PETROLEUM POTENTIAL AND OIL-SOURCE CORRELATION IN THE GREAT SOUTH ANDCANTERBURY BASINS

Pyrolytic analyses suggest that Cretaceous coaly sediments in the Grea t South and Canterbury Basins, southeast and east of South Island, New Zealand, exhibit mixed oil and gas potential, like their counterparts in Taranaki Basin. On the basis of isotopic and biomarker characteris tics together with maturity considerations, mid-Cretaceous coaly sedim ents are the most likely sources of the condensate and oil shows in Ka wau-1A well (Great South Basin), oil shows in deep Cretaceous strata i n Clipper-1 and Galleon-l wells (Canterbury Basin), and the stains in beach sands in northeastern Stewart Island. An oil stain in the upper Cretaceous in Galleon-l well is consistent with a Late Cretaceous coal source. Although some marine strata have petroleum potential, particu larly the Tartan Member (equivalent of the latest Paleocene Waipawa Bl ack Shale), they are often immature, and oils generated from such sour ces have yet to be discovered.