The Perth Basin: Challenging Misconceptions and Unveiling its Palynological Potential

Western Australia’s Perth Basin has emerged as a key piece of Australia’s energy puzzle and is a hub of ongoing exploration and discovery, with resources including oil and gas, CCUS, geothermal, groundwater, and hydrogen. But to truly unlock the basin’s potential, we must delve deeper into the realm of palynology – and clear up some current misconceptions.

Following the discovery of the Waitsia Field in 2014, the Perth Basin has seen a series of significant gas discoveries targeting deeper Permian plays. Strike Energy and Beach Energy both had significant successes in 2019 with their West Erregulla-2 and Beharra Springs Deep-1 wells, respectively. Whilst more recently, Mineral Resources have had further success with their Lockyer Deep-1 (2021) and North Erregulla Deep-1 (2023) wells. These discoveries have all added very substantial natural gas reserves to the region’s portfolio, highlighting the untapped potential of the Perth Basin.

But its importance extends beyond oil and gas. The federal government recently opened to public consultation an offshore greenhouse gas storage permit in the Perth Basin, bringing carbon capture and storage (CCS) into the spotlight. Furthermore, the basin’s extensive Leederville and Yarragadee aquifers are crucial freshwater aquifers, providing significant sources of groundwater for the entire region. On the geothermal front, Perth Basin’s potential is equally promising, with studies indicating that the region could offer significant geothermal resources, not to mention the geothermal exploration permits recently awarded across the region. Then there is natural hydrogen exploration, with new soil-gas measurements revealing persistent hydrogen concentrations along the Darling Fault.

Despite these exciting developments, our geological understanding of the Perth Basin is far from complete, and in palynological terms, it is massively understudied. The high thermal maturity in parts of the basin coupled with the small-scale palynological studies generally undertaken in the past has given rise to the belief that palynology is of limited use in the Perth Basin.

But this couldn’t be further from the truth.

Palynology is a crucial tool for stratigraphic correlations and reconstructing past environments, as well as helping constrain the geographical extent of key formations. All of this is important for multiple disciplines – even including civil engineering (different formations have different rock mechanic properties, so you don’t want to build on the wrong formation). Simply put, you can’t have a sound geological model without a detailed palaeontological foundation.

Breaking Misconceptions

Before we break any palynological misconceptions, we do need to honour these a little first, because it is true that certain areas of the Perth Basin, particularly the deeper Dandaragan Trough successions, are very challenging for palynology. The higher thermal maturities encountered by wells drilling these deeper sections often result in blackened, fragmented, and largely unidentifiable palynomorphs, if they are present at all.

However, most Perth Basin palynological assemblages, away from the deepest Dandaragan Trough wells, are rich, diverse, and well-preserved, revealing a wealth of critical geological information. Supporting this, some of our recent studies have shown just how useful palynology can be and importantly highlights that if anything, the Perth Basin is severely lacking in detailed, high-resolution palynological work. MGPalaeo has also been providing more direct exploration support with our Triassic and Permian hotshot services helping to inform critical drilling decisions.

Furthermore, even where the deeper Dandaragan assemblages (Permian) may be ‘cooked’, the Triassic to Cretaceous successions often still yield good assemblages providing critical stratigraphic controls. This information is increasingly important as companies seek to better understand these overburden successions as they develop their Permian ‘Kingia’ discoveries.

Elsewhere in the basin, the Jurassic discoveries by Strike Energy and Talon at the Walyering Field, have also highlighted the need to better understand the Mesozoic successions. Thus, we have been partnering with operators for EIS projects (Series 4 and 5) focusing on high-resolution Jurassic palynology to build an improved chronostratigraphic framework for this interval. And the good news is, the Jurassic is palynologically rich and abundant!

These projects will help us address another comment we hear about Perth Basin palynology, that it doesn’t deliver the same stratigraphic resolution as the North West Shelf palynology zonations. This is true, but the North West Shelf zonations were only developed by companies investing in numerous high-resolution studies, often with hundreds of palynological samples analysed per well. These EIS projects will be amongst the first high-density sampling projects to try and redress this balance.

Finally, we are also pulling together all the open file biostratigraphic data into one updated, consistent database for the entire Perth Basin. This will be the next addition to our AUSTRALIS database. Combining this with available chemo-, lithostratigraphic and geophysical log data has helped us establish an initial sequence stratigraphy for the basin – the next critical step in understanding the geology of the Perth Basin.

The Perth Basin is an increasingly important provider for Australia’s energy industry, and as our understanding of this region evolves, palynology continues to prove its worth. Don’t be fooled into believing past ideas about the use of palynology in the basin. Contact us and let us show you how palynology can help your exploration or engineering projects, or get in touch for more information on our Perth Basin database.