Acreage Release Data Packs

Open file biostratigraphic data is often a mix of vintage reports, some dating back to the 1950s and typically utilizing outdated zonation schemes, or is a mix of inhouse and industry schemes that creates more confusion than stratigraphic clarity.

For example, does your palynological dataset still contain the R. aemula Zone? Issues correlating this zone across the North West Shelf resulted in it being superseded by the C. ancorum, V. tabulata, and T. balmei zones almost a decade ago! …yet it still remains in many databases.

How about the also-defunct A. cinctum, C. halosa, and W. digitata zones?  Continuing with these outdated zones (all replaced for good reasons) usually results in miscorrelations. The raw data should always be reinterpreted to the latest zonal schemes to ensure consistent recognition of these key biostratigraphic zones.

It’s the same situation in the Otway Basin, where a number of different zonation schemes have been used, further complicated by the fact that the zonal names have remained largely unchanged but the definitions of these zones have evolved. In addition, two high resolution schemes have been used in recent years, developed over different fields in the region.

These biozone inconsistencies lead to limits on the resolution achievable from the open-source biostratigraphic data. This in turn leads to limits on the resolution of any sequence stratigraphic framework that may be built using this current data, and more crucially, results in erroneous geological modelling.

To build an accurate geological model centred on a robust sequence stratigraphic framework, accurate, quality-controlled, and consistent palynological data is a vital component – and this is not available from the open file datasets.

Simply put, you can’t correlate oranges with apples.

The other benefit to our Australian-wide data review is that we have been able to provide greater zonal resolution from a lot of open file interpretations, simply because the subzonal resolution hadn’t been developed at the time of analysis.

Even open file reports by the same analyst can benefit from a review, and we have revised many well interpretations using log profiles and offset well data, all of which allows us to see results more consistently.

Similar issues arise from inconsistent lithostratigraphic nomenclature. A single sedimentary unit may have multiple names, or even more confusingly, the same name may be applied to different definitions of that stratal package! As such, without any kind of consistency in terminology or definition, no accurate correlations between wells, or on a basin-wide scale, can be made without first updating your lithostratigraphic library.