The Canterbury Basin is located both onshore and offshore along the eastern coast of New Zealand’s South Island. It extends eastwards into the deep water of the Bounty Trough, to the south is the Great South Basin, and to the north it is bounded by the Chatham Rise.
Early exploration commenced in the onshore Canterbury Basin in 1941, whilst the first well drilled offshore was Endeavour-1 in 1970. Only five other wells have been drilled since 1970 in the offshore Canterbury, with Clipper-1 and Galleon-1 resulting in sub-commercial discoveries of condensate rich gas in 1984 and 1985 respectively.
The Canterbury Basin was formed in the mid Cretaceous during the final stages of the separation of Australia, New Zealand and Antarctica. The basin contains non marine mid Cretaceous aged sediments deposited in the opening rift basin overlain by marine and non-marine sediments of Late Cretaceous age, which in turn are overlain by a mostly marine Tertiary sequence.
The Canterbury Basin overlies Permian and Jurassic aged sediments deposited in older basins which preceded the onset of rifting in the Canterbury. Coaly sediments in these older rocks are considered the source rock for hydrocarbons. Coaly intervals in Cretaceous aged sediments are also considered rich source rocks. The Mid-Cretaceous Clipper Formation has good potential as a reservoir, as do the non-marine and marine sandstones deposited during the Late Cretaceous.