to create source rocks.
“Against the odds, the Velkerri rocks [in Beetaloo] not only contain organic-rich mudstones (ranging from about 4% to 8% total organic content), but the rocks have sat there largely undisturbed for more than a billion years and appear to be gas saturated.
“The mudstones were deposited in a marine environment a long way out from the coastline.
“The science on how the organic matter came to be there is still being debated, but it is thought that organic matter, derived from no more than bacteria and blue-green algae, grew in sunlit, shallow waters of an ancient ocean before dying and piling up on the ocean floor.
“The depositional environment also created some other key positives for today’s shale gas and liquid explorers.
“The Velkerri and, to a lesser extent the younger Kyalla formation are remarkably consistent across a vast area.
“The shales are also rich in microcrystalline quartz, which makes the Velkerri shales highly susceptible to fracture stimulation.
“In this respect, the Beetaloo is analogous to the Marcellus shale, which is among the most productive, low-cost shales of North America,” says the rewiew.
“The corporate stories behind exploration in the Beetaloo are almost as interesting as the geology.
“In the background, Santos geologists had worked out that the Beetaloo offered perhaps the best unconventional [fracking] opportunity in Australia.
“The company was keen to find a way in, but cash was tight as the business poured billions into Gladstone LNG.
“Working on a hunch that the true extent of the Beetaloo had yet to be defined, Santos commissioned a survey of the basement topography and discovered an even thicker sediment pile had been overlooked to the east of … what had previously been regarded as the core of the Beetaloo.”
