The Government has doubled the amount of land and sea available for oil and gas exploration.
The total is now 405,000 square kilometres, or 1.5 times New Zealand's entire surface area.
Energy and Resources Minister Simon Bridges made the announcement at an energy conference in Wellington on Wednesday.
Areas being offered include onshore parts of the East Coast, Taranaki and the West Coast; and offshore areas near Cape Reinga, the New Caledonia Basin and land on the East Coast, Taranaki and the West Coast.
Mr Bridges said the area is big for a reason: "Companies do want maximum areas where they think there is good prospectivity to explore and then hone in on their interest. So while they start relatively large, they move into very small areas."
Petroleum Exploration and Production Association chief executive David Robinson says oil companies will be interested in that for reasons other than just the size.
"There is a lot more information that's available for explorers to use, to help inform their decision-making. What they've put together is a better pack of information by accumulating all the information together and putting it in one place for the explorer to access."
The oil industry on Wednesday welcomed the Government's offer and geological data that it has made available.
However, one expert is warning not to expect thickets of oil rigs any time soon. He says Texas oil giant Anadarko's recent failure to find oil is common, and drilling in deep-sea basins like those off Taranaki and Otago can have as little as a one to five percent success rate.
Companies are now invited to develop prospecting plans; those with the most intensive work programme will win contracts to proceed.
A small number of demonstrators protested outside the conference as the minister stressed the economic importance of oil and gas. Organiser Fi Gibson said they were angry at the new offer.
"This comes despite the IPCC report which shows climate change is very real and come with real costs for New Zealand. This is moving in the opposite direction to today's block offer."