The technique centres on the CSIRO-developed HyLogger, which brings production-line efficiency to logging cores from mineral and petroleum exploration wells.
The HyLogger automates spectroscopic analysis (the use of reflected light) of drill core.
The instrument scans a 1m length of core in only 30 seconds and provides instant and objective information about the mineralogy, as well as high-resolution images.
Hylogger was developed with mineral exploration in mind, with hoped-for spin-offs in the search for petroleum.
It looks like the HyLogger could in fact be a powerful and inexpensive tool for petroleum explorers, following the release this week of a study by Geoscience Australia on 25 public-file drill cores in the southern Georgina Basin.
Geoscience Australia onshore hydrocarbons geoscientist Dr Bridget Ayling told Energy News that the HyLogger study of the southern Georgina Basin wells delivered everything that was expected, along with a surprise.
“We knew it would be a valuable tool for creating a picture of the basin geology and help us to correlate formations between wells,” she said.
“A lot is still unknown about the distribution of the main formations because of the sparsity of wells and seismic data.
“But the surprise was the absence of a spectral response from what we believe are the organic-rich sections of the Arthur Creek formation, which is the main source rock for unconventional exploration in the southern Georgina Basin.
“The lack of response to organic carbon means we have a powerful new tool for identifying the distribution and thickness of petroleum-generating source rocks.”
Ayling said the HyLogger data had been compared to geochemical laboratory measurements of some of the cores to verify the relationship between the lack of response and organic content.
“It’s a work in a progress but in the couple of wells we have already looked at, the data tends to agree,” she said.
“It’s an exciting observation and I think there will be even more applications for the HyLogger in petroleum exploration than we realise yet.”
One of the main findings of the research, which has been keenly anticipated by explorers in the southern Georgina Basin, is the wedge-shaped nature of the zone with no spectral response in the unconventional source rocks.
“The data show a wedge at the base of the Arthur Creek formation that correlates with an increased organic component, which is useful for explorers,” Ayling said.
“We are mapping how thick that wedge will be and working out what the total organic content will be and the thickness of that unit.
“Another important observation was the boundary seems to be gradational from an anoxic shale at the bottom and gradually decreasing in organic content upsection.
“We need to interpret the geochemistry data yet to quantify the cut-off for sections that would be regarded as prospective for petroleum explorers.
“But if can use spectral data to create a proxy for organic carbon, we will be able to produce some very useful maps.”
The HyLogger data is being released by Geoscience Australia with gamma log data in the southern Georgina Basin, which is another marker of the location and thickness of the organic content in the “hot” or radioactive Arthur Creek shale.
The new insights from HyLogger data in the southern Georgina Basin have important implications for petroleum explorers in onshore basins across the country.
The geological survey departments in most states are already well advanced in creating a huge catalogue of HyLogger data of open-file drill core.
The work is being undertaken with funding from AuScope, the CSIRO and the states to build a National Virtual Core Library that is the envy of prospectors and explorers around the world.
To date, the state and territory geological surveys have logged more than 650,000m of core and all of this data is available online and at no charge.
It will take a number of years to log the nation’s entire estimated inventory of about 8 million metres of open-file core. But the good news is that the private sector has recently begun offering HyLogger services.
ALS and Bureau Veritas offer HyLogging as a standard analytical service, which means petroleum explorers can generate their own data on free open-file core or from their own wells.
The new Hylogger results and the fact that so much data is already available or inexpensive to obtain means onshore explorers have a new tool that can rapidly compile a basin-wide picture of organic source rocks.
The value of HyLoggers is being recognised worldwide, with Perth-based distributor TDSmidth recently making sales to the geological surveys of China and Mexico.
The Geological Survey of Western Australia has also been researching the use of HyLoggers in petroleum exploration. This work focused on the spectral responses of oil shows themselves, rather than the mineralogy of the core.
Geoscience Australia is working towards the release of other products on the southern Georgina Basin early next year as part of its increasing focus on supporting onshore oil and gas exploration.
These products include a GIS package, which collates existing publicly available data, a Geoframe package, which loads in existing seismic data and a well folio for selected wells in the southern part of the basin.