200million barrel onshore poss 50 plus bagger, page-22

SUMMARY AND CONCLUSIONS

Although the late Paleocene Waipawa Black Shale has excellent oil potential, any oil that it may have sourced in the Great South and Canterbury Basins has yet to be discovered. It has probably not reached sufficient maturity anywhere in the basin to have generated
significant amounts of oil, and it may not be laterally
extensive if its deposition is confined to the upper slope
during a geologically short period.

As is commonly encountered with coaly source rocks,
conclusive biomarker correlation between oils/condensates
and individual coal samples was not possible. However,
biomarker and isotopic data are consistent with mid-
Cretaceous coaly sediments, similar to the Taniwha
Formation in Taranaki Basin, producing the condensate and
various oil shows in Cretaceous strata encountered in
Kawau-1 A, the deep Cretaceous oil shows in Galleon-1 and
Clipper-1, and the oil stains at Leask and Horseshoe Bays
on Stewart Island.

All cuttings samples analysed were of relatively advanced
maturity, but comparison with other coaly source rocks
in the Great South and Taranaki Basins suggests a similar
mixed gas and oil potential for all samples except those
from Kawau, which appear to have lower potential and
to be more gas prone. Oil encountered in the upper
Cretaceous sediments in Galleon-1 appears to be sourced
from Late Cretaceous coaly sediments as found in this
well, but from a more mature situation elsewhere.
Cretaceous coaly sediments have demonstrable oil
potential and are probably mature over quite a large area of the Great South and Canterbury Basins.

Consequently, the prospects for oil exploration may well be better than previously believed, if reservoirs of suitable size and porosity exist.


FROM: New Zealand Journal of Geology and Geophysics, 1997, Vol. 40:405-423 0028-8306/97/4004-0405 $7.00/0 © The Royal Society of New Zealand 1997 405

Petroleum potential and oil-source correlation in the Great South and Canterbury Basins