A model of a buried undersea volcano, rendered using information from seismic reflection surveys. Photo / Supplied
A model of a buried undersea volcano, rendered using information from seismic reflection surveys. Photo / Supplied
Buried deep off New Zealand's coasts lie hundreds of volcanoes, which geologists believe could offer rich, untapped resources.
These underwater giants are peppered across Zealandia, the almost 5 million sq km chunk of continental crust that forms 95 per cent of New Zealand, but have been covered up by sediments eroded from the area mainly occupied by our present landmass.
More than 100 lie in the offshore Canterbury basin alone.
While we know little about them, they have a profound influence on how sediment and water moves around our ocean floor, and on the thermal environment of sedimentary basins found beneath the sea.
They've now become all the more important with international exploration in countries like Chile and Brazil revealing, sometimes by accident, commercially viable quantities of oil and gas in extinct volcanic systems.
Here, no such discoveries have been made, partly because buried volcanoes are considered too risky to explore.
But scientists say part of that risk owes to the fact we don't have enough information to understand how they generate and trap hydrocarbons, which could be extracted to produce oil and gas.
"Our main hypothesis is that buried volcanoes can contain important hydrocarbon resources in New Zealand basins," said Professor Andy Nicol, a structural geologist at the University of Canterbury leading a new million-dollar study supported by the Government's Endeavour Fund.
His team hope to reveal how hydrocarbons move around inside the volcanoes by creating state-of-the-art 3D models.
They'll construct these using a combination of existing seismic reflection surveys imaging volcanoes offshore from Canterbury and Taranaki, with information from on-land volcanoes such as Tongariro and Banks Peninsula.
The models would map out their shape and interior, which could also lead to a better understanding of how all volcanoes generally work below ground.
"If the pressure and temperature conditions are not within well-defined windows, hydrocarbons will not form."
Once volcanoes go extinct, it's not known for how long they carry on driving basin temperatures.
A 3D rendering of an undersea volcano. Photo / Supplied
With all of the data, the researchers will put together numerical models of petroleum migration, helping them see how hydrocarbons flow around and into buried volcanoes, and ultimately which ones are more likely to hold oil and gas.
Nicol said this would be a "massive challenge" to do within the project's three-year timeframe - but if his team succeeded, there was every chance they could make a crucial contribution to understanding how the planet's buried volcanoes affect petroleum systems.
He noted that, in 2015, New Zealand was self-sufficient in natural gas, and domestic oil production made up about 40 per cent of what we used.
"There have been no commercially significant oil and gas discoveries in New Zealand for at least 10 years and our petroleum production is in decline."
Current predictions suggested we would be falling well short of domestic hydrocarbon demands by the mid-2030s, assuming projections of demand were correct and no new discoveries were made.
"While this research is not aimed at identifying specific exploration targets, we hope that it will provide information that could lead to more successful exploration.
"Even moderate sized oil and gas discoveries have the potential to contribute up to $500 million in export value each year and $100 to 200 million per annum in government revenue for 10 to 30 years, so their financial contribution could be significant."
In another $7.6 million new project, scientists will investigate gas hydrates: ice-like substances of natural gas that exist beneath large areas of the seafloor.
Storing large amounts of methane, they also represent a potentially large energy resource, and over recent years the Government has invited commercial bids from the petroleum industry to explore for them.
At the same time, active commercial exploration of conventional oil and gas has moved into deeper waters where future production will require drilling through gas hydrates.
But because gas hydrates are an important part of the natural marine environment, scientists need to learn more about the potential impacts of producing natural gas from them.
The project, led by GNS Science, will weigh up the balance between the economic opportunities and cultural values and environmental risks that might come with extracting gas hydrates.
