NZ shale gas – will we get lucky?

A member of the NZ Climate Science Coalition asked about shale gas exploration in New Zealand. He received the following reply. — RT

I can advise that several petroleum exploration companies are actively looking at shale gas potential in NZ.

At present almost all of the onshore eastern North Island (the “East Coast Basin”, east of the main North Island ranges) is covered by petroleum exploration permits, or by applications for permits. Operators of these permits are investigating shale gas potential as well as more conventional (sandstone) reservoir targets.

More recently there have been applications for new petroleum exploration permits in the onshore Canterbury basin, as well as in Marlborough and Southland, specifically targeting shale gas. It is unlikely that the offshore basins are prospective for shale gas at present, but as the technology develops, it may happen. Across the Tasman, there is also great interest in exploration for shale gas.

For various geological reasons, the eastern parts of NZ are probably more prospective for shale gas than the west, so there is potential for these exploration companies to discover and produce petroleum in areas outside of Taranaki, which is potentially of huge benefit to local economies as well as to the whole of NZ.

Concerning gas in aquifers and water wells, there are literally hundreds of natural (petroleum) gas seeps in NZ, for example there are at least 300 sites in the eastern North Island where natural gas bubbles to the surface. And I am aware of at least six locations where wells drilled in search of groundwater have encountered gas. One such well near Gisborne drilled long ago produced enough gas to supply energy to the whole township. Enterprising locals in remote areas managed to trap and utilise gas from natural seeps for cooking and heating at least the last 100 years back. Any little earthquake (a far more significant shake than any seismic impulse used for exploration) causes a greater (but temporary) rate of gas flow from these natural seeps.

Don’t ever be fooled by claims that petroleum exploration, seismic activity, or “fraccing/fracking” somehow leads to gas suddenly coming into aquifers, it has been there (and leaking out) for many thousands, or more likely millions of years.

The onshore gas seeps are only evident where the gas happens to come to the surface under some waterway, such as a river, stream, or lake. Methane and other petroleum gases naturally come to the surface by slow but persistent seepage in virtually all of NZ’s onshore sedimentary basins (Northland, Waikato, Taranaki, Wanganui, East Coast, West Coast, Canterbury, Southland) and are detectable by analysing gas in soil or sub soil.

There are also numerous natural seeps of petroleum gas (mainly methane, but also other hydrocarbons) in NZ’s much larger offshore continental areas. There are whole communities of organisms that depend on these (often deep) sea bed gas seeps for their whole energy cycle without the need for light, oxygen or carbohydrates. There is very good evidence from the geological record that these natural offshore gas seeps have been active for at least the last 23 million years, and probably before then as well.

My whole point is that methane seeps are nothing new, and are beneficial to various parts of the natural biota.

I hope that the above is useful to the general discussion about shale gas, gas in water wells and the natural occurence of methane and other hydrocarbons.

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