Invictus’ Cabora Bassa Project oozes oil and gas potential
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Special Report: Evidence continues to mount for the potential of Invictus’ Cabora Bassa gas-condensate project in Zimbabwe to be Africa’s next hydrocarbon province.
Geochemical analysis of outcrop samples at the project have now confirmed that two highly prospective source rocks are present within Invictus Energy’s (ASX:IVZ) project, which was first defined by Mobil during the 1990s.
Source rocks are underground rock formations from which oil and gas are generated from and the confirmation that they are present drastically upgrades the likelihood that Cabora Bassa hosts a working hydrocarbon system.
The company said analysis of the older Permian-aged Mkanga formation indicated strong correlation to two oil seeps that were on trend in the neighbouring Mid Zambezi sub basin in Zimbabwe.
Additionally, analysis of the Triassic-aged Alternations Member source rock also confirms that it has good light oil and gas generation characteristics.
The Mkanga Formation rocks were found to have total organic content (TOC) values of up to 40 per cent and Hydrogen Index (HI) up to 380 while the Alternations Member rocks have TOC up to 35 per cent and HI of up to 209.
The TOC values are well above the recommended thresholds of 0.5 per cent and 2.5 per cent required for gas and oil generation respectively.
Invictus’ reprocessed seismic data also enables it to track the source rocks from outcrops at surface into the subsurface where the heat and pressure deeper in the basin make it likely that they have generated and expelled hydrocarbons.
“The new RockEval geochemistry data has provided evidence that the source rock sequences present in the Cabora Bassa Basin possess good to excellent gas and liquids potential and are comparable to African and West Australian basins which host multi-billion-barrel oil and multi TCF gas discoveries,” managing director Scott Macmillan said.
“The better seismic imaging has enabled the mapping of the outcrop source and reservoir sequences into the subsurface with greater confidence as well as providing a favourable view of the timing of two major episodes of generation of hydrocarbons into the multiple traps in the basin.
“The location of the source rock directly beneath reservoir positions them to charge the primary Upper Angwa Alternations Member target as well as shallower horizons in the Pebbly Arkose, Forest and Dande Formations.
“There is potential evidence of this shown by the seismic amplitude anomalies that conform to structure.”
Invictus noted the majority of samples from Mkanga showed correlation with Permian coals and carbonaceous shales of the Perth Basin in Western Australia while data from the lower part of the formation correlated with source rocks in the Lake Albert oil fields in Uganda.
Meanwhile, the lower Triassic source rocks within Cabora Bassa makes it comparable to the Morondava Basin in Madagascar, which hosts multi-billion-barrel heavy oil and tar sand discoveries in Tsimiroro and Bemolanga accumulations, as well as light oil in Manadaza and gas-condensate in Manambolo accumulations.
Mobil defined Cabora Bassa in the 1990s after spending $30m acquiring 2D seismic, gravity and aeromagnetic data but elected to surrender the project after its work indicated that it held gas rather than oil.
The project remained essentially untouched until it was picked up by Invictus, which reprocessed the Mobil data and increased the size of the Mzarabani primary target while identifying and quantifying other high potential horizons above and below the Alternations Member.
Unlike the situation during the 1990s, any gas discovery will also find a ready gas market in southern Africa while strong hints have also emerged that the project could indeed host the oil that eluded Mobil.